(**************************************************************************)
(*                                                                        *)
(*    Copyright 2012-2020 OCamlPro                                        *)
(*    Copyright 2012 INRIA                                                *)
(*                                                                        *)
(*  All rights reserved. This file is distributed under the terms of the  *)
(*  GNU Lesser General Public License version 2.1, with the special       *)
(*  exception on linking described in the file LICENSE.                   *)
(*                                                                        *)
(**************************************************************************)

open OpamTypes
open OpamStateTypes
open OpamStd.Op
open OpamPackage.Set.Op

let log fmt = OpamConsole.log "CLIENT" fmt
let slog = OpamConsole.slog

(* Splits a list of atoms into the installed and uninstalled ones*)
let get_installed_atoms t atoms =
  List.fold_left (fun (packages, not_installed) atom ->
      try
        let nv =
          OpamPackage.Set.find (OpamFormula.check atom) t.installed in
        nv :: packages, not_installed
      with Not_found ->
        packages, atom :: not_installed)
    ([],[]) atoms

(* Check atoms for pinned packages, and update them. Returns the state that
   may have been reloaded if there were changes *)
let update_dev_packages_t ?autolock ?(only_installed=false) atoms t =
  if OpamClientConfig.(!r.skip_dev_update) then t else
  let working_dir = OpamClientConfig.(!r.working_dir || !r.inplace_build) in
  let to_update =
    List.fold_left (fun to_update (name,_) ->
        try
          let nv = OpamPackage.package_of_name t.pinned name in
          if OpamSwitchState.is_dev_package t nv &&
             ( not only_installed ||
               OpamPackage.Set.exists (fun nv -> nv.name = name) t.installed )
          then
            OpamPackage.Set.add nv to_update
          else to_update
        with Not_found -> to_update)
      OpamPackage.Set.empty atoms
  in
  if OpamPackage.Set.is_empty to_update then t else (
    OpamConsole.header_msg "Synchronising pinned packages";
    try
      let working_dir =
        if working_dir then Some (OpamSwitchState.packages_of_atoms t atoms)
        else None
      in
      let _success, t, _pkgs =
        OpamUpdate.dev_packages t ?autolock ?working_dir to_update in
      OpamConsole.msg "\n";
      t
    with e ->
      OpamStd.Exn.fatal e;
      OpamConsole.msg "\n";
      t
  )

let compute_upgrade_t
    ?(strict_upgrade=true) ?(auto_install=false) ?(only_installed=false)
    ~all ~formula atoms t =
  let packages = OpamFormula.packages_of_atoms t.packages atoms in
  let names = OpamPackage.Name.Set.of_list (List.rev_map fst atoms) in
  let atoms =
    if strict_upgrade then
      List.map (fun (n, cstr as atom) ->
          if cstr <> None then atom else
          try
            let nv = OpamSwitchState.find_installed_package_by_name t n in
            let strict_upgrade_atom = (n, Some (`Gt, nv.version)) in
            if not (OpamSwitchState.is_dev_package t nv) &&
               not (OpamPackage.has_name t.pinned n) &&
               not (OpamPackage.Set.mem nv (Lazy.force t.reinstall)) &&
               OpamPackage.Set.exists
                 (not @* OpamSwitchState.avoid_version t)
                 (OpamFormula.packages_of_atoms
                    (Lazy.force t.available_packages)
                    [strict_upgrade_atom])
            then strict_upgrade_atom
            else atom
          with Not_found -> atom)
        atoms
    else
      atoms
  in
  let installed, not_installed =
    List.partition (fun (n,_) -> OpamPackage.has_name t.installed n) atoms
  in
  let atoms =
    if not_installed = [] ||
       auto_install ||
       not only_installed &&
       OpamConsole.confirm
         (match not_installed with
          | [_] -> "%s is not installed. Install it?"
          | _ -> "%s are not installed. Install them?")
         (OpamStd.Format.pretty_list
            (List.rev_map OpamFormula.short_string_of_atom not_installed))
    then atoms
    else installed
  in
  let to_install, to_upgrade =
    List.partition (fun (n,_) ->
        match OpamPackage.package_of_name_opt t.installed n with
        | None -> true
        | Some nv -> not (OpamPackage.Set.mem nv (Lazy.force t.available_packages)))
      atoms
  in
  let criteria = if to_install = [] then `Upgrade else `Default in
  if all then
    names,
    OpamSolution.resolve t Upgrade
      ~requested:packages
      ~reinstall:(Lazy.force t.reinstall)
      (OpamSolver.request
         ~install:to_install
         ~upgrade:to_upgrade
         ~deprequest:(OpamFormula.to_atom_formula formula)
         ~all:[]
         ~criteria ())
  else
  names,
  OpamSolution.resolve t Upgrade
    ~requested:packages
    (OpamSolver.request
       ~install:to_install
       ~upgrade:to_upgrade
       ~deprequest:(OpamFormula.to_atom_formula formula)
       ~criteria
       ())

let print_requested requested formula =
  OpamFormula.fold_left
    (fun req (name,_) -> OpamPackage.Name.Set.add name req)
    requested formula

let upgrade_t
    ?strict_upgrade ?auto_install ?ask ?(check=false) ?(terse=false)
    ?only_installed ~all atoms ?(formula=OpamFormula.Empty) t
  =
  log "UPGRADE %a"
    (slog @@ function [] -> "<all>" | a -> OpamFormula.string_of_atoms a)
    atoms;
  match
    compute_upgrade_t ?strict_upgrade ?auto_install ?only_installed ~all
      ~formula atoms t
  with
  | requested, Conflicts cs ->
    log "conflict!";
    if not (OpamPackage.Name.Set.is_empty requested) then
      (OpamConsole.error "Package conflict!";
       OpamConsole.errmsg "%s"
         (OpamCudf.string_of_conflicts t.packages
            (OpamSwitchState.unavailable_reason t) cs);
       OpamStd.Sys.exit_because `No_solution);
    let reasons, cycles =
      OpamCudf.conflict_explanations t.packages
        (OpamSwitchState.unavailable_reason t) cs in
    if cycles <> [] then begin
      OpamConsole.error
        "Dependency errors in the upgrade actions. Please update, and \
         report the following to the package maintainers if the error \
         persists:";
      OpamConsole.errmsg "%s\n%s\n"
        (OpamStd.Format.itemize (fun x -> x) cycles)
        "You may try upgrading packages individually to work around this."
    end else begin
      OpamConsole.warning
        "Upgrade is not possible because of conflicts or packages that \
         are no longer available:";
      OpamConsole.errmsg "  %s"
        (OpamStd.Format.itemize (OpamCudf.string_of_conflict ~start_column:2)
           reasons);
      OpamConsole.errmsg
        "\nYou may run \"opam upgrade --fixup\" to let opam fix the \
         current state.\n"
    end;
    OpamStd.Sys.exit_because `No_solution
  | requested, Success solution ->
    if check then
      OpamStd.Sys.exit_because
        (if OpamSolver.solution_is_empty solution
         then `False
         else `Success)
    else
    let packages = OpamPackage.packages_of_names t.packages requested in
    let t, result =
      OpamSolution.apply ?ask t ~requested:packages
        ~print_requested:(print_requested requested formula)
        solution
    in
    if result = Nothing_to_do then (
      let to_check =
        if OpamPackage.Name.Set.is_empty requested then t.installed
        else OpamPackage.packages_of_names t.installed requested
      in
      let latest =
        OpamPackage.Name.Set.fold (fun name acc ->
            OpamPackage.Set.add (OpamPackage.max_version t.packages name) acc)
          (OpamPackage.names_of_packages to_check)
          OpamPackage.Set.empty in
      let notuptodate = latest -- to_check in
      if OpamPackage.Set.is_empty notuptodate then
        OpamConsole.msg "Already up-to-date.\n"
      else if terse then
        OpamConsole.msg "No package build needed.\n"
      else
        (let hdmsg = "Everything as up-to-date as possible" in
         let unav = notuptodate -- Lazy.force t.available_packages in
         let unopt = notuptodate %% Lazy.force t.available_packages in
         let base =
           OpamPackage.packages_of_names unopt
             (OpamPackage.names_of_packages t.compiler_packages)
         in
         let unopt = unopt -- base in
         let conflicts =
           let get_formula pkg =
             OpamStd.Option.map
               (fun opam ->
                  OpamFilter.filter_formula ~default:false
                    (OpamPackageVar.resolve_switch ~package:pkg t)
                    (OpamFile.OPAM.conflicts opam))
               (OpamSwitchState.opam_opt t pkg)
           in
           OpamPackage.Set.fold (fun unopt_pkg map ->
               let set =
                 OpamSwitchState.conflicts_with t
                   (OpamPackage.Set.singleton unopt_pkg) latest in
               OpamPackage.Set.fold (fun installed_pkg map ->
                   match get_formula installed_pkg with
                   | None -> map
                   | Some conflicts_formula ->
                     OpamFormula.fold_left
                       (fun map (n,formula) ->
                          if OpamPackage.name unopt_pkg = n &&
                             OpamFormula.check_version_formula formula
                               (OpamPackage.version unopt_pkg)
                          then
                            OpamPackage.Map.update unopt_pkg
                              (OpamStd.List.cons (installed_pkg, formula)) [] map
                          else map
                       ) map conflicts_formula
                 ) set map
             ) unopt OpamPackage.Map.empty
         in
         (* First, folding on [latest] packages: for each one, check if
            a [unopt] package does not verify [latest] package
            dependency formula *)
         let incompatibilities =
           let get_formula pkg =
             OpamStd.Option.map (OpamPackageVar.all_depends t)
               (OpamSwitchState.opam_opt t pkg)
           in
           OpamPackage.Set.fold (fun latest_pkg map ->
               match get_formula latest_pkg with
               | None -> map
               | Some depends_formula ->
                 OpamPackage.Set.fold
                   (fun unopt_pkg map ->
                      OpamFormula.fold_left
                        (fun map (n, formula) ->
                           if OpamPackage.name unopt_pkg = n &&
                              formula <> OpamFormula.Empty &&
                              not (OpamFormula.check_version_formula formula
                                     (OpamPackage.version unopt_pkg))
                           then
                             OpamPackage.Map.update unopt_pkg
                               (OpamStd.List.cons (latest_pkg, formula)) [] map
                           else map
                        ) map depends_formula
                   ) unopt map
             ) latest OpamPackage.Map.empty
         in

         if (OpamConsole.verbose ()) && not (OpamPackage.Set.is_empty unav) then
           (OpamConsole.formatted_msg
              "%s.\n\
               The following newer versions couldn't be installed:\n"
              hdmsg;
            OpamConsole.msg "%s"
              (OpamStd.Format.itemize (fun p ->
                   Printf.sprintf "%s.%s: %s"
                     (OpamConsole.colorise `bold
                        (OpamPackage.name_to_string p))
                     (OpamPackage.version_to_string p)
                     (OpamSwitchState.unavailable_reason t
                        ~default:"unavailable for unknown reasons (this may \
                                  be a bug in opam)"
                        (OpamPackage.name p,
                         Atom (`Eq, OpamPackage.version p))))
                  (OpamPackage.Set.elements unav)))
         else
           OpamConsole.formatted_msg
             "%s (run with --verbose to show unavailable upgrades).\n" hdmsg;
         if not (OpamPackage.Set.is_empty unopt) then
           (let bullet =
              OpamConsole.(colorise `red
                             (utf8_symbol Symbols.asterisk_operator "--"))
              ^ " "
            in
            let string_dep pkg map reason =
              List.fold_right (fun (p, f) acc ->
                   Printf.sprintf "%s\n%s%s is installed and %s %s"
                     acc bullet
                     (OpamPackage.to_string p)
                     reason
                     (OpamFormula.to_string (Atom (pkg.name, f)))
                )
                (OpamStd.Option.default [] (OpamPackage.Map.find_opt pkg map))
                ""
            in
            OpamConsole.formatted_msg
              "\nThe following packages are not being upgraded because the new \
               versions conflict with other installed packages:\n";
            OpamConsole.msg "%s"
              (OpamStd.Format.itemize
                 (fun pkg -> Printf.sprintf "%s.%s%s%s"
                     (OpamConsole.colorise `bold
                        (OpamPackage.name_to_string pkg))
                     (OpamPackage.version_to_string pkg)
                     (string_dep pkg incompatibilities "requires")
                     (string_dep pkg conflicts "conflicts with")
                 ) (OpamPackage.Set.elements unopt))
           );
         OpamConsole.formatted_msg
           "However, you may \"opam upgrade\" these packages explicitly, \
            which will ask permission to downgrade or uninstall the \
            conflicting packages.\n";

