// Copyright 2013-2023 The Cobra Authors
//
// 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 cobra

import (
	"bytes"
	"fmt"
	"io"
	"os"
	"sort"
	"strings"

	"github.com/spf13/pflag"
)

// Annotations for Bash completion.
const (
	BashCompFilenameExt     = "cobra_annotation_bash_completion_filename_extensions"
	BashCompCustom          = "cobra_annotation_bash_completion_custom"
	BashCompOneRequiredFlag = "cobra_annotation_bash_completion_one_required_flag"
	BashCompSubdirsInDir    = "cobra_annotation_bash_completion_subdirs_in_dir"
)

func writePreamble(buf io.StringWriter, name string) {
	WriteStringAndCheck(buf, fmt.Sprintf("# bash completion for %-36s -*- shell-script -*-\n", name))
	WriteStringAndCheck(buf, fmt.Sprintf(`
__%[1]s_debug()
{
    if [[ -n ${BASH_COMP_DEBUG_FILE:-} ]]; then
        echo "$*" >> "${BASH_COMP_DEBUG_FILE}"
    fi
}

# Homebrew on Macs have version 1.3 of bash-completion which doesn't include
# _init_completion. This is a very minimal version of that function.
__%[1]s_init_completion()
{
    COMPREPLY=()
    _get_comp_words_by_ref "$@" cur prev words cword
}

__%[1]s_index_of_word()
{
    local w word=$1
    shift
    index=0
    for w in "$@"; do
        [[ $w = "$word" ]] && return
        index=$((index+1))
    done
    index=-1
}

__%[1]s_contains_word()
{
    local w word=$1; shift
    for w in "$@"; do
        [[ $w = "$word" ]] && return
    done
    return 1
}

__%[1]s_handle_go_custom_completion()
{
    __%[1]s_debug "${FUNCNAME[0]}: cur is ${cur}, words[*] is ${words[*]}, #words[@] is ${#words[@]}"

    local shellCompDirectiveError=%[3]d
    local shellCompDirectiveNoSpace=%[4]d
    local shellCompDirectiveNoFileComp=%[5]d
    local shellCompDirectiveFilterFileExt=%[6]d
    local shellCompDirectiveFilterDirs=%[7]d

    local out requestComp lastParam lastChar comp directive args

    # Prepare the command to request completions for the program.
    # Calling ${words[0]} instead of directly %[1]s allows handling aliases
    args=("${words[@]:1}")
    # Disable ActiveHelp which is not supported for bash completion v1
    requestComp="%[8]s=0 ${words[0]} %[2]s ${args[*]}"

    lastParam=${words[$((${#words[@]}-1))]}
    lastChar=${lastParam:$((${#lastParam}-1)):1}
    __%[1]s_debug "${FUNCNAME[0]}: lastParam ${lastParam}, lastChar ${lastChar}"

    if [ -z "${cur}" ] && [ "${lastChar}" != "=" ]; then
        # If the last parameter is complete (there is a space following it)
        # We add an extra empty parameter so we can indicate this to the go method.
        __%[1]s_debug "${FUNCNAME[0]}: Adding extra empty parameter"
        requestComp="${requestComp} \"\""
    fi

    __%[1]s_debug "${FUNCNAME[0]}: calling ${requestComp}"
    # Use eval to handle any environment variables and such
    out=$(eval "${requestComp}" 2>/dev/null)

    # Extract the directive integer at the very end of the output following a colon (:)
    directive=${out##*:}
    # Remove the directive
    out=${out%%:*}
    if [ "${directive}" = "${out}" ]; then
        # There is not directive specified
        directive=0
    fi
    __%[1]s_debug "${FUNCNAME[0]}: the completion directive is: ${directive}"
    __%[1]s_debug "${FUNCNAME[0]}: the completions are: ${out}"

