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

  extras: $ => [ /\s/, $.comment ],

  word: $ => $.identifier,

  rules: {
    // The production rules of the context-free grammar
    source_file: $ => $.scenario,
    scenario: $ => seq( 'Scenario', $.identifier, ':', repeat($.act), optional($.prototypes), optional($.resources)),
    act: $ => seq( 'Act', $.identifier, ':', repeat1($.rule)),
    rule: $ => prec.left(seq( '@', $.condition, optional( $.modifier), ':', repeat1($.action))),
    modifier: $ => seq( '%', $.identifier),
    condition: $ => choice( $.predicate, $.relation_expr, $.binary_expr ),
    relation_expr: $ => seq( $.scalar_expr, $.relation_op, $.scalar_expr ),
    relation_op: $ => choice( '<', '>', '<=', '>=', '==', '!=' ),
    binary_expr: $ => choice( $.and_expr, $.or_expr),
    and_expr: $ => prec.left(2, seq( $.condition, 'and', $.condition )),
    or_expr: $ => prec.left(1, seq( $.condition, 'or', $.condition )),
    predicate: $ => choice( $.atomic_predicate, $.function_application ),
    atomic_predicate: $ => choice( $.init_predicate, $.start_predicate, $.stop_predicate),
    init_predicate: $ => 'init',
    start_predicate: $ => 'start',
    stop_predicate: $ => 'stop',
    action: $ => $.function_application,
    function_application: $ => seq( $.identifier, '(', optional( seq( $.argument, repeat(seq(',',$.argument)))) , ')' ),
    argument: $ => choice( $.arg_expr, $.named_arg ),
    arg_expr: $ => choice( $.scalar_expr, $.coordinate_expr ),
    scalar_expr: $ => choice( $.identifier, $.record_expr, $.literal, $.function_application, $.arithmetic_expr ),
    named_arg: $ => seq( $.identifier, '=', $.arg_expr ),
    record_expr: $ => prec.left(seq( $.identifier, '.', $.identifier )),
    arithmetic_expr: $ => choice( $.product_expr, $.sum_expr),
    product_expr: $ => prec.left(2, seq( $.scalar_expr, choice('*','/'), $.scalar_expr )),
    sum_expr: $ => prec.left(1, seq( $.scalar_expr, choice('+','-'), $.scalar_expr )),
    coordinate_expr: $ => seq( $.scalar_expr, '|', $.scalar_expr, '|', $.scalar_expr ),

    prototypes: $ => seq( 'Prototypes', ':', repeat($.prototype)),
    prototype: $ => seq( $.identifier, ':', $.function_application),
    resources: $ => seq( 'Resources', ':', repeat($.resource)),
    resource: $ => seq( $.identifier, ':', $.function_application),

    literal: $ => choice ( $.numeric_literal, $.unit_literal, $.string_literal ),
    numeric_literal: $ => /[-+]?[0-9]+([.][0-9]+)?([eE][-+]?[0-9]+)?/,
    unit_literal: $ => seq( $.numeric_literal, $.unit ),
    unit: $ => choice( 'm', 'km', 'cm', 'mm', 'km/h', 'm/s', 'min', 'h', 's' ),
    string_literal: $ => token(seq('"', /[^"]*/, '"')),
    identifier: $ => /[A-Za-z][A-Za-z0-9_]*/,

    comment: $ => token(choice(seq('//', /.*/),
                               seq('/*', /[^*]*\*+([^/*][^*]*\*+)*/, '/')))

  }
});