/*global, print: true, printjson: true, txtdiff: true, txtHtmlToPlain: true*/
'use strict';

var log4js = require('log4js'),
	mongoose = require('mongoose'),
	logger;

module.exports.loadController = function (app, db) {
	logger = log4js.getLogger("systemjs.js");

	saveSystemJSFunc(function pastvuPatch() {
		var startTime = Date.now(),
			collection = db.comments;

		//Генерируем разницу для всех комментариев, которые уже имеют историю изменения текста
		print('Generate history text diffs for ' + collection.count({hist: {$exists: true}}) + ' photo comments');
		collection.find({hist: {$exists: true}}, {_id: 0, cid: 1, txt: 1, hist: 1}).forEach(handler);
		collection = db.commentsn;
		print('Generate history text diffs for ' + collection.count({hist: {$exists: true}}) + ' news comments');
		collection.find({hist: {$exists: true}}, {_id: 0, cid: 1, txt: 1, hist: 1}).forEach(handler);

		function handler(comment) {
			var txtfuture,
				txtcurrent,
				txtexist,
				h,
				i;

			if (comment.hist && comment.hist.length) {
				txtfuture = txtHtmlToPlain(comment.txt);

				for (i = comment.hist.length; i--;) {
					h = comment.hist[i];
					if (h.txt) {
						txtcurrent = txtHtmlToPlain(h.txt);
						h.txtd = txtdiff(txtcurrent, txtfuture);
						txtfuture = txtcurrent;
						txtexist = true;
					}
				}
				if (txtexist) {
					collection.update({cid: comment.cid}, {$set: {hist: comment.hist}});
				}
			}
		}

		return {message: 'FINISH in total ' + (Date.now() - startTime) / 1000 + 's'};
	});
	saveSystemJSFunc(function txtHtmlToPlain(txt) {
		var escapeChars = {
				lt: '<',
				gt: '>',
				quot: '"',
				amp: '&',
				apos: "'"
			},
			result = txt;

		result = result.replace(/<br\s*[\/]?>/gi, '\n'); //Заменяем <br> на \n
		result = stripTags(result); //Убираем обрамляющие тэги ahref
		result = unescapeHTML(result); //Возвращаем эскейпленные

		function stripTags(str) {
			if (str == null) {
				return '';
			}
			return String(str).replace(/<\/?[^>]+>/g, '');
		}

		function unescapeHTML(str) {
			if (str == null) {
				return '';
			}
			return String(str).replace(/\&([^;]+);/g, function (entity, entityCode) {
				var match;

				if (entityCode in escapeChars) {
					return escapeChars[entityCode];
				} else if (match = entityCode.match(/^#x([\da-fA-F]+)$/)) {
					return String.fromCharCode(parseInt(match[1], 16));
				} else if (match = entityCode.match(/^#(\d+)$/)) {
					return String.fromCharCode(~~match[1]);
				} else {
					return entity;
				}
			});
		}

		return result;
	});
	saveSystemJSFunc(function txtdiff(text1, text2) {
		var escapeChars = {
				lt: '<',
				gt: '>',
				quot: '"',
				amp: '&',
				apos: "'"
			},
			reversedEscapeChars = {},
			result = '',
			pattern_para = /\n/g,
			dmpconst = DMP(),
			dmp = new dmpconst.diff_match_patch(),
			diffs,
			operationType,
			text;

		for (var key in escapeChars) {
			reversedEscapeChars[escapeChars[key]] = key;
		}
		reversedEscapeChars["'"] = '#39';

		diffs = dmp.diff_main(text1, text2);
		dmp.diff_cleanupSemantic(diffs);

		for (var x = 0; x < diffs.length; x++) {
			operationType = diffs[x][0];    // Operation (insert, delete, equal)
			text = escapeHTML(diffs[x][1]).replace(pattern_para, '&para;<br>');
			switch (operationType) {
				case 1:
					result += '<span class="diffIns">' + text + '</span>';
					break;
				case -1:
					result += '<span class="diffDel">' + text + '</span>';
					break;
				default:
					result += '<span class="diffEq">' + text + '</span>';
			}
		}

		function escapeHTML(str) {
			if (str == null) {
				return '';
			}
			return String(str).replace(/[&<>"']/g, function (m) {
				return '&' + reversedEscapeChars[m] + ';';
			});
		}

		return result;
	});
	saveSystemJSFunc(function DMP() {
		function diff_match_patch() {

			// Defaults.
			// Redefine these in your program to override the defaults.

			// Number of seconds to map a diff before giving up (0 for infinity).
			this.Diff_Timeout = 1.0;
			// Cost of an empty edit operation in terms of edit characters.
			this.Diff_EditCost = 4;
			// At what point is no match declared (0.0 = perfection, 1.0 = very loose).
			this.Match_Threshold = 0.5;
			// How far to search for a match (0 = exact location, 1000+ = broad match).
			// A match this many characters away from the expected location will add
			// 1.0 to the score (0.0 is a perfect match).
			this.Match_Distance = 1000;
			// When deleting a large block of text (over ~64 characters), how close do
			// the contents have to be to match the expected contents. (0.0 = perfection,
			// 1.0 = very loose).  Note that Match_Threshold controls how closely the
			// end points of a delete need to match.
			this.Patch_DeleteThreshold = 0.5;
			// Chunk size for context length.
			this.Patch_Margin = 4;

			// The number of bits in an int.
			this.Match_MaxBits = 32;
		}


//  DIFF FUNCTIONS


		/**
		 * The data structure representing a diff is an array of tuples:
		 * [[DIFF_DELETE, 'Hello'], [DIFF_INSERT, 'Goodbye'], [DIFF_EQUAL, ' world.']]
		 * which means: delete 'Hello', add 'Goodbye' and keep ' world.'
		 */
		var DIFF_DELETE = -1;
		var DIFF_INSERT = 1;
		var DIFF_EQUAL = 0;

		/** @typedef {{0: number, 1: string}} */
		diff_match_patch.Diff;


		/**
		 * Find the differences between two texts.  Simplifies the problem by stripping
		 * any common prefix or suffix off the texts before diffing.
		 * @param {string} text1 Old string to be diffed.
		 * @param {string} text2 New string to be diffed.
		 * @param {boolean=} opt_checklines Optional speedup flag. If present and false,
		 *     then don't run a line-level diff first to identify the changed areas.
		 *     Defaults to true, which does a faster, slightly less optimal diff.
		 * @param {number} opt_deadline Optional time when the diff should be complete
		 *     by.  Used internally for recursive calls.  Users should set DiffTimeout
		 *     instead.
		 * @return {!Array.<!diff_match_patch.Diff>} Array of diff tuples.
		 */
		diff_match_patch.prototype.diff_main = function(text1, text2, opt_checklines,
														opt_deadline) {
			// Set a deadline by which time the diff must be complete.
			if (typeof opt_deadline == 'undefined') {
				if (this.Diff_Timeout <= 0) {
					opt_deadline = Number.MAX_VALUE;
				} else {
					opt_deadline = (new Date).getTime() + this.Diff_Timeout * 1000;
				}
			}
			var deadline = opt_deadline;