    if [ $((directive & shellCompDirectiveError)) -ne 0 ]; then
        # Error code.  No completion.
        __%[1]s_debug "${FUNCNAME[0]}: received error from custom completion go code"
        return
    else
        if [ $((directive & shellCompDirectiveNoSpace)) -ne 0 ]; then
            if [[ $(type -t compopt) = "builtin" ]]; then
                __%[1]s_debug "${FUNCNAME[0]}: activating no space"
                compopt -o nospace
            fi
        fi
        if [ $((directive & shellCompDirectiveNoFileComp)) -ne 0 ]; then
            if [[ $(type -t compopt) = "builtin" ]]; then
                __%[1]s_debug "${FUNCNAME[0]}: activating no file completion"
                compopt +o default
            fi
        fi
    fi

    if [ $((directive & shellCompDirectiveFilterFileExt)) -ne 0 ]; then
        # File extension filtering
        local fullFilter filter filteringCmd
        # Do not use quotes around the $out variable or else newline
        # characters will be kept.
        for filter in ${out}; do
            fullFilter+="$filter|"
        done

        filteringCmd="_filedir $fullFilter"
        __%[1]s_debug "File filtering command: $filteringCmd"
        $filteringCmd
    elif [ $((directive & shellCompDirectiveFilterDirs)) -ne 0 ]; then
        # File completion for directories only
        local subdir
        # Use printf to strip any trailing newline
        subdir=$(printf "%%s" "${out}")
        if [ -n "$subdir" ]; then
            __%[1]s_debug "Listing directories in $subdir"
            __%[1]s_handle_subdirs_in_dir_flag "$subdir"
        else
            __%[1]s_debug "Listing directories in ."
            _filedir -d
        fi
    else
        while IFS='' read -r comp; do
            COMPREPLY+=("$comp")
        done < <(compgen -W "${out}" -- "$cur")
    fi
}

__%[1]s_handle_reply()
{
    __%[1]s_debug "${FUNCNAME[0]}"
    local comp
    case $cur in
        -*)
            if [[ $(type -t compopt) = "builtin" ]]; then
                compopt -o nospace
            fi
            local allflags
            if [ ${#must_have_one_flag[@]} -ne 0 ]; then
                allflags=("${must_have_one_flag[@]}")
            else
                allflags=("${flags[*]} ${two_word_flags[*]}")
            fi
            while IFS='' read -r comp; do
                COMPREPLY+=("$comp")
            done < <(compgen -W "${allflags[*]}" -- "$cur")
            if [[ $(type -t compopt) = "builtin" ]]; then
                [[ "${COMPREPLY[0]}" == *= ]] || compopt +o nospace
            fi

            # complete after --flag=abc
            if [[ $cur == *=* ]]; then
                if [[ $(type -t compopt) = "builtin" ]]; then
                    compopt +o nospace
                fi

                local index flag
                flag="${cur%%=*}"
                __%[1]s_index_of_word "${flag}" "${flags_with_completion[@]}"
                COMPREPLY=()
                if [[ ${index} -ge 0 ]]; then
                    PREFIX=""
                    cur="${cur#*=}"
                    ${flags_completion[${index}]}
                    if [ -n "${ZSH_VERSION:-}" ]; then
                        # zsh completion needs --flag= prefix
                        eval "COMPREPLY=( \"\${COMPREPLY[@]/#/${flag}=}\" )"
                    fi
                fi
            fi

            if [[ -z "${flag_parsing_disabled}" ]]; then
                # If flag parsing is enabled, we have completed the flags and can return.
                # If flag parsing is disabled, we may not know all (or any) of the flags, so we fallthrough
                # to possibly call handle_go_custom_completion.
                return 0;
            fi
            ;;
    esac

    # check if we are handling a flag with special work handling
    local index
    __%[1]s_index_of_word "${prev}" "${flags_with_completion[@]}"
    if [[ ${index} -ge 0 ]]; then
        ${flags_completion[${index}]}
        return
    fi

