/*
   Copyright 2017 Remko Popma

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
 */
package picocli;

import static java.lang.String.format;

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.Writer;
import java.net.InetAddress;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashSet;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.Callable;

import picocli.CommandLine.Command;
import picocli.CommandLine.HelpCommand;
import picocli.CommandLine.IExecutionExceptionHandler;
import picocli.CommandLine.IFactory;
import picocli.CommandLine.Model.ArgSpec;
import picocli.CommandLine.Model.CommandSpec;
import picocli.CommandLine.Model.OptionSpec;
import picocli.CommandLine.Model.PositionalParamSpec;
import picocli.CommandLine.Option;
import picocli.CommandLine.Parameters;
import picocli.CommandLine.ParseResult;
import picocli.CommandLine.Spec;

/**
 * Stand-alone tool that generates bash auto-complete scripts for picocli-based command line applications.
 */
public class AutoComplete {
    /** Normal exit code of this application ({@value}). */
    public static final int EXIT_CODE_SUCCESS = 0;
    /** Exit code of this application when the specified command line arguments are invalid ({@value}). */
    public static final int EXIT_CODE_INVALID_INPUT = 1;
    /** Exit code of this application when the specified command script exists ({@value}). */
    public static final int EXIT_CODE_COMMAND_SCRIPT_EXISTS = 2;
    /** Exit code of this application when the specified completion script exists ({@value}). */
    public static final int EXIT_CODE_COMPLETION_SCRIPT_EXISTS = 3;
    /** Exit code of this application when an exception was encountered during operation ({@value}). */
    public static final int EXIT_CODE_EXECUTION_ERROR = 4;

    private AutoComplete() { }

    /**
     * Generates a bash completion script for the specified command class.
     * @param args command line options. Specify at least the {@code commandLineFQCN} mandatory parameter, which is
     *      the fully qualified class name of the annotated {@code @Command} class to generate a completion script for.
     *      Other parameters are optional. Specify {@code -h} to see details on the available options.
     */
    public static void main(String... args) {
        IExecutionExceptionHandler errorHandler = new IExecutionExceptionHandler() {
            public int handleExecutionException(Exception ex, CommandLine commandLine, ParseResult parseResult) {
                ex.printStackTrace();
                commandLine.usage(commandLine.getErr());
                return EXIT_CODE_EXECUTION_ERROR;
            }
        };
        int exitCode = new CommandLine(new App())
                .setExecutionExceptionHandler(errorHandler)
                .execute(args);
        if ((exitCode == EXIT_CODE_SUCCESS && exitOnSuccess()) || (exitCode != EXIT_CODE_SUCCESS && exitOnError())) {
            System.exit(exitCode);
        }
    }

    private static boolean exitOnSuccess() {
        return syspropDefinedAndNotFalse("picocli.autocomplete.systemExitOnSuccess");
    }

    private static boolean exitOnError() {
        return syspropDefinedAndNotFalse("picocli.autocomplete.systemExitOnError");
    }

    private static boolean syspropDefinedAndNotFalse(String key) {
        String value = System.getProperty(key);
        return value != null && !"false".equalsIgnoreCase(value);
    }

    /**
     * CLI command class for generating completion script.
     */
    @Command(name = "picocli.AutoComplete", mixinStandardHelpOptions = true, showAtFileInUsageHelp = true,
            version = "picocli.AutoComplete " + CommandLine.VERSION, sortOptions = false,
            description = "Generates a bash completion script for the specified command class.",
            footerHeading = "%n@|bold System Properties:|@%n",
            footer = {"Set the following system properties to control the exit code of this program:",
                    "",
                    "* `\"@|yellow picocli.autocomplete.systemExitOnSuccess|@\"`",
                    "   call `System.exit(0)` when execution completes normally.",
                    "* `\"@|yellow picocli.autocomplete.systemExitOnError|@\"`",
                    "   call `System.exit(ERROR_CODE)` when an error occurs.",
                    "",
                    "If these system properties are not defined or have value \"false\", this program completes without terminating the JVM.",
                    "",
                    "Example",
                    "-------",
                    "  java -cp \"myapp.jar;picocli-4.6.3.jar\" \\",
                    "              picocli.AutoComplete my.pkg.MyClass"
            },
            exitCodeListHeading = "%nExit Codes:%n",
            exitCodeList = {
                    "0:Successful program execution",
                    "1:Usage error: user input for the command was incorrect, " +
                            "e.g., the wrong number of arguments, a bad flag, " +
                            "a bad syntax in a parameter, etc.",
                    "2:The specified command script exists (Specify `--force` to overwrite).",
                    "3:The specified completion script exists (Specify `--force` to overwrite).",
                    "4:An exception occurred while generating the completion script."
            },
            exitCodeOnInvalidInput = EXIT_CODE_INVALID_INPUT,
            exitCodeOnExecutionException = EXIT_CODE_EXECUTION_ERROR)
    private static class App implements Callable<Integer> {

        @Parameters(arity = "1", description = "Fully qualified class name of the annotated " +
                "`@Command` class to generate a completion script for.")
        String commandLineFQCN;

        @Option(names = {"-c", "--factory"}, description = "Optionally specify the fully qualified class name of the custom factory to use to instantiate the command class. " +
                "When omitted, the default picocli factory is used.")
        String factoryClass;

        @Option(names = {"-n", "--name"}, description = "Optionally specify the name of the command to create a completion script for. " +
                "When omitted, the annotated class `@Command(name = \"...\")` attribute is used. " +
                "If no `@Command(name = ...)` attribute exists, '<CLASS-SIMPLE-NAME>' (in lower-case) is used.")
        String commandName;

        @Option(names = {"-o", "--completionScript"},
                description = "Optionally specify the path of the completion script file to generate. " +
                        "When omitted, a file named '<commandName>_completion' " +
                        "is generated in the current directory.")
        File autoCompleteScript;

        @Option(names = {"-w", "--writeCommandScript"},
                description = "Write a '<commandName>' sample command script to the same directory " +
                        "as the completion script.")
        boolean writeCommandScript;