			// Check for null inputs.
			if (text1 == null || text2 == null) {
				throw new Error('Null input. (diff_main)');
			}

			// Check for equality (speedup).
			if (text1 == text2) {
				if (text1) {
					return [[DIFF_EQUAL, text1]];
				}
				return [];
			}

			if (typeof opt_checklines == 'undefined') {
				opt_checklines = true;
			}
			var checklines = opt_checklines;

			// Trim off common prefix (speedup).
			var commonlength = this.diff_commonPrefix(text1, text2);
			var commonprefix = text1.substring(0, commonlength);
			text1 = text1.substring(commonlength);
			text2 = text2.substring(commonlength);

			// Trim off common suffix (speedup).
			commonlength = this.diff_commonSuffix(text1, text2);
			var commonsuffix = text1.substring(text1.length - commonlength);
			text1 = text1.substring(0, text1.length - commonlength);
			text2 = text2.substring(0, text2.length - commonlength);

			// Compute the diff on the middle block.
			var diffs = this.diff_compute_(text1, text2, checklines, deadline);

			// Restore the prefix and suffix.
			if (commonprefix) {
				diffs.unshift([DIFF_EQUAL, commonprefix]);
			}
			if (commonsuffix) {
				diffs.push([DIFF_EQUAL, commonsuffix]);
			}
			this.diff_cleanupMerge(diffs);
			return diffs;
		};


		/**
		 * Find the differences between two texts.  Assumes that the texts do not
		 * have any common prefix or suffix.
		 * @param {string} text1 Old string to be diffed.
		 * @param {string} text2 New string to be diffed.
		 * @param {boolean} checklines Speedup flag.  If false, then don't run a
		 *     line-level diff first to identify the changed areas.
		 *     If true, then run a faster, slightly less optimal diff.
		 * @param {number} deadline Time when the diff should be complete by.
		 * @return {!Array.<!diff_match_patch.Diff>} Array of diff tuples.
		 * @private
		 */
		diff_match_patch.prototype.diff_compute_ = function(text1, text2, checklines,
															deadline) {
			var diffs;

			if (!text1) {
				// Just add some text (speedup).
				return [[DIFF_INSERT, text2]];
			}

			if (!text2) {
				// Just delete some text (speedup).
				return [[DIFF_DELETE, text1]];
			}

			var longtext = text1.length > text2.length ? text1 : text2;
			var shorttext = text1.length > text2.length ? text2 : text1;
			var i = longtext.indexOf(shorttext);
			if (i != -1) {
				// Shorter text is inside the longer text (speedup).
				diffs = [[DIFF_INSERT, longtext.substring(0, i)],
					[DIFF_EQUAL, shorttext],
					[DIFF_INSERT, longtext.substring(i + shorttext.length)]];
				// Swap insertions for deletions if diff is reversed.
				if (text1.length > text2.length) {
					diffs[0][0] = diffs[2][0] = DIFF_DELETE;
				}
				return diffs;
			}

			if (shorttext.length == 1) {
				// Single character string.
				// After the previous speedup, the character can't be an equality.
				return [[DIFF_DELETE, text1], [DIFF_INSERT, text2]];
			}

			// Check to see if the problem can be split in two.
			var hm = this.diff_halfMatch_(text1, text2);
			if (hm) {
				// A half-match was found, sort out the return data.
				var text1_a = hm[0];
				var text1_b = hm[1];
				var text2_a = hm[2];
				var text2_b = hm[3];
				var mid_common = hm[4];
				// Send both pairs off for separate processing.
				var diffs_a = this.diff_main(text1_a, text2_a, checklines, deadline);
				var diffs_b = this.diff_main(text1_b, text2_b, checklines, deadline);
				// Merge the results.
				return diffs_a.concat([[DIFF_EQUAL, mid_common]], diffs_b);
			}

			if (checklines && text1.length > 100 && text2.length > 100) {
				return this.diff_lineMode_(text1, text2, deadline);
			}

			return this.diff_bisect_(text1, text2, deadline);
		};


		/**
		 * Do a quick line-level diff on both strings, then rediff the parts for
		 * greater accuracy.
		 * This speedup can produce non-minimal diffs.
		 * @param {string} text1 Old string to be diffed.
		 * @param {string} text2 New string to be diffed.
		 * @param {number} deadline Time when the diff should be complete by.
		 * @return {!Array.<!diff_match_patch.Diff>} Array of diff tuples.
		 * @private
		 */
		diff_match_patch.prototype.diff_lineMode_ = function(text1, text2, deadline) {
			// Scan the text on a line-by-line basis first.
			var a = this.diff_linesToChars_(text1, text2);
			text1 = a.chars1;
			text2 = a.chars2;
			var linearray = a.lineArray;

			var diffs = this.diff_main(text1, text2, false, deadline);

			// Convert the diff back to original text.
			this.diff_charsToLines_(diffs, linearray);
			// Eliminate freak matches (e.g. blank lines)
			this.diff_cleanupSemantic(diffs);

			// Rediff any replacement blocks, this time character-by-character.
			// Add a dummy entry at the end.
			diffs.push([DIFF_EQUAL, '']);
			var pointer = 0;
			var count_delete = 0;
			var count_insert = 0;
			var text_delete = '';
			var text_insert = '';
			while (pointer < diffs.length) {
				switch (diffs[pointer][0]) {
					case DIFF_INSERT:
						count_insert++;
						text_insert += diffs[pointer][1];
						break;
					case DIFF_DELETE:
						count_delete++;
						text_delete += diffs[pointer][1];
						break;
					case DIFF_EQUAL:
						// Upon reaching an equality, check for prior redundancies.
						if (count_delete >= 1 && count_insert >= 1) {
							// Delete the offending records and add the merged ones.
							diffs.splice(pointer - count_delete - count_insert,
									count_delete + count_insert);
							pointer = pointer - count_delete - count_insert;
							var a = this.diff_main(text_delete, text_insert, false, deadline);
							for (var j = a.length - 1; j >= 0; j--) {
								diffs.splice(pointer, 0, a[j]);
							}
							pointer = pointer + a.length;
						}
						count_insert = 0;
						count_delete = 0;
						text_delete = '';
						text_insert = '';
						break;
				}
				pointer++;
			}
			diffs.pop();  // Remove the dummy entry at the end.

			return diffs;
		};


