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

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

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

    expression: $ => choice(
      $.identifier,
      $.tool,
      seq($.identifier, $.operator, $.expression),
      seq($.value, $.operator, $.value)
    ),

    value: $ => choice(
      $.integer,
      $.float,
      $.string,
      $.list,
      $.empty,
    ),

    yield: $ => "->",

    chain: $ => ";",
    
    identifier: $ => /[a-zA-Z|_|.]+(_[a-zA-Z]+)*/,

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

    tool: $ => choice(
      "random",
      "random_boolean",
      "random_integer",
      "random_string",
      "random_float"      
    ),

    float: $ => /\d+\.\d*/,
    
    integer: $ => /\d+/,

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

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

    empty: $ => "()",

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