jarvish 1.6.0

use clap::Parser;

use crate::engine::CommandResult;

/// ビルトインコマンドの名前と説明の一覧（アルファベット順）。
const BUILTIN_COMMANDS: &[(&str, &str)] = &[
    ("alias", "Set or display aliases"),
    ("cd", "Change the current directory"),
    ("cwd", "Print the current working directory"),
    ("dirs", "Display directory stack"),
    ("exit", "Exit the shell"),
    ("export", "Set or display environment variables"),
    ("help", "Display help for builtin commands"),
    ("history", "Display or manage command history"),
    ("popd", "Pop directory from stack and change to it"),
    ("pushd", "Push directory onto stack and change to it"),
    ("source", "Load a configuration file (TOML)"),
    ("type", "Display information about command type"),
    ("unalias", "Remove aliases"),
    ("unset", "Remove environment variables"),
    ("which", "Locate a command (builtin, alias, or external)"),
];

/// help: ビルトインコマンドのヘルプを表示する。
#[derive(Parser)]
#[command(name = "help", about = "Display help for builtin commands")]
struct HelpArgs {
    /// Command name to show help for
    command: Option<String>,
}

/// help: ビルトインコマンドのヘルプを表示する。
/// - 引数なし → 全ビルトインコマンドの一覧を表示
/// - `help <command>` → 指定コマンドの詳細ヘルプを表示
pub(super) fn execute(args: &[&str]) -> CommandResult {
    let parsed = match super::parse_args::<HelpArgs>("help", args) {
        Ok(a) => a,
        Err(result) => return result,
    };

    match parsed.command {
        None => list_builtins(),
        Some(cmd) => show_command_help(&cmd),
    }
}

/// 全ビルトインコマンドの一覧を表示する。
fn list_builtins() -> CommandResult {
    let mut output = String::from("Jarvis Shell builtins:\n");

    for (name, desc) in BUILTIN_COMMANDS {
        output.push_str(&format!("  {name:<10}{desc}\n"));
    }

    print!("{output}");
    CommandResult::success(output)
}

/// 指定コマンドの詳細ヘルプを表示する。
/// ビルトインコマンドの場合は `dispatch_builtin(cmd, &["--help"])` に委譲する。
fn show_command_help(cmd: &str) -> CommandResult {
    if !super::is_builtin(cmd) {
        let msg = format!("jarvish: help: no such builtin: {cmd}\n");
        eprint!("{msg}");
        return CommandResult::error(msg, 1);
    }

    // 対象コマンドの --help を呼び出して詳細ヘルプを表示
    super::dispatch_builtin(cmd, &["--help"]).unwrap_or_else(|| {
        CommandResult::error(format!("jarvish: help: {cmd}: unexpected error\n"), 1)
    })
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::engine::LoopAction;

    #[test]
    fn help_no_args_lists_all_builtins() {
        let result = execute(&[]);
        assert_eq!(result.exit_code, 0);
        assert_eq!(result.action, LoopAction::Continue);
        assert!(result.stdout.contains("Jarvis Shell builtins:"));
        assert!(result.stdout.contains("cd"));
        assert!(result.stdout.contains("cwd"));
        assert!(result.stdout.contains("exit"));
        assert!(result.stdout.contains("export"));
        assert!(result.stdout.contains("help"));
        assert!(result.stdout.contains("history"));
        assert!(result.stdout.contains("unset"));
    }

    #[test]
    fn help_specific_command_shows_detail() {
        let result = execute(&["cd"]);
        assert_eq!(result.exit_code, 0);
        assert_eq!(result.action, LoopAction::Continue);
        // cd の --help 出力にはコマンド名が含まれるはず
        assert!(result.stdout.contains("cd"));
    }

    #[test]
    fn help_unknown_command_returns_error() {
        let result = execute(&["nonexistent"]);
        assert_ne!(result.exit_code, 0);
        assert!(result.stderr.contains("no such builtin"));
    }

    #[test]
    fn help_help_returns_success() {
        let result = execute(&["--help"]);
        assert_eq!(result.exit_code, 0);
        assert!(result.stdout.contains("help"));
    }

    #[test]
    fn help_for_each_builtin_succeeds() {
        for (name, _) in BUILTIN_COMMANDS {
            let result = execute(&[name]);
            assert_eq!(result.exit_code, 0, "help {name} should succeed");
        }
    }
}