        @Option(names = {"-f", "--force"}, description = "Overwrite existing script files.")
        boolean overwriteIfExists;

        @Spec CommandSpec spec;

        public Integer call() throws Exception {
            IFactory factory = CommandLine.defaultFactory();
            if (factoryClass != null) {
                factory = (IFactory) factory.create(Class.forName(factoryClass));
            }
            Class<?> cls = Class.forName(commandLineFQCN);
            Object instance = factory.create(cls);
            CommandLine commandLine = new CommandLine(instance, factory);

            if (commandName == null) {
                commandName = commandLine.getCommandName(); //new CommandLine.Help(commandLine.commandDescriptor).commandName;
                if (CommandLine.Help.DEFAULT_COMMAND_NAME.equals(commandName)) {
                    commandName = cls.getSimpleName().toLowerCase();
                }
            }
            if (autoCompleteScript == null) {
                autoCompleteScript = new File(commandName + "_completion");
            }
            File commandScript = null;
            if (writeCommandScript) {
                commandScript = new File(autoCompleteScript.getAbsoluteFile().getParentFile(), commandName);
            }
            if (commandScript != null && !overwriteIfExists && checkExists(commandScript)) {
                return EXIT_CODE_COMMAND_SCRIPT_EXISTS;
            }
            if (!overwriteIfExists && checkExists(autoCompleteScript)) {
                return EXIT_CODE_COMPLETION_SCRIPT_EXISTS;
            }

            AutoComplete.bash(commandName, autoCompleteScript, commandScript, commandLine);
            return EXIT_CODE_SUCCESS;
        }

        private boolean checkExists(final File file) {
            if (file.exists()) {
                PrintWriter err = spec.commandLine().getErr();
                err.printf("ERROR: picocli.AutoComplete: %s exists. Specify --force to overwrite.%n", file.getAbsolutePath());
                spec.commandLine().usage(err);
                return true;
            }
            return false;
        }
    }

    /**
     * Command that generates a Bash/ZSH completion script for its top-level command.
     * <p>
     * This class can be used as a subcommand for the top-level command in your application.
     * Users can then install completion for the top-level command by running the following command:
     * </p><pre>
     * source &lt;(top-level-command [sub-command] generate-completion)
     * </pre>
     * @since 4.1
     */
    @Command(name = "generate-completion", version = "generate-completion " + CommandLine.VERSION,
            mixinStandardHelpOptions = true,
            description = {
                "Generate bash/zsh completion script for ${ROOT-COMMAND-NAME:-the root command of this command}.",
                "Run the following command to give `${ROOT-COMMAND-NAME:-$PARENTCOMMAND}` TAB completion in the current shell:",
                "",
                "  source <(${PARENT-COMMAND-FULL-NAME:-$PARENTCOMMAND} ${COMMAND-NAME})",
                ""},
            optionListHeading = "Options:%n",
            helpCommand = true
    )
    public static class GenerateCompletion implements Runnable {

        @Spec CommandLine.Model.CommandSpec spec;

        public void run() {
            String script = AutoComplete.bash(
                    spec.root().name(),
                    spec.root().commandLine());
            // not PrintWriter.println: scripts with Windows line separators fail in strange ways!
            spec.commandLine().getOut().print(script);
            spec.commandLine().getOut().print('\n');
            spec.commandLine().getOut().flush();
        }
    }

    private interface Function<T, V> {
        V apply(T t);
    }

    /**
     * Drops all characters that are not valid for bash function and identifier names.
     */
    private static class Bashify implements Function<CharSequence, String> {
        public String apply(CharSequence value) {
            return bashify(value);
        }
    }
    private static String bashify(CharSequence value) {
        StringBuilder builder = new StringBuilder();
        for (int i = 0; i < value.length(); i++) {
            char c = value.charAt(i);
            if (Character.isLetterOrDigit(c) || c == '_') {
                builder.append(c);
            } else if (Character.isSpaceChar(c)) {
                builder.append('_');
            }
        }
        return builder.toString();
    }

    private static class NullFunction implements Function<CharSequence, String> {
        public String apply(CharSequence value) { return value.toString(); }
    }

    private interface Predicate<T> {
        boolean test(T t);
    }
    private static class BooleanArgFilter implements Predicate<ArgSpec> {
        public boolean test(ArgSpec f) {
            return f.type() == Boolean.TYPE || f.type() == Boolean.class;
        }
    }
    private static <T> Predicate<T> negate(final Predicate<T> original) {
        return new Predicate<T>() {
            public boolean test(T t) {
                return !original.test(t);
            }
        };
    }
    private static <K, T extends K> List<T> filter(List<T> list, Predicate<K> filter) {
        List<T> result = new ArrayList<T>();
        for (T t : list) { if (filter.test(t)) { result.add(t); } }
        return result;
    }
    private static class CommandDescriptor {
        final String functionName;
        final String parentFunctionName;
        final String parentWithoutTopLevelCommand;
        final String commandName;
        final CommandLine commandLine;

        CommandDescriptor(String functionName, String parentFunctionName, String parentWithoutTopLevelCommand, String commandName, CommandLine commandLine) {
            this.functionName = functionName;
            this.parentFunctionName = parentFunctionName;
            this.parentWithoutTopLevelCommand = parentWithoutTopLevelCommand;
            this.commandName = commandName;
            this.commandLine = commandLine;
        }
    }