    # we are parsing a flag and don't have a special handler, no completion
    if [[ ${cur} != "${words[cword]}" ]]; then
        return
    fi

    local completions
    completions=("${commands[@]}")
    if [[ ${#must_have_one_noun[@]} -ne 0 ]]; then
        completions+=("${must_have_one_noun[@]}")
    elif [[ -n "${has_completion_function}" ]]; then
        # if a go completion function is provided, defer to that function
        __%[1]s_handle_go_custom_completion
    fi
    if [[ ${#must_have_one_flag[@]} -ne 0 ]]; then
        completions+=("${must_have_one_flag[@]}")
    fi
    while IFS='' read -r comp; do
        COMPREPLY+=("$comp")
    done < <(compgen -W "${completions[*]}" -- "$cur")

    if [[ ${#COMPREPLY[@]} -eq 0 && ${#noun_aliases[@]} -gt 0 && ${#must_have_one_noun[@]} -ne 0 ]]; then
        while IFS='' read -r comp; do
            COMPREPLY+=("$comp")
        done < <(compgen -W "${noun_aliases[*]}" -- "$cur")
    fi

    if [[ ${#COMPREPLY[@]} -eq 0 ]]; then
        if declare -F __%[1]s_custom_func >/dev/null; then
            # try command name qualified custom func
            __%[1]s_custom_func
        else
            # otherwise fall back to unqualified for compatibility
            declare -F __custom_func >/dev/null && __custom_func
        fi
    fi

    # available in bash-completion >= 2, not always present on macOS
    if declare -F __ltrim_colon_completions >/dev/null; then
        __ltrim_colon_completions "$cur"
    fi

    # If there is only 1 completion and it is a flag with an = it will be completed
    # but we don't want a space after the =
    if [[ "${#COMPREPLY[@]}" -eq "1" ]] && [[ $(type -t compopt) = "builtin" ]] && [[ "${COMPREPLY[0]}" == --*= ]]; then
       compopt -o nospace
    fi
}

# The arguments should be in the form "ext1|ext2|extn"
__%[1]s_handle_filename_extension_flag()
{
    local ext="$1"
    _filedir "@(${ext})"
}

__%[1]s_handle_subdirs_in_dir_flag()
{
    local dir="$1"
    pushd "${dir}" >/dev/null 2>&1 && _filedir -d && popd >/dev/null 2>&1 || return
}

__%[1]s_handle_flag()
{
    __%[1]s_debug "${FUNCNAME[0]}: c is $c words[c] is ${words[c]}"

    # if a command required a flag, and we found it, unset must_have_one_flag()
    local flagname=${words[c]}
    local flagvalue=""
    # if the word contained an =
    if [[ ${words[c]} == *"="* ]]; then
        flagvalue=${flagname#*=} # take in as flagvalue after the =
        flagname=${flagname%%=*} # strip everything after the =
        flagname="${flagname}=" # but put the = back
    fi
    __%[1]s_debug "${FUNCNAME[0]}: looking for ${flagname}"
    if __%[1]s_contains_word "${flagname}" "${must_have_one_flag[@]}"; then
        must_have_one_flag=()
    fi

    # if you set a flag which only applies to this command, don't show subcommands
    if __%[1]s_contains_word "${flagname}" "${local_nonpersistent_flags[@]}"; then
      commands=()
    fi

    # keep flag value with flagname as flaghash
    # flaghash variable is an associative array which is only supported in bash > 3.
    if [[ -z "${BASH_VERSION:-}" || "${BASH_VERSINFO[0]:-}" -gt 3 ]]; then
        if [ -n "${flagvalue}" ] ; then
            flaghash[${flagname}]=${flagvalue}
        elif [ -n "${words[ $((c+1)) ]}" ] ; then
            flaghash[${flagname}]=${words[ $((c+1)) ]}
        else
            flaghash[${flagname}]="true" # pad "true" for bool flag
        fi
    fi

    # skip the argument to a two word flag
    if [[ ${words[c]} != *"="* ]] && __%[1]s_contains_word "${words[c]}" "${two_word_flags[@]}"; then
        __%[1]s_debug "${FUNCNAME[0]}: found a flag ${words[c]}, skip the next argument"
        c=$((c+1))
        # if we are looking for a flags value, don't show commands
        if [[ $c -eq $cword ]]; then
            commands=()
        fi
    fi

    c=$((c+1))