		/**
		 * Find the 'middle snake' of a diff, split the problem in two
		 * and return the recursively constructed diff.
		 * See Myers 1986 paper: An O(ND) Difference Algorithm and Its Variations.
		 * @param {string} text1 Old string to be diffed.
		 * @param {string} text2 New string to be diffed.
		 * @param {number} deadline Time at which to bail if not yet complete.
		 * @return {!Array.<!diff_match_patch.Diff>} Array of diff tuples.
		 * @private
		 */
		diff_match_patch.prototype.diff_bisect_ = function(text1, text2, deadline) {
			// Cache the text lengths to prevent multiple calls.
			var text1_length = text1.length;
			var text2_length = text2.length;
			var max_d = Math.ceil((text1_length + text2_length) / 2);
			var v_offset = max_d;
			var v_length = 2 * max_d;
			var v1 = new Array(v_length);
			var v2 = new Array(v_length);
			// Setting all elements to -1 is faster in Chrome & Firefox than mixing
			// integers and undefined.
			for (var x = 0; x < v_length; x++) {
				v1[x] = -1;
				v2[x] = -1;
			}
			v1[v_offset + 1] = 0;
			v2[v_offset + 1] = 0;
			var delta = text1_length - text2_length;
			// If the total number of characters is odd, then the front path will collide
			// with the reverse path.
			var front = (delta % 2 != 0);
			// Offsets for start and end of k loop.
			// Prevents mapping of space beyond the grid.
			var k1start = 0;
			var k1end = 0;
			var k2start = 0;
			var k2end = 0;
			for (var d = 0; d < max_d; d++) {
				// Bail out if deadline is reached.
				if ((new Date()).getTime() > deadline) {
					break;
				}

				// Walk the front path one step.
				for (var k1 = -d + k1start; k1 <= d - k1end; k1 += 2) {
					var k1_offset = v_offset + k1;
					var x1;
					if (k1 == -d || (k1 != d && v1[k1_offset - 1] < v1[k1_offset + 1])) {
						x1 = v1[k1_offset + 1];
					} else {
						x1 = v1[k1_offset - 1] + 1;
					}
					var y1 = x1 - k1;
					while (x1 < text1_length && y1 < text2_length &&
						text1.charAt(x1) == text2.charAt(y1)) {
						x1++;
						y1++;
					}
					v1[k1_offset] = x1;
					if (x1 > text1_length) {
						// Ran off the right of the graph.
						k1end += 2;
					} else if (y1 > text2_length) {
						// Ran off the bottom of the graph.
						k1start += 2;
					} else if (front) {
						var k2_offset = v_offset + delta - k1;
						if (k2_offset >= 0 && k2_offset < v_length && v2[k2_offset] != -1) {
							// Mirror x2 onto top-left coordinate system.
							var x2 = text1_length - v2[k2_offset];
							if (x1 >= x2) {
								// Overlap detected.
								return this.diff_bisectSplit_(text1, text2, x1, y1, deadline);
							}
						}
					}
				}

				// Walk the reverse path one step.
				for (var k2 = -d + k2start; k2 <= d - k2end; k2 += 2) {
					var k2_offset = v_offset + k2;
					var x2;
					if (k2 == -d || (k2 != d && v2[k2_offset - 1] < v2[k2_offset + 1])) {
						x2 = v2[k2_offset + 1];
					} else {
						x2 = v2[k2_offset - 1] + 1;
					}
					var y2 = x2 - k2;
					while (x2 < text1_length && y2 < text2_length &&
						text1.charAt(text1_length - x2 - 1) ==
						text2.charAt(text2_length - y2 - 1)) {
						x2++;
						y2++;
					}
					v2[k2_offset] = x2;
					if (x2 > text1_length) {
						// Ran off the left of the graph.
						k2end += 2;
					} else if (y2 > text2_length) {
						// Ran off the top of the graph.
						k2start += 2;
					} else if (!front) {
						var k1_offset = v_offset + delta - k2;
						if (k1_offset >= 0 && k1_offset < v_length && v1[k1_offset] != -1) {
							var x1 = v1[k1_offset];
							var y1 = v_offset + x1 - k1_offset;
							// Mirror x2 onto top-left coordinate system.
							x2 = text1_length - x2;
							if (x1 >= x2) {
								// Overlap detected.
								return this.diff_bisectSplit_(text1, text2, x1, y1, deadline);
							}
						}
					}
				}
			}
			// Diff took too long and hit the deadline or
			// number of diffs equals number of characters, no commonality at all.
			return [[DIFF_DELETE, text1], [DIFF_INSERT, text2]];
		};


		/**
		 * Given the location of the 'middle snake', split the diff in two parts
		 * and recurse.
		 * @param {string} text1 Old string to be diffed.
		 * @param {string} text2 New string to be diffed.
		 * @param {number} x Index of split point in text1.
		 * @param {number} y Index of split point in text2.
		 * @param {number} deadline Time at which to bail if not yet complete.
		 * @return {!Array.<!diff_match_patch.Diff>} Array of diff tuples.
		 * @private
		 */
		diff_match_patch.prototype.diff_bisectSplit_ = function(text1, text2, x, y,
																deadline) {
			var text1a = text1.substring(0, x);
			var text2a = text2.substring(0, y);
			var text1b = text1.substring(x);
			var text2b = text2.substring(y);

			// Compute both diffs serially.
			var diffs = this.diff_main(text1a, text2a, false, deadline);
			var diffsb = this.diff_main(text1b, text2b, false, deadline);

			return diffs.concat(diffsb);
		};


		/**
		 * Split two texts into an array of strings.  Reduce the texts to a string of
		 * hashes where each Unicode character represents one line.
		 * @param {string} text1 First string.
		 * @param {string} text2 Second string.
		 * @return {{chars1: string, chars2: string, lineArray: !Array.<string>}}
		 *     An object containing the encoded text1, the encoded text2 and
		 *     the array of unique strings.
		 *     The zeroth element of the array of unique strings is intentionally blank.
		 * @private
		 */
		diff_match_patch.prototype.diff_linesToChars_ = function(text1, text2) {
			var lineArray = [];  // e.g. lineArray[4] == 'Hello\n'
			var lineHash = {};   // e.g. lineHash['Hello\n'] == 4

			// '\x00' is a valid character, but various debuggers don't like it.
			// So we'll insert a junk entry to avoid generating a null character.
			lineArray[0] = '';