    private static final String SCRIPT_HEADER = "" +
            "#!/usr/bin/env bash\n" +
            "#\n" +
            "# %1$s Bash Completion\n" +
            "# =======================\n" +
            "#\n" +
            "# Bash completion support for the `%1$s` command,\n" +
            "# generated by [picocli](http://picocli.info/) version %2$s.\n" +
            "#\n" +
            "# Installation\n" +
            "# ------------\n" +
            "#\n" +
            "# 1. Source all completion scripts in your .bash_profile\n" +
            "#\n" +
            "#   cd $YOUR_APP_HOME/bin\n" +
            "#   for f in $(find . -name \"*_completion\"); do line=\". $(pwd)/$f\"; grep \"$line\" ~/.bash_profile || echo \"$line\" >> ~/.bash_profile; done\n" +
            "#\n" +
            "# 2. Open a new bash console, and type `%1$s [TAB][TAB]`\n" +
            "#\n" +
            "# 1a. Alternatively, if you have [bash-completion](https://github.com/scop/bash-completion) installed:\n" +
            "#     Place this file in a `bash-completion.d` folder:\n" +
            "#\n" +
            "#   * /etc/bash-completion.d\n" +
            "#   * /usr/local/etc/bash-completion.d\n" +
            "#   * ~/bash-completion.d\n" +
            "#\n" +
            "# Documentation\n" +
            "# -------------\n" +
            "# The script is called by bash whenever [TAB] or [TAB][TAB] is pressed after\n" +
            "# '%1$s (..)'. By reading entered command line parameters,\n" +
            "# it determines possible bash completions and writes them to the COMPREPLY variable.\n" +
            "# Bash then completes the user input if only one entry is listed in the variable or\n" +
            "# shows the options if more than one is listed in COMPREPLY.\n" +
            "#\n" +
            "# References\n" +
            "# ----------\n" +
            "# [1] http://stackoverflow.com/a/12495480/1440785\n" +
            "# [2] http://tiswww.case.edu/php/chet/bash/FAQ\n" +
            "# [3] https://www.gnu.org/software/bash/manual/html_node/The-Shopt-Builtin.html\n" +
            "# [4] http://zsh.sourceforge.net/Doc/Release/Options.html#index-COMPLETE_005fALIASES\n" +
            "# [5] https://stackoverflow.com/questions/17042057/bash-check-element-in-array-for-elements-in-another-array/17042655#17042655\n" +
            "# [6] https://www.gnu.org/software/bash/manual/html_node/Programmable-Completion.html#Programmable-Completion\n" +
            "# [7] https://stackoverflow.com/questions/3249432/can-a-bash-tab-completion-script-be-used-in-zsh/27853970#27853970\n" +
            "#\n" +
            "\n" +
            "if [ -n \"$BASH_VERSION\" ]; then\n" +
            "  # Enable programmable completion facilities when using bash (see [3])\n" +
            "  shopt -s progcomp\n" +
            "elif [ -n \"$ZSH_VERSION\" ]; then\n" +
            "  # Make alias a distinct command for completion purposes when using zsh (see [4])\n" +
            "  setopt COMPLETE_ALIASES\n" +
            "  alias compopt=complete\n" +
            "\n" +
            "  # Enable bash completion in zsh (see [7])\n" +
            "  # Only initialize completions module once to avoid unregistering existing completions.\n" +
            "  if ! type compdef > /dev/null; then\n" +
            "    autoload -U +X compinit && compinit\n" +
            "  fi\n" +
            "  autoload -U +X bashcompinit && bashcompinit\n" +
            "fi\n" +
            "\n" +
            "# CompWordsContainsArray takes an array and then checks\n" +
            "# if all elements of this array are in the global COMP_WORDS array.\n" +
            "#\n" +
            "# Returns zero (no error) if all elements of the array are in the COMP_WORDS array,\n" +
            "# otherwise returns 1 (error).\n" +
            "function CompWordsContainsArray() {\n" +
            "  declare -a localArray\n" +
            "  localArray=(\"$@\")\n" +
            "  local findme\n" +
            "  for findme in \"${localArray[@]}\"; do\n" +
            "    if ElementNotInCompWords \"$findme\"; then return 1; fi\n" +
            "  done\n" +
            "  return 0\n" +
            "}\n" +
            "function ElementNotInCompWords() {\n" +
            "  local findme=\"$1\"\n" +
            "  local element\n" +
            "  for element in \"${COMP_WORDS[@]}\"; do\n" +
            "    if [[ \"$findme\" = \"$element\" ]]; then return 1; fi\n" +
            "  done\n" +
            "  return 0\n" +
            "}\n" +
            "\n" +
            "# The `currentPositionalIndex` function calculates the index of the current positional parameter.\n" +
            "#\n" +
            "# currentPositionalIndex takes three parameters:\n" +
            "# the command name,\n" +
            "# a space-separated string with the names of options that take a parameter, and\n" +
            "# a space-separated string with the names of boolean options (that don't take any params).\n" +
            "# When done, this function echos the current positional index to std_out.\n" +
            "#\n" +
            "# Example usage:\n" +
            "# local currIndex=$(currentPositionalIndex \"mysubcommand\" \"$ARG_OPTS\" \"$FLAG_OPTS\")\n" +
            "function currentPositionalIndex() {\n" +
            "  local commandName=\"$1\"\n" +
            "  local optionsWithArgs=\"$2\"\n" +
            "  local booleanOptions=\"$3\"\n" +
            "  local previousWord\n" +
            "  local result=0\n" +
            "\n" +
            "  for i in $(seq $((COMP_CWORD - 1)) -1 0); do\n" +
            "    previousWord=${COMP_WORDS[i]}\n" +
            "    if [ \"${previousWord}\" = \"$commandName\" ]; then\n" +
            "      break\n" +
            "    fi\n" +
            "    if [[ \"${optionsWithArgs}\" =~ ${previousWord} ]]; then\n" +
            "      ((result-=2)) # Arg option and its value not counted as positional param\n" +
            "    elif [[ \"${booleanOptions}\" =~ ${previousWord} ]]; then\n" +
            "      ((result-=1)) # Flag option itself not counted as positional param\n" +
            "    fi\n" +
            "    ((result++))\n" +
            "  done\n" +
            "  echo \"$result\"\n" +
            "}\n" +
            "\n";

    private static final String SCRIPT_FOOTER = "" +
            "\n" +
            "# Define a completion specification (a compspec) for the\n" +
            "# `%1$s`, `%1$s.sh`, and `%1$s.bash` commands.\n" +
            "# Uses the bash `complete` builtin (see [6]) to specify that shell function\n" +
            "# `_complete_%1$s` is responsible for generating possible completions for the\n" +
            "# current word on the command line.\n" +
            "# The `-o default` option means that if the function generated no matches, the\n" +
            "# default Bash completions and the Readline default filename completions are performed.\n" +
            "complete -F _complete_%1$s -o default %1$s %1$s.sh %1$s.bash\n";

    private static String sanitizeScriptName(String scriptName) {
        return scriptName
                .replaceAll("\\.sh", "")
                .replaceAll("\\.bash", "")
                .replaceAll("\\.\\/", "");
    }