}

__%[1]s_handle_noun()
{
    __%[1]s_debug "${FUNCNAME[0]}: c is $c words[c] is ${words[c]}"

    if __%[1]s_contains_word "${words[c]}" "${must_have_one_noun[@]}"; then
        must_have_one_noun=()
    elif __%[1]s_contains_word "${words[c]}" "${noun_aliases[@]}"; then
        must_have_one_noun=()
    fi

    nouns+=("${words[c]}")
    c=$((c+1))
}

__%[1]s_handle_command()
{
    __%[1]s_debug "${FUNCNAME[0]}: c is $c words[c] is ${words[c]}"

    local next_command
    if [[ -n ${last_command} ]]; then
        next_command="_${last_command}_${words[c]//:/__}"
    else
        if [[ $c -eq 0 ]]; then
            next_command="_%[1]s_root_command"
        else
            next_command="_${words[c]//:/__}"
        fi
    fi
    c=$((c+1))
    __%[1]s_debug "${FUNCNAME[0]}: looking for ${next_command}"
    declare -F "$next_command" >/dev/null && $next_command
}

__%[1]s_handle_word()
{
    if [[ $c -ge $cword ]]; then
        __%[1]s_handle_reply
        return
    fi
    __%[1]s_debug "${FUNCNAME[0]}: c is $c words[c] is ${words[c]}"
    if [[ "${words[c]}" == -* ]]; then
        __%[1]s_handle_flag
    elif __%[1]s_contains_word "${words[c]}" "${commands[@]}"; then
        __%[1]s_handle_command
    elif [[ $c -eq 0 ]]; then
        __%[1]s_handle_command
    elif __%[1]s_contains_word "${words[c]}" "${command_aliases[@]}"; then
        # aliashash variable is an associative array which is only supported in bash > 3.
        if [[ -z "${BASH_VERSION:-}" || "${BASH_VERSINFO[0]:-}" -gt 3 ]]; then
            words[c]=${aliashash[${words[c]}]}
            __%[1]s_handle_command
        else
            __%[1]s_handle_noun
        fi
    else
        __%[1]s_handle_noun
    fi
    __%[1]s_handle_word
}

`, name, ShellCompNoDescRequestCmd,
		ShellCompDirectiveError, ShellCompDirectiveNoSpace, ShellCompDirectiveNoFileComp,
		ShellCompDirectiveFilterFileExt, ShellCompDirectiveFilterDirs, activeHelpEnvVar(name)))
}

// writePostscript writes postscript code to the provided buffer for a given command name.
//
// Parameters:
//   - buf: io.StringWriter where the postscript code will be written.
//   - name: The name of the command for which the postscript code is being generated.
//
// This function handles the generation of completion script postscript code for a Bash or similar shell. It replaces colons in the command name with double underscores, initializes completion variables and functions, and sets up the completion behavior using the 'complete' command.
func writePostscript(buf io.StringWriter, name string) {
	name = strings.ReplaceAll(name, ":", "__")
	WriteStringAndCheck(buf, fmt.Sprintf("__start_%s()\n", name))
	WriteStringAndCheck(buf, fmt.Sprintf(`{
    local cur prev words cword split
    declare -A flaghash 2>/dev/null || :
    declare -A aliashash 2>/dev/null || :
    if declare -F _init_completion >/dev/null 2>&1; then
        _init_completion -s || return
    else
        __%[1]s_init_completion -n "=" || return
    fi

    local c=0
    local flag_parsing_disabled=
    local flags=()
    local two_word_flags=()
    local local_nonpersistent_flags=()
    local flags_with_completion=()
    local flags_completion=()
    local commands=("%[1]s")
    local command_aliases=()
    local must_have_one_flag=()
    local must_have_one_noun=()
    local has_completion_function=""
    local last_command=""
    local nouns=()
    local noun_aliases=()

