/*jslint browser: true, indent: 4 */
/*
Example use of ScrollGuard: a simple, unobtrusive lazy loader.

Each time the user scrolled to the bottom of the page:

 1. Look if there is content to load (lookForNextPage)
 2. If new content, get content using Ajax (getNextPage)
 3. Append the new content and do some polish (appencContent)

*/
(function (g) {
    "use strict";
    var lookForNextPage,
        getNextPage,
        appendContent;

    if (g.ScrollGuard === undefined) {
        throw new Error("scrollguard.js is required!");
    }

    appendContent = function (content) {
        var body, rows, i, max, newContent, table;

        body = document.createElement("div");
        body.innerHTML = content;

        newContent = document.createDocumentFragment();
        rows = body.querySelectorAll(".main-c table tr");

        for (i = 1, max = rows.length; i < max; i += 1) {
            newContent.appendChild(rows[i]);
        }

        table = document.querySelector(".main-c table").tBodies[0];
        table.replaceChild(newContent, table.querySelector("tr.pagination"));
    };

    lookForNextPage = function () {
        var nextPage = document.getElementById("pager-next");

        if (nextPage) {
            getNextPage(nextPage.href);
        }
    };

    getNextPage = function (href) {
        var request = new XMLHttpRequest();

        request.onreadystatechange = function () {
            if (request.readyState === 4) {
                if (request.status === 200 || request.status === 304) {
                    appendContent(request.responseText);
                }
            }
        };

        request.open("GET", href, true);
        request.send(null);
    };

    if (document.getElementById("pager-next")) {
        g.ScrollGuard.add(lookForNextPage, -1);
        g.ScrollGuard.start();
    }
}(this));