    /**
     * Generates source code for an autocompletion bash script for the specified picocli-based application,
     * and writes this script to the specified {@code out} file, and optionally writes an invocation script
     * to the specified {@code command} file.
     * @param scriptName the name of the command to generate a bash autocompletion script for
     * @param commandLine the {@code CommandLine} instance for the command line application
     * @param out the file to write the autocompletion bash script source code to
     * @param command the file to write a helper script to that invokes the command, or {@code null} if no helper script file should be written
     * @throws IOException if a problem occurred writing to the specified files
     */
    public static void bash(String scriptName, File out, File command, CommandLine commandLine) throws IOException {
        String autoCompleteScript = bash(scriptName, commandLine);
        Writer completionWriter = null;
        Writer scriptWriter = null;
        try {
            completionWriter = new FileWriter(out);
            completionWriter.write(autoCompleteScript);

            if (command != null) {
                scriptWriter = new FileWriter(command);
                scriptWriter.write("" +
                        "#!/usr/bin/env bash\n" +
                        "\n" +
                        "LIBS=path/to/libs\n" +
                        "CP=\"${LIBS}/myApp.jar\"\n" +
                        "java -cp \"${CP}\" '" + ((Object) commandLine.getCommand()).getClass().getName() + "' $@");
            }
        } finally {
            if (completionWriter != null) { completionWriter.close(); }
            if (scriptWriter != null)     { scriptWriter.close(); }
        }
    }

    /**
     * Generates and returns the source code for an autocompletion bash script for the specified picocli-based application.
     * @param scriptName the name of the command to generate a bash autocompletion script for
     * @param commandLine the {@code CommandLine} instance for the command line application
     * @return source code for an autocompletion bash script
     */
    public static String bash(String scriptName, CommandLine commandLine) {
        if (scriptName == null)  { throw new NullPointerException("scriptName"); }
        if (commandLine == null) { throw new NullPointerException("commandLine"); }
        scriptName = sanitizeScriptName(scriptName);
        StringBuilder result = new StringBuilder();
        result.append(format(SCRIPT_HEADER, scriptName, CommandLine.VERSION));

        List<CommandDescriptor> hierarchy = createHierarchy(scriptName, commandLine);
        result.append(generateEntryPointFunction(scriptName, commandLine, hierarchy));

        for (CommandDescriptor descriptor : hierarchy) {
            if (descriptor.commandLine.getCommandSpec().usageMessage().hidden()) { continue; } // #887 skip hidden subcommands
            result.append(generateFunctionForCommand(descriptor.functionName, descriptor.commandName, descriptor.commandLine));
        }
        result.append(format(SCRIPT_FOOTER, scriptName));
        return result.toString();
    }

    private static List<CommandDescriptor> createHierarchy(String scriptName, CommandLine commandLine) {
        List<CommandDescriptor> result = new ArrayList<CommandDescriptor>();
        result.add(new CommandDescriptor("_picocli_" + scriptName, "", "", scriptName, commandLine));
        createSubHierarchy(scriptName, "", commandLine, result);
        return result;
    }

    private static void createSubHierarchy(String scriptName, String parentWithoutTopLevelCommand, CommandLine commandLine, List<CommandDescriptor> out) {
        // breadth-first: generate command lists and function calls for predecessors + each subcommand
        for (Map.Entry<String, CommandLine> entry : commandLine.getSubcommands().entrySet()) {
            CommandSpec spec = entry.getValue().getCommandSpec();
            if (spec.usageMessage().hidden()) { continue; } // #887 skip hidden subcommands
            String commandName = entry.getKey(); // may be an alias
            String functionNameWithoutPrefix = bashify(concat("_", parentWithoutTopLevelCommand.replace(' ', '_'), commandName));
            String functionName = concat("_", "_picocli", scriptName, functionNameWithoutPrefix);
            String parentFunctionName = parentWithoutTopLevelCommand.length() == 0
                ? concat("_", "_picocli", scriptName)
                : concat("_", "_picocli", scriptName, bashify(parentWithoutTopLevelCommand.replace(' ', '_')));

            // remember the function name and associated subcommand so we can easily generate a function later
            out.add(new CommandDescriptor(functionName, parentFunctionName, parentWithoutTopLevelCommand, commandName, entry.getValue()));
        }

        // then recursively do the same for all nested subcommands
        for (Map.Entry<String, CommandLine> entry : commandLine.getSubcommands().entrySet()) {
            if (entry.getValue().getCommandSpec().usageMessage().hidden()) { continue; } // #887 skip hidden subcommands
            String commandName = entry.getKey();
            String newParent = concat(" ", parentWithoutTopLevelCommand, commandName);
            createSubHierarchy(scriptName, newParent, entry.getValue(), out);
        }
    }

