using namespace System.Management.Automation
using namespace System.Management.Automation.Language

Register-ArgumentCompleter -Native -CommandName 'just' -ScriptBlock {
    param($wordToComplete, $commandAst, $cursorPosition)

    $commandElements = $commandAst.CommandElements
    $command = @(
        'just'
        for ($i = 1; $i -lt $commandElements.Count; $i++) {
            $element = $commandElements[$i]
            if ($element -isnot [StringConstantExpressionAst] -or
                $element.StringConstantType -ne [StringConstantType]::BareWord -or
                $element.Value.StartsWith('-')) {
                break
        }
        $element.Value
    }) -join ';'

    $completions = @(switch ($command) {
        'just' {
            [CompletionResult]::new('--chooser', 'chooser', [CompletionResultType]::ParameterName, 'Override binary invoked by `--choose`')
            [CompletionResult]::new('--color', 'color', [CompletionResultType]::ParameterName, 'Print colorful output')
            [CompletionResult]::new('--command-color', 'command-color', [CompletionResultType]::ParameterName, 'Echo recipe lines in <COMMAND-COLOR>')
            [CompletionResult]::new('--dump-format', 'dump-format', [CompletionResultType]::ParameterName, 'Dump justfile as <FORMAT>')
            [CompletionResult]::new('--list-heading', 'list-heading', [CompletionResultType]::ParameterName, 'Print <TEXT> before list')
            [CompletionResult]::new('--list-prefix', 'list-prefix', [CompletionResultType]::ParameterName, 'Print <TEXT> before each list item')
            [CompletionResult]::new('-f', 'f', [CompletionResultType]::ParameterName, 'Use <JUSTFILE> as justfile')
            [CompletionResult]::new('--justfile', 'justfile', [CompletionResultType]::ParameterName, 'Use <JUSTFILE> as justfile')
            [CompletionResult]::new('--set', 'set', [CompletionResultType]::ParameterName, 'Override <VARIABLE> with <VALUE>')
            [CompletionResult]::new('--shell', 'shell', [CompletionResultType]::ParameterName, 'Invoke <SHELL> to run recipes')
            [CompletionResult]::new('--shell-arg', 'shell-arg', [CompletionResultType]::ParameterName, 'Invoke shell with <SHELL-ARG> as an argument')
            [CompletionResult]::new('-d', 'd', [CompletionResultType]::ParameterName, 'Use <WORKING-DIRECTORY> as working directory. --justfile must also be set')
            [CompletionResult]::new('--working-directory', 'working-directory', [CompletionResultType]::ParameterName, 'Use <WORKING-DIRECTORY> as working directory. --justfile must also be set')
            [CompletionResult]::new('-c', 'c', [CompletionResultType]::ParameterName, 'Run an arbitrary command with the working directory, `.env`, overrides, and exports set')
            [CompletionResult]::new('--command', 'command', [CompletionResultType]::ParameterName, 'Run an arbitrary command with the working directory, `.env`, overrides, and exports set')
            [CompletionResult]::new('--completions', 'completions', [CompletionResultType]::ParameterName, 'Print shell completion script for <SHELL>')
            [CompletionResult]::new('-s', 's', [CompletionResultType]::ParameterName, 'Show information about <RECIPE>')
            [CompletionResult]::new('--show', 'show', [CompletionResultType]::ParameterName, 'Show information about <RECIPE>')
            [CompletionResult]::new('--dotenv-filename', 'dotenv-filename', [CompletionResultType]::ParameterName, 'Search for environment file named <DOTENV-FILENAME> instead of `.env`')
            [CompletionResult]::new('-E', 'E', [CompletionResultType]::ParameterName, 'Load <DOTENV-PATH> as environment file instead of searching for one')
            [CompletionResult]::new('--dotenv-path', 'dotenv-path', [CompletionResultType]::ParameterName, 'Load <DOTENV-PATH> as environment file instead of searching for one')
            [CompletionResult]::new('--check', 'check', [CompletionResultType]::ParameterName, 'Run `--fmt` in ''check'' mode. Exits with 0 if justfile is formatted correctly. Exits with 1 and prints a diff if formatting is required.')
            [CompletionResult]::new('--yes', 'yes', [CompletionResultType]::ParameterName, 'Automatically confirm all recipes.')
            [CompletionResult]::new('-n', 'n', [CompletionResultType]::ParameterName, 'Print what just would do without doing it')
            [CompletionResult]::new('--dry-run', 'dry-run', [CompletionResultType]::ParameterName, 'Print what just would do without doing it')
            [CompletionResult]::new('--highlight', 'highlight', [CompletionResultType]::ParameterName, 'Highlight echoed recipe lines in bold')
            [CompletionResult]::new('--no-deps', 'no-deps', [CompletionResultType]::ParameterName, 'Don''t run recipe dependencies')
