/*
 * Copyright (c) 2006-2016, openmetaverse.co
 * Copyright (c) 2019, Cinderblocks Design Co.
 * All rights reserved.
 *
 * - Redistribution and use in source and binary forms, with or without 
 *   modification, are permitted provided that the following conditions are met:
 *
 * - Redistributions of source code must retain the above copyright notice, this
 *   list of conditions and the following disclaimer.
 * - Neither the name of the openmetaverse.co nor the names 
 *   of its contributors may be used to endorse or promote products derived from
 *   this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE 
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 
 * POSSIBILITY OF SUCH DAMAGE.
 */

using System;
using System.Net;
using System.IO;
using System.Threading;
using System.Security.Cryptography.X509Certificates;

namespace OpenMetaverse.Http
{
    public static class CapsBase
    {
        public delegate void OpenWriteEventHandler(HttpWebRequest request);
        public delegate void DownloadProgressEventHandler(HttpWebRequest request, HttpWebResponse response, int bytesReceived, int totalBytesToReceive);
        public delegate void RequestCompletedEventHandler(HttpWebRequest request, HttpWebResponse response, byte[] responseData, Exception error);

        static CapsBase()
        {
            ServicePointManager.ServerCertificateValidationCallback = (sender, certificate, chain, sslPolicyErrors) => true;
        }

        private class RequestState
        {
            public HttpWebRequest Request;
            public byte[] UploadData;
            public int MillisecondsTimeout;
            public OpenWriteEventHandler OpenWriteCallback;
            public DownloadProgressEventHandler DownloadProgressCallback;
            public RequestCompletedEventHandler CompletedCallback;

            public RequestState(HttpWebRequest request, byte[] uploadData, int millisecondsTimeout, OpenWriteEventHandler openWriteCallback,
                DownloadProgressEventHandler downloadProgressCallback, RequestCompletedEventHandler completedCallback)
            {
                Request = request;
                UploadData = uploadData;
                MillisecondsTimeout = millisecondsTimeout;
                OpenWriteCallback = openWriteCallback;
                DownloadProgressCallback = downloadProgressCallback;
                CompletedCallback = completedCallback;
            }
        }

        public static HttpWebRequest UploadDataAsync(Uri address, X509Certificate2 clientCert, string contentType, byte[] data,
            int millisecondsTimeout, OpenWriteEventHandler openWriteCallback, DownloadProgressEventHandler downloadProgressCallback,
            RequestCompletedEventHandler completedCallback)
        {
            // Create the request
            var request = SetupRequest(address, clientCert);
            request.ContentLength = data.Length;
            if (!string.IsNullOrEmpty(contentType))
                request.ContentType = contentType;
            request.Method = "POST";

            // Create an object to hold all of the state for this request
            var state = new RequestState(request, data, millisecondsTimeout, openWriteCallback,
                downloadProgressCallback, completedCallback);

            // Start the request for a stream to upload to
            IAsyncResult result = request.BeginGetRequestStream(OpenWrite, state);
            // Register a timeout for the request
            ThreadPool.RegisterWaitForSingleObject(result.AsyncWaitHandle, TimeoutCallback, state, millisecondsTimeout, true);

            return request;
        }

        public static HttpWebRequest DownloadStringAsync(Uri address, X509Certificate2 clientCert, int millisecondsTimeout,
            DownloadProgressEventHandler downloadProgressCallback, RequestCompletedEventHandler completedCallback)
        {
            // Create the request
            HttpWebRequest request = SetupRequest(address, clientCert);
            request.Method = "GET";
            DownloadDataAsync(request, millisecondsTimeout, downloadProgressCallback, completedCallback);
            return request;
        }

        public static void DownloadDataAsync(HttpWebRequest request, int millisecondsTimeout,
            DownloadProgressEventHandler downloadProgressCallback, RequestCompletedEventHandler completedCallback)
        {
            // Create an object to hold all of the state for this request
            RequestState state = new RequestState(request, null, millisecondsTimeout, null, downloadProgressCallback,
                completedCallback);

            // Start the request for the remote server response
            IAsyncResult result = request.BeginGetResponse(GetResponse, state);
            // Register a timeout for the request
            ThreadPool.RegisterWaitForSingleObject(result.AsyncWaitHandle, TimeoutCallback, state, millisecondsTimeout, true);
        }

        private static HttpWebRequest SetupRequest(Uri address, X509Certificate2 clientCert)
        {
            if (address == null)
                throw new ArgumentNullException(nameof(address));

            // Create the request
            var request = (HttpWebRequest)WebRequest.Create(address);

            // Add the client certificate to the request if one was given
            if (clientCert != null)
                request.ClientCertificates.Add(clientCert);

