<?php

/*

 * Copyright 2011 Nathan Gelderloos, Ethan Zonca, Nathan Phillip Brink

 *

 * This file is part of SlatePermutate.

 *

 * SlatePermutate is free software: you can redistribute it and/or modify

 * it under the terms of the GNU Affero General Public License as published by

 * the Free Software Foundation, either version 3 of the License, or

 * (at your option) any later version.

 *

 * SlatePermutate is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 * GNU Affero General Public License for more details.

 *

 * You should have received a copy of the GNU Affero General Public License

 * along with SlatePermutate.  If not, see <http://www.gnu.org/licenses/>.

 */

/**

 * \file

 * \brief

 *   Crawler implementation for Cedarville University.

 */

/**

 * \brief

 *   Parse given html into an array, first row is row headers.

 *

 * \param $html

 *   HTML that PHP's DOM would willingly would eat.

 */

function table_parse($html)

{

  libxml_use_internal_errors(true); // Suppress warnings

  $arr = array();

  $dom = new DOMDocument;

  if(!$html)

    return NULL;

  $dom->loadHTML($html);

  $dom->preserveWhiteSpace = FALSE;

  $tables = $dom->getElementsByTagName('table');

  $rows = $tables->item(0)->getElementsByTagName('tr'); // Get first table on page 

  foreach ($rows as $rownum => $row) {

    $cols = $row->getElementsByTagName('td');

    foreach($cols as $colnum => $col){

      $arr[$rownum][$colnum] = $col->nodeValue;

    }

  }

  return $arr;

}

/** Crawls Cedarville course listings. $season is "fa" or "sp", year is 4-digit year */

function cedarville_crawl($semester, $verbosity = 1)

{  

  $season = strtolower(substr($semester->season_get(), 0, 2));

  $year = $semester->year_get();

  $season_string = $year . $season;

  $basepath = 'http://cedarville.edu/courses/schedule/';

  if ($verbosity)

    echo "cedarville_crawl(): Beginning crawl of Cedarville:\n";

  if ($verbosity > 1)

    echo "cedarville_crawl(): Determining list of departments.\n";

  /*

   * We need two passes because the first department's code name is

   * not accessible available in the first pageload.

   */

  $departments = array();

  if (cedarville_crawl_departments_get($basepath . $year . $season . '_index.htm', $departments, $season_string))

    return 1;

  if (!count($departments))

    {

      echo "cedarville_crawl(): Unable to get a listing of departments.\n";

      return 1;

    }

  /* find the first department whose name we don't yet know */

  if (cedarville_crawl_departments_get($basepath . $year . $season . '_' . current(array_keys($departments)) . '_all.htm', $departments, $season_string))

    return 1;

  $tables = array();

  foreach ($departments as $department => $dept_name)

    {

      echo 'cedarville_crawl(): Crawling department ' . $department . ' (' . $dept_name . ")...\n";

      $html = file_get_contents($basepath . $year . $season . '_' . $department . '_' . 'all.htm');

      if (!$html)

	continue;

      $tables[$department] = table_parse(cedarville_html_fix($html));

    }

  $meeting_type_maps = array('LAB' => 'lab', 'LECT' => 'lecture');

  foreach ($tables as $dept_table)

    {

      /*

       * Discard the first row, which has the contents of the <th />

       * elements.

       */

      unset($dept_table[0]);

      foreach($dept_table as $course_table)

	{

	  /*

	   * format:

	   * 0: course synonym, an unsigned integer.

	   * 1: section spec, parsable by Section::parse().

	   * 2: friendly course title.

	   * 3: Instructor name.

	   * 4: Number of credit hours in decimal notation.

	   * 5: Fee.

	   * 6: Meeting time, explained below.

	   * 7: Cap.

	   * 8-10: Textbook link. Most rows only have column 8, not

	   *       all the way through 10. This information seems

	   *       quite useless.

	   *

	   * Section meeting time/place format:

	   *

	   * Confusing example: ' ILB  WI219   TR    08:30A-09:45A'

	   * Complete example plus lab: ' LEC  TYL203  MWF   08:00A-08:50A LAB  ENS118  TR    03:00P-04:30P'

	   *

	   * Appears to have format:

	   * <meeting_info>: <type> <room> <days> <time_start>-<time_end> <meeting_info>

	   *

	   * It appears tht <type> may be:

	   * LEC: normal lecture meeting.

	   * ONL: online course.

	   * ILB: ethan says a partially online course...?

	   * HYB: hybrid of...?

	   * FLD: field...?

	   * FE2: ?

	   * CLN: ?