			/**
			 * Split a text into an array of strings.  Reduce the texts to a string of
			 * hashes where each Unicode character represents one line.
			 * Modifies linearray and linehash through being a closure.
			 * @param {string} text String to encode.
			 * @return {string} Encoded string.
			 * @private
			 */
			function diff_linesToCharsMunge_(text) {
				var chars = '';
				// Walk the text, pulling out a substring for each line.
				// text.split('\n') would would temporarily double our memory footprint.
				// Modifying text would create many large strings to garbage collect.
				var lineStart = 0;
				var lineEnd = -1;
				// Keeping our own length variable is faster than looking it up.
				var lineArrayLength = lineArray.length;
				while (lineEnd < text.length - 1) {
					lineEnd = text.indexOf('\n', lineStart);
					if (lineEnd == -1) {
						lineEnd = text.length - 1;
					}
					var line = text.substring(lineStart, lineEnd + 1);
					lineStart = lineEnd + 1;

					if (lineHash.hasOwnProperty ? lineHash.hasOwnProperty(line) :
						(lineHash[line] !== undefined)) {
						chars += String.fromCharCode(lineHash[line]);
					} else {
						chars += String.fromCharCode(lineArrayLength);
						lineHash[line] = lineArrayLength;
						lineArray[lineArrayLength++] = line;
					}
				}
				return chars;
			}

			var chars1 = diff_linesToCharsMunge_(text1);
			var chars2 = diff_linesToCharsMunge_(text2);
			return {chars1: chars1, chars2: chars2, lineArray: lineArray};
		};


		/**
		 * Rehydrate the text in a diff from a string of line hashes to real lines of
		 * text.
		 * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
		 * @param {!Array.<string>} lineArray Array of unique strings.
		 * @private
		 */
		diff_match_patch.prototype.diff_charsToLines_ = function(diffs, lineArray) {
			for (var x = 0; x < diffs.length; x++) {
				var chars = diffs[x][1];
				var text = [];
				for (var y = 0; y < chars.length; y++) {
					text[y] = lineArray[chars.charCodeAt(y)];
				}
				diffs[x][1] = text.join('');
			}
		};


		/**
		 * Determine the common prefix of two strings.
		 * @param {string} text1 First string.
		 * @param {string} text2 Second string.
		 * @return {number} The number of characters common to the start of each
		 *     string.
		 */
		diff_match_patch.prototype.diff_commonPrefix = function(text1, text2) {
			// Quick check for common null cases.
			if (!text1 || !text2 || text1.charAt(0) != text2.charAt(0)) {
				return 0;
			}
			// Binary search.
			// Performance analysis: http://neil.fraser.name/news/2007/10/09/
			var pointermin = 0;
			var pointermax = Math.min(text1.length, text2.length);
			var pointermid = pointermax;
			var pointerstart = 0;
			while (pointermin < pointermid) {
				if (text1.substring(pointerstart, pointermid) ==
					text2.substring(pointerstart, pointermid)) {
					pointermin = pointermid;
					pointerstart = pointermin;
				} else {
					pointermax = pointermid;
				}
				pointermid = Math.floor((pointermax - pointermin) / 2 + pointermin);
			}
			return pointermid;
		};


		/**
		 * Determine the common suffix of two strings.
		 * @param {string} text1 First string.
		 * @param {string} text2 Second string.
		 * @return {number} The number of characters common to the end of each string.
		 */
		diff_match_patch.prototype.diff_commonSuffix = function(text1, text2) {
			// Quick check for common null cases.
			if (!text1 || !text2 ||
				text1.charAt(text1.length - 1) != text2.charAt(text2.length - 1)) {
				return 0;
			}
			// Binary search.
			// Performance analysis: http://neil.fraser.name/news/2007/10/09/
			var pointermin = 0;
			var pointermax = Math.min(text1.length, text2.length);
			var pointermid = pointermax;
			var pointerend = 0;
			while (pointermin < pointermid) {
				if (text1.substring(text1.length - pointermid, text1.length - pointerend) ==
					text2.substring(text2.length - pointermid, text2.length - pointerend)) {
					pointermin = pointermid;
					pointerend = pointermin;
				} else {
					pointermax = pointermid;
				}
				pointermid = Math.floor((pointermax - pointermin) / 2 + pointermin);
			}
			return pointermid;
		};


		/**
		 * Determine if the suffix of one string is the prefix of another.
		 * @param {string} text1 First string.
		 * @param {string} text2 Second string.
		 * @return {number} The number of characters common to the end of the first
		 *     string and the start of the second string.
		 * @private
		 */
		diff_match_patch.prototype.diff_commonOverlap_ = function(text1, text2) {
			// Cache the text lengths to prevent multiple calls.
			var text1_length = text1.length;
			var text2_length = text2.length;
			// Eliminate the null case.
			if (text1_length == 0 || text2_length == 0) {
				return 0;
			}
			// Truncate the longer string.
			if (text1_length > text2_length) {
				text1 = text1.substring(text1_length - text2_length);
			} else if (text1_length < text2_length) {
				text2 = text2.substring(0, text1_length);
			}
			var text_length = Math.min(text1_length, text2_length);
			// Quick check for the worst case.
			if (text1 == text2) {
				return text_length;
			}

			// Start by looking for a single character match
			// and increase length until no match is found.
			// Performance analysis: http://neil.fraser.name/news/2010/11/04/
			var best = 0;
			var length = 1;
			while (true) {
				var pattern = text1.substring(text_length - length);
				var found = text2.indexOf(pattern);
				if (found == -1) {
					return best;
				}
				length += found;
				if (found == 0 || text1.substring(text_length - length) ==
					text2.substring(0, length)) {
					best = length;
					length++;
				}
			}
		};


		/**
		 * Do the two texts share a substring which is at least half the length of the
		 * longer text?
		 * This speedup can produce non-minimal diffs.
		 * @param {string} text1 First string.
		 * @param {string} text2 Second string.
		 * @return {Array.<string>} Five element Array, containing the prefix of
		 *     text1, the suffix of text1, the prefix of text2, the suffix of
		 *     text2 and the common middle.  Or null if there was no match.
		 * @private
		 */
		diff_match_patch.prototype.diff_halfMatch_ = function(text1, text2) {
			if (this.Diff_Timeout <= 0) {
				// Don't risk returning a non-optimal diff if we have unlimited time.
				return null;
			}
			var longtext = text1.length > text2.length ? text1 : text2;
			var shorttext = text1.length > text2.length ? text2 : text1;
			if (longtext.length < 4 || shorttext.length * 2 < longtext.length) {
				return null;  // Pointless.
			}
			var dmp = this;  // 'this' becomes 'window' in a closure.