    private static String generateEntryPointFunction(String scriptName,
                                                     CommandLine commandLine,
                                                     List<CommandDescriptor> hierarchy) {
        String FUNCTION_HEADER = "" +
                "# Bash completion entry point function.\n" +
                "# _complete_%1$s finds which commands and subcommands have been specified\n" +
                "# on the command line and delegates to the appropriate function\n" +
                "# to generate possible options and subcommands for the last specified subcommand.\n" +
                "function _complete_%1$s() {\n" +
//        # Edge case: if command line has no space after subcommand, then don't assume this subcommand is selected
//        if [ "${COMP_LINE}" = "${COMP_WORDS[0]} abc" ];    then _picocli_mycmd; return $?; fi
//        if [ "${COMP_LINE}" = "${COMP_WORDS[0]} abcdef" ]; then _picocli_mycmd; return $?; fi
//        if [ "${COMP_LINE}" = "${COMP_WORDS[0]} generate-completion" ]; then _picocli_mycmd; return $?; fi
//        if [ "${COMP_LINE}" = "${COMP_WORDS[0]} abcdef sub1" ]; then _picocli_mycmd_abcdef; return $?; fi
//        if [ "${COMP_LINE}" = "${COMP_WORDS[0]} abcdef sub2" ]; then _picocli_mycmd_abcdef; return $?; fi
//
//                "  CMDS1=(%1$s gettingstarted)\n" +
//                "  CMDS2=(%1$s tool)\n" +
//                "  CMDS3=(%1$s tool sub1)\n" +
//                "  CMDS4=(%1$s tool sub2)\n" +
//                "\n" +
//                "  if CompWordsContainsArray "${cmds4[@]}" ; then _picocli_basic_tool_sub2; return $?; fi\n" +
//                "  if CompWordsContainsArray "${cmds3[@]}" ; then _picocli_basic_tool_sub1; return $?; fi\n" +
//                "  if CompWordsContainsArray "${cmds2[@]}" ; then _picocli_basic_tool; return $?; fi\n" +
//                "  if CompWordsContainsArray "${cmds1[@]}" ; then _picocli_basic_gettingstarted; return $?; fi\n" +
//                "  _picocli_%1$s; return $?;\n" +
//                "}\n" +
//                "\n" +
//                "complete -F _complete_%1$s %1$s\n" +
//                "\n";
                "";
            String FUNCTION_FOOTER = "\n" +
                "  # No subcommands were specified; generate completions for the top-level command.\n" +
                "  _picocli_%1$s; return $?;\n" +
                "}\n";

        StringBuilder buff = new StringBuilder(1024);
        buff.append(format(FUNCTION_HEADER, scriptName));

        generatedEdgeCaseFunctionCalls(buff, hierarchy);
        generateFunctionCallsToArrContains(buff, hierarchy);

        buff.append(format(FUNCTION_FOOTER, scriptName));
        return buff.toString();
    }

    // https://github.com/remkop/picocli/issues/1468
    private static void generatedEdgeCaseFunctionCalls(StringBuilder buff, List<CommandDescriptor> hierarchy) {
        buff.append("  # Edge case: if command line has no space after subcommand, then don't assume this subcommand is selected (remkop/picocli#1468).\n");
        for (CommandDescriptor descriptor : hierarchy.subList(1, hierarchy.size())) { // skip top-level command
            String withoutTopLevelCommand = concat(" ", descriptor.parentWithoutTopLevelCommand, descriptor.commandName);
            buff.append(format("  if [ \"${COMP_LINE}\" = \"${COMP_WORDS[0]} %1$s\" ];    then %2$s; return $?; fi\n", withoutTopLevelCommand, descriptor.parentFunctionName));
        }
        buff.append("\n");
    }

    private static void generateFunctionCallsToArrContains(StringBuilder buff,
                                                           List<CommandDescriptor> hierarchy) {
        buff.append("  # Find the longest sequence of subcommands and call the bash function for that subcommand.\n");
        List<String> functionCalls = new ArrayList<String>();
        for (CommandDescriptor descriptor : hierarchy.subList(1, hierarchy.size())) { // skip top-level command
            int count = functionCalls.size();
            String withoutTopLevelCommand = concat(" ", descriptor.parentWithoutTopLevelCommand, descriptor.commandName);

            functionCalls.add(format("  if CompWordsContainsArray \"${cmds%2$d[@]}\"; then %1$s; return $?; fi\n", descriptor.functionName, count));
            buff.append(      format("  local cmds%2$d=(%1$s)\n", withoutTopLevelCommand, count));
        }

        buff.append("\n");
        Collections.reverse(functionCalls);
        for (String func : functionCalls) {
            buff.append(func);
        }
    }
    private static String concat(String infix, String... values) {
        return concat(infix, Arrays.asList(values));
    }
    private static String concat(String infix, List<String> values) {
        return concat(infix, values, null, new NullFunction());
    }
    private static <V, T extends V> String concat(String infix, List<T> values, T lastValue, Function<V, String> normalize) {
        StringBuilder sb = new StringBuilder();
        for (T val : values) {
            if (sb.length() > 0) { sb.append(infix); }
            sb.append(normalize.apply(val));
        }
        if (lastValue == null) { return sb.toString(); }
        if (sb.length() > 0) { sb.append(infix); }
        return sb.append(normalize.apply(lastValue)).toString();
    }

    private static String generateFunctionForCommand(String functionName, String commandName, CommandLine commandLine) {
        String FUNCTION_HEADER = "" +
                "\n" +
                "# Generates completions for the options and subcommands of the `%s` %scommand.\n" +
                "function %s() {\n" +
                "  # Get completion data\n" +
                "  local curr_word=${COMP_WORDS[COMP_CWORD]}\n" +
                "%s" +
                "\n" +
                "  local commands=\"%s\"\n" +  // local commands="gettingstarted tool"
                "  local flag_opts=\"%s\"\n" + // local flag_opts="--verbose -V -x --extract -t --list"
                "  local arg_opts=\"%s\"\n";   // local arg_opts="--host --option --file -f -u --timeUnit"
        String FUNCTION_FOOTER = "" +
                "\n" +
                "  if [[ \"${curr_word}\" == -* ]]; then\n" +
                "    COMPREPLY=( $(compgen -W \"${flag_opts} ${arg_opts}\" -- \"${curr_word}\") )\n" +
                "  else\n" +
                "    local positionals=\"\"\n" +
                "%s" +
                "    COMPREPLY=( $(compgen -W \"${commands} ${positionals}\" -- \"${curr_word}\") )\n" +
                "  fi\n" +
                "}\n";

