/*
 * 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 escape(s) {
    var n = s;
    n = n.replace(/&/g, "&");
    n = n.replace(/</g, "&lt;");
    n = n.replace(/>/g, "&gt;");
    n = n.replace(/"/g, "&quot;");

    return n;
}

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

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

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

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

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