			/**
			 * Does a substring of shorttext exist within longtext such that the substring
			 * is at least half the length of longtext?
			 * Closure, but does not reference any external variables.
			 * @param {string} longtext Longer string.
			 * @param {string} shorttext Shorter string.
			 * @param {number} i Start index of quarter length substring within longtext.
			 * @return {Array.<string>} Five element Array, containing the prefix of
			 *     longtext, the suffix of longtext, the prefix of shorttext, the suffix
			 *     of shorttext and the common middle.  Or null if there was no match.
			 * @private
			 */
			function diff_halfMatchI_(longtext, shorttext, i) {
				// Start with a 1/4 length substring at position i as a seed.
				var seed = longtext.substring(i, i + Math.floor(longtext.length / 4));
				var j = -1;
				var best_common = '';
				var best_longtext_a, best_longtext_b, best_shorttext_a, best_shorttext_b;
				while ((j = shorttext.indexOf(seed, j + 1)) != -1) {
					var prefixLength = dmp.diff_commonPrefix(longtext.substring(i),
						shorttext.substring(j));
					var suffixLength = dmp.diff_commonSuffix(longtext.substring(0, i),
						shorttext.substring(0, j));
					if (best_common.length < suffixLength + prefixLength) {
						best_common = shorttext.substring(j - suffixLength, j) +
							shorttext.substring(j, j + prefixLength);
						best_longtext_a = longtext.substring(0, i - suffixLength);
						best_longtext_b = longtext.substring(i + prefixLength);
						best_shorttext_a = shorttext.substring(0, j - suffixLength);
						best_shorttext_b = shorttext.substring(j + prefixLength);
					}
				}
				if (best_common.length * 2 >= longtext.length) {
					return [best_longtext_a, best_longtext_b,
						best_shorttext_a, best_shorttext_b, best_common];
				} else {
					return null;
				}
			}

			// First check if the second quarter is the seed for a half-match.
			var hm1 = diff_halfMatchI_(longtext, shorttext,
				Math.ceil(longtext.length / 4));
			// Check again based on the third quarter.
			var hm2 = diff_halfMatchI_(longtext, shorttext,
				Math.ceil(longtext.length / 2));
			var hm;
			if (!hm1 && !hm2) {
				return null;
			} else if (!hm2) {
				hm = hm1;
			} else if (!hm1) {
				hm = hm2;
			} else {
				// Both matched.  Select the longest.
				hm = hm1[4].length > hm2[4].length ? hm1 : hm2;
			}

			// A half-match was found, sort out the return data.
			var text1_a, text1_b, text2_a, text2_b;
			if (text1.length > text2.length) {
				text1_a = hm[0];
				text1_b = hm[1];
				text2_a = hm[2];
				text2_b = hm[3];
			} else {
				text2_a = hm[0];
				text2_b = hm[1];
				text1_a = hm[2];
				text1_b = hm[3];
			}
			var mid_common = hm[4];
			return [text1_a, text1_b, text2_a, text2_b, mid_common];
		};


		/**
		 * Reduce the number of edits by eliminating semantically trivial equalities.
		 * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
		 */
		diff_match_patch.prototype.diff_cleanupSemantic = function(diffs) {
			var changes = false;
			var equalities = [];  // Stack of indices where equalities are found.
			var equalitiesLength = 0;  // Keeping our own length var is faster in JS.
			/** @type {?string} */
			var lastequality = null;
			// Always equal to diffs[equalities[equalitiesLength - 1]][1]
			var pointer = 0;  // Index of current position.
			// Number of characters that changed prior to the equality.
			var length_insertions1 = 0;
			var length_deletions1 = 0;
			// Number of characters that changed after the equality.
			var length_insertions2 = 0;
			var length_deletions2 = 0;
			while (pointer < diffs.length) {
				if (diffs[pointer][0] == DIFF_EQUAL) {  // Equality found.
					equalities[equalitiesLength++] = pointer;
					length_insertions1 = length_insertions2;
					length_deletions1 = length_deletions2;
					length_insertions2 = 0;
					length_deletions2 = 0;
					lastequality = diffs[pointer][1];
				} else {  // An insertion or deletion.
					if (diffs[pointer][0] == DIFF_INSERT) {
						length_insertions2 += diffs[pointer][1].length;
					} else {
						length_deletions2 += diffs[pointer][1].length;
					}
					// Eliminate an equality that is smaller or equal to the edits on both
					// sides of it.
					if (lastequality && (lastequality.length <=
						Math.max(length_insertions1, length_deletions1)) &&
						(lastequality.length <= Math.max(length_insertions2,
							length_deletions2))) {
						// Duplicate record.
						diffs.splice(equalities[equalitiesLength - 1], 0,
							[DIFF_DELETE, lastequality]);
						// Change second copy to insert.
						diffs[equalities[equalitiesLength - 1] + 1][0] = DIFF_INSERT;
						// Throw away the equality we just deleted.
						equalitiesLength--;
						// Throw away the previous equality (it needs to be reevaluated).
						equalitiesLength--;
						pointer = equalitiesLength > 0 ? equalities[equalitiesLength - 1] : -1;
						length_insertions1 = 0;  // Reset the counters.
						length_deletions1 = 0;
						length_insertions2 = 0;
						length_deletions2 = 0;
						lastequality = null;
						changes = true;
					}
				}
				pointer++;
			}

			// Normalize the diff.
			if (changes) {
				this.diff_cleanupMerge(diffs);
			}
			this.diff_cleanupSemanticLossless(diffs);

			// Find any overlaps between deletions and insertions.
			// e.g: <del>abcxxx</del><ins>xxxdef</ins>
			//   -> <del>abc</del>xxx<ins>def</ins>
			// e.g: <del>xxxabc</del><ins>defxxx</ins>
			//   -> <ins>def</ins>xxx<del>abc</del>
			// Only extract an overlap if it is as big as the edit ahead or behind it.
			pointer = 1;
			while (pointer < diffs.length) {
				if (diffs[pointer - 1][0] == DIFF_DELETE &&
					diffs[pointer][0] == DIFF_INSERT) {
					var deletion = diffs[pointer - 1][1];
					var insertion = diffs[pointer][1];
					var overlap_length1 = this.diff_commonOverlap_(deletion, insertion);
					var overlap_length2 = this.diff_commonOverlap_(insertion, deletion);
					if (overlap_length1 >= overlap_length2) {
						if (overlap_length1 >= deletion.length / 2 ||
							overlap_length1 >= insertion.length / 2) {
							// Overlap found.  Insert an equality and trim the surrounding edits.
							diffs.splice(pointer, 0,
								[DIFF_EQUAL, insertion.substring(0, overlap_length1)]);
							diffs[pointer - 1][1] =
								deletion.substring(0, deletion.length - overlap_length1);
							diffs[pointer + 1][1] = insertion.substring(overlap_length1);
							pointer++;
						}
					} else {
						if (overlap_length2 >= deletion.length / 2 ||
							overlap_length2 >= insertion.length / 2) {
							// Reverse overlap found.
							// Insert an equality and swap and trim the surrounding edits.
							diffs.splice(pointer, 0,
								[DIFF_EQUAL, deletion.substring(0, overlap_length2)]);
							diffs[pointer - 1][0] = DIFF_INSERT;
							diffs[pointer - 1][1] =
								insertion.substring(0, insertion.length - overlap_length2);
							diffs[pointer + 1][0] = DIFF_DELETE;
							diffs[pointer + 1][1] =
								deletion.substring(overlap_length2);
							pointer++;
						}
					}
					pointer++;
				}
				pointer++;
			}
		};