    __%[1]s_handle_word
}

`, name))
	WriteStringAndCheck(buf, fmt.Sprintf(`if [[ $(type -t compopt) = "builtin" ]]; then
    complete -o default -F __start_%s %s
else
    complete -o default -o nospace -F __start_%s %s
fi

`, name, name, name, name))
	WriteStringAndCheck(buf, "# ex: ts=4 sw=4 et filetype=sh\n")
}

// writeCommands writes the command definitions to a buffer.
//
// It takes an io.StringWriter and a *Command as parameters. The function iterates through
// the commands associated with the given Command instance. If a command is not available and
// is not the help command, it skips that command. For each valid command, it writes its name to the buffer
// in the format 'commands+=(<command_name>)' and calls writeCmdAliases to write any aliases for the command.
//
// The function includes a newline character at the end of the output.
//
// It returns nothing but may log errors through WriteStringAndCheck.
func writeCommands(buf io.StringWriter, cmd *Command) {
	WriteStringAndCheck(buf, "    commands=()\n")
	for _, c := range cmd.Commands() {
		if !c.IsAvailableCommand() && c != cmd.helpCommand {
			continue
		}
		WriteStringAndCheck(buf, fmt.Sprintf("    commands+=(%q)\n", c.Name()))
		writeCmdAliases(buf, c)
	}
	WriteStringAndCheck(buf, "\n")
}

// writeFlagHandler writes the flag completion handler for a given command and its annotations.
//
// Parameters:
//   buf - an io.StringWriter where the completion handler will be written
//   name - the name of the flag
//   annotations - a map containing annotations for the flag, including types like BashCompFilenameExt, BashCompCustom, and BashCompSubdirsInDir
//   cmd - the command associated with the flag
//
// Returns:
//   This function does not return any value. It writes to the buffer provided.
func writeFlagHandler(buf io.StringWriter, name string, annotations map[string][]string, cmd *Command) {
	for key, value := range annotations {
		switch key {
		case BashCompFilenameExt:
			WriteStringAndCheck(buf, fmt.Sprintf("    flags_with_completion+=(%q)\n", name))

			var ext string
			if len(value) > 0 {
				ext = fmt.Sprintf("__%s_handle_filename_extension_flag ", cmd.Root().Name()) + strings.Join(value, "|")
			} else {
				ext = "_filedir"
			}
			WriteStringAndCheck(buf, fmt.Sprintf("    flags_completion+=(%q)\n", ext))
		case BashCompCustom:
			WriteStringAndCheck(buf, fmt.Sprintf("    flags_with_completion+=(%q)\n", name))

			if len(value) > 0 {
				handlers := strings.Join(value, "; ")
				WriteStringAndCheck(buf, fmt.Sprintf("    flags_completion+=(%q)\n", handlers))
			} else {
				WriteStringAndCheck(buf, "    flags_completion+=(:)\n")
			}
		case BashCompSubdirsInDir:
			WriteStringAndCheck(buf, fmt.Sprintf("    flags_with_completion+=(%q)\n", name))

			var ext string
			if len(value) == 1 {
				ext = fmt.Sprintf("__%s_handle_subdirs_in_dir_flag ", cmd.Root().Name()) + value[0]
			} else {
				ext = "_filedir -d"
			}
			WriteStringAndCheck(buf, fmt.Sprintf("    flags_completion+=(%q)\n", ext))
		}
	}
}

const cbn = "\")\n"

// writeShortFlag writes a short flag to the provided buffer.
//
// Parameters:
//   - buf: The io.StringWriter where the flag will be written.
//   - flag: A pointer to the pflag.Flag representing the flag to write.
//   - cmd: A pointer to the Command associated with the flag.
//
// It constructs a formatted string based on the flag's shorthand and annotations, then writes it to the buffer using WriteStringAndCheck.
// Additionally, it calls writeFlagHandler to handle any specific logic for the flag.
func writeShortFlag(buf io.StringWriter, flag *pflag.Flag, cmd *Command) {
	name := flag.Shorthand
	format := "    "
	if len(flag.NoOptDefVal) == 0 {
		format += "two_word_"
	}
	format += "flags+=(\"-%s" + cbn
	WriteStringAndCheck(buf, fmt.Sprintf(format, name))
	writeFlagHandler(buf, "-"+name, flag.Annotations, cmd)
}

