using MediaBrowser.Common.Configuration;
using MediaBrowser.Common.Extensions;
using MediaBrowser.Common.IO;
using MediaBrowser.Common.Net;
using MediaBrowser.Model.Logging;
using MediaBrowser.Model.Net;
using MediaBrowser.Model.Serialization;
using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Net;
using System.Net.Cache;
using System.Net.Http;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace MediaBrowser.Common.Implementations.HttpClientManager
{
    /// <summary>
    /// Class HttpClientManager
    /// </summary>
    public class HttpClientManager : IHttpClient
    {
        /// <summary>
        /// The _logger
        /// </summary>
        private readonly ILogger _logger;

        /// <summary>
        /// The _app paths
        /// </summary>
        private readonly IApplicationPaths _appPaths;

        private readonly IJsonSerializer _jsonSerializer;
        private readonly FileSystemRepository _cacheRepository;

        /// <summary>
        /// Initializes a new instance of the <see cref="HttpClientManager" /> class.
        /// </summary>
        /// <param name="appPaths">The kernel.</param>
        /// <param name="logger">The logger.</param>
        /// <param name="jsonSerializer">The json serializer.</param>
        /// <exception cref="System.ArgumentNullException">
        /// appPaths
        /// or
        /// logger
        /// </exception>
        public HttpClientManager(IApplicationPaths appPaths, ILogger logger, IJsonSerializer jsonSerializer)
        {
            if (appPaths == null)
            {
                throw new ArgumentNullException("appPaths");
            }
            if (logger == null)
            {
                throw new ArgumentNullException("logger");
            }

            _logger = logger;
            _jsonSerializer = jsonSerializer;
            _appPaths = appPaths;

            _cacheRepository = new FileSystemRepository(Path.Combine(_appPaths.CachePath, "downloads"));
        }

        /// <summary>
        /// Holds a dictionary of http clients by host.  Use GetHttpClient(host) to retrieve or create a client for web requests.
        /// DON'T dispose it after use.
        /// </summary>
        /// <value>The HTTP clients.</value>
        private readonly ConcurrentDictionary<string, HttpClient> _httpClients = new ConcurrentDictionary<string, HttpClient>();

        /// <summary>
        /// Gets
        /// </summary>
        /// <param name="host">The host.</param>
        /// <returns>HttpClient.</returns>
        /// <exception cref="System.ArgumentNullException">host</exception>
        private HttpClient GetHttpClient(string host)
        {
            if (string.IsNullOrEmpty(host))
            {
                throw new ArgumentNullException("host");
            }

            HttpClient client;
            if (!_httpClients.TryGetValue(host, out client))
            {
                var handler = new WebRequestHandler
                {
                    CachePolicy = new RequestCachePolicy(RequestCacheLevel.BypassCache),
                    AutomaticDecompression = DecompressionMethods.None
                };

                client = new HttpClient(handler);
                client.Timeout = TimeSpan.FromSeconds(15);
                _httpClients.TryAdd(host, client);
            }

            return client;
        }

        /// <summary>
        /// Performs a GET request and returns the resulting stream
        /// </summary>
        /// <param name="options">The options.</param>
        /// <returns>Task{Stream}.</returns>
        /// <exception cref="HttpException"></exception>
        /// <exception cref="MediaBrowser.Model.Net.HttpException"></exception>
        public async Task<Stream> Get(HttpRequestOptions options)
        {
            ValidateParams(options.Url, options.CancellationToken);

            HttpResponseInfo cachedInfo = null;

            var urlHash = options.Url.GetMD5().ToString();
            var cachedInfoPath = _cacheRepository.GetResourcePath(urlHash + ".js");
            var cachedReponsePath = _cacheRepository.GetResourcePath(urlHash + ".dat");

            if (options.EnableResponseCache)
            {
                try
                {
                    cachedInfo = _jsonSerializer.DeserializeFromFile<HttpResponseInfo>(cachedInfoPath);
                }
                catch (FileNotFoundException)
                {

                }

                if (cachedInfo != null)
                {
                    var now = DateTime.UtcNow;

                    var isCacheValid = (!cachedInfo.MustRevalidate && !string.IsNullOrEmpty(cachedInfo.Etag) && (now - cachedInfo.RequestDate).TotalDays < 7)
                        || (cachedInfo.Expires.HasValue && cachedInfo.Expires.Value > now);

                    if (isCacheValid)
                    {
                        _logger.Debug("Cache is still valid for {0}", options.Url);

                        try
                        {
                            return GetCachedResponse(cachedReponsePath);
                        }
                        catch (FileNotFoundException)
                        {