        // Get the fields annotated with @Option and @Parameters for the specified CommandLine.
        CommandSpec commandSpec = commandLine.getCommandSpec();

        // Build a list of "flag" options that take no parameters and "arg" options that do take parameters, and subcommands.
        String flagOptionNames = optionNames(filter(commandSpec.options(), new BooleanArgFilter()));
        List<OptionSpec> argOptionFields = filter(commandSpec.options(), negate(new BooleanArgFilter()));
        String argOptionNames = optionNames(argOptionFields);

        Set<String> subCommands = new LinkedHashSet<String>();
        for (String sub : commandLine.getSubcommands().keySet()) {
            if (!commandLine.getSubcommands().get(sub).getCommandSpec().usageMessage().hidden()) {
                subCommands.add(sub); // #1076 Don't generate Autocomplete for hidden commands
            }
        }
        // If the command is a HelpCommand, append parent subcommands to the autocompletion list.
        if (commandLine.getParent() != null && ((Object) commandLine.getCommand()) instanceof HelpCommand) {
            subCommands = new LinkedHashSet<String>(subCommands);
            for (CommandLine subCommandLine : commandLine.getParent().getSubcommands().values()) {
                if (commandLine == subCommandLine) { continue; }  // Skip the HelpCommand itself
                if (subCommandLine.getCommandSpec().usageMessage().hidden()) { continue; } // #887 skip hidden subcommands
                subCommands.add(subCommandLine.getCommandName());
            }
        }
        String commands = concat(" ", new ArrayList<String>(subCommands)).trim();

        // Generate the header: the function declaration, CURR_WORD, PREV_WORD and COMMANDS, FLAG_OPTS and ARG_OPTS.
        StringBuilder buff = new StringBuilder(1024);
        String sub = functionName.equals("_picocli_" + commandName) ? "" : "sub";
        String previous_word = argOptionFields.isEmpty() ? "" : "  local prev_word=${COMP_WORDS[COMP_CWORD-1]}\n";
        buff.append(format(FUNCTION_HEADER, commandName, sub, functionName, previous_word, commands, flagOptionNames, argOptionNames));

        // Generate completion lists for options with a known set of valid values (including java enums)
        for (OptionSpec f : commandSpec.options()) {
            if (f.hidden()) { continue; } // #887 skip hidden options
            if (f.completionCandidates() != null) {
                generateCompletionCandidates(buff, f);
            }
        }
        // TODO generate completion lists for other option types:
        // Charset, Currency, Locale, TimeZone, ByteOrder,
        // javax.crypto.Cipher, javax.crypto.KeyGenerator, javax.crypto.Mac, javax.crypto.SecretKeyFactory
        // java.security.AlgorithmParameterGenerator, java.security.AlgorithmParameters, java.security.KeyFactory, java.security.KeyPairGenerator, java.security.KeyStore, java.security.MessageDigest, java.security.Signature
        // sql.Types?

        // Now generate the "case" switches for the options whose arguments we can generate completions for
        buff.append(generateOptionsSwitch(argOptionFields));

        // Generate completion lists for positional params with a known set of valid values (including java enums)
        for (PositionalParamSpec f : commandSpec.positionalParameters()) {
            if (f.completionCandidates() != null) {
                generatePositionParamCompletionCandidates(buff, f);
            }
        }

        String paramsCases = generatePositionalParamsCases(commandSpec.positionalParameters(), "", "${curr_word}");
        String posParamsFooter = "";
        if (paramsCases.length() > 0) {
            String POSITIONAL_PARAMS_FOOTER = "" +
                    "    local currIndex\n" +
                    "    currIndex=$(currentPositionalIndex \"%s\" \"${arg_opts}\" \"${flag_opts}\")\n" +
                    "%s";
            posParamsFooter = format(POSITIONAL_PARAMS_FOOTER, commandName, paramsCases);
        }
        // Generate the footer: a default COMPREPLY to fall back to, and the function closing brace.
        buff.append(format(FUNCTION_FOOTER, posParamsFooter));
        return buff.toString();
    }

    private static void generatePositionParamCompletionCandidates(StringBuilder buff, PositionalParamSpec f) {
        String paramName = bashify(f.paramLabel());
        buff.append(format("  local %s_pos_param_args=\"%s\" # %d-%d values\n",
                paramName,
                concat(" ", extract(f.completionCandidates())).trim(),
                f.index().min(), f.index().max()));
    }

    private static void generateCompletionCandidates(StringBuilder buff, OptionSpec f) {
        buff.append(format("  local %s_option_args=\"%s\" # %s values\n",
                bashify(f.paramLabel()),
                concat(" ", extract(f.completionCandidates())).trim(),
                f.longestName()));
    }
    private static List<String> extract(Iterable<String> generator) {
        List<String> result = new ArrayList<String>();
        for (String e : generator) {
            result.add(e);
        }
        return result;
    }

    private static String generatePositionalParamsCases(List<PositionalParamSpec> posParams, String indent, String currWord) {
        StringBuilder buff = new StringBuilder(1024);
        for (PositionalParamSpec param : posParams) {
            if (param.hidden()) { continue; } // #887 skip hidden params
            Class<?> type = param.type();
            if (param.typeInfo().isMultiValue()) {
                type = param.typeInfo().getAuxiliaryTypes()[0];
            }
            String paramName = bashify(param.paramLabel());
            String ifOrElif = buff.length() > 0 ? "elif" : "if";
            int min = param.index().min();
            int max = param.index().max();
            if (param.completionCandidates() != null) {
                buff.append(format("%s    %s (( currIndex >= %d && currIndex <= %d )); then\n", indent, ifOrElif, min, max));
                buff.append(format("%s      positionals=$( compgen -W \"$%s_pos_param_args\" -- \"%s\" )\n", indent, paramName, currWord));
            } else if (type.equals(File.class) || "java.nio.file.Path".equals(type.getName())) {
                buff.append(format("%s    %s (( currIndex >= %d && currIndex <= %d )); then\n", indent, ifOrElif, min, max));
                buff.append(format("%s      local IFS=$'\\n'\n", indent));
                buff.append(format("%s      type compopt &>/dev/null && compopt -o filenames\n", indent)); // #1464 workaround for old bash
                buff.append(format("%s      positionals=$( compgen -f -- \"%s\" ) # files\n", indent, currWord));
            } else if (type.equals(InetAddress.class)) {
                buff.append(format("%s    %s (( currIndex >= %d && currIndex <= %d )); then\n", indent, ifOrElif, min, max));
                buff.append(format("%s      type compopt &>/dev/null && compopt -o filenames\n", indent)); // #1464 workaround for old bash
                buff.append(format("%s      positionals=$( compgen -A hostname -- \"%s\" )\n", indent, currWord));
            }
        }
        if (buff.length() > 0) {
            buff.append(format("%s    fi\n", indent));
        }
        return buff.toString();
    }