// writeFlag writes a flag definition to the buffer in a specific format.
//
// Parameters:
//   - buf: The io.StringWriter where the flag definition will be written.
//   - flag: The pflag.Flag object representing the flag being written.
//   - cmd: The Command object associated with the flag.
//
// Returns:
//   None
//
// This function handles the formatting and writing of a single flag, including handling cases for flags without default values and two-word flags. It also calls writeFlagHandler to process any additional annotations or handlers related to the flag.
func writeFlag(buf io.StringWriter, flag *pflag.Flag, cmd *Command) {
	name := flag.Name
	format := "    flags+=(\"--%s"
	if len(flag.NoOptDefVal) == 0 {
		format += "="
	}
	format += cbn
	WriteStringAndCheck(buf, fmt.Sprintf(format, name))
	if len(flag.NoOptDefVal) == 0 {
		format = "    two_word_flags+=(\"--%s" + cbn
		WriteStringAndCheck(buf, fmt.Sprintf(format, name))
	}
	writeFlagHandler(buf, "--"+name, flag.Annotations, cmd)
}

// writeLocalNonPersistentFlag writes the local non-persistent flags to the provided buffer.
//
// Parameters:
//   - buf: The io.StringWriter where the flags will be written.
//   - flag: A pointer to the pflag.Flag that contains the details of the flag.
//
// This function constructs a string representation of the flag and appends it to the buffer. If the flag has a shorthand,
// it also writes the shorthand version of the flag to the buffer.
func writeLocalNonPersistentFlag(buf io.StringWriter, flag *pflag.Flag) {
	name := flag.Name
	format := "    local_nonpersistent_flags+=(\"--%[1]s" + cbn
	if len(flag.NoOptDefVal) == 0 {
		format += "    local_nonpersistent_flags+=(\"--%[1]s=" + cbn
	}
	WriteStringAndCheck(buf, fmt.Sprintf(format, name))
	if len(flag.Shorthand) > 0 {
		WriteStringAndCheck(buf, fmt.Sprintf("    local_nonpersistent_flags+=(\"-%s\")\n", flag.Shorthand))
	}
}

// prepareCustomAnnotationsForFlags sets up custom annotations for go completions for registered flags.
//
// It takes a pointer to a Command and iterates over the flagCompletionFunctions map, adding custom annotations to each flag's Annotations field. The custom annotation is a Bash completion command that calls the __*_go_custom_completion function for the specified flag, ensuring that the root command name is correctly set for the prefix of the completion script.
func prepareCustomAnnotationsForFlags(cmd *Command) {
	flagCompletionMutex.RLock()
	defer flagCompletionMutex.RUnlock()
	for flag := range flagCompletionFunctions {
		// Make sure the completion script calls the __*_go_custom_completion function for
		// every registered flag.  We need to do this here (and not when the flag was registered
		// for completion) so that we can know the root command name for the prefix
		// of __<prefix>_go_custom_completion
		if flag.Annotations == nil {
			flag.Annotations = map[string][]string{}
		}
		flag.Annotations[BashCompCustom] = []string{fmt.Sprintf("__%[1]s_handle_go_custom_completion", cmd.Root().Name())}
	}
}

// writeFlags writes the flags for a command to the provided buffer.
// It handles both local and inherited flags, excluding non-completable ones.
// If flag parsing is disabled, it sets the corresponding variable in the buffer.
func writeFlags(buf io.StringWriter, cmd *Command) {
	prepareCustomAnnotationsForFlags(cmd)
	WriteStringAndCheck(buf, `    flags=()
    two_word_flags=()
    local_nonpersistent_flags=()
    flags_with_completion=()
    flags_completion=()

