use std::fmt;

use crate::fs::feature::xattr;
use crate::options::flags;
use crate::options::parser::MatchedFlags;

static USAGE_PART1: &str = "Usage:
  eza [options] [files...]

META OPTIONS
  --help                     show list of command-line options
  -v, --version              show version of eza

DISPLAY OPTIONS
  -1, --oneline              display one entry per line
  -l, --long                 display extended file metadata as a table
  -G, --grid                 display entries as a grid (default)
  -x, --across               sort the grid across, rather than downwards
  -R, --recurse              recurse into directories
  -T, --tree                 recurse into directories as a tree
  -X, --dereference          dereference symbolic links when displaying information
  -F, --classify=WHEN        display type indicator by file names (always, auto, never)
  --colo[u]r=WHEN            when to use terminal colours (always, auto, never)
  --colo[u]r-scale           highlight levels of 'field' distinctly(all, age, size)
  --colo[u]r-scale-mode      use gradient or fixed colors in --color-scale (fixed, gradient)
  --icons=WHEN               when to display icons (always, auto, never)
  --no-quotes                don't quote file names with spaces
  --hyperlink                display entries as hyperlinks
  --absolute                 display entries with their absolute path (on, follow, off)
  -w, --width COLS           set screen width in columns


FILTERING AND SORTING OPTIONS
  -a, --all                  show hidden and 'dot' files. Use this twice to also
                             show the '.' and '..' directories
  -A, --almost-all           equivalent to --all; included for compatibility with `ls -A`
  -d, --list-dirs            list directories as files; don't list their contents
  -L, --level DEPTH          limit the depth of recursion
  -r, --reverse              reverse the sort order
  -s, --sort SORT_FIELD      which field to sort by
  --group-directories-first  list directories before other files
  -D, --only-dirs            list only directories
  -f, --only-files           list only files
  -I, --ignore-glob GLOBS    glob patterns (pipe-separated) of files to ignore";

static GIT_FILTER_HELP: &str = "  \
  --git-ignore               ignore files mentioned in '.gitignore'";

static USAGE_PART2: &str = "  \
  Valid sort fields:         name, Name, extension, Extension, size, type,
                             modified, accessed, created, inode, and none.
                             date, time, old, and new all refer to modified.

LONG VIEW OPTIONS
  -b, --binary               list file sizes with binary prefixes
  -B, --bytes                list file sizes in bytes, without any prefixes
  -g, --group                list each file's group
  --smart-group              only show group if it has a different name from owner
  -h, --header               add a header row to each column
  -H, --links                list each file's number of hard links
  -i, --inode                list each file's inode number
  -m, --modified             use the modified timestamp field
  -M, --mounts               show mount details (Linux and Mac only)
  -n, --numeric              list numeric user and group IDs
  -O, --flags                list file flags (Mac, BSD, and Windows only)
  -S, --blocksize            show size of allocated file system blocks
  -t, --time FIELD           which timestamp field to list (modified, accessed, created)
  -u, --accessed             use the accessed timestamp field
  -U, --created              use the created timestamp field
  --changed                  use the changed timestamp field
  --time-style               how to format timestamps (default, iso, long-iso,
                             full-iso, relative, or a custom style '+<FORMAT>'
                             like '+%Y-%m-%d %H:%M')
  --total-size               show the size of a directory as the size of all
                             files and directories inside (unix only)
  --no-permissions           suppress the permissions field
  -o, --octal-permissions    list each file's permission in octal format
  --no-filesize              suppress the filesize field
  --no-user                  suppress the user field
  --no-time                  suppress the time field
  --stdin                    read file names from stdin, one per line or other separator 
                             specified in environment";

static GIT_VIEW_HELP: &str = "  \
  --git                      list each file's Git status, if tracked or ignored
  --no-git                   suppress Git status (always overrides --git,
                             --git-repos, --git-repos-no-status)
  --git-repos                list root of git-tree status";
static EXTENDED_HELP: &str = "  \
  -@, --extended             list each file's extended attributes and sizes";
static SECATTR_HELP: &str = "  \
  -Z, --context              list each file's security context";

/// All the information needed to display the help text, which depends
/// on which features are enabled and whether the user only wants to
/// see one section’s help.
#[derive(PartialEq, Eq, Debug, Copy, Clone)]
pub struct HelpString;

impl HelpString {
    /// Determines how to show help, if at all, based on the user’s
    /// command-line arguments. This one works backwards from the other
    /// ‘deduce’ functions, returning Err if help needs to be shown.
    ///
    /// We don’t do any strict-mode error checking here: it’s OK to give
    /// the --help or --long flags more than once. Actually checking for
    /// errors when the user wants help is kind of petty!
    pub fn deduce(matches: &MatchedFlags<'_>) -> Option<Self> {
        if matches.count(&flags::HELP) > 0 {
            Some(Self)
        } else {
            None
        }
    }
}

impl fmt::Display for HelpString {
    /// Format this help options into an actual string of help
    /// text to be displayed to the user.
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
        write!(f, "{USAGE_PART1}")?;

        if cfg!(feature = "git") {
            write!(f, "\n{GIT_FILTER_HELP}")?;
        }

        write!(f, "\n{USAGE_PART2}")?;

        if cfg!(feature = "git") {
            write!(f, "\n{GIT_VIEW_HELP}")?;
        }

        if xattr::ENABLED {
            write!(f, "\n{EXTENDED_HELP}")?;
            write!(f, "\n{SECATTR_HELP}")?;
        }

        writeln!(f)
    }
}

#[cfg(test)]
mod test {
    use crate::options::{Options, OptionsResult};
    use std::ffi::OsStr;

    #[test]
    fn help() {
        let args = vec![OsStr::new("--help")];
        let opts = Options::parse(args, &None);
        assert!(matches!(opts, OptionsResult::Help(_)));
    }

    #[test]
    fn help_with_file() {
        let args = vec![OsStr::new("--help"), OsStr::new("me")];
        let opts = Options::parse(args, &None);
        assert!(matches!(opts, OptionsResult::Help(_)));
    }

    #[test]
    fn unhelpful() {
        let args = vec![];
        let opts = Options::parse(args, &None);
        assert!(!matches!(opts, OptionsResult::Help(_))); // no help when --help isn’t passed
    }
}
