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

  rules: {
    source_file: $ => repeat(choice($.comment, $.expression)),

    comment: $ => /(#)(.+?)([\n\r])/,

    expression: $ => choice(
      $.identifier,
      $.integer,
      $.string,
      $.list,
      $.macro,
      seq($.identifier, $.operator, $.identifier)
    ),
    
    identifier: $ => /[a-zA-Z|_|.]+(_[a-zA-Z]+)*/,

    operator: $ => choice(
      '=',
      '-',
      '+',
      ';',
      '/',
      '|',
      '&'
    ),

    integer: $ => /\d/,

    string: $ => /"(.*?)\"/,

    function: $ => /'(.*?)\'/,

    list: $ => seq(
      '(',
      repeat1(seq($.expression, optional(','))),
      ')'
    ),

    macro: $ => choice(
      "assert",
      "assert_equal"
    )
  }
});