        )
    );
    OpamSolution.check_solution t (Success result);
    t

let upgrade t ?formula ?check ?only_installed ~all names =
  let atoms = OpamSolution.sanitize_atom_list t names in
  let t = update_dev_packages_t ~autolock:true ?only_installed atoms t in
  upgrade_t ?check ~strict_upgrade:(not all) ?only_installed ~all
    atoms ?formula t

let fixup ?(formula=OpamFormula.Empty) t =
  (* @LG reimplement as an alias for 'opam upgrade --criteria=fixup --best-effort --update-invariant *)
  log "FIXUP";
  let resolve pkgs =
    pkgs,
    OpamSolution.resolve t Upgrade
      ~requested:pkgs
      (OpamSolver.request
         ~install:(OpamSolution.atoms_of_packages pkgs)
         ~all:[]
         ~criteria:`Fixup
         ~deprequest:(OpamFormula.to_atom_formula formula)
         ())
  in
  let is_success = function
    | _, Success _ -> true
    | _, Conflicts cs ->
      log "conflict: %a"
        (slog (OpamCudf.string_of_conflicts t.packages @@
               OpamSwitchState.unavailable_reason t))
        cs;
      false
  in
  let requested, solution =
    let s =
      log "fixup-1/ keep installed packages with orphaned versions and roots";
      resolve (t.installed_roots %% t.installed
               %% Lazy.force t.available_packages)
    in
    if is_success s then s else
    let s =
      log "fixup-2/ last resort: no constraints. This should never fail";
      resolve OpamPackage.Set.empty
    in
    s
    (* Could still fail with uninstallable base packages actually, but we
       can only fix so far *)
  in
  let t, result = match solution with
    | Conflicts cs -> (* ouch... *)
      OpamConsole.error
        "It appears that the switch invariant is no longer satisfiable. \
         Either fix the package prerequisites or change the invariant \
         with 'opam switch set-invariant'.";
      OpamConsole.errmsg "%s"
        (OpamCudf.string_of_conflicts t.packages
           (OpamSwitchState.unavailable_reason t) cs);
      t, Conflicts cs
    | Success solution ->
      let print_requested =
        print_requested (OpamPackage.names_of_packages requested) formula
      in
      let t, res =
        OpamSolution.apply ~ask:true t
          ~requested
          ~print_requested
          solution in
      t, Success res
  in
  OpamSolution.check_solution t result;
  t

let update
    gt ~repos_only ~dev_only ?(all=false) names =
  log "UPDATE %a" (slog @@ String.concat ", ") names;
  let rt = OpamRepositoryState.load `Lock_none gt in
  let st, repos_only =
    match OpamStateConfig.get_switch_opt () with
    | None -> OpamSwitchState.load_virtual gt rt, true
    | Some sw -> OpamSwitchState.load `Lock_none gt rt sw, repos_only
  in
  let repo_names =
    let all_repos = OpamRepositoryName.Map.keys rt.repositories in
    if dev_only then []
    else if names <> [] then
      List.filter
        (fun r -> List.mem (OpamRepositoryName.to_string r) names)
        all_repos
    else if all then all_repos
    else OpamSwitchState.repos_list st
  in
  let packages, ignore_packages =
    if repos_only then OpamPackage.Set.empty, OpamPackage.Set.empty else
    let packages = st.installed ++ st.pinned in
    let packages =
      if names = [] then packages else
        OpamPackage.Set.filter (fun nv ->
            let name = OpamPackage.Name.to_string nv.name in
            let pkg = OpamPackage.to_string nv in
            List.exists (fun s -> s = name || s = pkg) names &&
            let pinned = OpamPinned.package_opt st nv.name in
            pinned = None || pinned = Some nv
          ) packages
    in
    let dev_packages, nondev_packages =
      OpamPackage.Set.partition (OpamSwitchState.is_dev_package st) packages
    in
    let dev_packages = dev_packages -- (st.compiler_packages -- st.pinned) in
    let nondev_packages =
      if names = [] || OpamPackage.Set.is_empty nondev_packages then
        OpamPackage.Set.empty
      else
        (OpamConsole.warning
           "The following are not development packages (no dynamic or version \
            controlled upstream) and can't be updated individually: %s\n\
            You may want to update your repositories with just %s or to \
            upgrade your package%s with %s %s"
           (OpamStd.List.concat_map ", " ~last_sep:"and" OpamPackage.to_string
              (OpamPackage.Set.elements nondev_packages))
           (OpamConsole.colorise `bold "opam update")
           (if OpamPackage.Set.is_singleton nondev_packages then "" else "s")
           (OpamConsole.colorise `bold "opam upgrade")
           (OpamConsole.colorise `bold
              (OpamStd.List.concat_map " " OpamPackage.name_to_string
                 (OpamPackage.Set.elements nondev_packages)));
         nondev_packages)
    in
    let dirty_dev_packages, dev_packages =
      if names <> [] || OpamClientConfig.(!r.drop_working_dir) then
        OpamPackage.Set.empty, dev_packages
      else
        OpamPackage.Set.partition
          (fun nv ->
             let src_cache = OpamSwitchState.source_dir st nv in
             let cache_url =
               OpamUrl.of_string (OpamFilename.Dir.to_string src_cache)
             in
             match OpamSwitchState.primary_url st nv with
             | Some { OpamUrl.backend = #OpamUrl.version_control as vc; _ } ->
               (try
                 OpamProcess.Job.run @@
                 OpamRepository.is_dirty { cache_url with OpamUrl.backend = vc }
                with OpamSystem.Process_error _ ->
                  log "Skipping %s, not a git repo" (OpamPackage.to_string nv);
                  false)
             | _ -> false)
          dev_packages
    in
    OpamPackage.Set.iter (fun nv ->
        OpamConsole.note "%s has previously been updated with --working-dir, \
                          not resetting unless explicitly selected"
          (OpamPackage.to_string nv))
      dirty_dev_packages;
    dev_packages, nondev_packages
  in

  let remaining =
    let ps = packages ++ ignore_packages in
    List.filter (fun n -> not (
        List.mem (OpamRepositoryName.of_string n) repo_names ||
        (try OpamPackage.has_name ps (OpamPackage.Name.of_string n)
         with Failure _ -> false) ||
        (try OpamPackage.Set.mem (OpamPackage.of_string n) ps
         with Failure _ -> false)
      )) names
  in
  if remaining <> [] then
    OpamConsole.error
      "Unknown repositories or installed packages: %s"
      (String.concat ", " remaining);

  (* Do the updates *)
  let rt_before = rt in
  let repo_update_failure, rt =
    if repo_names = [] then [], rt else
      OpamRepositoryState.with_write_lock rt @@ fun rt ->
      OpamConsole.header_msg "Updating package repositories";
      OpamRepositoryCommand.update_with_auto_upgrade rt repo_names
  in
  let repo_changed =
    not
      (OpamRepositoryName.Map.equal
         (OpamPackage.Map.equal (OpamFile.OPAM.effectively_equal))
         rt_before.repo_opams rt.repo_opams)
  in

  (* st is still based on the old rt, it's not a problem at this point, but
     don't return it *)
  let (dev_update_success, dev_changed), st =
    if OpamPackage.Set.is_empty packages then
      (true, false), st
    else
      OpamSwitchState.with_write_lock st @@ fun st ->
      let working_dir =
        if OpamClientConfig.(!r.working_dir) && names <> [] then
          Some (OpamPackage.packages_of_names packages
                  (OpamPackage.Name.(Set.of_list (List.map of_string names))))
        else None
      in
      OpamConsole.header_msg "Synchronising development packages";
      let success, st, updates =
        OpamUpdate.dev_packages st ~autolock:true ?working_dir packages
      in
      if OpamClientConfig.(!r.json_out <> None) then
        OpamJson.append "dev-packages-updates"
          (OpamPackage.Set.to_json updates);
      (success, not (OpamPackage.Set.is_empty updates)), st
  in
  OpamSwitchState.drop st;
  repo_update_failure = [] && dev_update_success && remaining = [] &&
  OpamPackage.Set.is_empty ignore_packages,
  repo_changed || dev_changed,
  rt

let init_checks ?(hard_fail_exn=true) init_config =
  (* Check for the external dependencies *)
  let check_external_dep name =
    OpamSystem.resolve_command name <> None
  in
  OpamConsole.msg "Checking for available remotes: ";
  let repo_types =
    ["rsync", "rsync and local";
     "git", "git"; "hg", "mercurial"; "darcs", "darcs"]
  in
  let available_repos, unavailable_repos =
    List.partition (check_external_dep @* fst) repo_types in
  OpamConsole.msg "%s.%s\n"
    (match available_repos with
     | [] -> "none"
     | r -> String.concat ", " (List.map snd r))
    (if unavailable_repos = [] then " Perfect!" else
       "\n" ^ OpamStd.Format.itemize (fun (cmd,msg) ->
           Printf.sprintf
             "you won't be able to use %s repositories unless you \
              install the %s command on your system."
             msg (OpamConsole.colorise `bold cmd))
         unavailable_repos);
  let soft_fail =
    if OpamCudfSolver.has_builtin_solver () then false else
    let external_solvers = ["aspcud"; "packup"; "mccs"] in
    if not (List.exists check_external_dep external_solvers) then
      (OpamConsole.error
         "No external solver found. You should get one of %s, or use a \
          version of opam compiled with a built-in solver (see \
          http://opam.ocaml.org/doc/External_solvers.html for \
          details)"
         (OpamStd.Format.pretty_list ~last:"or"
            (List.map (OpamConsole.colorise `bold) external_solvers));
       true)
    else false
  in
  let env v =
    let vs = OpamVariable.Full.variable v in
    OpamStd.Option.(Op.(of_Not_found
                          (OpamStd.List.assoc OpamVariable.equal vs)
                          OpamSysPoll.variables >>= Lazy.force))
  in
  let filter_tools =
    OpamStd.List.filter_map (fun (cmd,str,oflt) ->
        match oflt with
        | None -> Some (cmd,str)
        | Some flt -> if (OpamFilter.eval_to_bool env flt) then
            Some (cmd,str) else None)
  in
  let check_tool logf tools =
    match List.filter (not @* (List.exists check_external_dep) @* fst) tools with
    | [] -> false
    | missing -> (logf
                    (OpamStd.Format.itemize
                       (fun (miss,msg) -> Printf.sprintf "%s%s"
                           (OpamStd.List.concat_map " or "
                              (OpamConsole.colorise `bold) miss)
                           (match msg with | None -> "" | Some m -> ": "^m))
                       missing);
                  true)
  in
  let advised_deps =
    filter_tools (OpamFile.InitConfig.recommended_tools init_config)
  in
  let _ = check_tool
      (fun s -> OpamConsole.warning
          "Recommended dependencies -- most packages rely on these:";
        OpamConsole.errmsg "%s" s)
      advised_deps in

  let required_deps =
    filter_tools (OpamFile.InitConfig.required_tools init_config)
  in
  let hard_fail =
    let msg = if hard_fail_exn then OpamConsole.error else OpamConsole.warning in
    check_tool (fun s -> msg
                   "Missing dependencies -- \
                    the following commands are required for opam to operate:";
                 OpamConsole.errmsg "%s" s)
      required_deps
  in

  if hard_fail && hard_fail_exn then OpamStd.Sys.exit_because `Configuration_error
  else not (soft_fail || hard_fail)