	   * LAB: Lab

	   * LES: something for some PFMU/PLMU class?

	   */

	  $synonym = $course_table[0];

	  $section_parts = Section::parse($course_table[1]);

	  if (count($section_parts) < 3)

	    {

	      error_log('Error parsing section_id. Given `' . $course_table[1] . '\', interpreted as `'

			. implode('-', $section_parts) . '\'. Skipping.');

	      continue;

	    }

	  $instructor = $course_table[3];

	  /*

	   * Each course may have multiple meeting times associated

	   * with it at Cedarville. We are not sure how to handle this

	   * quite, because different class sections may be tied with

	   * different lab meetings and stuff...

	   */

	  $meetings_str = $course_table[6];

	  if (strpos($meetings_str, 'TBA') !== FALSE)

	    {

	      if ($verbosity > 1)

		error_log('Skipping ' . implode('-', $section_parts) . ' because its meeting time info has `TBA\' in it.');

	      continue;

	    }

	  $meetings = array();

	  $meeting_multiple_types = array();

	  while (strlen($meetings_str) > 5)

	    {

	      if (!preg_match(';^ ([A-Z]+) +([A-Z]+[A-Z0-9]*) +([MTWRF]{1,5}) +([0-9:AP]+)-([0-9:AP]+);',

			      $meetings_str, $meeting_matches))

		{

		  if (preg_match(';^Dates:[^0-9]+([/0-9]{8})-([/0-9]{8});',

				 $meetings_str, $meeting_matches))

		    {

		      if ($verbosity > 4)

			error_log('Skipping some meeting data for '

				  . implode('-', $section_parts) . ' because it is a date range: `'

				  . $meeting_matches[0] . '\'');

		      $meetings_str = substr($meetings_str, strlen($meeting_matches[0]));

		      continue;

		    }

		  if ($verbosity > 0)

		    error_log('Error parsing meeting time. Given `' . $meetings_str . '\'. Skipping '

			      . implode('-', $section_parts));

		  break;

		}

	      /* prepare for parsing the next meeting time */

	      $meetings_str = substr($meetings_str, strlen($meeting_matches[0]));

	      $days = school_crawl_days_str_format($meeting_matches[3]);

	      $time_start = school_crawl_time_format(strptime($meeting_matches[4] . 'M', '%I:%M%p'));

	      $time_end = school_crawl_time_format(strptime($meeting_matches[5] . 'M', '%I:%M%p'));

	      $room = $meeting_matches[2];

	      $type = $meeting_matches[1];

	      while (isset($meeting_type_maps[$type]))

		$type = $meeting_type_maps[$type];

	      $type = strtolower($type);

	      $meetings[] = new SectionMeeting($days, $time_start, $time_end,

					       $room, $type);

	    }

	  $semester->section_add($section_parts['department'], $section_parts['course'],

				 new Section($section_parts['section'], $meetings,

					     $synonym, $instructor));

	}

    }

  return 0;

}

/**

 * \brief

 *   Scan cedarville's course listing pages for departments.

 *

 * \return

 *   An associative array mapping department codes onto department

 *   friendly names.

 */

function cedarville_crawl_departments_get($dept_url, array &$departments, $season_string)

{

  $html = file_get_contents($dept_url);

  $dept_dom = new DOMDocument();

  if (!$dept_dom->loadHTML(cedarville_html_fix($html)))

    {

      echo "cedarville_crawl(): Error determining list of available departments: Unable to parse HTML.\n";

      return 1;

    }

  $xpath = new DOMXPath($dept_dom);

  $dept_node_list = $xpath->query('/descendant::div[@id="contenttext"]/child::span[position()=1 or position()=2]/child::a');

  foreach ($dept_node_list as $dept_node)

    {

      $href = $dept_node->getAttribute('href');

      if (!preg_match('/^' . preg_quote($season_string, '/') . '_([a-z]+)_[a-z]+\.htm$/', $href, $matches))

	{

	  echo 'cedarvillege_crawl(): Error determining list of available departments: Unable to parse the department string out of href="' . $href . "\".\n";

	  return 1;

	}

      $dept = $matches[1];

      $departments[$dept] = $dept_node->textContent;

    }

  return 0;

}

/**

 * \brief

 *   Fix some incorrect usage of the HTML entity delimiter, the ampersand.

 */

function cedarville_html_fix($html)

{

  $html = preg_replace('/&&/', '&&', $html);

  $html = preg_replace('/&([^;]{5})/', '&$1', $html);

  $html = preg_replace('/ID="(LINKS|HERE)"/', '', $html);

  return $html;

}