            [CompletionResult]::new('--no-dotenv', 'no-dotenv', [CompletionResultType]::ParameterName, 'Don''t load `.env` file')
            [CompletionResult]::new('--no-highlight', 'no-highlight', [CompletionResultType]::ParameterName, 'Don''t highlight echoed recipe lines in bold')
            [CompletionResult]::new('-q', 'q', [CompletionResultType]::ParameterName, 'Suppress all output')
            [CompletionResult]::new('--quiet', 'quiet', [CompletionResultType]::ParameterName, 'Suppress all output')
            [CompletionResult]::new('--shell-command', 'shell-command', [CompletionResultType]::ParameterName, 'Invoke <COMMAND> with the shell used to run recipe lines and backticks')
            [CompletionResult]::new('--clear-shell-args', 'clear-shell-args', [CompletionResultType]::ParameterName, 'Clear shell arguments')
            [CompletionResult]::new('-u', 'u', [CompletionResultType]::ParameterName, 'Return list and summary entries in source order')
            [CompletionResult]::new('--unsorted', 'unsorted', [CompletionResultType]::ParameterName, 'Return list and summary entries in source order')
            [CompletionResult]::new('--unstable', 'unstable', [CompletionResultType]::ParameterName, 'Enable unstable features')
            [CompletionResult]::new('-v', 'v', [CompletionResultType]::ParameterName, 'Use verbose output')
            [CompletionResult]::new('--verbose', 'verbose', [CompletionResultType]::ParameterName, 'Use verbose output')
            [CompletionResult]::new('--changelog', 'changelog', [CompletionResultType]::ParameterName, 'Print changelog')
            [CompletionResult]::new('--choose', 'choose', [CompletionResultType]::ParameterName, 'Select one or more recipes to run using a binary chooser. If `--chooser` is not passed the chooser defaults to the value of $JUST_CHOOSER, falling back to `fzf`')
            [CompletionResult]::new('--dump', 'dump', [CompletionResultType]::ParameterName, 'Print justfile')
            [CompletionResult]::new('-e', 'e', [CompletionResultType]::ParameterName, 'Edit justfile with editor given by $VISUAL or $EDITOR, falling back to `vim`')
            [CompletionResult]::new('--edit', 'edit', [CompletionResultType]::ParameterName, 'Edit justfile with editor given by $VISUAL or $EDITOR, falling back to `vim`')
            [CompletionResult]::new('--evaluate', 'evaluate', [CompletionResultType]::ParameterName, 'Evaluate and print all variables. If a variable name is given as an argument, only print that variable''s value.')
            [CompletionResult]::new('--fmt', 'fmt', [CompletionResultType]::ParameterName, 'Format and overwrite justfile')
            [CompletionResult]::new('--init', 'init', [CompletionResultType]::ParameterName, 'Initialize new justfile in project root')
            [CompletionResult]::new('-l', 'l', [CompletionResultType]::ParameterName, 'List available recipes and their arguments')
            [CompletionResult]::new('--list', 'list', [CompletionResultType]::ParameterName, 'List available recipes and their arguments')
            [CompletionResult]::new('--summary', 'summary', [CompletionResultType]::ParameterName, 'List names of available recipes')
            [CompletionResult]::new('--variables', 'variables', [CompletionResultType]::ParameterName, 'List names of variables')
            [CompletionResult]::new('-h', 'h', [CompletionResultType]::ParameterName, 'Print help information')
            [CompletionResult]::new('--help', 'help', [CompletionResultType]::ParameterName, 'Print help information')
            [CompletionResult]::new('-V', 'V', [CompletionResultType]::ParameterName, 'Print version information')
            [CompletionResult]::new('--version', 'version', [CompletionResultType]::ParameterName, 'Print version information')
            break
        }
    })

    function Get-JustFileRecipes([string[]]$CommandElements) {
        $justFileIndex = $commandElements.IndexOf("--justfile");

        if ($justFileIndex -ne -1 && $justFileIndex + 1 -le $commandElements.Length) {
            $justFileLocation = $commandElements[$justFileIndex + 1]
        }

        $justArgs = @("--summary")

        if (Test-Path $justFileLocation) {
            $justArgs += @("--justfile", $justFileLocation)
        }

        $recipes = $(just @justArgs) -split ' '
        return $recipes | ForEach-Object { [CompletionResult]::new($_) }
    }

    $elementValues = $commandElements | Select-Object -ExpandProperty Value
    $recipes = Get-JustFileRecipes -CommandElements $elementValues
    $completions += $recipes
    $completions.Where{ $_.CompletionText -like "$wordToComplete*" } |
        Sort-Object -Property ListItemText
}