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+/**
+ * This diff utility is taken from:
+ * https://github.com/Slava/diff.js
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2014 Slava
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+/**
+ * USAGE:
+ * diff(text1, text2);
+ */
+
+/**
+ * Longest Common Subsequence
+ *
+ * @param A - sequence of atoms - Array
+ * @param B - sequence of atoms - Array
+ * @param equals - optional comparator of atoms - returns true or false,
+ * if not specified, triple equals operator is used
+ * @returns Array - sequence of atoms, one of LCSs, edit script from A to B
+ */
+var LCS = function (A, B, /* optional */ equals) {
+ // We just compare atoms with default equals operator by default
+ if (equals === undefined)
+ equals = function (a, b) { return a === b; };
+
+ // NOTE: all intervals from now on are both sides inclusive
+ // Get the points in Edit Graph, one of the LCS paths goes through.
+ // The points are located on the same diagonal and represent the middle
+ // snake ([D/2] out of D+1) in the optimal edit path in edit graph.
+ // @param startA, endA - substring of A we are working on
+ // @param startB, endB - substring of B we are working on
+ // @returns Array - [
+ // [x, y], - beginning of the middle snake
+ // [u, v], - end of the middle snake
+ // D, - optimal edit distance
+ // LCS ] - length of LCS
+ var findMidSnake = function (startA, endA, startB, endB) {
+ var N = endA - startA + 1;
+ var M = endB - startB + 1;
+ var Max = N + M;
+ var Delta = N - M;
+ var halfMaxCeil = (Max + 1) / 2 | 0;
+
+ var foundOverlap = false;
+ var overlap = null;
+
+ // Maps -Max .. 0 .. +Max, diagonal index to endpoints for furthest reaching
+ // D-path on current iteration.
+ var V = {};
+ // Same but for reversed paths.
+ var U = {};
+
+ // Special case for the base case, D = 0, k = 0, x = y = 0
+ V[1] = 0;
+ // Special case for the base case reversed, D = 0, k = 0, x = N, y = M
+ U[Delta - 1] = N;
+
+ // Iterate over each possible length of edit script
+ for (var D = 0; D <= halfMaxCeil; D++) {
+ // Iterate over each diagonal
+ for (var k = -D; k <= D && !overlap; k += 2) {
+ // Positions in sequences A and B of furthest going D-path on diagonal k.
+ var x, y;
+
+ // Choose from each diagonal we extend
+ if (k === -D || (k !== D && V[k - 1] < V[k + 1]))
+ // Extending path one point down, that's why x doesn't change, y
+ // increases implicitly
+ x = V[k + 1];
+ else
+ // Extending path one point to the right, x increases
+ x = V[k - 1] + 1;
+
+ // We can calculate the y out of x and diagonal index.
+ y = x - k;
+
+ if (isNaN(y) || x > N || y > M)
+ continue;
+
+ var xx = x;
+ // Try to extend the D-path with diagonal paths. Possible only if atoms
+ // A_x match B_y
+ while (x < N && y < M // if there are atoms to compare
+ && equals(A[startA + x], B[startB + y])) {
+ x++; y++;
+ }
+
+ // We can safely update diagonal k, since on every iteration we consider
+ // only even or only odd diagonals and the result of one depends only on
+ // diagonals of different iteration.
+ V[k] = x;
+
+ // Check feasibility, Delta is checked for being odd.
+ if ((Delta & 1) === 1 && inRange(k, Delta - (D - 1), Delta + (D - 1)))
+ // Forward D-path can overlap with reversed D-1-path
+ if (V[k] >= U[k])
+ // Found an overlap, the middle snake, convert X-components to dots
+ overlap = [xx, x].map(toPoint, k); // XXX ES5
+ }
+
+ if (overlap)
+ var SES = D * 2 - 1;
+
+ // Iterate over each diagonal for reversed case
+ for (var k = -D; k <= D && !overlap; k += 2) {
+ // The real diagonal we are looking for is k + Delta
+ var K = k + Delta;
+ var x, y;
+ if (k === D || (k !== -D && U[K - 1] < U[K + 1]))
+ x = U[K - 1];
+ else
+ x = U[K + 1] - 1;
+
+ y = x - K;
+ if (isNaN(y) || x < 0 || y < 0)
+ continue;
+ var xx = x;
+ while (x > 0 && y > 0 && equals(A[startA + x - 1], B[startB + y - 1])) {
+ x--; y--;
+ }
+ U[K] = x;
+
+ if (Delta % 2 === 0 && inRange(K, -D, D))
+ if (U[K] <= V[K])
+ overlap = [x, xx].map(toPoint, K); // XXX ES5
+ }
+
+ if (overlap) {
+ SES = SES || D * 2;
+ // Remember we had offset of each sequence?
