/*
 * This work is licensed under the Creative Commons Attribution 2.5 License. 
 * To view a copy of this license, visit http://creativecommons.org/licenses/by/2.5/
 * or send a letter to Creative Commons, 543 Howard Street, 5th Floor, 
 * San Francisco, California, 94105, USA.
 * 
 * Original developer: David Betz <dfb@davidbetz.net>
 * 
*/

using System;
using System.Collections.Generic;
using System.Text;
using System.Net;
using System.IO;
using System.Xml;

namespace FeedBuilder
{
    class FeedFormatDetector
    {
        public static AbstractReader Detect(Uri uri)
        {
            return Detect(uri.AbsoluteUri);
        }

        public static AbstractReader Detect(String url)
        {
            if (!url.StartsWith("http://") && !url.StartsWith("https://"))
            {
                throw new FeedReaderException("Feed url must begin with either http:// or https://");
            }

            String feedData = "";

            HttpWebRequest myRequest = (HttpWebRequest)WebRequest.Create(url);
            using (HttpWebResponse myHttpWebResponse = (HttpWebResponse)myRequest.GetResponse())
            {
                using (Stream streamResponse = myHttpWebResponse.GetResponseStream())
                {
                    using (StreamReader streamRead = new StreamReader(streamResponse))
                    {
                        Char[] readBuffer = new Char[256];
                        int count = streamRead.Read(readBuffer, 0, 256);

                        StringBuilder builder = new StringBuilder();
                        while (count > 0)
                        {
                            String resultData = new String(readBuffer, 0, count);
                            Console.WriteLine(resultData);
                            builder.Append(resultData);
                            count = streamRead.Read(readBuffer, 0, 256);

                        }

                        feedData = builder.ToString().Trim();
                    }
                }
            }

            AbstractReader reader;
            XmlDocument doc = new XmlDocument();
            doc.Load(url);

            if (doc.DocumentElement != null && doc.DocumentElement.ChildNodes != null)
            {
                if (doc.DocumentElement.Name.ToLower() == "rss")
                {

                    // Yes this loads the URL again... RSS.NET simply would NOT let
                    // me pass it the data.  Perhaps they will fix this bug in the
                    // future.
                    reader = new RssReader(url);
                }
                else if (doc.DocumentElement.Name.ToLower() == "feed")
                {
                    reader = new AtomReader(feedData);
                }
                else
                {
                    throw new FeedReaderException("Unknown feed format");
                }
            }
            else
            {
                throw new FeedReaderException("Invalid feed");
            }

            return reader;
        }
    }
}