    private static String generateOptionsSwitch(List<OptionSpec> argOptions) {
        String optionsCases = generateOptionsCases(argOptions, "", "${curr_word}");

        if (optionsCases.length() == 0) {
            return "";
        }

        return "\n"
                + "  type compopt &>/dev/null && compopt +o default\n" // #1464 workaround for old bash
                + "\n"
                + "  case ${prev_word} in\n"
                + optionsCases
                + "  esac\n";
    }

    private static String generateOptionsCases(List<OptionSpec> argOptionFields, String indent, String currWord) {
        StringBuilder buff = new StringBuilder(1024);
        for (OptionSpec option : argOptionFields) {
            if (option.hidden()) { continue; } // #887 skip hidden options
            Class<?> type = option.type();
            if (option.typeInfo().isMultiValue()){
                type = option.typeInfo().getAuxiliaryTypes()[0];
            }
            if (option.completionCandidates() != null) {
                buff.append(format("%s    %s)\n", indent, concat("|", option.names()))); // "    -u|--timeUnit)\n"
                buff.append(format("%s      COMPREPLY=( $( compgen -W \"${%s_option_args}\" -- \"%s\" ) )\n", indent, bashify(option.paramLabel()), currWord));
                buff.append(format("%s      return $?\n", indent));
                buff.append(format("%s      ;;\n", indent));
            } else if (type.equals(File.class) || "java.nio.file.Path".equals(type.getName())) {
                buff.append(format("%s    %s)\n", indent, concat("|", option.names()))); // "    -f|--file)\n"
                buff.append(format("%s      local IFS=$'\\n'\n", indent));
                buff.append(format("%s      type compopt &>/dev/null && compopt -o filenames\n", indent)); // #1464 workaround for old bash
                buff.append(format("%s      COMPREPLY=( $( compgen -f -- \"%s\" ) ) # files\n", indent, currWord));
                buff.append(format("%s      return $?\n", indent));
                buff.append(format("%s      ;;\n", indent));
            } else if (type.equals(InetAddress.class)) {
                buff.append(format("%s    %s)\n", indent, concat("|", option.names()))); // "    -h|--host)\n"
                buff.append(format("%s      type compopt &>/dev/null && compopt -o filenames\n", indent)); // #1464 workaround for old bash
                buff.append(format("%s      COMPREPLY=( $( compgen -A hostname -- \"%s\" ) )\n", indent, currWord));
                buff.append(format("%s      return $?\n", indent));
                buff.append(format("%s      ;;\n", indent));
            } else {
                buff.append(format("%s    %s)\n", indent, concat("|", option.names()))); // no completions available
                buff.append(format("%s      return\n", indent));
                buff.append(format("%s      ;;\n", indent));
            }
        }
        return buff.toString();
    }

    private static String optionNames(List<OptionSpec> options) {
        List<String> result = new ArrayList<String>();
        for (OptionSpec option : options) {
            if (option.hidden()) { continue; } // #887 skip hidden options
            result.addAll(Arrays.asList(option.names()));
        }
        return concat(" ", result, "", new NullFunction()).trim();
    }

    public static int complete(CommandSpec spec, String[] args, int argIndex, int positionInArg, int cursor, List<CharSequence> candidates) {
        if (spec == null)       { throw new NullPointerException("spec is null"); }
        if (args == null)       { throw new NullPointerException("args is null"); }
        if (candidates == null) { throw new NullPointerException("candidates list is null"); }
        if (argIndex == args.length) {
            String[] copy = new String[args.length + 1];
            System.arraycopy(args, 0, copy, 0, args.length);
            args = copy;
            args[argIndex] = "";
        }
        if (argIndex < 0      || argIndex >= args.length)                 { throw new IllegalArgumentException("Invalid argIndex " + argIndex + ": args array only has " + args.length + " elements."); }
        if (positionInArg < 0 || positionInArg > args[argIndex].length()) { throw new IllegalArgumentException("Invalid positionInArg " + positionInArg + ": args[" + argIndex + "] (" + args[argIndex] + ") only has " + args[argIndex].length() + " characters."); }

        String currentArg = args[argIndex];
        boolean reset = spec.parser().collectErrors();
        try {
            String committedPrefix = currentArg.substring(0, positionInArg);

            spec.parser().collectErrors(true);
            CommandLine parser = new CommandLine(spec);
            ParseResult parseResult = parser.parseArgs(args);
            if (argIndex >= parseResult.tentativeMatch.size()) {
                Object startPoint = findCompletionStartPoint(parseResult);
                addCandidatesForArgsFollowing(startPoint, candidates);
            } else {
                Object obj = parseResult.tentativeMatch.get(argIndex);
                if (obj instanceof CommandSpec) { // subcommand
                    addCandidatesForArgsFollowing(((CommandSpec) obj).parent(), candidates);

                } else if (obj instanceof OptionSpec) { // option
                    int sep = currentArg.indexOf(spec.parser().separator());
                    if (sep < 0 || positionInArg < sep) { // no '=' or cursor before '='
                        addCandidatesForArgsFollowing(findCommandFor((OptionSpec) obj, spec), candidates);
                    } else {
                        addCandidatesForArgsFollowing((OptionSpec) obj, candidates);