let rec is_git_for_windows git =
  (* The resource file compiled for Git for Windows sets the ProductVersion
     string to M.m.r.windows.b where M.m.r is the git version and b is the
     revision number of Git for Windows. This differentiates it from very old
     pre-GfW builds and also from Cygwin/MSYS2 builds of Git (which don't have
     version blocks at all). The resource file is not localised cf.:
     - https://github.com/git/git/blob/master/git.rc#L7
     - https://github.com/git-for-windows/git/blob/main/SECURITY.md#L45
     - https://github.com/git/git/blob/master/GIT-VERSION-GEN#L15
  *)
  match OpamStubs.getVersionInfo git with
  | Some {OpamStubsTypes.strings =
            [(_, {productVersionString = Some version; _})]; _} ->
    begin
      try Scanf.sscanf version "%u.%u.%u.windows.%u%!" (fun _ _ _ _ -> true)
      with Scanf.Scan_failure _ | Failure _ | End_of_file ->  false
    end
  | _ ->
    (* The Scoop package manager installs a shim git.exe (see
       https://github.com/ScoopInstaller/Shim) which will fail our test of the
       version information block, while actually being Git for Windows.
       If git.shim and scoop.cmd are found with git.exe and we can parse the
       path line from git.shim, then we test the executable pointed to instead.
    *)
    let dir = Filename.dirname git in
    let git_shim = Filename.concat dir "git.shim" in
    let scoop = Filename.concat dir "scoop.cmd" in
    let find_path_value (key, value) =
      if String.trim key = "path" then
        Some (String.trim value)
      else
        None
    in
    let test_scoop_shim s =
      let new_git =
        let last = String.length s - 1 in
        if last > 0 && s.[0] = '"' && s.[last] = '"' then
          String.sub s 1 (last - 1)
        else s
      in
      log "%s appears to be a Scoop shim; trying %s" git new_git;
      is_git_for_windows new_git
    in
    if Sys.file_exists git_shim && Sys.file_exists scoop then
      OpamSystem.read git_shim
      |> String.split_on_char '\n'
      |> List.filter_map (Fun.flip OpamStd.String.cut_at '=')
      |> OpamStd.List.find_map_opt find_path_value
      |> OpamStd.Option.map_default test_scoop_shim false
    else
      false

let string_of_kind = function
  | `Msys2 -> "MSYS2"
  | `Cygwin -> "Cygwin"

let git_for_windows kind mechanism cygwin_is_tweakable =
  let resolve_git_in p =
    OpamSystem.resolve_command ~env:[||] (Filename.concat p "git.exe")
  in
  let gits =
    OpamStd.Env.get "PATH"
    |> OpamStd.Sys.split_path_variable
    |> OpamStd.List.fold_left_map (fun gits p ->
        match resolve_git_in p with
        | Some git when not (OpamStd.String.Set.mem git gits) ->
          OpamStd.String.Set.add git gits,
          Some (git, OpamSystem.bin_contains_bash p)
        | _ -> gits, None) OpamStd.String.Set.empty
    |> snd
    |> List.filter_map Fun.id
  in
  let abort_action = "install Git for Windows." in
  let gits, gfw_message, abort_action =
    if gits = [] then
      (* Git has not been found in PATH. See if it instead can be found in the
         initial environment. This deals with the possibility that the user
         has installed Git for Windows, but not restarted the terminal (so
         PATH has not been updated) *)
      let env = OpamStubs.get_initial_environment () in
      match OpamSystem.resolve_command ~env:(Array.of_list env) "git" with
      | Some git when is_git_for_windows git ->
        [], Some "It looks as though Git for Windows has been installed but \
                  the shell needs to be restarted. You may wish to abort and \
                  re-run opam init from a fresh session.",
        "restart your shell."
      | _ ->
        (* Git is neither in the current nor the initial PATH. There is one
           further possibility: the user may have installed Git for Windows
           but selected the option not to update the environment. The final
           hint given searches the Windows Registry for both a system-wide
           and user-specific installation and, if found, both displays a
           warning suggesting that the machine be reconfigured to enable them
           in PATH, but also gives the opportunity to use the git-location
           mechanism to select it for opam's internal use. *)
        let test_for_installation ((gits, gfw_message, abort_action) as acc)
            (hive, key) =
          let process root =
            let git_location = Filename.concat root "cmd" in
            let git = Filename.concat git_location "git.exe" in
            if OpamSystem.resolve_command ~env:[||] git <> None
            && is_git_for_windows git then
              let gits =
                (git, OpamSystem.bin_contains_bash git_location)::gits
              and message, action =
                Some "It looks as though Git for Windows has been installed, \
                      but configured not to put the git binary in your PATH. \
                      You can either abort and reconfigure your environment \
                      (or re-run the Git for Windows installer) to enable \
                      this, or you can use the menu below to have opam use \
                      this Git installation internally.",
                "reconfigure Git for Windows."
              in
              if message = None then
                gits, gfw_message, action
              else
                gits, message, abort_action
            else
              acc
          in
          let key = Filename.concat key "GitForWindows" in
          OpamStubs.readRegistry hive key "InstallPath" OpamStubsTypes.REG_SZ
          |> OpamStd.Option.map_default process acc
        in
        let installations = [
          (* Machine-wide installation *)
          (OpamStubsTypes.HKEY_LOCAL_MACHINE, "SOFTWARE");
          (* User-specific installation *)
          (OpamStubsTypes.HKEY_CURRENT_USER, "Software");
        ] in
        List.fold_left test_for_installation
          (gits, None, abort_action) installations
    else
      gits, None, abort_action
  in
  let get_git_location ?git_location () =
    let bin =
      match git_location with
      | Some _ -> git_location
      | None ->
        OpamConsole.read
          "Please enter the path containing git.exe (e.g. \
           C:\\Program Files\\Git\\cmd):"
    in
    match bin with
    | None -> None
    | Some git_location ->
      match resolve_git_in git_location,
            OpamSystem.bin_contains_bash git_location with
      | Some _, false ->
        OpamConsole.msg "Using Git from %s" git_location;
        Some git_location
      | Some _, true ->
        OpamConsole.error
          "A bash executable was found in %s, which will override \
           Cygwin's bash. Please check your binary path."
          git_location;
        None
      | None, _ ->
        OpamConsole.error "No Git executable found in %s." git_location;
        None
  in
  let options =
    (List.filter_map (fun (git, bash) ->
         if bash then
           None
         else
         let bin = Filename.dirname git in
         Some (`Location bin, "Use found git in "^bin))
        gits)
    @ [
      `Specify, "Enter the location of your Git installation";
      `Abort, ("Abort initialisation to " ^ abort_action);
    ]
  in
  let add_or_use_git root =
    let bindir = OpamSysInteract.Cygwin.bindir_for_root kind root in
    if resolve_git_in (OpamFilename.Dir.to_string bindir) = None then
      "Add Git to"
    else
      "Use Git from"
  in
  let default, options =
    match mechanism with
    | `Internal ->
      assert cygwin_is_tweakable;
      let internal =
        `Default, Printf.sprintf
          "Install Git with along with %s internally" (string_of_kind kind)
      in
      `Default, internal::options
    | `Root root ->
      assert cygwin_is_tweakable;
      let root =
        `Default, Printf.sprintf
          "%s the %s installation in %s"
          (add_or_use_git root)
          (string_of_kind kind)
          (OpamFilename.Dir.to_string root)
      in
      `Default, root::options
    | `Path root ->
      match OpamSystem.resolve_command "git.exe" with
      | Some git ->
        let options =
          if Filename.dirname git = root then
            let option =
              `Default, Printf.sprintf
                "Use %s Git from the installation at %s in PATH"
                (string_of_kind kind) root
            in
            option::options
          else
            (`Default, Printf.sprintf "Use Git from PATH")::options
        in
        `Default, options
      | None ->
        if cygwin_is_tweakable then
          let option =
            `Default, Printf.sprintf
              "%s %s installation in %s (from PATH)"
              (add_or_use_git (OpamFilename.Dir.of_string root))
              (string_of_kind kind)
              root
          in
          `Default, option::options
        else
          (fst (List.hd options)), options
  in
  let rec loop ?git_location () =
    match get_git_location ?git_location () with
    | Some _ as git_location -> git_location, false
    | None -> menu ()
  and menu () =
    let prompt () =
      OpamStd.Option.iter (OpamConsole.warning "%s\n") gfw_message;
      OpamConsole.menu "Which Git should opam use?"
        ~default ~yes:default ~no:default ~options
    in
    match prompt () with
    | `Default -> None, cygwin_is_tweakable
    | `Specify -> loop ()
    | `Location git_location -> loop ~git_location ()
    | `Abort ->
      OpamConsole.note
        "Once your chosen Git is installed, open a new PowerShell or Command \
         Prompt window, and relaunch opam init.";
      OpamStd.Sys.exit_because `Aborted
  in
  let git_location, use_cygwin =
    let git_found =
      match OpamSystem.resolve_command "git" with
      | None -> false
      | Some git -> is_git_for_windows git
    in
    if not git_found && OpamStd.Sys.tty_out then
      (OpamConsole.header_msg "Git";
       OpamConsole.msg
         "Cygwin Git is functional but can have credentials issues for private \
          repositories, we recommend using:\n%s\n"
         (OpamStd.Format.itemize (fun s -> s)
            [ "Install via 'winget install Git.Git'";
              "Git for Windows can be downloaded and installed from \
               https://gitforwindows.org" ]);
       menu ())
    else
      None, not git_found && cygwin_is_tweakable
  in
  OpamStd.Option.iter (fun _ ->
      OpamConsole.msg
        "You can change that later with \
         'opam option \"git-location=C:\\A\\Path\\bin\"'")
    git_location;
  Option.map OpamFilename.Dir.of_string git_location, use_cygwin

let check_git_location_or_exit git_location source =
  let git =
    Filename.concat (OpamFilename.Dir.to_string git_location) "git.exe"
  in
  if OpamSystem.resolve_command ~env:[||] git = None then
    OpamConsole.error_and_exit `Not_found
      "The location specified with %s does not appear to contain a Git \
       executable!" source

(* Default search mechanisms for Cygwin/MSYS2 *)
let cygwin_searches = [
  `Cygwins
    (OpamStubsTypes.HKEY_LOCAL_MACHINE, "SOFTWARE\\Cygwin\\Installations");
  `Cygwins
    (OpamStubsTypes.HKEY_CURRENT_USER, "Software\\Cygwin\\Installations");
  `Test "C:\\cygwin64";
  `Test "C:\\msys64";
  `Msys2_generic;
  `ScoopMsys2;
]

(* cygwin_searches is a sequence of `Path and `Test mechanisms based on the
   cygwin_searches list above. If specified, the ~first parameter allows a
   different first mechanism to be returned. *)
let cygwin_searches ?first () =
  let cygwin_searches =
    match first with
    | Some first -> first::cygwin_searches
    | None -> cygwin_searches
  in
  let rec seq searches () =
    match searches with
    | ((`Path | `Test _) as search)::searches ->
      (* Return the next mechanism *)
      Seq.Cons(search, seq searches)
    | (`Cygwins (hive, key))::searches ->
      (* Search the given registry hive key for Cygwin locations *)
      let possibles = OpamStubs.enumRegistry hive key OpamStubsTypes.REG_SZ in
      let map (_, path) =
        let path =
          if OpamStd.String.starts_with ~prefix:"\\??\\" path then
            String.sub path 4 (String.length path - 4)
          else
            path
        in
        `Test path
      in
      seq (List.map map possibles @ searches) ()
    | `ScoopMsys2::searches ->
      (* Scoop installs an msys2.cmd shim in PATH. If this is encountered, parse
         it. *)
      begin match OpamStd.Sys.resolve_in_path "msys2.cmd" with
        | None ->
          seq searches ()
        | Some msys2 ->
          let re =
            Re.(compile @@ seq [
                bos;
                str "@\"";
                group @@ rep @@ diff any (char '"');
                char '"';
                rep any;
                str " -msys2";
                alt [char ' '; eos]
              ])
          in
          let parse_line s =
            Stdlib.Option.bind (Re.exec_opt re s) (Fun.flip Re.Group.get_opt 1)
          in
          let msys2_shell =
            OpamSystem.read msys2
            |> String.split_on_char '\n'
            |> OpamStd.List.find_map_opt parse_line
          in
          match msys2_shell with
          | None ->
            seq searches ()
          | Some msys2_shell ->
            Seq.Cons(`Test (Filename.dirname msys2_shell), seq searches)
      end
    | `Msys2_generic::searches ->
      (* Some package managers put the root msys64 directory into PATH, in which
         case there will be msys2.exe - if that can be resolved in PATH, try
         that. *)
      begin match OpamSystem.resolve_command "msys2.exe" with
        | None ->
          seq searches ()
        | Some msys2 ->
          Seq.Cons(`Test (Filename.dirname msys2), seq searches)
      end
    | [] -> Seq.Nil
  in
  seq cygwin_searches