		/**
		 * Look for single edits surrounded on both sides by equalities
		 * which can be shifted sideways to align the edit to a word boundary.
		 * e.g: The c<ins>at c</ins>ame. -> The <ins>cat </ins>came.
		 * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
		 */
		diff_match_patch.prototype.diff_cleanupSemanticLossless = function(diffs) {
			/**
			 * Given two strings, compute a score representing whether the internal
			 * boundary falls on logical boundaries.
			 * Scores range from 6 (best) to 0 (worst).
			 * Closure, but does not reference any external variables.
			 * @param {string} one First string.
			 * @param {string} two Second string.
			 * @return {number} The score.
			 * @private
			 */
			function diff_cleanupSemanticScore_(one, two) {
				if (!one || !two) {
					// Edges are the best.
					return 6;
				}

				// Each port of this function behaves slightly differently due to
				// subtle differences in each language's definition of things like
				// 'whitespace'.  Since this function's purpose is largely cosmetic,
				// the choice has been made to use each language's native features
				// rather than force total conformity.
				var char1 = one.charAt(one.length - 1);
				var char2 = two.charAt(0);
				var nonAlphaNumeric1 = char1.match(diff_match_patch.nonAlphaNumericRegex_);
				var nonAlphaNumeric2 = char2.match(diff_match_patch.nonAlphaNumericRegex_);
				var whitespace1 = nonAlphaNumeric1 &&
					char1.match(diff_match_patch.whitespaceRegex_);
				var whitespace2 = nonAlphaNumeric2 &&
					char2.match(diff_match_patch.whitespaceRegex_);
				var lineBreak1 = whitespace1 &&
					char1.match(diff_match_patch.linebreakRegex_);
				var lineBreak2 = whitespace2 &&
					char2.match(diff_match_patch.linebreakRegex_);
				var blankLine1 = lineBreak1 &&
					one.match(diff_match_patch.blanklineEndRegex_);
				var blankLine2 = lineBreak2 &&
					two.match(diff_match_patch.blanklineStartRegex_);

				if (blankLine1 || blankLine2) {
					// Five points for blank lines.
					return 5;
				} else if (lineBreak1 || lineBreak2) {
					// Four points for line breaks.
					return 4;
				} else if (nonAlphaNumeric1 && !whitespace1 && whitespace2) {
					// Three points for end of sentences.
					return 3;
				} else if (whitespace1 || whitespace2) {
					// Two points for whitespace.
					return 2;
				} else if (nonAlphaNumeric1 || nonAlphaNumeric2) {
					// One point for non-alphanumeric.
					return 1;
				}
				return 0;
			}

			var pointer = 1;
			// Intentionally ignore the first and last element (don't need checking).
			while (pointer < diffs.length - 1) {
				if (diffs[pointer - 1][0] == DIFF_EQUAL &&
					diffs[pointer + 1][0] == DIFF_EQUAL) {
					// This is a single edit surrounded by equalities.
					var equality1 = diffs[pointer - 1][1];
					var edit = diffs[pointer][1];
					var equality2 = diffs[pointer + 1][1];

					// First, shift the edit as far left as possible.
					var commonOffset = this.diff_commonSuffix(equality1, edit);
					if (commonOffset) {
						var commonString = edit.substring(edit.length - commonOffset);
						equality1 = equality1.substring(0, equality1.length - commonOffset);
						edit = commonString + edit.substring(0, edit.length - commonOffset);
						equality2 = commonString + equality2;
					}

					// Second, step character by character right, looking for the best fit.
					var bestEquality1 = equality1;
					var bestEdit = edit;
					var bestEquality2 = equality2;
					var bestScore = diff_cleanupSemanticScore_(equality1, edit) +
						diff_cleanupSemanticScore_(edit, equality2);
					while (edit.charAt(0) === equality2.charAt(0)) {
						equality1 += edit.charAt(0);
						edit = edit.substring(1) + equality2.charAt(0);
						equality2 = equality2.substring(1);
						var score = diff_cleanupSemanticScore_(equality1, edit) +
							diff_cleanupSemanticScore_(edit, equality2);
						// The >= encourages trailing rather than leading whitespace on edits.
						if (score >= bestScore) {
							bestScore = score;
							bestEquality1 = equality1;
							bestEdit = edit;
							bestEquality2 = equality2;
						}
					}

					if (diffs[pointer - 1][1] != bestEquality1) {
						// We have an improvement, save it back to the diff.
						if (bestEquality1) {
							diffs[pointer - 1][1] = bestEquality1;
						} else {
							diffs.splice(pointer - 1, 1);
							pointer--;
						}
						diffs[pointer][1] = bestEdit;
						if (bestEquality2) {
							diffs[pointer + 1][1] = bestEquality2;
						} else {
							diffs.splice(pointer + 1, 1);
							pointer--;
						}
					}
				}
				pointer++;
			}
		};

// Define some regex patterns for matching boundaries.
		diff_match_patch.nonAlphaNumericRegex_ = /[^a-zA-Z0-9]/;
		diff_match_patch.whitespaceRegex_ = /\s/;
		diff_match_patch.linebreakRegex_ = /[\r\n]/;
		diff_match_patch.blanklineEndRegex_ = /\n\r?\n$/;
		diff_match_patch.blanklineStartRegex_ = /^\r?\n\r?\n/;

		/**
		 * Reduce the number of edits by eliminating operationally trivial equalities.
		 * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
		 */
		diff_match_patch.prototype.diff_cleanupEfficiency = function(diffs) {
			var changes = false;
			var equalities = [];  // Stack of indices where equalities are found.
			var equalitiesLength = 0;  // Keeping our own length var is faster in JS.
			/** @type {?string} */
			var lastequality = null;
			// Always equal to diffs[equalities[equalitiesLength - 1]][1]
			var pointer = 0;  // Index of current position.
			// Is there an insertion operation before the last equality.
			var pre_ins = false;
			// Is there a deletion operation before the last equality.
			var pre_del = false;
			// Is there an insertion operation after the last equality.
			var post_ins = false;
			// Is there a deletion operation after the last equality.
			var post_del = false;
			while (pointer < diffs.length) {
				if (diffs[pointer][0] == DIFF_EQUAL) {  // Equality found.
					if (diffs[pointer][1].length < this.Diff_EditCost &&
						(post_ins || post_del)) {
						// Candidate found.
						equalities[equalitiesLength++] = pointer;
						pre_ins = post_ins;
						pre_del = post_del;
						lastequality = diffs[pointer][1];
					} else {
						// Not a candidate, and can never become one.
						equalitiesLength = 0;
						lastequality = null;
					}
					post_ins = post_del = false;
				} else {  // An insertion or deletion.
					if (diffs[pointer][0] == DIFF_DELETE) {
						post_del = true;
					} else {
						post_ins = true;
					}
					/*
					 * Five types to be split:
					 * <ins>A</ins><del>B</del>XY<ins>C</ins><del>D</del>
					 * <ins>A</ins>X<ins>C</ins><del>D</del>
					 * <ins>A</ins><del>B</del>X<ins>C</ins>
					 * <ins>A</del>X<ins>C</ins><del>D</del>
					 * <ins>A</ins><del>B</del>X<del>C</del>
					 */
					if (lastequality && ((pre_ins && pre_del && post_ins && post_del) ||
						((lastequality.length < this.Diff_EditCost / 2) &&
							(pre_ins + pre_del + post_ins + post_del) == 3))) {
						// Duplicate record.
						diffs.splice(equalities[equalitiesLength - 1], 0,
							[DIFF_DELETE, lastequality]);
						// Change second copy to insert.
						diffs[equalities[equalitiesLength - 1] + 1][0] = DIFF_INSERT;
						equalitiesLength--;  // Throw away the equality we just deleted;
						lastequality = null;
						if (pre_ins && pre_del) {
							// No changes made which could affect previous entry, keep going.
							post_ins = post_del = true;
							equalitiesLength = 0;
						} else {
							equalitiesLength--;  // Throw away the previous equality.
							pointer = equalitiesLength > 0 ?
								equalities[equalitiesLength - 1] : -1;
							post_ins = post_del = false;
						}
						changes = true;
					}
				}
				pointer++;
			}

