import { BuiltinCommand } from './builtin_command';
import { BooleanArgument, PositionalArguments } from '../argument';
import { CommandArguments } from '../arguments';
import { CommandType } from '../commands';
import type { IRunContext, ITabCompleteContext } from '../context';
import { ExitCode } from '../exit_code';
import type { ITabCompleteResult } from '../tab_complete';

class HelpArguments extends CommandArguments {
  description =
    "Show help for built-in commands. With no arguments, lists available builtins. With names, shows each command's help (equivalent to '<cmd> --help').";
  help = new BooleanArgument('h', 'help', 'display this help and exit');
  positional = new PositionalArguments({
    tabComplete: async (context: ITabCompleteContext) => ({
      possibles: context.commandRegistry?.commandNames(CommandType.Builtin) ?? []
    })
  });
}

export class HelpCommand extends BuiltinCommand {
  get name(): string {
    return 'help';
  }

  async tabComplete(context: ITabCompleteContext): Promise<ITabCompleteResult> {
    return await new HelpArguments().tabComplete(context);
  }

  protected async _run(context: IRunContext): Promise<number> {
    const { args, stdout, stderr, commandRegistry } = context;
    const parsed = new HelpArguments().parse(args);

    if (parsed.help.isSet) {
      parsed.writeHelp(stdout);
      return ExitCode.SUCCESS;
    }

    const targets = parsed.positional.strings;
    const builtins = commandRegistry ? commandRegistry.commandNames(CommandType.Builtin) : [];

    if (targets.length === 0) {
      stdout.write('Built-in commands:\n');
      for (const name of builtins) {
        stdout.write(`  ${name}\n`);
      }
      stdout.write('\n');
      stdout.write(
        'For detailed help, type <command-name> --help (e.g., `history --help` or `alias -h`).'
      );
      return ExitCode.SUCCESS;
    }

    let overallExit: number = ExitCode.SUCCESS;

    for (const target of targets) {
      if (!builtins.includes(target)) {
        stderr.write(`help: unknown built-in: ${target}\n`);
        overallExit = ExitCode.GENERAL_ERROR;
        continue;
      }

      const runner = commandRegistry.get(target);
      if (runner === null) {
        stderr.write(`help: failed to get command '${target}'\n`);
        overallExit = ExitCode.GENERAL_ERROR;
        continue;
      }

      const subContext: IRunContext = {
        ...context,
        name: target,
        args: ['--help']
      };

      stdout.write(`\n=== help for ${target} ===\n`);
      await runner.run(subContext);
    }

    return overallExit;
  }
}