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// Web Crawler in AjSharp 
// http://ajlopez.wordpress.com/category/ajsharp/

// Build and launch agents

object WebCrawler
{
	sub Process(url, fn)
	{
		uri = new System.Uri(url);
		downloader = new Downloader();
		harvester = new Harvester();
		resolver = new Resolver(uri,5);
		processor = new Processor(fn);
		
		downloader.Harvester = harvester;
		downloader.Processor = processor;
		harvester.Resolver = resolver;
		resolver.Downloader = downloader;
		
		downloader.Process(uri, 0);
	}
}

// Downloads a page

agent Downloader 
{
	sub Process(uri,depth)
	{
		client = new System.Net.WebClient();
		content = client.DownloadString(uri);
		PrintLine("Downloaded: " + uri);
		this.Harvester.Process(uri,depth,content);
		this.Processor.Process(uri, content);
	}
}

// Process the content retrieved

agent Processor
{
	function Processor(fn)
	{
		this.fn = fn; // function to invoke
	}
	
	sub Process(uri, content)
	{
		// Add your logic
		this.fn(uri, content);
	}
}

// Get links from page

agent Harvester
{
	sub Process(uri,depth,content)
	{
		matches = System.Text.RegularExpressions.Regex.Matches(content, "href=\\s*\"([^&\"]*)\"");
		results = new List();
		
		foreach (match in matches) {
			value = match.Groups[1].Value;
			
			if (!results.Contains(value))
				results.Add(value);
		}
		
		foreach (result in results) 
			if (result.StartsWith("http"))
				this.Resolver.Process(new System.Uri(result), depth+1);
	}
}

// Filter invalid or already processed links

agent Resolver
{
	var processed = new List();	
	
	function Resolver(uri,maxdepth)
	{
		this.host = uri.Host;
		this.maxdepth = maxdepth;
	}
	
	sub Process(uri,depth) 
	{
		if (depth > this.maxdepth)
			return;
			
		if (uri.Host != this.host)
			return;
		
		if (uri.Scheme != System.Uri.UriSchemeHttp && uri.Scheme != System.Uri.UriSchemeHttps)
			return;
			
		if (processed.Contains(uri))
			return;
			
		processed.Add(uri);
			
		PrintLine("New Link: " + uri);
		this.Downloader.Process(uri,depth); 		
	}
}

// Example

WebCrawler.Process("http://ajlopez.wordpress.com", function(uri,content) { PrintLine("From ajlopez.wordpress "+uri);});
WebCrawler.Process("http://ajlopez.zoomblog.com", function(uri,content) { PrintLine("From ajlopez.zoomblog "+uri);});