// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

function validateLinks(links, callback) {
  var results = [];
  var pendingRequests = 0;

  function fetchLink(link) {
    if (!/^http(s?):\/\//.test(link.href))
      return;
    var xhr = new XMLHttpRequest();
    xhr.open("HEAD", link.href, true);
    xhr.onreadystatechange = function() {
      if (xhr.readyState < xhr.HEADERS_RECEIVED || xhr.processed)
        return;
      if (!xhr.status || xhr.status >= 400) {
        results.push({
            href: link.href,
            text: link.text,
            status: xhr.statusText
        });
      }
      xhr.processed = true;
      xhr.abort();
      if (!--pendingRequests) {
        callback({ total: links.length, badlinks: results });
      }
    }
    try {
      xhr.send(null);
      pendingRequests++;
    } catch (e) {
      console.error("XHR failed for " + link.href + ", " + e);
    }
  }

  for (var i = 0; i < links.length; ++i)
    fetchLink(links[i]);
}

chrome.extension.onRequest.addListener(function(request, sender, callback) {
  var tabId = request.tabId;
  chrome.tabs.executeScript(tabId, { file: "content.js" }, function() {
    chrome.tabs.sendRequest(tabId, {}, function(results) {
      validateLinks(results, callback);
    });
  });
});