/**
 * @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,
        $.eqexp,
        $.vardef,
        $.callexp,
        $.funcdef,
        $.lambda,
        $.seqexp,
        $.ifexp,
        $.tern_ifexp,
        $.block,
        $.parexp,
      ),

    num: (_) => /\d+/,

    bool: (_) => choice("T", "F"),

    word: (_) => /[a-zA-Z_]\w*/,

    seqexp: ($) =>
      prec.left(
        -1, // lowest
        seq(field("first", $._exp), repeat1(seq(";", field("rest", $._exp)))),
      ),

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

    eqexp: ($) =>
      prec.left(2, seq(field("left", $._exp), "==", field("right", $._exp))),

    binexp: ($) =>
      choice(
        prec.left(
          3,
          seq(
            field("left", $._exp),
            field("op", choice("+", "-")),
            field("right", $._exp),
          ),
        ),
        prec.left(
          4,
          seq(
            field("left", $._exp),
            field("op", choice("*", "/")),
            field("right", $._exp),
          ),
        ),
      ),

    callexp: ($) =>
      prec.left(
        5,
        seq(field("fn", $.word), "(", optional(commaSep($._exp)), ")"),
      ),

    funcdef: ($) =>
      prec.right(
        6,
        seq(
          field("name", $.word),
          field("params", $.params),
          field("body", $._exp),
        ),
      ),

    lambda: ($) =>
      prec.right(
        6,
        seq("\\", field("params", $.params), field("body", $._exp)),
      ),

    parexp: ($) => seq("(", $._exp, ")"),

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

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

    ifexp: ($) =>
      prec.right(
        seq(
          "if",
          field("cond", $._exp),
          field("then", $._exp),
          optional("else"),
          field("else", $._exp),
        ),
      ),

    tern_ifexp: ($) =>
      seq(
        "?",
        field("cond", $._exp),
        field("then", $._exp),
        field("else", $._exp),
      ),
  },
});

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