/**

 		* Number of leading context "lines" to preserve.

 		*

 		* This should be left at zero for this class, but subclasses may want to

 		* set this to other values.

 		*/

		var $_leading_context_lines = 0;

		/**

 		* Number of trailing context "lines" to preserve.

 		*

 		* This should be left at zero for this class, but subclasses may want to

 		* set this to other values.

 		*/

		var $_trailing_context_lines = 0;

		/**

 		* Constructor.

 		*/

		function Text_Diff_Renderer($params = array())

		{

				foreach ($params as $param => $value) {

						$v = '_' . $param;

						if (isset($this->$v)) {

								$this->$v = $value;

						}

				}

		}

		/**

 		* Get any renderer parameters.

 		*

 		* @return array  All parameters of this renderer object.

 		*/

		function getParams()

		{

				$params = array();

				foreach (get_object_vars($this) as $k => $v) {

						if ($k[0] == '_') {

								$params[substr($k, 1)] = $v;

						}

				}

				return $params;

		}

		/**

 		* Renders a diff.

 		*

 		* @param Text_Diff $diff  A Text_Diff object.

 		*

 		* @return string  The formatted output.

 		*/

		function render($diff)

		{

				$xi = $yi = 1;

				$block = false;

				$context = array();

				$nlead = $this->_leading_context_lines;

				$ntrail = $this->_trailing_context_lines;

				$output = $this->_startDiff();

				$diffs = $diff->getDiff();

				foreach ($diffs as $i => $edit) {

						if (is_a($edit, 'Text_Diff_Op_copy')) {

								if (is_array($block)) {

										$keep = $i == count($diffs) - 1 ? $ntrail : $nlead + $ntrail;

										if (count($edit->orig) <= $keep) {

												$block[] = $edit;

										} else {

												if ($ntrail) {

														$context = array_slice($edit->orig, 0, $ntrail);

														$block[] = &new Text_Diff_Op_copy($context);

												}

												$output .= $this->_block($x0, $ntrail + $xi - $x0,

 																								$y0, $ntrail + $yi - $y0,

 																								$block);

												$block = false;

										}

								}

								$context = $edit->orig;

						} else {

								if (!is_array($block)) {

										$context = array_slice($context, count($context) - $nlead);

										$x0 = $xi - count($context);

										$y0 = $yi - count($context);

										$block = array();

										if ($context) {

												$block[] = &new Text_Diff_Op_copy($context);

										}

								}

								$block[] = $edit;

						}

						if ($edit->orig) {

								$xi += count($edit->orig);

						}

						if ($edit->final) {

								$yi += count($edit->final);

						}

				}

				if (is_array($block)) {

						$output .= $this->_block($x0, $xi - $x0,

 																		$y0, $yi - $y0,

 																		$block);

				}

				return $output . $this->_endDiff();

		}

		function _block($xbeg, $xlen, $ybeg, $ylen, &$edits)

		{

				$output = $this->_startBlock($this->_blockHeader($xbeg, $xlen, $ybeg, $ylen));

				foreach ($edits as $edit) {

						switch (strtolower(get_class($edit))) {

						case 'text_diff_op_copy':

								$output .= $this->_context($edit->orig);

								break;

						case 'text_diff_op_add':

								$output .= $this->_added($edit->final);

								break;

						case 'text_diff_op_delete':

								$output .= $this->_deleted($edit->orig);

								break;

						case 'text_diff_op_change':

								$output .= $this->_changed($edit->orig, $edit->final);

								break;

						}

				}

				return $output . $this->_endBlock();

		}

		function _startDiff()

		{

				return '';

		}

		function _endDiff()

		{

				return '';

		}

		function _blockHeader($xbeg, $xlen, $ybeg, $ylen)

		{

				if ($xlen > 1) {

						$xbeg .= ',' . ($xbeg + $xlen - 1);

				}

				if ($ylen > 1) {

						$ybeg .= ',' . ($ybeg + $ylen - 1);

				}

				return $xbeg . ($xlen ? ($ylen ? 'c' : 'd') : 'a') . $ybeg;

		}

		function _startBlock($header)

		{

				return $header . "\n";

		}

		function _endBlock()

		{

				return '';

		}

		function _lines($lines, $prefix = ' ')

		{

				return $prefix . implode("\n$prefix", $lines) . "\n";

		}

		function _context($lines)

		{

				return $this->_lines($lines);

		}

		function _added($lines)

		{

				return $this->_lines($lines, '>');

		}

		function _deleted($lines)

		{

				return $this->_lines($lines, '<');

		}

		function _changed($orig, $final)

		{

				return $this->_deleted($orig) . "---\n" . $this->_added($final);

		}