<?php
  
  /**
   * The code has been taken from hashbangcode.
   * 
   * On @license http://www.hashbangcode.com/about it says: "All of the code
   * placed onto this site has been tested to the best of our ability and
   * resources so it should work out of the box. If you spot any problems then
   * please let us know! You should be aware the all the code here is "use at
   * your own risk" and we can't take any responsibility for loss of data or
   * server downtime as a result of the code on this site." which is as close to
   * a license as it gets. :(
   * 
   * @author philipnorton42: @link http://www.hashbangcode.com/users/philipnorton42 
   * 
   * @link https://github.com/philipnorton42/PDFSearch
   * @link http://www.hashbangcode.com/blog/zend-lucene-and-pdf-documents-part-2-pdf-data-extraction-437.html  
   */
  class App_Search_Helper_PdfParser {
  
  	/**
  	 * Convert a PDF into text.
  	 *
  	 * @param string $data The pdf content.
  	 * @return string The extracted text from the PDF
  	 */
  	public function pdf2txt($data) {
  		/**
  		 * Split apart the PDF document into sections. We will address each
  		 * section separately.
  		 */
  		$a_obj = $this->getDataArray($data, "obj", "endobj");
  		$j = 0;
  
  		/**
  		 * Attempt to extract each part of the PDF document into a "filter"
  		 * element and a "data" element. This can then be used to decode the
  		 * data.
  		 */
  		foreach ($a_obj as $obj) {
  			$a_filter = $this->getDataArray($obj, "<<", ">>");
  			if (is_array($a_filter) && isset($a_filter[0])) {
  				$a_chunks[$j]["filter"] = $a_filter[0];
  				$a_data = $this->getDataArray($obj, "stream", "endstream");
  				if (is_array($a_data) && isset($a_data[0])) {
  					$a_chunks[$j]["data"] = trim(substr($a_data[0], strlen("stream"), strlen($a_data[0]) - strlen("stream") - strlen("endstream")));
  				}
  				$j++;
  			}
  		}
  
  		$result_data = NULL;
  
  		// decode the chunks
  		foreach ($a_chunks as $chunk) {
  			// Look at each chunk decide if we can decode it by looking at the contents of the filter
  			if (isset($chunk["data"])) {
  				// look at the filter to find out which encoding has been used
  				if (strpos($chunk["filter"], "FlateDecode") !== false) {
  					// Use gzuncompress but supress error messages.
  					$data = @ gzuncompress($chunk["data"]);
  					if (trim($data) != "") {
  						// If we got data then attempt to extract it.
  						$result_data .= ' ' . $this->ps2txt($data);
  					}
  				}
  			}
  		}
  		/**
  		 * Make sure we don't have large blocks of white space before and after
  		 * our string. Also extract alphanumerical information to reduce
  		 * redundant data.
  		 */
  		$result_data = trim(preg_replace('/([^a-z0-9 ])/i', ' ', $result_data));
  
  		// Return the data extracted from the document.
  		if ($result_data == "") {
  			return NULL;
  		} else {
  			return $result_data;
  		}
  	}
  
  	/**
  	 * Convert a small chunk of data into text.
  	 *
  	 * @param string $ps_data The chunk of data to convert.
  	 * @return string The string extracted from the data.
  	 */
  	public function ps2txt($ps_data) {
  		// Stop this function returning bogus information from non-data string.
  		if (ord($ps_data[0]) < 10) {
  			return $ps_data;
  		}
  		if (substr($ps_data, 0, 8) == '/CIDInit') {
  			return '';
  		}
  
  		$result = "";
  
  		$a_data = $this->getDataArray($ps_data, "[", "]");
  
  		// Extract the data.
  		if (is_array($a_data)) {
  			foreach ($a_data as $ps_text) {
  				$a_text = $this->getDataArray($ps_text, "(", ")");
  				if (is_array($a_text)) {
  					foreach ($a_text as $text) {
  						$result .= substr($text, 1, strlen($text) - 2);
  					}
  				}
  			}
  		}
  
  		// Didn't catch anything, try a different way of extracting the data
  		if (trim($result) == "") {
  			// the data may just be in raw format (outside of [] tags)
  			$a_text = $this->getDataArray($ps_data, "(", ")");
  			if (is_array($a_text)) {
  				foreach ($a_text as $text) {
  					$result .= substr($text, 1, strlen($text) - 2);
  				}
  			}
  		}
  
  		// Remove any stray characters left over.
  		$result = preg_replace('/\b([^a|i])\b/i', ' ', $result);
  		return trim($result);
  	}
  
  	/**
  	 * Convert a section of data into an array, separated by the start and end words.
  	 *
  	 * @param string $data The data.
  	 * @param string $start_word The start of each section of data.
  	 * @param string $end_word The end of each section of data.
  	 * @return array The array of data.
  	 */
  	public function getDataArray($data, $start_word, $end_word) {
  		$start = 0;
  		$end = 0;
  		$a_result = array();
  
  		while ($start !== false && $end !== false) {
  			$start = strpos($data, $start_word, $end);
  			$end = strpos($data, $end_word, $start);
  			if ($end !== false && $start !== false) {
  				// data is between start and end
  				$a_result[] = substr($data, $start, $end - $start + strlen($end_word));
  			}
  		}
  
  		return $a_result;
  	}
  
  }