let rec cygwin_menu ~bypass_checks header =
  let start = Unix.gettimeofday () in
  let test_mechanism (roots, count, mechanisms) search =
    match test_mechanism ~bypass_checks header search with
    | Some ((kind, `Root root) as mechanism) ->
      if OpamFilename.Dir.Set.mem root roots then
        roots, count, mechanisms
      else
      let roots = OpamFilename.Dir.Set.add root roots in
      let mechanisms =
        (`Chosen mechanism,
         Printf.sprintf
           "Use %s installation found in %s"
           (string_of_kind kind)
           (OpamFilename.Dir.to_string root))::mechanisms
      in
      let count = succ count in
      if OpamConsole.disp_status_line ()
      && Unix.gettimeofday () -. start >= 0.5 then
        OpamConsole.status_line
          "Searching for Cygwin/MSYS2 installations: %d found so far" count;
      roots, count, mechanisms
    | _ -> roots, count, mechanisms
  in
  let detected =
    let _, _, mechanisms =
      Seq.fold_left test_mechanism
        (OpamFilename.Dir.Set.empty, 0, []) (cygwin_searches ())
    in
    List.rev mechanisms
  in
  OpamConsole.clear_status ();
  let internal_option = `Chosen (`Cygwin, `Internal) in
  let options =
    (internal_option,
     "Automatically create an internal Cygwin installation that will be \
      managed by opam (recommended)") ::
    (detected @
     [`Specify, "Use an" ^ (if detected = [] then "" else "other") ^
                " existing Cygwin/MSYS2 installation";
      `Abort, "Abort initialisation"])
  in
  let options, default, warn_path =
    (* First of all see if cygcheck can be found in PATH *)
    let cygcheck =
      OpamSystem.resolve_command "cygcheck.exe"
      |> Option.map OpamSysInteract.Cygwin.analyse_install
    in
    begin match cygcheck with
      | Some (Error _) | None ->
        (* cygcheck wasn't in PATH, so default to the internal installation *)
        options, `Chosen (`Cygwin, `Internal), None
      | Some (Ok (kind, root)) ->
        let pacman =
          OpamFilename.Op.(OpamSysInteract.Cygwin.bindir_for_root `Msys2 root // "pacman.exe")
          |> OpamFilename.to_string
        in
        let root = OpamFilename.Dir.to_string root in
        let path_option = `Chosen (kind, `Path root) in
        let options =
          (path_option, Printf.sprintf
             "Use tools found in PATH (%s installation at %s)"
             (string_of_kind kind) root)::options
        in
        if bypass_checks then
          options, path_option, None
        else
        (* Check whether cygcheck is still available in the initial environment.
           This allows a warning to be displayed reminding the user to continue
           running opam from a Cygwin/MSYS2 shell that has been manually started,
           but is not displayed if they have permanently configured their PATH to
           include Cygwin/MSYS2. *)
        let env = OpamStubs.get_initial_environment () in
        let cygcheck =
          OpamSystem.resolve_command ~env:(Array.of_list env) "cygcheck.exe"
          |> Option.map OpamSysInteract.Cygwin.analyse_install
        in
        begin match cygcheck with
          | Some (Ok (kind2, root2)) ->
            let root2 = OpamFilename.Dir.to_string root2 in
            if (kind : [`Cygwin | `Msys2]) = kind2 && String.equal root root2 then
              let default, warning =
                if kind = `Msys2 && OpamSystem.resolve_command pacman = None then
                  internal_option, Some
                    (Printf.sprintf
                       "The current PATH gives an installation of MSYS2 at %s, \
                        but it does not include the package manager, \
                        pacman.exe (this is expected behaviour for the Git \
                        Bash shell from Git for Windows). It's recommended \
                        you use a full MSYS2 installation, rather than one \
                        without its package manager." root)
                else
                  path_option, None
              in
              options, default, warning
            else
            let warning = Printf.sprintf
                "The current PATH gives an installation of %s at %s, but your \
                 system appears to default to an installation of %s at %s for \
                 new terminal sessions. You will need to ensure that the \
                 correct installation is available in PATH when you run opam \
                 in future."
                (string_of_kind kind) root (string_of_kind kind2) root2
            in
            options, internal_option, Some warning
          | Some (Error _) ->
            let warning = Printf.sprintf
                "The current PATH gives an installation of %s at %s, but it \
                 doesn't appear to be correctly available for new terminal \
                 sessions. You will need to ensure that the correct \
                 installation is available in PATH when you run opam in \
                 future." (string_of_kind kind) root
            in
            options, internal_option, Some warning
          | None ->
            match OpamStd.Sys.guess_shell_compat () with
            | SH_sh | SH_bash | SH_zsh | SH_csh | SH_fish ->
              let default, warning =
                if kind = `Msys2 && OpamSystem.resolve_command pacman = None then
                  internal_option, Printf.sprintf
                    "The current PATH gives an installation of MSYS2 at %s, \
                     but it does not include the package manager, pacman.exe \
                     (this is expected behaviour for the Git Bash shell from \
                     Git for Windows). It's recommended you use a full MSYS2 \
                     installation, rather than one without its package \
                     manager.\n You will need to run opam from a terminal \
                     session in future."
                    root
                else
                  path_option, Printf.sprintf
                    "You will need to run opam from a terminal session for %s \
                     in future." root
              in
              options, default, Some warning
            | SH_pwsh _ | SH_cmd ->
              let warning = Printf.sprintf
                  "You appear to have added %s to PATH for this session only. \
                   You will need to do this again before running opam in future."
                  root
              in
              options, internal_option, Some warning
        end
    end
  in
  Lazy.force header;
  OpamConsole.msg
    "\n\
     opam and the OCaml ecosystem in general require various Unix tools in \
     order to operate correctly. At present, this requires the installation \
     of Cygwin to provide these tools.\n\n";
  match OpamConsole.menu "How should opam obtain Unix tools?"
          ~default ~yes:default ~no:default ~options with
  | `Chosen (kind, `Internal) ->
    assert (kind = `Cygwin);
    Some (kind, `Internal OpamInitDefaults.required_packages_for_cygwin)
  | `Chosen (kind, ((`Root _) as mechanism)) ->
    Some (kind, mechanism)
  | `Chosen ((_, `Path _) as mechanism) ->
    OpamStd.Option.iter (OpamConsole.warning "%s") warn_path;
    Some mechanism
  | `Specify ->
    begin
      match OpamConsole.read
              "Enter the prefix of an existing Cygwin installation \
               (e.g. C:\\cygwin64)" with
      | None -> None
      | Some entry ->
        match OpamSysInteract.Cygwin.analyse_install entry with
        | Ok (kind, root) ->
          Some (kind, `Root root)
        | Error msg ->
          OpamConsole.error "%s" msg;
          cygwin_menu ~bypass_checks header
    end
  | `Abort -> OpamStd.Sys.exit_because `Aborted

and test_mechanism ~bypass_checks header = function
  | (`Internal _) as mechanism -> Some (`Cygwin, mechanism)
  | `Path ->
    let cygcheck =
      OpamSystem.resolve_command "cygcheck.exe"
      |> Option.map OpamSysInteract.Cygwin.analyse_install
    in
    begin match cygcheck with
      | Some (Ok (kind, root)) ->
        Some (kind, `Path (OpamFilename.Dir.to_string root))
      | Some (Error _) | None ->
        None
    end
  | `Test dir ->
    begin match OpamSysInteract.Cygwin.analyse_install dir with
      | Ok (kind, root) -> Some (kind, `Root root)
      | Error _ -> None
    end
  | `Location dir ->
    begin match OpamSysInteract.Cygwin.analyse_install dir with
      | Ok (kind, root) -> Some (kind, `Root root)
      | Error msg ->
        OpamConsole.error_and_exit `Not_found "%s" msg
    end
  | `Menu -> cygwin_menu ~bypass_checks header

let string_of_cygwin_setup = function
  | `internal pkgs ->
    let pkgs =
      if pkgs = [] then ""
      else
        " with " ^ String.concat ", " (List.map OpamSysPkg.to_string pkgs)
    in
    "Internal" ^ pkgs
  | `default_location -> "Search"
  | `location dir -> "External from " ^ OpamFilename.Dir.to_string dir
  | `no -> "Path-only (and no tweaking)"

let string_of_git_location_cli = function
  | Left location -> "Using git-location=" ^ OpamFilename.Dir.to_string location
  | Right () -> "git-location disabled via CLI"

let initialise_msys2 root =
  let bindir = OpamSysInteract.Cygwin.bindir_for_root `Msys2 root in
  let pacman = OpamFilename.Op.(bindir // "pacman.exe") in
  let gnupg_dir = OpamFilename.Op.(root / "etc" / "pacman.d" / "gnupg") in
  if OpamFilename.exists pacman && not (OpamFilename.exists_dir gnupg_dir) then
    let cmd =
      OpamFilename.Op.(bindir // "bash.exe")
      |> OpamFilename.to_string
    in
    let answer =
      let cmd = OpamConsole.colorise `yellow (cmd ^ " -lc \"uname -a\"") in
      OpamConsole.menu ~default:`Yes ~unsafe_yes:`Yes ~yes:`Ignore ~no:`Quit
        "MSYS2 appears not to have been initialised. opam can:"
        ~options:[
          `Yes, Printf.sprintf
            "Run %s to initialise it" cmd;
          `No, Printf.sprintf
            "Wait while you %s manually (e.g. in another terminal)" cmd;
          `Ignore, "Continue anyway (but note that external dependency \
                    may not work correctly until MSYS2 is initialised)";
          `Quit, "Abort initialisation";
        ]
    in
    OpamConsole.msg "\n";
    match answer with
    | `Yes ->
      if OpamConsole.disp_status_line () then
        OpamConsole.status_line "Initialising MSYS2 (this may take a minute)";
      let r =
        OpamProcess.run
          (OpamProcess.command ~name:(OpamSystem.temp_file "command")
             ~allow_stdin:false cmd ["-lc"; "uname -a"])
      in
      OpamProcess.cleanup ~force:true r;
      OpamConsole.clear_status ();
      if not (OpamProcess.is_success r) then
        OpamConsole.error_and_exit `Aborted "MSYS2 failed to initialise"
    | `No ->
      OpamConsole.pause "Standing by, press enter to continue when done.";
      OpamConsole.msg "\n"
    | `Ignore ->
      ()
    | `Quit ->
      OpamStd.Sys.exit_because `Aborted

let determine_windows_configuration ?cygwin_setup ?git_location
                                    ~bypass_checks config =
  OpamStd.Option.iter
    (log "Cygwin (from CLI): %a" (slog string_of_cygwin_setup)) cygwin_setup;
  (* Check whether symlinks can be created. Developer Mode is not the only way
     to do this, but it's the easiest. *)
  if (not (Unix.has_symlink ())) then begin
    OpamConsole.header_msg "Windows Developer Mode";
    OpamConsole.msg
      "opam does not require Developer Mode to be enabled on Windows, but it is\n\
       recommended, in particular because it enables support for symlinks without\n\
       requiring opam to be run elevated (which we do %s recommend doing).\n\
       \n\
       More information on enabling Developer Mode may be obtained from\n\
       https://learn.microsoft.com/en-gb/windows/apps/get-started/enable-your-device-for-development\n"
      (OpamConsole.colorise `bold "not")
  end;

  (* Augment ~git_location (from the CLI) with information from opamrc and
     validate --git-location/git-location *)
  let git_location =
    match git_location, OpamFile.Config.git_location config with
    | None, None -> None
    | Some (Right ()), git_location_opamrc ->
      if git_location_opamrc <> None then
        OpamConsole.note
          "'--no-git-location' specified; field 'git-location' in opamrc has \
           been ignored";
      git_location
    | None, Some git_location ->
      check_git_location_or_exit git_location
        "the 'git-location' field in opamrc";
      Some (Left git_location)
    | (Some (Left git_location)) as result, git_location_opamrc ->
      if git_location_opamrc <> None then
        OpamConsole.note
          "'--git-location' specified; field 'git-location' in opamrc has been \
           ignored";
      check_git_location_or_exit git_location "--git-location";
      result
  in
  OpamStd.Option.iter (log "%a" (slog string_of_git_location_cli)) git_location;

