Frankenstein - TypeScript Preprocessor

frankenstein.php

<?php

function parse($file)
{
  $result_stack = [];
  $tokens = token_get_all("<?php " . file_get_contents($file));
  for ($i = 0, $l = sizeof($tokens); $i < $l; $i++) {

    // T_OPEN
    if (is_open($tokens[$i])) {
      // Expect whitespace
      if (token_at(T_WHITESPACE, ++$i, $tokens)) {
        // Expect simple string
        if (token_at(T_CONSTANT_ENCAPSED_STRING, ++$i, $tokens)) {
          $reference = codegen_open(token_val($tokens[$i]));
          // Expect semicolon
          if (token_at(";", ++$i, $tokens)) {
            $result_stack[] = $reference;
          } else {
            throw new Exception("Expecting semicolon in `open`.");
          }
        } else {
          throw new Exception("Excepting filename in `open`.");
        }
      } else {
        throw new Exception("Expecting whitespace after `open`.");
      }

    // T_LAMBDA
    } elseif (is_lambda($tokens[$i])) {
      $result_stack[] = codegen_lambda();
    // T_LET
    } elseif (is_let($tokens[$i])) {
      $result_stack[] = codegen_let();
    // T_THIS
    } elseif (is_this($tokens[$i])) {
      $result_stack[] = codegen_this();
    // T_TYPESIG
    } elseif (is_typesig($tokens[$i])) {
      $result_stack[] = codegen_typesig();
    } else {
      $result_stack[] = $tokens[$i];
    }
  }

  echo translate_to_source($result_stack);
}

parse($argv[1]);

function codegen_typesig()
{
  return make_token(":");
}

function codegen_this()
{
  return make_token("this.");
}

function codegen_let()
{
  return make_token("var");
}

function codegen_lambda()
{
  return make_token("() =>");
}

function codegen_open($filename)
{
  return make_token("/// <reference path={$filename} />",
    T_CONSTANT_ENCAPSED_STRING);
}

function token_at($token, $pos, &$stack)
{
  return is_string($stack[$pos])
    ? $stack[$pos] === $token
    : $stack[$pos][0] === $token;
}

function is_typesig($combinator)
{
  return $combinator[0] === T_PAAMAYIM_NEKUDOTAYIM && $combinator[1] === "::";
}

function is_this($combinator)
{
  return $combinator === "@";
}

function is_open($combinator)
{
  return $combinator[0] === T_STRING && $combinator[1] === "open";
}

function is_let($combinator)
{
  return $combinator[0] === T_STRING && $combinator[1] === "let";
}

function is_lambda($combinator)
{
  return $combinator[0] === T_STRING && $combinator[1] === "λ";
}

function make_token($value, $key = null)
{
  return isset($key)
    ? [$key, $value, 1]
    : $value; // Literal
}

function token_val($token)
{
  return is_string($token)
    ? $token
    : $token[1];
}

function translate_to_source($stack)
{
  $source = [];
  for ($i = 1, $l = sizeof($stack); $i < $l; $i++) {
    if (is_string($stack[$i])) {
      $source[] = $stack[$i];
    } else {
      $source[] = $stack[$i][1];
    }
  }

  return implode("", $source);
}