// Private methods.
/// <summary>
/// Crawls the feed at the specified parameters.
/// </summary>
/// <param name="asyncResult">The asynchronous result.</param>
/// <param name="feedId">The feed.</param>
/// <param name="timeId">The time.</param>
/// <param name="category">The category.</param>
/// <param name="regionId">The region.</param>
/// <param name="obj">The standard feed object.</param>
/// <returns>The crawl result.</returns>
private CrawlResult CrawlFeed(
SpiderAsyncResult asyncResult,
YouTubeStandardFeed feedId,
YouTubeTimeId timeId,
string category,
string regionId,
ref DbObjectStandardFeed obj)
{
// If the asynchronousn operation has been canceled, do nothing.
if (asyncResult.IsCanceled) return CrawlResult.Canceled;
// Compute the feed key.
string key = this.EncodeFeedKey(feedId, timeId, category, regionId);
// Compute the feed URI starting at index 1 and ask for 1 result.
Uri uri = YouTubeUri.GetStandardFeed(feedId, regionId, category, timeId, 1, 1);
// Create a new video request.
YouTubeRequestFeed<Video> request = new YouTubeRequestFeed<Video>(this.crawler.YouTube.Settings);
// Set the feed URL.
obj.Url = uri.AbsoluteUri;
try
{
// Begin an asynchronous request for the standard feed.
AsyncWebResult result = request.Begin(uri, (AsyncWebResult webResult) => { }) as AsyncWebResult;
// Add the result of the web operation to the collection of web requests.
AsyncWebOperation operation = asyncResult.AddAsyncWeb(request, result);
// Wait for the asynchronous operation to complete.
result.AsyncWaitHandle.WaitOne();
// Remove the result of the web operation from the collection of web requests.
asyncResult.RemoveAsyncWeb(operation);
// Complete the request and get the video feed.
Feed<Video> feed = request.End(result);
// If the operation completed successfully, set the browsable to true.
obj.Browsable = true;
// Set the response HTTP code.
obj.HttpCode = (int)(result as AsyncWebResult).Response.StatusCode;
// Return the result.
return (feed.FailuresAtom.Count == 0) && (feed.FailuresEntry.Count == 0) ? CrawlResult.Success : CrawlResult.Warning;
}
catch (WebException exception)
{
if (exception.Status == WebExceptionStatus.RequestCanceled)
{
return CrawlResult.Canceled;
}
else
{
// If the operation failed with a web exception, set the browsable to false.
obj.Browsable = false;
// Set the response HTTP code.
obj.HttpCode = (int)(exception.Response as HttpWebResponse).StatusCode;
// Return the result.
return CrawlResult.Fail;
}
}
catch (Exception)
{
// If the operation failed with a web exception, set the browsable to false.
obj.Browsable = false;
// Set the response HTTP code to null.
obj.HttpCode = null;
// Return the result.
return CrawlResult.Fail;
}
}
// Public methods.
/// <summary>
/// Begins an asynchronous spider crawling using the specified user state.
/// </summary>
/// <param name="callback"></param>
/// <param name="userState">The user state.</param>
/// <returns>The result of the asynchronous spider operation.</returns>
public IAsyncResult BeginCrawl(SpiderCallback callback, object userState = null)
{
// Update the spider state.
base.OnStarted();
try
{
// Compute the standard feeds to crawl.
Dictionary<string, DbObjectStandardFeed> feeds = new Dictionary<string, DbObjectStandardFeed>();
// For all standard feeds.
foreach (YouTubeStandardFeed feed in InetApi.YouTube.Api.V2.YouTube.StandardFeeds)
{
// If the feed is not selected, continue.
if (!this.GetFeedSelected(feed)) continue;
// Get the valid times for this feed.
YouTubeTimeId[] times = YouTubeUri.GetValidTime(feed);
// For all times corresponding to this feed.
foreach (YouTubeTimeId time in times)
{
// Create a new standard feed object.
DbObjectStandardFeed obj = new DbObjectStandardFeed();
obj.Id = this.EncodeFeedKey(feed, time, null, null);
obj.FeedId = (int)feed;
obj.TimeId = (int)time;
obj.Category = null;
obj.Region = null;
feeds.Add(obj.Id, obj);
// For all assignable and non-deprecated categories.
foreach (YouTubeCategory category in this.crawler.YouTube.Categories)
{
// If the category supports browsable regions.
if (category.Browsable != null)
{
// Create a new standard feed object.
obj = new DbObjectStandardFeed();
obj.Id = this.EncodeFeedKey(feed, time, category.Label, null);
obj.FeedId = (int)feed;
obj.TimeId = (int)time;
obj.Category = category.Term;
obj.Region = null;
feeds.Add(obj.Id, obj);
// For all browsable regions.
foreach (string region in category.Browsable)
{
// Create a new standard feed object.
obj = new DbObjectStandardFeed();
obj.Id = this.EncodeFeedKey(feed, time, category.Label, region);
obj.FeedId = (int)feed;
obj.TimeId = (int)time;
obj.Category = category.Label;
obj.Region = region;
feeds.Add(obj.Id, obj);
}
}
}
}
}
// Raise the crawl feeds started event.
if (this.FeedsCrawlStarted != null) this.FeedsCrawlStarted(this, new SpiderInfoEventArgs<CrawlInfo>(this, new CrawlInfo(feeds)));
// Create a new spider asynchronous result.
SpiderAsyncResult asyncResult = new SpiderAsyncResult(userState);
// Set the crawl result counters.
int counterSuccess = 0;
int counterWarning = 0;
int counterFailed = 0;
int counterPending = feeds.Count;
// Execute the crawl on the thread pool.
ThreadPool.QueueUserWorkItem((object state) =>
{
// Set the feed index.
int index = 0;
// For each feed in the feeds collection.
foreach(KeyValuePair<string, DbObjectStandardFeed> feed in feeds)
{
// Check if the crawl has been canceled.
if (asyncResult.IsCanceled) break;
// Increment the feed index.
index++;
// Get the object.
DbObjectStandardFeed obj = feed.Value;
// Call the feed started event handler.
if (this.FeedCrawlStarted != null) this.FeedCrawlStarted(this, new SpiderInfoEventArgs<FeedStartedInfo>(this, new FeedStartedInfo(obj, index, feeds.Count)));
// Crawl the feed.
CrawlResult result = this.CrawlFeed(
asyncResult,
(YouTubeStandardFeed)obj.FeedId,
(YouTubeTimeId)obj.TimeId,
obj.Category,
obj.Region,
ref obj);
// Call the feed finished event handler.
if (this.FeedCrawlFinished != null) this.FeedCrawlFinished(this, new SpiderInfoEventArgs<FeedFinishedInfo>(this, new FeedFinishedInfo(obj, index, feeds.Count, result)));
}
// Set the result.
asyncResult.Result = feeds;
// Raise the crawl feeds finished event.
if (this.FeedsCrawlFinished != null) this.FeedsCrawlFinished(this, new SpiderInfoEventArgs<CrawlInfo>(this, new CrawlInfo(feeds)));
// Update the spider state.
base.OnFinished();
});
// Returns the spider object as the asynchronous state.
return asyncResult;
}
catch (Exception)
{
// If an exception occurs, update the spider state.
base.OnFinished();
// Rethrow the exception.
throw;
}
}