  (* Checks and initialisation for both Cygwin/MSYS2 and Git (which is made
     mandatory on Windows)

     The aim of this process is to determine four things:
     - An optional directory containing git.exe but not shadowing any of
       the executables in OpamEnv.cygwin_non_shadowed_programs. This is written
       to git-location in ~/.opam/config and the resulting directory appears
       as the first entry for Path on opam process calls
       (see OpamStd.Env.cyg_env)
     - Whether sys-pkg-manager-cmd should contain entries for either "cygwin"
       or "msys2". The presence of one of those values also causes opam to add
       the directory containing the package manager to Path
       (see OpamCoreConfig.cygbin)
     - Whether an internal installation of Cygwin is required, and if it needs
       the git package

     The process is affected by various CLI options:
     - --no-git-location causes git-location in opamrc to be ignored
     - --git-location overrides git-location in opamrc and short-circuits
       searching PATH for git.exe
     - --no-cygwin-setup specifies that Cygwin/MSYS2 should be found in PATH
       and no additional handling should be done
     - --cygwin-internal-install specifies that opam should maintain its own
       internal installation of Cygwin and make that fully available on Path
       when building packages and executing commands internally. If
       --git-location is not in use, and git.exe is not already installed, this
       installation may include Cygwin's git package
     - --cygwin-local-install specifies that opam should either search for
       Cygwin/MSYS2 installations or, if --cygwin-location is specified, use
       the Cygwin/MSYS2 installation specified.
  *)

  let apply_git_location config git_location =
    let config = OpamFile.Config.with_git_location git_location config in
    let git_location = OpamFilename.Dir.to_string git_location in
    OpamCoreConfig.update ~git_location ();
    config
  in

  (* If --git-location has been specified, apply it now *)
  let config, git_location, git_determined, git_required_from_cygwin =
    match git_location with
    | Some (Left git_location) ->
      apply_git_location config git_location, Some git_location, true, false
    | Some (Right ()) ->
      config, None, true, (OpamSystem.resolve_command "git.exe" = None)
    | None ->
      config, None, false, false
  in

  (* Based on the supplied command line options, determine which mechanisms can
     be tried to acquire a Unix environment.
     mechanisms - list of things to try from:
       `Path - search for cygcheck.exe in PATH and test from there
       `Test - search given root directory for cygcheck.exe (either in bin
               or usr\bin)
       `Location - as `Test, but _must_ succeed (--cygwin-location)
       `Internal - create a Cygwin internal with the given packages
       `Menu - interactive mode permitted
     tweakable - can pacman / Cygwin setup be used to adjust setup
                 (--no-cygwin-setup disables this)
  *)
  (* --bypass-checks => --no-cygwin-setup if nothing else was specified *)
  let cygwin_setup =
    if bypass_checks && cygwin_setup = None then
      Some `no
    else
      cygwin_setup
  in
  let mechanisms, cygwin_tweakable =
    match cygwin_setup with
    | Some (`internal packages) ->
      (* git, if needed, will be added later *)
      let packages = OpamInitDefaults.required_packages_for_cygwin @ packages in
      Seq.return (`Internal packages), true
    | Some `no ->
      if git_required_from_cygwin then
        OpamConsole.error_and_exit `Not_found
          "Both --no-cygwin-setup and --no-git-location have been specified, \
           but Git was not found in PATH. opam requires Git - please either \
           install Git for Windows and make it available in PATH or re-run \
           opam init with less restrictive command line options."
      else
        Seq.return `Path, false
    | Some `default_location ->
      cygwin_searches ~first:`Path (), true
    | Some (`location dir) ->
      Seq.return (`Location (OpamFilename.Dir.to_string dir)), true
    | None ->
      Seq.return `Menu, true
  in

  let header = lazy (OpamConsole.header_msg "Unix support infrastructure") in

  (* Reduce mechanisms to a single mechanism (which may therefore display a
     menu). *)
  let kind, mechanism =
    let test_mechanism = test_mechanism ~bypass_checks header in
    match OpamCompat.Seq.find_map test_mechanism mechanisms with
    | Some result -> result
    | None ->
      Lazy.force header;
      OpamConsole.error_and_exit `Not_found
        "A solution for Unix infrastructure is required, but the options \
         given to opam have not yielded one!"
  in

  (* If --git-location is in use, then there's no further checking required on
     the Git executable. If not, then before cygbin is potentially applied
     through --cygwin-location, determine if we need to check that Git for
     Windows is not going to be shadowed. *)
  let have_git_for_windows_in_path, git_in_path_dir =
    if git_location = None then
      match OpamSystem.resolve_command "git.exe" with
      | Some git ->
        is_git_for_windows git, Filename.dirname git
      | None ->
        false, ""
    else
      false, ""
  in

  (* Apply cygbin, if necessary *)
  let config, msys2_check_root =
    let apply cygcheck =
      let cygbin = OpamFilename.Dir.to_string (OpamFilename.dirname cygcheck) in
      OpamCoreConfig.update ~cygbin ();
      let family = match kind with `Msys2 -> "msys2" | `Cygwin -> "cygwin" in
      OpamFile.Config.with_sys_pkg_manager_cmd
        (OpamStd.String.Map.add family cygcheck
           (OpamFile.Config.sys_pkg_manager_cmd config))
        config
    in
    let open OpamFilename.Op in
    let config, msys2_check_root =
      match mechanism with
      | `Path root ->
        let msys2_check_root =
          if kind = `Msys2 then
            Some (OpamFilename.Dir.of_string root)
          else
            None
        in
        (* For opam init --reinit, it may be necessary to remove
           sys-pkg-manager-path *)
        OpamFile.Config.with_sys_pkg_manager_cmd
          OpamStd.String.Map.empty config, msys2_check_root
      | `Internal _ ->
        (* The directory gets applied, but obviously it's not yet been
           installed *)
        let cygcheck =
          OpamSysInteract.Cygwin.internal_cygroot () / "bin" // "cygcheck.exe"
        in
        apply cygcheck, None
      | `Root root ->
        let bindir = OpamSysInteract.Cygwin.bindir_for_root kind root in
        (* If the user has specified --no-git-location and Git for Windows was
           in PATH and the given location occludes it, then this is our last
           chance to warn about it. *)
        if git_determined && have_git_for_windows_in_path &&
           OpamFilename.exists (bindir // "git.exe") then
          OpamConsole.warning
            "Git for Windows is in PATH (from %s), but it will be shadowed \
             when opam builds packages and executes commands internally. It is \
             recommended that only Git for Windows is used, and this could be \
             ensured by uninstalling the Git package from %s"
            git_in_path_dir (OpamFilename.Dir.to_string bindir);
        if kind = `Msys2 then
          apply (bindir // "pacman.exe"), Some root
        else
          apply (bindir // "cygcheck.exe"), None
    in
    config, msys2_check_root
  in

  (* Display the menu for Git configuration, if possible and required *)
  let config, mechanism, cygwin_packages, git_location =
    let mechanism, cygwin_packages =
      match mechanism with
      | `Internal pkgs ->
        `Internal, pkgs
      | (`Root _ | `Path _) as mechanism ->
        let cygwin_packages =
          if cygwin_tweakable && not OpamStateConfig.(!r.no_depexts) then
            OpamInitDefaults.required_packages_for_cygwin
          else
            []
        in
        mechanism, cygwin_packages
    in
    if git_location = None && not git_determined
       && not have_git_for_windows_in_path then
      let git_location, from_cygwin =
        git_for_windows kind mechanism cygwin_tweakable
      in
      let config =
        OpamStd.Option.map_default (apply_git_location config)
          config git_location
      in
      let cygwin_packages =
        if cygwin_tweakable && from_cygwin then
          OpamSysPkg.of_string "git" :: cygwin_packages
        else
          cygwin_packages
      in
      config, mechanism, cygwin_packages, git_location
    else
      config, mechanism, cygwin_packages, git_location
  in

  log "Unix support mechanism: %s %s" (string_of_kind kind)
    (match mechanism with
     | `Path root -> Printf.sprintf "from PATH (%s)" root
     | `Internal -> "internal installation"
     | `Root root ->
       "local installation at " ^ OpamFilename.Dir.to_string root);
  if cygwin_packages <> [] then
    log "Systems packages to check for: %s"
      (String.concat ", " (List.map OpamSysPkg.to_string cygwin_packages));
  log "git-location %s"
    (OpamStd.Option.map_default
       (fun d -> Printf.sprintf "= %s" (OpamFilename.Dir.to_string d))
       "is not in use" git_location);

  let mechanism, cygwin_packages =
    match mechanism with
    | `Path _ | `Root _ -> None, cygwin_packages
    | `Internal -> Some cygwin_packages, []
  in
  config, mechanism, cygwin_packages, msys2_check_root

let update_with_init_config ?(overwrite=false) config init_config =
  let module I = OpamFile.InitConfig in
  let module C = OpamFile.Config in
  let setifnew getter setter v conf =
    if overwrite then setter v conf
    else if getter conf = getter C.empty then setter v conf
    else conf
  in
  config |>
  (match I.jobs init_config with
      | Some j -> setifnew C.jobs C.with_jobs j
      | None -> fun c -> c) |>
  setifnew C.dl_tool C.with_dl_tool_opt (I.dl_tool init_config) |>
  setifnew C.dl_cache C.with_dl_cache (I.dl_cache init_config) |>
  setifnew C.dl_jobs C.with_dl_jobs
    (OpamStd.Option.default OpamStateConfig.(default.dl_jobs)
       (I.dl_jobs init_config)) |>
  setifnew C.criteria C.with_criteria (I.solver_criteria init_config) |>
  setifnew C.solver C.with_solver_opt (I.solver init_config) |>
  setifnew C.wrappers C.with_wrappers (I.wrappers init_config) |>
  setifnew C.global_variables C.with_global_variables
    (I.global_variables init_config) |>
  setifnew C.eval_variables C.with_eval_variables
    (I.eval_variables init_config) |>
  setifnew C.default_compiler C.with_default_compiler
    (I.default_compiler init_config) |>
  setifnew C.default_invariant C.with_default_invariant
    (I.default_invariant init_config) |>
  setifnew C.sys_pkg_manager_cmd C.with_sys_pkg_manager_cmd
    (I.sys_pkg_manager_cmd init_config) |>
  setifnew C.git_location C.with_git_location_opt
    (I.git_location init_config)

let check_for_sys_packages config system_packages =
  if system_packages <> [] then
    let ((missing, _) as set) =
      OpamSysInteract.packages_status config
        (OpamSysPkg.Set.of_list system_packages)
    in
    if not (OpamSysPkg.Set.is_empty missing) then
      let vars = OpamFile.Config.global_variables config in
      let env =
        List.map (fun (v, c, s) -> v, (lazy (Some c), s)) vars
        |> OpamVariable.Map.of_list
      in
      (*Lazy.force header;*)
      OpamSolution.print_depext_msg set;
      OpamSolution.install_sys_packages ~confirm:true env config missing ()

let reinit ?(init_config=OpamInitDefaults.init_config()) ~interactive
    ?dot_profile ?update_config ?env_hook ?completion ?inplace
    ?(check_sandbox=true) ?(bypass_checks=false)
    ?cygwin_setup ?git_location
    config shell =
  log "RE-INIT";
  let root = OpamStateConfig.(!r.root_dir) in
  let config = update_with_init_config config init_config in
  let config, mechanism, system_packages, msys2_check_root =
    if Sys.win32 then
      determine_windows_configuration ?cygwin_setup ?git_location
                                      ~bypass_checks config
    else
      config, None, [], None
  in