+ for (var i = 0; i < 2; i++) for (var j = 0; j < 2; j++)
+ overlap[i][j] += [startA, startB][j] - i;
+ return overlap.concat([ SES, (Max - SES) / 2 ]);
+ }
+ }
+ };
+
+ var lcsAtoms = [];
+ var lcs = function (startA, endA, startB, endB) {
+ var N = endA - startA + 1;
+ var M = endB - startB + 1;
+
+ if (N > 0 && M > 0) {
+ var middleSnake = findMidSnake(startA, endA, startB, endB);
+ // A[x;u] == B[y,v] and is part of LCS
+ var x = middleSnake[0][0], y = middleSnake[0][1];
+ var u = middleSnake[1][0], v = middleSnake[1][1];
+ var D = middleSnake[2];
+
+ if (D > 1) {
+ lcs(startA, x - 1, startB, y - 1);
+ if (x <= u) {
+ [].push.apply(lcsAtoms, A.slice(x, u + 1));
+ }
+ lcs(u + 1, endA, v + 1, endB);
+ } else if (M > N)
+ [].push.apply(lcsAtoms, A.slice(startA, endA + 1));
+ else
+ [].push.apply(lcsAtoms, B.slice(startB, endB + 1));
+ }
+ };
+
+ lcs(0, A.length - 1, 0, B.length - 1);
+ return lcsAtoms;
+};
+
+// Helpers
+var inRange = function (x, l, r) {
+ return (l <= x && x <= r) || (r <= x && x <= l);
+};
+
+// Takes X-component as argument, diagonal as context,
+// returns array-pair of form x, y
+var toPoint = function (x) {
+ return [x, x - this]; // XXX context is not the best way to pass diagonal
+};
+
+// Wrappers
+LCS.StringLCS = function (A, B) {
+ return LCS(A.split(''), B.split('')).join('');
+};
+
+/**
+ * Diff sequence
+ *
+ * @param A - sequence of atoms - Array
+ * @param B - sequence of atoms - Array
+ * @param equals - optional comparator of atoms - returns true or false,
+ * if not specified, triple equals operator is used
+ * @returns Array - sequence of objects in a form of:
+ * - operation: one of "none", "add", "delete"
+ * - atom: the atom found in either A or B
+ * Applying operations from diff sequence you should be able to transform A to B
+ */
+function diff(A, B, equals) {
+ // We just compare atoms with default equals operator by default
+ if (equals === undefined)
+ equals = function (a, b) { return a === b; };
+
+ var diff = [];
+ var i = 0, j = 0;
+ var N = A.length, M = B.length, K = 0;
+
+ while (i < N && j < M && equals(A[i], B[j]))
+ i++, j++;
+
+ while (i < N && j < M && equals(A[N-1], B[M-1]))
+ N--, M--, K++;
+
+ [].push.apply(diff, A.slice(0, i).map(function (atom) {
+ return { operation: "none", atom: atom }; }));
+
+ var lcs = LCS(A.slice(i, N), B.slice(j, M), equals);
+
+ for (var k = 0; k < lcs.length; k++) {
+ var atom = lcs[k];
+ var ni = customIndexOf.call(A, atom, i, equals);
+ var nj = customIndexOf.call(B, atom, j, equals);
+
+ // XXX ES5 map
+ // Delete unmatched atoms from A
+ [].push.apply(diff, A.slice(i, ni).map(function (atom) {
+ return { operation: "delete", atom: atom };
+ }));
+
+ // Add unmatched atoms from B
+ [].push.apply(diff, B.slice(j, nj).map(function (atom) {
+ return { operation: "add", atom: atom };
+ }));
+
+ // Add the atom found in both sequences
+ diff.push({ operation: "none", atom: atom });
+
+ i = ni + 1;
+ j = nj + 1;
+ }
+
+ // Don't forget about the rest
+
+ [].push.apply(diff, A.slice(i, N).map(function (atom) {
+ return { operation: "delete", atom: atom };
+ }));
+
+ [].push.apply(diff, B.slice(j, M).map(function (atom) {
+ return { operation: "add", atom: atom };
+ }));
+
+ [].push.apply(diff, A.slice(N, N + K).map(function (atom) {
+ return { operation: "none", atom: atom }; }));
+
+ return diff;
+};
+
+// Accepts custom comparator
+var customIndexOf = function(item, start, equals){
+ var arr = this;
+ for (var i = start; i < arr.length; i++)
+ if (equals(item, arr[i]))
+ return i;
+ return -1;
+};
+
+function textDiff(text1, text2) {
+ return diff(text1.split("\n"), text2.split("\n"));
+}
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