`)

	if cmd.DisableFlagParsing {
		WriteStringAndCheck(buf, "    flag_parsing_disabled=1\n")
	}

	localNonPersistentFlags := cmd.LocalNonPersistentFlags()
	cmd.NonInheritedFlags().VisitAll(func(flag *pflag.Flag) {
		if nonCompletableFlag(flag) {
			return
		}
		writeFlag(buf, flag, cmd)
		if len(flag.Shorthand) > 0 {
			writeShortFlag(buf, flag, cmd)
		}
		// localNonPersistentFlags are used to stop the completion of subcommands when one is set
		// if TraverseChildren is true we should allow to complete subcommands
		if localNonPersistentFlags.Lookup(flag.Name) != nil && !cmd.Root().TraverseChildren {
			writeLocalNonPersistentFlag(buf, flag)
		}
	})
	cmd.InheritedFlags().VisitAll(func(flag *pflag.Flag) {
		if nonCompletableFlag(flag) {
			return
		}
		writeFlag(buf, flag, cmd)
		if len(flag.Shorthand) > 0 {
			writeShortFlag(buf, flag, cmd)
		}
	})

	WriteStringAndCheck(buf, "\n")
}

// writeRequiredFlag appends to the buffer a line that specifies which flags are required for the command.
// It takes an io.StringWriter and a Command as parameters. The function checks each non-inherited flag of the command
// and adds it to the must_have_one_flag array if it is annotated with BashCompOneRequiredFlag. If the flag is not of type bool,
// it appends "=" after the flag name in the array.
// This function does not return any values, but it may write strings to the buffer and handle errors through WriteStringAndCheck.
// It also uses nonCompletableFlag to determine if a flag should be skipped.
func writeRequiredFlag(buf io.StringWriter, cmd *Command) {
	WriteStringAndCheck(buf, "    must_have_one_flag=()\n")
	flags := cmd.NonInheritedFlags()
	flags.VisitAll(func(flag *pflag.Flag) {
		if nonCompletableFlag(flag) {
			return
		}
		if _, ok := flag.Annotations[BashCompOneRequiredFlag]; ok {
			format := "    must_have_one_flag+=(\"--%s"
			if flag.Value.Type() != "bool" {
				format += "="
			}
			format += cbn
			WriteStringAndCheck(buf, fmt.Sprintf(format, flag.Name))

			if len(flag.Shorthand) > 0 {
				WriteStringAndCheck(buf, fmt.Sprintf("    must_have_one_flag+=(\"-%s"+cbn, flag.Shorthand))
			}
		}
	})
}

// writeRequiredNouns writes the required nouns for a command to a buffer.
//
// It takes an io.StringWriter and a pointer to a Command as parameters. The Command should have valid arguments defined in ValidArgs or a function to provide them through ValidArgsFunction.
//
// This function sorts the valid arguments, removes any descriptions following a tab character (not supported by bash completion), and appends each noun to the buffer in the format required for command-line interface validation.
//
// If a ValidArgsFunction is provided, it also sets a flag indicating that a completion function is available.
func writeRequiredNouns(buf io.StringWriter, cmd *Command) {
	WriteStringAndCheck(buf, "    must_have_one_noun=()\n")
	sort.Strings(cmd.ValidArgs)
	for _, value := range cmd.ValidArgs {
		// Remove any description that may be included following a tab character.
		// Descriptions are not supported by bash completion.
		value = strings.SplitN(value, "\t", 2)[0]
		WriteStringAndCheck(buf, fmt.Sprintf("    must_have_one_noun+=(%q)\n", value))
	}
	if cmd.ValidArgsFunction != nil {
		WriteStringAndCheck(buf, "    has_completion_function=1\n")
	}
}

// writeCmdAliases writes the command aliases to the provided buffer.
//
// Parameters:
//   - buf: An io.StringWriter where the aliases will be written.
//   - cmd: A pointer to a Command struct containing the aliases to be written.
//
// Returns:
//   - None
func writeCmdAliases(buf io.StringWriter, cmd *Command) {
	if len(cmd.Aliases) == 0 {
		return
	}

	sort.Strings(cmd.Aliases)