  OpamStd.Option.iter initialise_msys2 msys2_check_root;
  OpamStd.Option.iter OpamSysInteract.Cygwin.install mechanism;
  check_for_sys_packages config system_packages;

  let _all_ok =
    if bypass_checks then false else
      init_checks ~hard_fail_exn:false init_config
  in
  let custom_init_scripts =
    let env v =
      let vs = OpamVariable.Full.variable v in
      OpamStd.Option.(Op.(of_Not_found
                            (OpamStd.List.assoc OpamVariable.equal vs)
                            OpamSysPoll.variables >>= Lazy.force))
    in
    OpamStd.List.filter_map (fun ((nam,scr),oflt) -> match oflt with
        | None -> Some (nam,scr)
        | Some flt ->
          if OpamFilter.eval_to_bool env flt then Some (nam,scr) else None)
      (OpamFile.InitConfig.init_scripts init_config)
  in
  OpamEnv.write_custom_init_scripts root custom_init_scripts;
  let config =
    if check_sandbox then
      OpamAuxCommands.check_and_revert_sandboxing root config
    else config
  in
  OpamFile.Config.write (OpamPath.config root) config;
  OpamEnv.setup root ~interactive
    ?dot_profile ?update_config ?env_hook ?completion ?inplace shell;
  let gt = OpamGlobalState.load `Lock_write in
  let rt = OpamRepositoryState.load `Lock_write gt in
  OpamConsole.header_msg "Updating repositories";
  let _failed, rt =
    OpamRepositoryCommand.update_with_auto_upgrade rt
      (OpamRepositoryName.Map.keys rt.repos_definitions)
  in
  OpamRepositoryState.drop rt

let has_space s = OpamStd.String.contains_char s ' '

let default_redirect_root = OpamFilename.Dir.of_string "C:\\opamroot"

let setup_redirection target =
  let {contents = {OpamStateConfig.original_root_dir = root; _}} =
    OpamStateConfig.r
  in
  let target =
    match target with
    | Some target -> target
    | None ->
      OpamFilename.mkdir default_redirect_root;
      let readme = OpamFilename.Op.(default_redirect_root // "ReadMe.txt") in
      if not (OpamFilename.exists readme) then
        OpamFilename.write readme
          "This directory is used to contain redirected opam roots.\n\n\
           The contents may be shared with other users on this system.";
      OpamSystem.mk_unique_dir ~dir:(OpamFilename.Dir.to_string default_redirect_root) ()
  in
  let root_dir = OpamFilename.Dir.of_string target in
  OpamFilename.write (OpamPath.redirected root) target;
  OpamStateConfig.update ~root_dir ();
  root_dir

let get_redirected_root () =
  let {contents = {OpamStateConfig.original_root_dir = root; root_from; _}} =
    OpamStateConfig.r
  in
  let r = OpamConsole.colorise `bold (OpamFilename.Dir.to_string root) in
  let collision =
    let collision = OpamConsole.utf8_symbol OpamConsole.Symbols.collision "" in
    if collision = "" then
      ""
    else
      " " ^ collision
  in
  let options = [
    `Redirect, Printf.sprintf
      "Redirect files to a directory in %s"
      (OpamConsole.colorise `bold (OpamFilename.Dir.to_string default_redirect_root));
    `Ask, "Redirect files to an alternate directory";
    `Endure, Printf.sprintf
      "Do not redirect anything and stick with %s%s" r collision;
    `Quit, "Abort initialisation"
  ] in
  let default, explanation =
    match root_from with
    | `Command_line ->
      (* The user has been explicit with --root; nemo salvet modo... *)
      `Endure,
      "You have specified a root directory for opam containing a space."
    | `Env ->
      (* The user has perhaps carelessly set an environment variable *)
      `Redirect,
      "Your OPAMROOT environment variable contains a space."
    | `Default ->
      (* The user has fallen victim to the defaults of Windows Setup and has a
         space in their user name *)
      `Redirect,
      Printf.sprintf
        "By default, opam would store its data in:\n\
           %s\n\
         however, this directory contains a space." r
  in
  let rec ask () =
    let check r =
      if Filename.is_relative r then begin
        OpamConsole.msg
          "That path is relative!\n\
           Please enter an absolute path without spaces.\n";
        ask ()
      end else if has_space r then begin
        OpamConsole.msg
          "That path contains contains a space!\n\
           Please enter an absolute path without spaces.\n";
        ask ()
      end else
        Some (Some r)
    in
    OpamStd.Option.replace check (OpamConsole.read "Root directory for opam: ")
  in
  let rec menu () =
    match OpamConsole.menu "Where should opam store files?" ~options
            ~default ~yes:default ~no:default with
    | `Redirect ->
      Some None
    | `Endure ->
      None
    | `Ask ->
      let r = ask () in
      if r = None then
        menu ()
      else
        r
    | `Quit ->
      OpamStd.Sys.exit_because `Aborted
  in
  OpamConsole.header_msg "opam root file store";
  OpamConsole.msg
    "\n\
     %s\n\
     \n\
     Many parts of the OCaml ecosystem do not presently work correctly\n\
     when installed to directories containing spaces. You have been warned!%s\n\
     \n" explanation collision;
  Option.map setup_redirection (menu ())

let init
    ~init_config ~interactive
    ?repo ?(bypass_checks=false)
    ?dot_profile ?update_config ?env_hook ?(completion=true)
    ?(check_sandbox=true)
    ?cygwin_setup ?git_location
    shell =
  log "INIT %a"
    (slog @@ OpamStd.Option.to_string OpamRepositoryBackend.to_string) repo;
  let original_root = OpamStateConfig.(!r.original_root_dir) in
  let root_empty =
    not (OpamFilename.exists_dir original_root)
    || OpamFilename.dir_is_empty original_root in
  let root = OpamStateConfig.(!r.root_dir) in
  let root, remove_root =
    let ignore_non_fatal f x =
      try f x
      with e -> OpamStd.Exn.fatal e
    in
    let new_root =
      if root_empty &&
         Sys.win32 &&
         has_space (OpamFilename.Dir.to_string root) then
        get_redirected_root ()
      else
        None
    in
    match new_root with
    | None ->
      root, (fun () -> ignore_non_fatal OpamFilename.rmdir root)
    | Some root ->
      root, (fun () ->
        ignore_non_fatal OpamFilename.rmdir root;
        ignore_non_fatal OpamFilename.rmdir original_root
      )
  in
  let config_f = OpamPath.config root in

  let gt, rt, default_compiler =
    if OpamFile.exists config_f then (
      OpamConsole.msg "Opam has already been initialized.\n";
      let gt = OpamGlobalState.load `Lock_write in
      if OpamFile.Config.installed_switches gt.config = [] then
        OpamConsole.msg
          "... but you have no switches installed, use `opam switch \
           create <compiler-or-version>' to get started.";
      gt, OpamRepositoryState.load `Lock_none gt, []
    ) else (
      if not root_empty then (
        OpamConsole.warning "%s exists and is not empty"
          (OpamFilename.Dir.to_string original_root);
        if not (OpamConsole.confirm "Proceed?") then
          OpamStd.Sys.exit_because `Aborted);
      try
        (* Create the content of ~/.opam/config *)
        let repos = match repo with
          | Some r -> [r.repo_name, (r.repo_url, r.repo_trust)]
          | None -> OpamFile.InitConfig.repositories init_config
        in
        let config =
          update_with_init_config
            OpamFile.Config.(with_opam_root_version root_version empty)
            init_config |>
          OpamFile.Config.with_repositories (List.map fst repos)
        in
        let config, mechanism, system_packages, msys2_check_root =
          if Sys.win32 then
            determine_windows_configuration ?cygwin_setup ?git_location
                                            ~bypass_checks config
          else
            config, None, [], None
        in

        OpamStd.Option.iter initialise_msys2 msys2_check_root;
        OpamStd.Option.iter OpamSysInteract.Cygwin.install mechanism;
        check_for_sys_packages config system_packages;

        let dontswitch =
          if bypass_checks then false else
          let all_ok = init_checks init_config in
          if not all_ok &&
             not (OpamConsole.confirm "Continue initialisation anyway ?")
          then OpamStd.Sys.exit_because `Configuration_error
          else not all_ok
        in
        let custom_scripts =
          let env v =
            let vs = OpamVariable.Full.variable v in
            OpamStd.Option.(Op.(of_Not_found
                                  (OpamStd.List.assoc OpamVariable.equal vs)
                                  OpamSysPoll.variables >>= Lazy.force))
          in
          let scripts = OpamFile.InitConfig.init_scripts init_config in
          OpamStd.List.filter_map (fun ((nam,scr),oflt) -> match oflt with
              | None -> Some (nam,scr)
              | Some flt -> if OpamFilter.eval_to_bool env flt then
                  Some (nam,scr) else None) scripts
        in
        OpamEnv.write_custom_init_scripts root custom_scripts;
        let config =
          if check_sandbox then
            OpamAuxCommands.check_and_revert_sandboxing root config
          else config
        in
        OpamFile.Config.write config_f config;
        let repos_config =
          OpamRepositoryName.Map.of_list repos |>
          OpamRepositoryName.Map.map OpamStd.Option.some
        in
        OpamFile.Repos_config.write (OpamPath.repos_config root)
          repos_config;

        log "updating repository state";
        let gt = OpamGlobalState.load `Lock_write in
        let rt = OpamRepositoryState.load `Lock_write gt in
        OpamConsole.header_msg "Fetching repository information";
        let failed, rt =
          OpamRepositoryCommand.update_with_auto_upgrade rt
            (List.map fst repos)
        in
        if failed <> [] then
          (if root_empty then
             remove_root ();
           OpamConsole.error_and_exit `Sync_error
             "Initial download of repository failed.");
        let default_compiler =
          if dontswitch then [] else
          let chrono = OpamConsole.timer () in
          let alternatives =
            OpamFormula.to_dnf
              (OpamFile.InitConfig.default_compiler init_config)
          in
          let invariant = OpamFile.InitConfig.default_invariant init_config in
          let virt_st =
            OpamSwitchState.load_virtual ~avail_default:false gt rt
          in
          let univ =
            OpamSwitchState.universe virt_st
              ~requested:OpamPackage.Set.empty Query
          in
          let univ = { univ with u_invariant = invariant } in
          let default_compiler =
            OpamStd.List.find_opt
              (OpamSolver.atom_coinstallability_check univ)
            alternatives
            |> OpamStd.Option.default []
          in
          log "Selected default compiler %s in %0.3fs"
            (OpamFormula.string_of_atoms default_compiler)
            (chrono ());
          default_compiler
        in
        gt, OpamRepositoryState.unlock ~cleanup:false rt, default_compiler
      with e ->
        OpamStd.Exn.finalise e @@ fun () ->
        if not (OpamConsole.debug ()) && root_empty then begin
          OpamSystem.release_all_locks ();
          remove_root ()
        end)
  in
  OpamEnv.setup root ~interactive
    ?dot_profile ?update_config ?env_hook ~completion shell;
  gt, rt, default_compiler

let check_installed ~build ~post t atoms =
  let available = (Lazy.force t.available_packages) in
  let uninstalled = OpamPackage.Set.Op.(available -- t.installed) in
  let pkgs =
    OpamPackage.to_map
      (OpamFormula.packages_of_atoms available atoms)
  in
  let test = OpamStateConfig.(!r.build_test) in
  let doc = OpamStateConfig.(!r.build_doc) in
  let dev_setup = OpamStateConfig.(!r.dev_setup) in
  let env package var =
    let content =
      OpamFilter.deps_var_env ~build ~post ~test ~doc ~dev_setup
        ~dev:(OpamSwitchState.is_dev_package t package) var
    in
    match content with
    | None -> OpamPackageVar.resolve_switch ~package t var
    | Some _ -> content
  in
  OpamPackage.Name.Map.fold (fun name versions map ->
      let compliant, missing_opt =
        OpamPackage.Version.Set.fold (fun version (found, missing) ->
            if found then (found, missing)
            else
            let pkg = OpamPackage.create name version in
            let cnf_formula =
              OpamSwitchState.opam t pkg
              |> OpamFile.OPAM.depends
              |> OpamFilter.filter_formula ~default:false (env pkg)
              |> OpamFormula.to_cnf
            in
            let missing_conj =
              List.filter
                (List.for_all (fun ((n,_vc) as atom) ->
                     OpamPackage.Set.for_all
                       (fun p -> not (OpamFormula.check atom p))
                       (OpamPackage.packages_of_name t.installed n)))
                cnf_formula
            in
            if missing_conj = [] then true, None
            else false, Some (pkg,missing_conj))
          versions (false,None)
      in
      if compliant then map else
      match missing_opt with
      | None -> assert false (* version set can't be empty *)
      | Some (pkg, missing_conj) ->
        OpamPackage.Map.add pkg
          (OpamPackage.names_of_packages
             (List.fold_left (fun names disj ->
                  OpamPackage.Set.union names
                    (OpamFormula.packages_of_atoms uninstalled disj))
                 OpamPackage.Set.empty missing_conj))
          map
    ) pkgs OpamPackage.Map.empty

