/*
 * Javascript Diff Algorithm
 *  By John Resig (http://ejohn.org/)
 *  Modified by Chu Alan "sprite"
 *  Modified by Rodrigo Fernandes "rtfpessoa"
 *
 * Released under the MIT license.
 *
 * More Info:
 *  http://ejohn.org/projects/javascript-diff-algorithm/
 */

function JsDiff(o, n) {
    o = o.replace(/\s+$/, '');
    n = n.replace(/\s+$/, '');

    var out = diff(o == "" ? [] : o.split(/\s+/), n == "" ? [] : n.split(/\s+/));
    var str = "";

    var oSpace = o.match(/\s+/g);
    if (oSpace == null) {
        oSpace = ["\n"];
    } else {
        oSpace.push("\n");
    }
    var nSpace = n.match(/\s+/g);
    if (nSpace == null) {
        nSpace = ["\n"];
    } else {
        nSpace.push("\n");
    }

    if (out.n.length == 0) {
        for (var i = 0; i < out.o.length; i++) {
            str += '<del>' + out.o[i] + oSpace[i] + "</del>";
        }
    } else {
        if (out.n[0].text == null) {
            for (n = 0; n < out.o.length && out.o[n].text == null; n++) {
                str += '<del>' + out.o[n] + oSpace[n] + "</del>";
            }
        }

        for (var i = 0; i < out.n.length; i++) {
            if (out.n[i].text == null) {
                str += '<ins>' + out.n[i] + nSpace[i] + "</ins>";
            } else {
                var pre = "";

                for (n = out.n[i].row + 1; n < out.o.length && out.o[n].text == null; n++) {
                    pre += '<del>' + out.o[n] + oSpace[n] + "</del>";
                }
                str += " " + out.n[i].text + nSpace[i] + pre;
            }
        }
    }

    return str;
}

function diff(o, n) {
    var ns = new Object();
    var os = new Object();

    for (var i = 0; i < n.length; i++) {
        if (ns[n[i]] == null)
            ns[n[i]] = {rows: new Array(), o: null};
        ns[n[i]].rows.push(i);
    }

    for (var i = 0; i < o.length; i++) {
        if (os[o[i]] == null)
            os[o[i]] = {rows: new Array(), n: null};
        os[o[i]].rows.push(i);
    }

    for (var i in ns) {
        if (ns[i].rows.length == 1 && typeof(os[i]) != "undefined" && os[i].rows.length == 1) {
            n[ns[i].rows[0]] = {text: n[ns[i].rows[0]], row: os[i].rows[0]};
            o[os[i].rows[0]] = {text: o[os[i].rows[0]], row: ns[i].rows[0]};
        }
    }

    for (var i = 0; i < n.length - 1; i++) {
        if (n[i].text != null && n[i + 1].text == null && n[i].row + 1 < o.length && o[n[i].row + 1].text == null &&
          n[i + 1] == o[n[i].row + 1]) {
            n[i + 1] = {text: n[i + 1], row: n[i].row + 1};
            o[n[i].row + 1] = {text: o[n[i].row + 1], row: i + 1};
        }
    }

    for (var i = n.length - 1; i > 0; i--) {
        if (n[i].text != null && n[i - 1].text == null && n[i].row > 0 && o[n[i].row - 1].text == null &&
          n[i - 1] == o[n[i].row - 1]) {
            n[i - 1] = {text: n[i - 1], row: n[i].row - 1};
            o[n[i].row - 1] = {text: o[n[i].row - 1], row: i - 1};
        }
    }

    return {o: o, n: n};
}