// Request.cs
//
//  Copyright (C) 2008 Amr Hassan
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// 
// You should have received a copy of the GNU General Public License
// along with this program; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
//
//

using System;
using System.Reflection;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Web;
using System.Net;
using System.Text;
using System.Xml;
using System.IO;
using System.Threading;

namespace Lastfm.Services
{
	internal class Request
	{
        private TimeSpan _delay = TimeSpan.FromMilliseconds(50.0);
		const string ROOT = "http://ws.audioscrobbler.com/2.0/";
		
		public string MethodName {get; private set;}
		public Session Session {get; private set;}
		
		public RequestParameters Parameters {get; private set;}
		
		internal static DateTime? lastCallTime {get; set;}
		
		public Request(string methodName, Session session, RequestParameters parameters)
		{
			this.MethodName = methodName;
			this.Session = session;
			this.Parameters = parameters;
			
			this.Parameters["method"] = this.MethodName;
			this.Parameters["api_key"] = this.Session.APIKey;
			if (Session.Authenticated)
			{
				this.Parameters["sk"] = this.Session.SessionKey;
				signIt();
			}
		}
		
		internal void signIt()
		{
			// because auth.getSession requires a signature without session key. 
			this.Parameters["api_sig"] = this.getSignature();
		}
		
		private string getSignature()
		{
			string str = "";
			foreach(string key in this.Parameters.Keys)
				str += key + this.Parameters[key];
			
			str += this.Session.APISecret;
			
			return Utilities.md5(str);
			
		}
		
		private void delay()
		{
			// If the last call was less than one second ago, it would delay execution for a second.
			
			if (Request.lastCallTime == null)
				Request.lastCallTime = new Nullable<DateTime>(DateTime.Now);

            if (DateTime.Now.Subtract(lastCallTime.Value) > this._delay)
            {
                Thread.Sleep(this._delay);
            }
		}

		public XmlDocument execute()
		{
            XmlDocument document = HttpRuntime.Cache[this.GetCacheKey()] as XmlDocument;
		    if (document == null)
		    {
		        // delays the execution if necessary.
		        this.delay();

		        // Go on normally from here.
		        byte[] data = Parameters.ToBytes();

		        /* RANT 
			     * The most annoying thing i've ever encountered in my life.
			     * The freakin "Expect: 100-continue" kept being added to my headers collection
			     * making the post call always fail. I've waisted a whole day hunting down this
			     * bug, and finally i fired up wireshark sniffing my calls and found out about it.
			     * After googling the problem now that i know what it is exactly, I found
			     * the solution there: http://haacked.com/archive/2004/05/15/http-web-request-expect-100-continue.aspx
			     * so, thank you for saving my sanity. This works now. time to move on...
			    */
		        System.Net.ServicePointManager.Expect100Continue = false;

		        HttpWebRequest request = (HttpWebRequest) WebRequest.Create(ROOT);
		        request.ContentLength = data.Length;
		        request.UserAgent = Utilities.UserAgent;
		        request.ContentType = "application/x-www-form-urlencoded";
		        request.Method = "POST";
		        request.Headers["Accept-Charset"] = "utf-8";

		        request.Proxy = null;

		        Stream writeStream = request.GetRequestStream();
		        writeStream.Write(data, 0, data.Length);
		        writeStream.Close();

		        HttpWebResponse webresponse;
		        try
		        {
		            webresponse = (HttpWebResponse) request.GetResponse();
		        }
		        catch (WebException e)
		        {
		            webresponse = (HttpWebResponse) e.Response;
		        }

                document = new XmlDocument();
                Stream responseStream = webresponse.GetResponseStream();
                document.Load(new StreamReader(responseStream, Encoding.UTF8));
                this.checkForErrors(document);
                HttpRuntime.Cache[this.GetCacheKey()] = document;
		    }

            return document;
		}

        private string GetCacheKey()
        {
            return ("lastfm-sharp:" + this.MethodName + this.Parameters.ToString());
        }
		
		private void checkForErrors(XmlDocument document)
		{
			XmlNode n = document.GetElementsByTagName("lfm")[0];
			
			string status = n.Attributes[0].InnerText;
			
			if (status == "failed")
			{
				XmlNode err = document.GetElementsByTagName("error")[0];
				ServiceExceptionType type = (ServiceExceptionType)Convert.ToInt32(err.Attributes[0].InnerText);
				string description = err.InnerText;
				
				throw new ServiceException(type, description);
			}
		}
	}
}