let assume_built_restrictions ?available_packages t atoms =
  let missing = check_installed ~build:false ~post:false t atoms in
  let atoms =
    if OpamPackage.Map.is_empty missing then atoms else
      (OpamConsole.warning
         "You specified '--assume-built' but the following dependencies \
          aren't installed, skipping\n%s\
          Launch 'opam install %s --deps-only' (and recompile) to \
          install them.\n"
         (OpamStd.Format.itemize (fun (nv, names) ->
              Printf.sprintf "%s: %s" (OpamPackage.name_to_string nv)
                (OpamStd.List.concat_map " " OpamPackage.Name.to_string
                   (OpamPackage.Name.Set.elements names)))
             (OpamPackage.Map.bindings missing))
         (OpamStd.List.concat_map " " OpamPackage.name_to_string
            (OpamPackage.Map.keys missing));
       List.filter (fun (n,_) ->
           not (OpamPackage.Map.exists (fun nv _ ->
               OpamPackage.name nv = n) missing))
         atoms)
  in
  let pinned =
    (* Not pinned atoms already removed. *)
    OpamPackage.Set.filter
      (fun p -> List.exists (fun a -> OpamFormula.check a p) atoms)
      t.pinned
  in
  let installed_dependencies =
    OpamSwitchState.dependencies ~build:false ~post:false
      ~depopts:false ~installed:true ~unavailable:false
      t pinned
  in
  let available_packages =
    match available_packages with
    | Some a -> a
    | None -> Lazy.force t.available_packages
  in
  let uninstalled_dependencies =
    (OpamPackage.Map.values missing
     |> List.fold_left OpamPackage.Name.Set.union OpamPackage.Name.Set.empty
     |> OpamPackage.packages_of_names available_packages)
    -- installed_dependencies
  in
  let available_packages = lazy (
    (available_packages -- uninstalled_dependencies) ++ t.installed ++ pinned
  ) in
  let fixed_atoms =
    List.map (fun nv ->
        (OpamPackage.name nv , Some (`Eq, OpamPackage.version nv)))
      (OpamPackage.Set.elements pinned @
       OpamPackage.Set.elements installed_dependencies)
  in
  { t with available_packages }, fixed_atoms

let filter_unpinned_locally t atoms f =
  OpamStd.List.filter_map (fun at ->
      let n,_ = at in
      if OpamSwitchState.is_pinned t n &&
         OpamStd.Option.Op.(OpamPinned.package_opt t n >>=
                            OpamSwitchState.primary_url t >>=
                            OpamUrl.local_dir) <> None
      then
        Some (f at)
      else
        (OpamConsole.warning
           "Package %s is not pinned locally and assume built \
            option is set, skipping"
           (OpamPackage.Name.to_string n);
         None))
    atoms

let install_t t ?ask ?(ignore_conflicts=false) ?(depext_only=false)
    ?(download_only=false) atoms ?(formula=OpamFormula.Empty)
    add_to_roots ~deps_only ~assume_built =
  log "INSTALL %a" (slog OpamFormula.string_of_atoms) atoms;
  let available_packages = Lazy.force t.available_packages in

  let atoms =
    let compl = function
      | (_, Some _) as at -> at
      | (name, None) as at ->
        match OpamPinned.package_opt t name with
        | Some nv -> OpamSolution.eq_atom_of_package nv
        | None -> at
    in
    if assume_built then filter_unpinned_locally t atoms compl
    else List.map compl atoms
  in
  let names =
    OpamPackage.Name.Set.of_list (List.rev_map fst atoms)
  in
  let dname_map =
    if deps_only then
      (* pkgname -> name of fake package for handling pkg deps *)
      OpamPackage.Name.Set.fold (fun name ->
          let open OpamPackage.Name in
          let rec nodup i name =
            if OpamPackage.has_name t.packages name then
              nodup (i+1) @@
              of_string (Printf.sprintf "deps-of-%d-%s" i (to_string name))
            else name
          in
          let dname = nodup 2 @@ of_string ("deps-of-" ^ to_string name) in
          OpamPackage.Name.Map.add name dname)
        names OpamPackage.Name.Map.empty
    else OpamPackage.Name.Map.empty
  in
  let t, deps_of_packages =
    (* add deps-of-xxx packages to replace each atom *)
    OpamPackage.Name.Map.fold (fun name dname (t, deps_of_packages) ->
        let ats = List.filter (fun (n,_) -> n = name) atoms in
        let nvs = OpamSwitchState.packages_of_atoms t ats in
        OpamPackage.Set.fold (fun nv (t, deps_of_packages) ->
            let module O = OpamFile.OPAM in
            let dnv = OpamPackage.create dname nv.version in
            let opam = OpamSwitchState.opam t nv in
            let depends =
              OpamFormula.map (fun (n,c as at) ->
                  try Atom (OpamPackage.Name.Map.find n dname_map, c)
                  with Not_found -> Atom at)
                (O.depends opam)
            in
            let conflicts =
              let vstring = OpamPackage.Version.to_string nv.version in
              OpamFormula.ors
                (Atom (nv.name, Atom (Constraint (`Neq, FString vstring))) ::
                 if ignore_conflicts then [] else [ O.conflicts opam ])
            in
            let url =
              if OpamSwitchState.is_dev_package t nv then
                Some (OpamFile.URL.create OpamUrl.{empty with backend = `git})
              else None
            in
            let dopam =
              O.create dnv |>
              O.with_depends depends |>
              O.with_conflicts conflicts |>
              O.with_depexts (O.depexts opam) |>
              O.with_url_opt url |>
              (* Note: the following avoids selecting unavailable versions as
                 much possible, but it won't really work for packages that
                 already have the flag *)
              O.with_flags (if OpamPackage.Set.mem nv (available_packages)
                            then O.flags opam else [Pkgflag_AvoidVersion])
            in
            let t =
              if OpamPackage.Set.mem nv t.installed
              then {t with installed = OpamPackage.Set.add dnv t.installed}
              else t
            in
            OpamSwitchState.update_package_metadata dnv dopam t,
            OpamPackage.Set.add dnv deps_of_packages)
          nvs (t, deps_of_packages))
      dname_map (t, OpamPackage.Set.empty)
  in
  let pkg_skip, pkg_new =
    get_installed_atoms t atoms in
  let atoms, deps_atoms =
    if deps_only then
      [],
      List.map (fun (n, c) -> OpamPackage.Name.Map.find n dname_map, c) atoms
    else
      atoms, []
  in
  let pkg_reinstall =
    if assume_built then OpamPackage.Set.of_list pkg_skip
    else if deps_only then OpamPackage.Set.empty
    (* NOTE: As we only install dependency packages, there are no intersections
       between t.reinstall and pkg_skip *)
    else Lazy.force t.reinstall %% OpamPackage.Set.of_list pkg_skip
  in
  (* Add the packages to the list of package roots and display a
     warning for already installed package roots. *)
  let current_roots = t.installed_roots in
  let t =
    if deps_only then t else
      List.fold_left (fun t nv ->
          if OpamPackage.Set.mem nv t.installed then
            match add_to_roots with
            | None ->
              if not (OpamPackage.Set.mem nv pkg_reinstall) then
                OpamConsole.note
                  "Package %s is already installed (current version is %s)."
                  (OpamPackage.Name.to_string nv.name)
                  (OpamPackage.Version.to_string nv.version);
              t
            | Some true ->
              if OpamPackage.Set.mem nv t.installed_roots then
                OpamConsole.note
                  "Package %s is already installed as a root."
                  (OpamPackage.Name.to_string nv.name);
              { t with installed_roots =
                         OpamPackage.Set.add nv t.installed_roots }
            | Some false ->
              if OpamPackage.Set.mem nv t.installed_roots then begin
                if OpamPackage.Set.mem nv t.compiler_packages then
                  OpamConsole.note
                    "Package %s is part of the switch invariant and won't be \
                     uninstalled unless the invariant is updated."
                    (OpamPackage.name_to_string nv);
                { t with installed_roots =
                           OpamPackage.Set.remove nv t.installed_roots }
              end else
                (OpamConsole.note
                   "Package %s is already marked as 'installed automatically'."
                   (OpamPackage.Name.to_string nv.name);
                 t)
          else t
        ) t pkg_skip in
  if t.installed_roots <> current_roots then (
    let diff = t.installed_roots -- current_roots in
    if not (OpamPackage.Set.is_empty diff) then
      let diff = OpamPackage.Set.elements diff in
      let diff = List.rev (List.rev_map OpamPackage.to_string diff) in
      OpamConsole.msg
        "Adding %s to the list of installed roots.\n"
        (OpamStd.Format.pretty_list diff)
    else (
      let diff = current_roots -- t.installed_roots in
      let diff = OpamPackage.Set.elements diff in
      let diff = List.rev (List.rev_map OpamPackage.to_string diff) in
      OpamConsole.msg
        "Removing %s from the list of installed roots.\n"
        (OpamStd.Format.pretty_list diff)
    );
    OpamSwitchAction.write_selections t
  );

  OpamSolution.check_availability t available_packages atoms;

  if pkg_new = [] && OpamPackage.Set.is_empty pkg_reinstall &&
     formula = OpamFormula.Empty
  then t else
  let t, atoms =
    if assume_built then
      assume_built_restrictions ~available_packages t atoms
    else t, atoms
  in
  let request =
    OpamSolver.request ()
      ~install:(atoms @ deps_atoms)
      ~deprequest:(OpamFormula.to_atom_formula formula)
  in
  let requested =
    OpamPackage.Name.Set.of_list (List.rev_map fst (atoms @ deps_atoms))
  in
  let packages = OpamFormula.packages_of_atoms t.packages (atoms @ deps_atoms) in
  let solution =
    let reinstall = if assume_built then Some pkg_reinstall else None in
    OpamSolution.resolve t Install
      ~requested:packages
      ?reinstall
      request in
  let t = {t with installed = t.installed -- deps_of_packages} in
  let t, solution = match solution with
    | Conflicts cs ->
      log "conflict!";
      OpamConsole.error "Package conflict!";
      let (conflicts, _cycles) as explanations =
        OpamCudf.conflict_explanations_raw t.packages cs
      in
      let has_missing_depexts =
        let check = function
          | `Missing (_, _, fdeps) ->
            OpamFormula.fold_right (fun a x ->
                match OpamSwitchState.unavailable_reason_raw t x with
                | `MissingDepexts _ -> true
                | _ -> a)
              false fdeps
          | _ -> false
        in
        List.exists check conflicts
      in
      let extra_message =
        if has_missing_depexts then
          let gt = t.switch_global in
          OpamStd.Option.map_default (fun s -> s ^ ".\n\n") ""
            (OpamSysInteract.repo_enablers ~env:gt.global_variables gt.config)
        else ""
      in
      OpamConsole.errmsg "%s%s"
        (OpamCudf.string_of_explanations
           (OpamSwitchState.unavailable_reason t) explanations)
        extra_message;
      t, if depext_only then None else Some (Conflicts cs)
    | Success solution ->
      let skip =
        let inst = OpamSolver.new_packages solution in
        OpamPackage.Name.Map.fold (fun n dn map ->
            match OpamPackage.package_of_name_opt inst dn with
            | Some dpkg ->
              (* todo: display the versions that have been chosen if there was
                 an ambiguity ? *)
              OpamPackage.Map.add dpkg (OpamPackage.create n dpkg.version) map
            | None -> map)
          dname_map OpamPackage.Map.empty
      in
      if depext_only then
        (OpamSolution.install_depexts ~force_depext:true ~confirm:false t
           (OpamSolver.all_packages solution)), None
      else
        let add_roots =
          match add_to_roots, deps_only with
          | (Some true | None), true ->
            let pkgs_solution = OpamSolver.all_packages solution in
            let requested_deps =
              OpamPackage.Set.fold (fun nv acc ->
                  OpamFormula.Or
                    (OpamPackageVar.all_depends t (OpamSwitchState.opam t nv)
                       ~depopts:false ~build:true ~post:false,
                     acc))
                (OpamPackage.packages_of_names pkgs_solution requested)
                (* solution contains 'deps-to-xxx' virtual packages
                   and requested is deps-to-xxx packages *)
                OpamFormula.Empty
            in
            Some (OpamPackage.names_of_packages
                    (OpamFormula.packages pkgs_solution requested_deps))
          | Some true, false -> Some requested
          | Some false, _ -> Some OpamPackage.Name.Set.empty
          | None, false -> None
        in
        let t, res =
          OpamSolution.apply ?ask t
            ~requested:packages
            ~print_requested:(print_requested requested formula)
            ?add_roots ~skip
            ~download_only ~assume_built solution in
        t, Some (Success res)
  in
  OpamStd.Option.iter (OpamSolution.check_solution t) solution;
  t