	WriteStringAndCheck(buf, fmt.Sprint(`    if [[ -z "${BASH_VERSION:-}" || "${BASH_VERSINFO[0]:-}" -gt 3 ]]; then`, "\n"))
	for _, value := range cmd.Aliases {
		WriteStringAndCheck(buf, fmt.Sprintf("        command_aliases+=(%q)\n", value))
		WriteStringAndCheck(buf, fmt.Sprintf("        aliashash[%q]=%q\n", value, cmd.Name()))
	}
	WriteStringAndCheck(buf, `    fi`)
	WriteStringAndCheck(buf, "\n")
}
// writeArgAliases writes argument aliases for a command to the buffer and checks for errors.
//
// Parameters:
//   - buf: The string writer where the alias information will be written.
//   - cmd: The command whose aliases are being written.
//
// This function formats and appends argument aliases of the given command to the buffer,
// ensuring they are sorted alphabetically. It also handles any errors that occur during
// the writing process using WriteStringAndCheck.
func writeArgAliases(buf io.StringWriter, cmd *Command) {
	WriteStringAndCheck(buf, "    noun_aliases=()\n")
	sort.Strings(cmd.ArgAliases)
	for _, value := range cmd.ArgAliases {
		WriteStringAndCheck(buf, fmt.Sprintf("    noun_aliases+=(%q)\n", value))
	}
}

// gen recursively generates a set of functions to call the provided command and its subcommands.
//
// Parameters:
//   - buf: an io.StringWriter to write the generated functions to.
//   - cmd: the current command to generate functions for.
func gen(buf io.StringWriter, cmd *Command) {
	for _, c := range cmd.Commands() {
		if !c.IsAvailableCommand() && c != cmd.helpCommand {
			continue
		}
		gen(buf, c)
	}
	commandName := cmd.CommandPath()
	commandName = strings.ReplaceAll(commandName, " ", "_")
	commandName = strings.ReplaceAll(commandName, ":", "__")

	if cmd.Root() == cmd {
		WriteStringAndCheck(buf, fmt.Sprintf("_%s_root_command()\n{\n", commandName))
	} else {
		WriteStringAndCheck(buf, fmt.Sprintf("_%s()\n{\n", commandName))
	}

	WriteStringAndCheck(buf, fmt.Sprintf("    last_command=%q\n", commandName))
	WriteStringAndCheck(buf, "\n")
	WriteStringAndCheck(buf, "    command_aliases=()\n")
	WriteStringAndCheck(buf, "\n")

	writeCommands(buf, cmd)
	writeFlags(buf, cmd)
	writeRequiredFlag(buf, cmd)
	writeRequiredNouns(buf, cmd)
	writeArgAliases(buf, cmd)
	WriteStringAndCheck(buf, "}\n\n")
}

// GenBashCompletion generates a bash completion file and writes it to the provided writer.
//
// Parameters:
//   - w: io.Writer - The writer to which the bash completion file will be written.
//
// Returns:
//   - error: If an error occurs during the generation or writing process, it is returned.
func (c *Command) GenBashCompletion(w io.Writer) error {
	buf := new(bytes.Buffer)
	writePreamble(buf, c.Name())
	if len(c.BashCompletionFunction) > 0 {
		buf.WriteString(c.BashCompletionFunction + "\n")
	}
	gen(buf, c)
	writePostscript(buf, c.Name())

	_, err := buf.WriteTo(w)
	return err
}

// nonCompletableFlag checks if a flag is hidden or deprecated and returns true if it should not be completed.
func nonCompletableFlag(flag *pflag.Flag) bool {
	return flag.Hidden || len(flag.Deprecated) > 0
}

// GenBashCompletionFile generates a bash completion file for the command.
//
// Parameters:
// filename - The path to the output bash completion file.
//
// Returns:
// error - An error if the file could not be created or written, nil otherwise.
func (c *Command) GenBashCompletionFile(filename string) error {
	outFile, err := os.Create(filename)
	if err != nil {
		return err
	}
	defer outFile.Close()

	return c.GenBashCompletion(outFile)
}