			if (changes) {
				this.diff_cleanupMerge(diffs);
			}
		};


		/**
		 * Reorder and merge like edit sections.  Merge equalities.
		 * Any edit section can move as long as it doesn't cross an equality.
		 * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
		 */
		diff_match_patch.prototype.diff_cleanupMerge = function(diffs) {
			diffs.push([DIFF_EQUAL, '']);  // Add a dummy entry at the end.
			var pointer = 0;
			var count_delete = 0;
			var count_insert = 0;
			var text_delete = '';
			var text_insert = '';
			var commonlength;
			while (pointer < diffs.length) {
				switch (diffs[pointer][0]) {
					case DIFF_INSERT:
						count_insert++;
						text_insert += diffs[pointer][1];
						pointer++;
						break;
					case DIFF_DELETE:
						count_delete++;
						text_delete += diffs[pointer][1];
						pointer++;
						break;
					case DIFF_EQUAL:
						// Upon reaching an equality, check for prior redundancies.
						if (count_delete + count_insert > 1) {
							if (count_delete !== 0 && count_insert !== 0) {
								// Factor out any common prefixies.
								commonlength = this.diff_commonPrefix(text_insert, text_delete);
								if (commonlength !== 0) {
									if ((pointer - count_delete - count_insert) > 0 &&
										diffs[pointer - count_delete - count_insert - 1][0] ==
										DIFF_EQUAL) {
										diffs[pointer - count_delete - count_insert - 1][1] +=
											text_insert.substring(0, commonlength);
									} else {
										diffs.splice(0, 0, [DIFF_EQUAL,
											text_insert.substring(0, commonlength)]);
										pointer++;
									}
									text_insert = text_insert.substring(commonlength);
									text_delete = text_delete.substring(commonlength);
								}
								// Factor out any common suffixies.
								commonlength = this.diff_commonSuffix(text_insert, text_delete);
								if (commonlength !== 0) {
									diffs[pointer][1] = text_insert.substring(text_insert.length -
										commonlength) + diffs[pointer][1];
									text_insert = text_insert.substring(0, text_insert.length -
										commonlength);
									text_delete = text_delete.substring(0, text_delete.length -
										commonlength);
								}
							}
							// Delete the offending records and add the merged ones.
							if (count_delete === 0) {
								diffs.splice(pointer - count_insert,
										count_delete + count_insert, [DIFF_INSERT, text_insert]);
							} else if (count_insert === 0) {
								diffs.splice(pointer - count_delete,
										count_delete + count_insert, [DIFF_DELETE, text_delete]);
							} else {
								diffs.splice(pointer - count_delete - count_insert,
										count_delete + count_insert, [DIFF_DELETE, text_delete],
									[DIFF_INSERT, text_insert]);
							}
							pointer = pointer - count_delete - count_insert +
								(count_delete ? 1 : 0) + (count_insert ? 1 : 0) + 1;
						} else if (pointer !== 0 && diffs[pointer - 1][0] == DIFF_EQUAL) {
							// Merge this equality with the previous one.
							diffs[pointer - 1][1] += diffs[pointer][1];
							diffs.splice(pointer, 1);
						} else {
							pointer++;
						}
						count_insert = 0;
						count_delete = 0;
						text_delete = '';
						text_insert = '';
						break;
				}
			}
			if (diffs[diffs.length - 1][1] === '') {
				diffs.pop();  // Remove the dummy entry at the end.
			}

			// Second pass: look for single edits surrounded on both sides by equalities
			// which can be shifted sideways to eliminate an equality.
			// e.g: A<ins>BA</ins>C -> <ins>AB</ins>AC
			var changes = false;
			pointer = 1;
			// Intentionally ignore the first and last element (don't need checking).
			while (pointer < diffs.length - 1) {
				if (diffs[pointer - 1][0] == DIFF_EQUAL &&
					diffs[pointer + 1][0] == DIFF_EQUAL) {
					// This is a single edit surrounded by equalities.
					if (diffs[pointer][1].substring(diffs[pointer][1].length -
						diffs[pointer - 1][1].length) == diffs[pointer - 1][1]) {
						// Shift the edit over the previous equality.
						diffs[pointer][1] = diffs[pointer - 1][1] +
							diffs[pointer][1].substring(0, diffs[pointer][1].length -
								diffs[pointer - 1][1].length);
						diffs[pointer + 1][1] = diffs[pointer - 1][1] + diffs[pointer + 1][1];
						diffs.splice(pointer - 1, 1);
						changes = true;
					} else if (diffs[pointer][1].substring(0, diffs[pointer + 1][1].length) ==
						diffs[pointer + 1][1]) {
						// Shift the edit over the next equality.
						diffs[pointer - 1][1] += diffs[pointer + 1][1];
						diffs[pointer][1] =
							diffs[pointer][1].substring(diffs[pointer + 1][1].length) +
							diffs[pointer + 1][1];
						diffs.splice(pointer + 1, 1);
						changes = true;
					}
				}
				pointer++;
			}
			// If shifts were made, the diff needs reordering and another shift sweep.
			if (changes) {
				this.diff_cleanupMerge(diffs);
			}
		};