let install t ?formula ?autoupdate ?add_to_roots
    ?(deps_only=false) ?(ignore_conflicts=false) ?(assume_built=false)
    ?(download_only=false) ?(depext_only=false) names =
  let atoms = OpamSolution.sanitize_atom_list ~permissive:true t names in
  let autoupdate_atoms = match autoupdate with
    | None -> atoms
    | Some a -> OpamSolution.sanitize_atom_list ~permissive:true t a
  in
  let t = update_dev_packages_t autoupdate_atoms t in
  install_t t atoms ?formula add_to_roots
    ~ignore_conflicts ~depext_only ~deps_only ~download_only ~assume_built

let remove_t ?ask ~autoremove ~force ?(formula=OpamFormula.Empty) atoms t =
  log "REMOVE autoremove:%b %a" autoremove
    (slog OpamFormula.string_of_atoms) atoms;

  let nothing_to_do = ref true in
  let packages, not_installed =
    get_installed_atoms t atoms in
  if not_installed <> [] then (
    if force then
      let force_remove atom =
        let candidates = OpamPackage.Set.filter (OpamFormula.check atom) t.packages in
        try
          let nv = OpamPackage.max_version candidates (fst atom) in
          OpamConsole.note "Forcing removal of (uninstalled) %s" (OpamPackage.to_string nv);
          OpamProcess.Job.run (OpamAction.remove_package t nv);
          OpamAction.cleanup_package_artefacts t nv;
          nothing_to_do := false
        with Not_found ->
          OpamConsole.error "No package %s found for (forced) removal.\n"
            (OpamFormula.short_string_of_atom atom)
      in
      List.iter force_remove not_installed
    else
      OpamConsole.note "%s %s not installed.\n"
        (OpamStd.Format.pretty_list
           (List.map OpamFormula.short_string_of_atom not_installed))
        (match not_installed with [_] -> "is" | _ -> "are")
  );

  if autoremove || packages <> [] then (
    let packages = OpamPackage.Set.of_list packages in
    let to_remove =
      if autoremove then
        let keep =
          OpamSwitchState.invariant_root_packages t
          ++ t.installed_roots
             %% t.installed
          -- packages
        in
        let keep_cone =
          keep |> OpamSwitchState.dependencies t
            ~build:true ~post:true ~depopts:true ~installed:true
        in
        let autoremove =
          packages ++ (t.installed -- keep_cone)
        in
        if atoms = [] then autoremove else
        (* restrict to the dependency cone of removed pkgs *)
        let remove_cone =
          packages |> OpamSwitchState.reverse_dependencies t
            ~build:true ~post:true ~depopts:false ~installed:true
        in
        autoremove %%
        (remove_cone |> OpamSwitchState.dependencies t
           ~build:true ~post:true ~depopts:false ~installed:true)
      else
        packages
    in
    let request =
      OpamSolver.request
        ~remove:(OpamSolution.atoms_of_packages to_remove)
        ~deprequest:(OpamFormula.to_atom_formula formula)
        ()
    in
    let print_requested =
      print_requested (OpamPackage.names_of_packages packages) formula
    in
    let t, solution =
      OpamSolution.resolve_and_apply ?ask t Remove
        ~force_remove:force
        ~requested:packages
        ~print_requested
        ~add_roots:OpamPackage.Name.Set.empty
        request
    in
    OpamSolution.check_solution t solution;
    t
  ) else if !nothing_to_do then (
    OpamConsole.msg "Nothing to do.\n";
    t
  ) else t

let remove t ~autoremove ~force ?formula names =
  let atoms =
    OpamSolution.sanitize_atom_list ~installed:true ~permissive:true t names
  in
  remove_t ~autoremove ~force ?formula atoms t

let reinstall_t t ?ask ?(force=false) ~assume_built atoms =
  log "reinstall %a" (slog OpamFormula.string_of_atoms) atoms;

  let packages = OpamFormula.packages_of_atoms t.packages atoms in

  let atoms =
    if assume_built then filter_unpinned_locally t atoms (fun x -> x)
    else atoms
  in

  let reinstall, not_installed =
    get_installed_atoms t atoms in
  let to_install =
    if not_installed <> [] then
      if
        force || assume_built ||
        OpamConsole.confirm "%s %s not installed. Install %s?"
          (OpamStd.Format.pretty_list
             (List.rev_map OpamFormula.short_string_of_atom not_installed))
          (match not_installed with [_] -> "is" | _ -> "are")
          (match not_installed with [_] -> "it" | _ -> "them")
      then not_installed
      else OpamStd.Sys.exit_because `Aborted
    else []
  in

  let reinstall = OpamPackage.Set.of_list reinstall in

  let atoms =
    to_install @ OpamSolution.eq_atoms_of_packages reinstall in

  let requested =
    OpamFormula.packages_of_atoms t.installed atoms in

  let t, atoms =
    if assume_built then
      assume_built_restrictions t atoms
    else t, atoms
  in

  let request =
    let criteria = if to_install = [] then `Fixup else `Default in
    OpamSolver.request ~install:atoms ~criteria ()
  in

  let t, solution =
    OpamSolution.resolve_and_apply ?ask t Reinstall
      ~reinstall:requested
      ~requested:packages
      ~assume_built
      request in

  OpamSolution.check_solution t solution;
  t

let reinstall t ?(assume_built=false) names =
  let atoms = OpamSolution.sanitize_atom_list t names in
  let t = update_dev_packages_t atoms t in
  reinstall_t t ~assume_built atoms

module PIN = struct
  open OpamPinCommand

  let post_pin_action st was_pinned names =
    let names =
      OpamPackage.Set.Op.(st.pinned -- was_pinned)
      |> OpamPackage.names_of_packages
      |> (fun s ->
          List.fold_left
            (fun s p -> OpamPackage.Name.Set.add p s)
            s names)
      |> OpamPackage.Name.Set.elements
    in
    try
      upgrade_t
        ~strict_upgrade:false ~auto_install:true ~ask:true ~terse:true
        ~all:false
       (List.map (fun name -> name, None) names) st
    with e ->
      OpamConsole.note
        "Pinning command successful, but your installed packages \
         may be out of sync.";
      raise e

  let get_upstream t name =
    try match
        OpamStd.Option.Op.(
          OpamSwitchState.get_package t name |>
          OpamSwitchState.opam_opt t >>=
          OpamFile.OPAM.dev_repo
        )
      with
      | None ->
        OpamConsole.error_and_exit `Not_found
          "\"dev-repo\" field missing in %s metadata, you'll need to specify \
           the pinning location"
          (OpamPackage.Name.to_string name)
      | Some url -> url
    with Not_found ->
      OpamConsole.error_and_exit `Not_found
        "No package named %S found"
        (OpamPackage.Name.to_string name)

  let pin st name ?(edit=false) ?version ?(action=true) ?subpath ?locked target =
    try
      let pinned = st.pinned in
      let st =
        match target with
        | `Source url -> source_pin st name ?version ~edit ?subpath ?locked (Some url)
        | `Version v ->
          let st = version_pin st name v in
          if edit then OpamPinCommand.edit st name else st
        | `Source_version (srcv, version) ->
          let url =
            let nv = (OpamPackage.create name srcv) in
            match OpamPackage.Map.find_opt nv st.repos_package_index with
            | Some opam ->
              (match
                 OpamStd.Option.Op.(OpamFile.OPAM.url opam >>| OpamFile.URL.url)
               with
               | Some u -> u
               | None ->
                 OpamConsole.error_and_exit `Not_found
                   "Package %s has no url defined in its opam file description"
                   (OpamPackage.to_string nv))
            | None ->
              OpamConsole.error_and_exit `Not_found
                "Package %s has no known version %s in the repositories"
                (OpamPackage.Name.to_string name)
                (OpamPackage.Version.to_string version)
          in
          source_pin st name ~version ~edit ?locked (Some url)
        | `Dev_upstream ->
          source_pin st name ?version ~edit ?locked (Some (get_upstream st name))
        | `None -> source_pin st name ?version ~edit ?locked None
      in
      if action then (OpamConsole.msg "\n"; post_pin_action st pinned [name])
      else st
    with
    | OpamPinCommand.Aborted -> OpamStd.Sys.exit_because `Aborted
    | OpamPinCommand.Nothing_to_do -> st

  let url_pins st ?edit ?(action=true) ?locked ?(pre=fun _ -> ()) pins =
    let names = List.map (fun p -> p.pinned_name) pins in
    (match names with
     | _::_::_ ->
       if not (OpamConsole.confirm
                 "This will pin the following packages: %s. Continue?"
                 (OpamStd.List.concat_map ", "
                    OpamPackage.Name.to_string names))
       then
         OpamStd.Sys.exit_because `Aborted
     | _ -> ());
    let pins = OpamPinCommand.fetch_all_pins st pins in
    let pinned = st.pinned in
    let st =
      List.fold_left (fun st pin ->
          pre pin;
          try
            OpamPinCommand.source_pin st pin.pinned_name
              ?version:pin.pinned_version
              ?opam:pin.pinned_opam
              ?subpath:pin.pinned_subpath
              ?edit ?locked (Some pin.pinned_url)
          with
          | OpamPinCommand.Aborted -> OpamStd.Sys.exit_because `Aborted
          | OpamPinCommand.Nothing_to_do -> st)
        st pins
    in
    if action then
      (OpamConsole.msg "\n";
       post_pin_action st pinned names)
    else st

  let edit st ?(action=true) ?version ?locked name =
    let pinned = st.pinned in
    let st =
      if OpamPackage.has_name st.pinned name then
        edit st ?version name
      else
      let pin_nv =
        match version with
        | Some v ->
          let nv = OpamPackage.create name v in
          if OpamPackage.Set.mem nv st.packages then Some nv else None
        | None ->
          OpamStd.Option.of_Not_found (OpamSwitchState.get_package st) name
      in
      match pin_nv with
      | Some nv ->
        if OpamConsole.confirm
            "Package %s is not pinned. Edit as a new pinning to version %s?"
            (OpamPackage.Name.to_string name)
            (OpamPackage.version_to_string nv)
        then
          let target =
            OpamStd.Option.Op.(OpamSwitchState.url st nv >>| OpamFile.URL.url)
          in
          let opam = OpamPackage.Map.find_opt nv st.repos_package_index in
          try source_pin st name ~edit:true ?version ?opam ?locked target
          with OpamPinCommand.Aborted -> OpamStd.Sys.exit_because `Aborted
             | OpamPinCommand.Nothing_to_do -> st
        else
          OpamStd.Sys.exit_because `Aborted
      | None ->
        OpamConsole.error_and_exit `Not_found
          "Package is not pinned, and no existing version was supplied."
    in
    if action then post_pin_action st pinned [name]
    else st

  let unpin st ?(action=true) names =
    let pinned_before = st.pinned in
    let st = unpin st names in
    let installed_unpinned = (pinned_before -- st.pinned) %% st.installed in
    if action && not (OpamPackage.Set.is_empty installed_unpinned) then
      let all =
        OpamPackage.Set.fold (fun nv acc -> (nv.name, None) :: acc)
          installed_unpinned []
      in
      let requested =
        OpamPackage.packages_of_names pinned_before
          (OpamPackage.Name.Set.of_list names)
      in
      let st, solution =
        OpamSolution.resolve_and_apply st Upgrade
          ~requested
          (OpamSolver.request ~all ())
      in
      OpamSolution.check_solution st solution;
      st
    else st

  let list = list
end
