/**
 * @file SCL grammar for tree-sitter
 * @author Jacob Signorovitch <jacob.signorovitch@gmail.com>
 * @license MIT
 */

/// <reference types="tree-sitter-cli/dsl" />
// @ts-check

module.exports = grammar({
  name: "scl",

  conflicts: ($) => [[$.params, $._exp]],

  rules: {
    source_file: ($) => repeat($._exp),

    _exp: ($) =>
      choice(
        $.num,
        $.bool,
        $.word,
        $.binexp,
        $.callexp,
        $.parexp,
        $.block,
        $.vardef,
        $.lambda,
        $.funcdef,
        $.ifexp,
      ),

    num: (_) => /\d+/,
    bool: (_) => choice("TRUE", "T", "FALSE", "F"),
    word: (_) => /[a-zA-Z_]\w*/,

    binexp: ($) =>
      prec.left(
        1,
        seq(
          field("left", $._exp),
          field("op", choice("+", "-", "*", "/", "eq")),
          field("right", $._exp),
        ),
      ),

    callexp: ($) =>
      prec.left(
        1, // lower than funcdef
        seq(field("fn", $.word), "(", optional(commaSep($._exp)), ")"),
      ),

    parexp: ($) => seq("(", $._exp, ")"),
    block: ($) => seq("{", repeat($._exp), "}"),

    vardef: ($) =>
      prec.right(1, seq(field("name", $.word), "=", field("value", $._exp))),

    lambda: ($) =>
      prec.right(
        2,
        seq("\\", field("params", $.params), field("body", $._exp)),
      ),

    funcdef: ($) =>
      prec.right(
        3, // higher precedence than call
        seq(
          field("name", $.word),
          field("params", $.params),
          field("body", $._exp),
        ),
      ),

    params: ($) => seq("(", optional(commaSep($.word)), ")"),

    ifexp: ($) =>
      choice(
        seq(
          "_if",
          "(",
          field("cond", $._exp),
          ",",
          field("then", $._exp),
          ",",
          field("else", $._exp),
          ")",
        ),
        seq(
          "if",
          field("cond", $._exp),
          field("then", $._exp),
          choice(seq("else", field("else", $._exp)), field("else", $._exp)),
        ),
        seq(
          "?",
          field("cond", $._exp),
          field("then", $._exp),
          field("else", $._exp),
        ),
      ),
  },
});

function commaSep(rule) {
  return seq(rule, repeat(seq(",", rule)));
}