            // Leave idle connections to this endpoint open for up to 60 seconds
            request.ServicePoint.MaxIdleTime = 1000 * 60;
            // Disable stupid Expect-100: Continue header
            request.ServicePoint.Expect100Continue = false;
            // Crank up the max number of connections per endpoint
            // We set this manually here instead of in ServicePointManager to avoid interference with callers.
            if (request.ServicePoint.ConnectionLimit < Settings.MAX_HTTP_CONNECTIONS)
            {
                Logger.Log(
                    string.Format(
                        "In CapsBase.SetupRequest() setting conn limit for {0}:{1} to {2}", 
                        address.Host, address.Port, Settings.MAX_HTTP_CONNECTIONS), 
                    Helpers.LogLevel.Debug);
                request.ServicePoint.ConnectionLimit = Settings.MAX_HTTP_CONNECTIONS;
            }
            // Caps requests are never sent as trickles of data, so Nagle's
            // coalescing algorithm won't help us
            request.ServicePoint.UseNagleAlgorithm = false;
            // If not on mono, set accept-encoding header that allows response compression
            request.AutomaticDecompression = DecompressionMethods.GZip | DecompressionMethods.Deflate;
            return request;
        }

        private static void OpenWrite(IAsyncResult ar)
        {
            RequestState state = (RequestState)ar.AsyncState;

            try
            {
                // Get the stream to write our upload to
                using (Stream uploadStream = state.Request.EndGetRequestStream(ar))
                {
                    // Fire the callback for successfully opening the stream
                    state.OpenWriteCallback?.Invoke(state.Request);

                    // Write our data to the upload stream
                    uploadStream.Write(state.UploadData, 0, state.UploadData.Length);
                }

                // Start the request for the remote server response
                IAsyncResult result = state.Request.BeginGetResponse(GetResponse, state);
                // Register a timeout for the request
                ThreadPool.RegisterWaitForSingleObject(result.AsyncWaitHandle, TimeoutCallback, state,
                    state.MillisecondsTimeout, true);
            }
            catch (Exception ex)
            {
                //Logger.Log.Debug("CapsBase.OpenWrite(): " + ex.Message);
                state.CompletedCallback?.Invoke(state.Request, null, null, ex);
            }
        }

        private static void GetResponse(IAsyncResult ar)
        {
            var state = (RequestState)ar.AsyncState;
            HttpWebResponse response = null;
            byte[] responseData = null;
            Exception error = null;

            try
            {
                using (response = (HttpWebResponse)state.Request.EndGetResponse(ar))
                {
                    // Get the stream for downloading the response
                    using (var responseStream = response.GetResponseStream())
                    {
                        #region Read the response

                        // If Content-Length is set we create a buffer of the exact size, otherwise
                        // a MemoryStream is used to receive the response
                        bool nolength = (response.ContentLength <= 0) || (Type.GetType("Mono.Runtime") != null);
                        int size = (nolength) ? 8192 : (int)response.ContentLength;
                        MemoryStream ms = (nolength) ? new MemoryStream() : null;
                        byte[] buffer = new byte[size];

                        int bytesRead = 0;
                        int offset = 0;
                        int totalBytesRead = 0;
                        int totalSize = nolength ? 0 : size;

                        while ((bytesRead = responseStream.Read(buffer, offset, size)) != 0)
                        {
                            totalBytesRead += bytesRead;

                            if (nolength)
                            {
                                totalSize += (size - bytesRead);
                                ms.Write(buffer, 0, bytesRead);
                            }
                            else
                            {
                                offset += bytesRead;
                                size -= bytesRead;
                            }

                            // Fire the download progress callback for each chunk of received data
                            if (state.DownloadProgressCallback != null)
                                state.DownloadProgressCallback(state.Request, response, totalBytesRead, totalSize);
                        }

                        if (nolength)
                        {
                            responseData = ms.ToArray();
                            ms.Close();
                            ms.Dispose();
                        }
                        else
                        {
                            responseData = buffer;
                        }

                        #endregion Read the response
                    }
                }
            }
            catch (Exception ex)
            {
                // Logger.DebugLog("CapsBase.GetResponse(): " + ex.Message);
                error = ex;
            }

            state.CompletedCallback?.Invoke(state.Request, response, responseData, error);
        }

        private static void TimeoutCallback(object state, bool timedOut)
        {
            if (!timedOut) return;

            RequestState requestState = state as RequestState;
            //Logger.Log.Debug("CapsBase.TimeoutCallback(): Request to " + requestState.Request.RequestUri +
            //    " timed out after " + requestState.MillisecondsTimeout + " milliseconds");
            requestState?.Request?.Abort();
        }
    }
}