		/**
		 * loc is a location in text1, compute and return the equivalent location in
		 * text2.
		 * e.g. 'The cat' vs 'The big cat', 1->1, 5->8
		 * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
		 * @param {number} loc Location within text1.
		 * @return {number} Location within text2.
		 */
		diff_match_patch.prototype.diff_xIndex = function(diffs, loc) {
			var chars1 = 0;
			var chars2 = 0;
			var last_chars1 = 0;
			var last_chars2 = 0;
			var x;
			for (x = 0; x < diffs.length; x++) {
				if (diffs[x][0] !== DIFF_INSERT) {  // Equality or deletion.
					chars1 += diffs[x][1].length;
				}
				if (diffs[x][0] !== DIFF_DELETE) {  // Equality or insertion.
					chars2 += diffs[x][1].length;
				}
				if (chars1 > loc) {  // Overshot the location.
					break;
				}
				last_chars1 = chars1;
				last_chars2 = chars2;
			}
			// Was the location was deleted?
			if (diffs.length != x && diffs[x][0] === DIFF_DELETE) {
				return last_chars2;
			}
			// Add the remaining character length.
			return last_chars2 + (loc - last_chars1);
		};


		/**
		 * Convert a diff array into a pretty HTML report.
		 * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
		 * @return {string} HTML representation.
		 */
		diff_match_patch.prototype.diff_prettyHtml = function(diffs) {
			var html = [];
			var pattern_amp = /&/g;
			var pattern_lt = /</g;
			var pattern_gt = />/g;
			var pattern_para = /\n/g;
			for (var x = 0; x < diffs.length; x++) {
				var op = diffs[x][0];    // Operation (insert, delete, equal)
				var data = diffs[x][1];  // Text of change.
				var text = data.replace(pattern_amp, '&amp;').replace(pattern_lt, '&lt;')
					.replace(pattern_gt, '&gt;').replace(pattern_para, '&para;<br>');
				switch (op) {
					case DIFF_INSERT:
						html[x] = '<ins style="background:#e6ffe6;">' + text + '</ins>';
						break;
					case DIFF_DELETE:
						html[x] = '<del style="background:#ffe6e6;">' + text + '</del>';
						break;
					case DIFF_EQUAL:
						html[x] = '<span>' + text + '</span>';
						break;
				}
			}
			return html.join('');
		};


		/**
		 * Compute and return the source text (all equalities and deletions).
		 * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
		 * @return {string} Source text.
		 */
		diff_match_patch.prototype.diff_text1 = function(diffs) {
			var text = [];
			for (var x = 0; x < diffs.length; x++) {
				if (diffs[x][0] !== DIFF_INSERT) {
					text[x] = diffs[x][1];
				}
			}
			return text.join('');
		};


		/**
		 * Compute and return the destination text (all equalities and insertions).
		 * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
		 * @return {string} Destination text.
		 */
		diff_match_patch.prototype.diff_text2 = function(diffs) {
			var text = [];
			for (var x = 0; x < diffs.length; x++) {
				if (diffs[x][0] !== DIFF_DELETE) {
					text[x] = diffs[x][1];
				}
			}
			return text.join('');
		};


		/**
		 * Compute the Levenshtein distance; the number of inserted, deleted or
		 * substituted characters.
		 * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
		 * @return {number} Number of changes.
		 */
		diff_match_patch.prototype.diff_levenshtein = function(diffs) {
			var levenshtein = 0;
			var insertions = 0;
			var deletions = 0;
			for (var x = 0; x < diffs.length; x++) {
				var op = diffs[x][0];
				var data = diffs[x][1];
				switch (op) {
					case DIFF_INSERT:
						insertions += data.length;
						break;
					case DIFF_DELETE:
						deletions += data.length;
						break;
					case DIFF_EQUAL:
						// A deletion and an insertion is one substitution.
						levenshtein += Math.max(insertions, deletions);
						insertions = 0;
						deletions = 0;
						break;
				}
			}
			levenshtein += Math.max(insertions, deletions);
			return levenshtein;
		};


		/**
		 * Crush the diff into an encoded string which describes the operations
		 * required to transform text1 into text2.
		 * E.g. =3\t-2\t+ing  -> Keep 3 chars, delete 2 chars, insert 'ing'.
		 * Operations are tab-separated.  Inserted text is escaped using %xx notation.
		 * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
		 * @return {string} Delta text.
		 */
		diff_match_patch.prototype.diff_toDelta = function(diffs) {
			var text = [];
			for (var x = 0; x < diffs.length; x++) {
				switch (diffs[x][0]) {
					case DIFF_INSERT:
						text[x] = '+' + encodeURI(diffs[x][1]);
						break;
					case DIFF_DELETE:
						text[x] = '-' + diffs[x][1].length;
						break;
					case DIFF_EQUAL:
						text[x] = '=' + diffs[x][1].length;
						break;
				}
			}
			return text.join('\t').replace(/%20/g, ' ');
		};


		/**
		 * Given the original text1, and an encoded string which describes the
		 * operations required to transform text1 into text2, compute the full diff.
		 * @param {string} text1 Source string for the diff.
		 * @param {string} delta Delta text.
		 * @return {!Array.<!diff_match_patch.Diff>} Array of diff tuples.
		 * @throws {!Error} If invalid input.
		 */
		diff_match_patch.prototype.diff_fromDelta = function(text1, delta) {
			var diffs = [];
			var diffsLength = 0;  // Keeping our own length var is faster in JS.
			var pointer = 0;  // Cursor in text1
			var tokens = delta.split(/\t/g);
			for (var x = 0; x < tokens.length; x++) {
				// Each token begins with a one character parameter which specifies the
				// operation of this token (delete, insert, equality).
				var param = tokens[x].substring(1);
				switch (tokens[x].charAt(0)) {
					case '+':
						try {
							diffs[diffsLength++] = [DIFF_INSERT, decodeURI(param)];
						} catch (ex) {
							// Malformed URI sequence.
							throw new Error('Illegal escape in diff_fromDelta: ' + param);
						}
						break;
					case '-':
					// Fall through.
					case '=':
						var n = parseInt(param, 10);
						if (isNaN(n) || n < 0) {
							throw new Error('Invalid number in diff_fromDelta: ' + param);
						}
						var text = text1.substring(pointer, pointer += n);
						if (tokens[x].charAt(0) == '=') {
							diffs[diffsLength++] = [DIFF_EQUAL, text];
						} else {
							diffs[diffsLength++] = [DIFF_DELETE, text];
						}
						break;
					default:
						// Blank tokens are ok (from a trailing \t).
						// Anything else is an error.
						if (tokens[x]) {
							throw new Error('Invalid diff operation in diff_fromDelta: ' +
								tokens[x]);
						}
				}
			}
			if (pointer != text1.length) {
				throw new Error('Delta length (' + pointer +
					') does not equal source text length (' + text1.length + ').');
			}
			return diffs;
		};

		return {diff_match_patch: diff_match_patch};
	});

		/**
	 * Save function to db.system.js
	 * @param func
	 */
	function saveSystemJSFunc(func) {
		if (!func || !func.name) {
			logger.error('saveSystemJSFunc: function name is not defined');
		}
		db.db.collection('system.js').save(
			{
				_id: func.name,
				value: new mongoose.mongo.Code(func.toString())
			},
			function saveCallback(err) {
				if (err) {
					logger.error(err);
				}
			}
		);
	}
};
