module.exports = grammar({
  name: 'nixshell',

  rules: {
    source_file: $ => seq($.first_line, repeat($.next_line)),

    first_line: $ => seq($._shebang_open, $._opt_ws, optional(seq($._env, $._ws)), $._nix_shell),
    next_line: $ => seq($._newline, choice(
        $.annotation_line,
        repeat(/./),
    )),
    annotation_line: $ => seq($._shebang_open, $._opt_ws, $._nix_shell, $.nix_shell_args),

    // TODO: actually parse nix-shell arguments
    nix_shell_args: $ => ' -i bash',

    _shebang_open: $ => '#!',
    // TODO: allow `usr/bin/env`, `env`
    _env: $ => '/usr/bin/env',
    _nix_shell: $ => 'nix-shell',
    _ws: $ => / +/,
    _opt_ws: $ => / */,
    _newline: $ => '\n',
  }
});