<?php

abstract class PhabricatorCustomFieldMonogramParser
  extends Phobject {

  abstract protected function getPrefixes();
  abstract protected function getSuffixes();
  abstract protected function getInfixes();
  abstract protected function getMonogramPattern();

  public function parseCorpus($corpus) {
    $prefixes = $this->getPrefixes();
    $suffixes = $this->getSuffixes();
    $infixes = $this->getInfixes();

    $prefix_regex = $this->buildRegex($prefixes);
    $infix_regex = $this->buildRegex($infixes, true);
    $suffix_regex = $this->buildRegex($suffixes, true, true);

    $monogram_pattern = $this->getMonogramPattern();

    $pattern =
      '/'.
      '(?:^|\b)'.
      $prefix_regex.
      $infix_regex.
      '((?:'.$monogram_pattern.'[,\s]*)+)'.
      $suffix_regex.
      '(?:$|\b)'.
      '/';

    $matches = null;
    $ok = preg_match_all(
      $pattern,
      $corpus,
      $matches,
      PREG_SET_ORDER | PREG_OFFSET_CAPTURE);

    if ($ok === false) {
      throw new Exception(pht('Regular expression "%s" is invalid!', $pattern));
    }

    $results = array();
    foreach ($matches as $set) {
      $results[] = array(
        'match' => $set[0][0],
        'prefix' => $set[1][0],
        'infix' => $set[2][0],
        'monograms' => array_filter(preg_split('/[,\s]+/', $set[3][0])),
        'suffix' => idx(idx($set, 4, array()), 0, ''),
        'offset' => $set[0][1],
      );
    }

    return $results;
  }

  private function buildRegex(array $list, $optional = false, $final = false) {
    $parts = array();
    foreach ($list as $string) {
      $parts[] = preg_quote($string, '/');
    }
    $parts = implode('|', $parts);

    $maybe_tail = $final ? '' : '\s+';
    $maybe_optional = $optional ? '?' : '';

    return '(?i:('.$parts.')'.$maybe_tail.')'.$maybe_optional;
  }

}