prototype-3x5/notcl.js

/**
 * @typedef {Notcl.Command[]} Notcl.Script
 * @typedef {Notcl.Word[]} Notcl.Command
 * @typedef {object} Notcl.Word
 * @property {string} text
 */

var Notcl = (() => {
  const { AtLeast, Choose, End, Map, Regex, Sequence } = Peg;

  const InterCommandWhitespace = Regex(/\s+/y);

  const Comment = Regex(/#.*\n/y);

  const PreCommand = AtLeast(0, Choose(InterCommandWhitespace, Comment));

  const PreWordWhitespace = Regex(/[^\S\n;]*/y);

  const BasicWord = Map(Regex(/[^\s;]+/y), ([word]) => ({
    text: word,
  }));

  // WIP, need to be able to escape braces correctly
  // WIP, error if anything after closing brace

  const BracePattern = Map(
    Sequence(
      Regex(/\{/y),
      AtLeast(
        0,
        Choose(
          Map(Brace, (text) => `{${text}}`),
          Map(Regex(/[^{}]+/y), ([text]) => text)
        )
      ),
      Regex(/\}/y)
    ),
    ([_left, fragments, _right]) => fragments.join("")
  );
  /**
   * @type {Peg.Pattern<string>}
   */
  function Brace(source, index) {
    // Thunk to allow Brace to recurse
    return BracePattern(source, index);
  }

  const Word = Map(
    Sequence(
      PreWordWhitespace,
      Choose(
        Map(BracePattern, (text) => ({
          text,
        })),
        BasicWord
      )
    ),
    ([_, word]) => word
  );

  const CommandTerminator = Sequence(
    PreWordWhitespace,
    Choose(/** @type {Peg.Pattern<unknown>} */ (Regex(/[\n;]/y)), End)
  );

  const Command = Map(
    Sequence(PreCommand, AtLeast(0, Word), CommandTerminator),
    ([_padding, words, _end]) => words
  );

  return {
    /**
     * Parse out a Notcl script into an easier-to-interpret representation.
     * No script is actually executed yet.
     *
     * @param {string} code
     * @returns Script
     */
    parse(code) {
      /* Preprocess */
      // fold line endings
      code = code.replace(/(?<!\\)((\\\\)*)\\\n/g, "$1");

      function nextCommand() {
        const [words, nextIndex] = Command(code, 0) ?? [[], 0];
        code = code.substring(nextIndex);
        return words;
      }

      /* Loop through commands, with safety check */
      const script = /** @type {Notcl.Command[]} */ ([]);
      for (let i = 0; i < 1000 && code != ""; i++) {
        script.push(nextCommand());
      }

      return script;
    },
  };
})();