                        int sepLength = spec.parser().separator().length();
                        if (positionInArg < sep + sepLength) {
                            int posInSeparator = positionInArg - sep;
                            String prefix = spec.parser().separator().substring(posInSeparator);
                            for (int i = 0; i < candidates.size(); i++) {
                                candidates.set(i, prefix + candidates.get(i));
                            }
                            committedPrefix = currentArg.substring(sep, positionInArg);
                        } else {
                            committedPrefix = currentArg.substring(sep + sepLength, positionInArg);
                        }
                    }

                } else if (obj instanceof PositionalParamSpec) { // positional
                    //addCandidatesForArgsFollowing(obj, candidates);
                    addCandidatesForArgsFollowing(findCommandFor((PositionalParamSpec) obj, spec), candidates);

                } else {
                    int i = argIndex - 1;
                    while (i > 0 && !isPicocliModelObject(parseResult.tentativeMatch.get(i))) {i--;}
                    if (i < 0) { return -1; }
                    addCandidatesForArgsFollowing(parseResult.tentativeMatch.get(i), candidates);
                }
            }
            filterAndTrimMatchingPrefix(committedPrefix, candidates);
            return candidates.isEmpty() ? -1 : cursor;
        } finally {
            spec.parser().collectErrors(reset);
        }
    }
    private static Object findCompletionStartPoint(ParseResult parseResult) {
        List<Object> tentativeMatches = parseResult.tentativeMatch;
        for (int i = 1; i <= tentativeMatches.size(); i++) {
            Object found = tentativeMatches.get(tentativeMatches.size() - i);
            if (found instanceof CommandSpec) {
                return found;
            }
            if (found instanceof ArgSpec) {
                CommandLine.Range arity = ((ArgSpec) found).arity();
                if (i < arity.min()) {
                    return found; // not all parameters have been supplied yet
                } else {
                    return findCommandFor((ArgSpec) found, parseResult.commandSpec());
                }
            }
        }
        return parseResult.commandSpec();
    }

    private static CommandSpec findCommandFor(ArgSpec arg, CommandSpec cmd) {
        return (arg instanceof OptionSpec) ? findCommandFor((OptionSpec) arg, cmd) : findCommandFor((PositionalParamSpec) arg, cmd);
    }
    private static CommandSpec findCommandFor(OptionSpec option, CommandSpec commandSpec) {
        for (OptionSpec defined : commandSpec.options()) {
            if (defined == option) { return commandSpec; }
        }
        for (CommandLine sub : commandSpec.subcommands().values()) {
            CommandSpec result = findCommandFor(option, sub.getCommandSpec());
            if (result != null) { return result; }
        }
        return null;
    }
    private static CommandSpec findCommandFor(PositionalParamSpec positional, CommandSpec commandSpec) {
        for (PositionalParamSpec defined : commandSpec.positionalParameters()) {
            if (defined == positional) { return commandSpec; }
        }
        for (CommandLine sub : commandSpec.subcommands().values()) {
            CommandSpec result = findCommandFor(positional, sub.getCommandSpec());
            if (result != null) { return result; }
        }
        return null;
    }
    private static boolean isPicocliModelObject(Object obj) {
        return obj instanceof CommandSpec || obj instanceof OptionSpec || obj instanceof PositionalParamSpec;
    }

    private static void filterAndTrimMatchingPrefix(String prefix, List<CharSequence> candidates) {
        Set<CharSequence> replace = new HashSet<CharSequence>();
        for (CharSequence seq : candidates) {
            if (seq.toString().startsWith(prefix)) {
                replace.add(seq.subSequence(prefix.length(), seq.length()));
            }
        }
        candidates.clear();
        candidates.addAll(replace);
    }
    private static void addCandidatesForArgsFollowing(Object obj, List<CharSequence> candidates) {
        if (obj == null) { return; }
        if (obj instanceof CommandSpec) {
            addCandidatesForArgsFollowing((CommandSpec) obj, candidates);
        } else if (obj instanceof OptionSpec) {
            addCandidatesForArgsFollowing((OptionSpec) obj, candidates);
        } else if (obj instanceof PositionalParamSpec) {
            addCandidatesForArgsFollowing((PositionalParamSpec) obj, candidates);
        }
    }
    private static void addCandidatesForArgsFollowing(CommandSpec commandSpec, List<CharSequence> candidates) {
        if (commandSpec == null) { return; }
        for (Map.Entry<String, CommandLine> entry : commandSpec.subcommands().entrySet()) {
            if (entry.getValue().getCommandSpec().usageMessage().hidden()) { continue; } // #887 skip hidden subcommands
            candidates.add(entry.getKey());
            candidates.addAll(Arrays.asList(entry.getValue().getCommandSpec().aliases()));
        }
        candidates.addAll(commandSpec.optionsMap().keySet());
        for (PositionalParamSpec positional : commandSpec.positionalParameters()) {
            if (positional.hidden()) { continue; } // #887 skip hidden subcommands
            addCandidatesForArgsFollowing(positional, candidates);
        }
    }
    private static void addCandidatesForArgsFollowing(OptionSpec optionSpec, List<CharSequence> candidates) {
        if (optionSpec != null && !optionSpec.hidden()) {
            addCompletionCandidates(optionSpec.completionCandidates(), candidates);
        }
    }
    private static void addCandidatesForArgsFollowing(PositionalParamSpec positionalSpec, List<CharSequence> candidates) {
        if (positionalSpec != null && !positionalSpec.hidden()) {
            addCompletionCandidates(positionalSpec.completionCandidates(), candidates);
        }
    }
    private static void addCompletionCandidates(Iterable<String> completionCandidates, List<CharSequence> candidates) {
        if (completionCandidates != null) {
            for (String candidate : completionCandidates) { candidates.add(candidate); }
        }
    }
}