                        }
                    }
                }
            }

            options.CancellationToken.ThrowIfCancellationRequested();

            var message = GetHttpRequestMessage(options);

            if (options.EnableResponseCache && cachedInfo != null)
            {
                if (!string.IsNullOrEmpty(cachedInfo.Etag))
                {
                    message.Headers.Add("If-None-Match", cachedInfo.Etag);
                }
                else if (cachedInfo.LastModified.HasValue)
                {
                    message.Headers.IfModifiedSince = new DateTimeOffset(cachedInfo.LastModified.Value);
                }
            }

            if (options.ResourcePool != null)
            {
                await options.ResourcePool.WaitAsync(options.CancellationToken).ConfigureAwait(false);
            }

            _logger.Info("HttpClientManager.Get url: {0}", options.Url);

            try
            {
                options.CancellationToken.ThrowIfCancellationRequested();

                var response = await GetHttpClient(GetHostFromUrl(options.Url)).SendAsync(message, HttpCompletionOption.ResponseHeadersRead, options.CancellationToken).ConfigureAwait(false);

                if (options.EnableResponseCache)
                {
                    if (response.StatusCode != HttpStatusCode.NotModified)
                    {
                        EnsureSuccessStatusCode(response);
                    }

                    options.CancellationToken.ThrowIfCancellationRequested();

                    cachedInfo = UpdateInfoCache(cachedInfo, options.Url, cachedInfoPath, response);

                    if (response.StatusCode == HttpStatusCode.NotModified)
                    {
                        _logger.Debug("Server indicates not modified for {0}. Returning cached result.", options.Url);
                        
                        return GetCachedResponse(cachedReponsePath);
                    }

                    if (!string.IsNullOrEmpty(cachedInfo.Etag) || cachedInfo.LastModified.HasValue ||
                        (cachedInfo.Expires.HasValue && cachedInfo.Expires.Value > DateTime.UtcNow))
                    {
                        await UpdateResponseCache(response, cachedReponsePath).ConfigureAwait(false);

                        return GetCachedResponse(cachedReponsePath);
                    }
                }
                else
                {
                    EnsureSuccessStatusCode(response);

                    options.CancellationToken.ThrowIfCancellationRequested();
                }

                return await response.Content.ReadAsStreamAsync().ConfigureAwait(false);
            }
            catch (OperationCanceledException ex)
            {
                throw GetCancellationException(options.Url, options.CancellationToken, ex);
            }
            catch (HttpRequestException ex)
            {
                _logger.ErrorException("Error getting response from " + options.Url, ex);

                throw new HttpException(ex.Message, ex);
            }
            catch (Exception ex)
            {
                _logger.ErrorException("Error getting response from " + options.Url, ex);

                throw;
            }
            finally
            {
                if (options.ResourcePool != null)
                {
                    options.ResourcePool.Release();
                }
            }
        }

        /// <summary>
        /// Performs a GET request and returns the resulting stream
        /// </summary>
        /// <param name="url">The URL.</param>
        /// <param name="resourcePool">The resource pool.</param>
        /// <param name="cancellationToken">The cancellation token.</param>
        /// <returns>Task{Stream}.</returns>
        public Task<Stream> Get(string url, SemaphoreSlim resourcePool, CancellationToken cancellationToken)
        {
            return Get(new HttpRequestOptions
            {
                Url = url,
                ResourcePool = resourcePool,
                CancellationToken = cancellationToken,
            });
        }

        /// <summary>
        /// Gets the specified URL.
        /// </summary>
        /// <param name="url">The URL.</param>
        /// <param name="cancellationToken">The cancellation token.</param>
        /// <returns>Task{Stream}.</returns>
        public Task<Stream> Get(string url, CancellationToken cancellationToken)
        {
            return Get(url, null, cancellationToken);
        }

        /// <summary>
        /// Gets the cached response.
        /// </summary>
        /// <param name="responsePath">The response path.</param>
        /// <returns>Stream.</returns>
        private Stream GetCachedResponse(string responsePath)
        {
            return File.OpenRead(responsePath);
        }

        /// <summary>
        /// Updates the cache.
        /// </summary>
        /// <param name="cachedInfo">The cached info.</param>
        /// <param name="url">The URL.</param>
        /// <param name="path">The path.</param>
        /// <param name="response">The response.</param>
        private HttpResponseInfo UpdateInfoCache(HttpResponseInfo cachedInfo, string url, string path, HttpResponseMessage response)
        {
            var fileExists = true;

            if (cachedInfo == null)
            {
                cachedInfo = new HttpResponseInfo();
                fileExists = false;
            }

            cachedInfo.Url = url;
            cachedInfo.RequestDate = DateTime.UtcNow;

            var etag = response.Headers.ETag;
            if (etag != null)
            {
                cachedInfo.Etag = etag.Tag;
            }

            var modified = response.Content.Headers.LastModified;

            if (modified.HasValue)
            {
                cachedInfo.LastModified = modified.Value.UtcDateTime;
            }
            else if (response.Headers.Age.HasValue)
            {
                cachedInfo.LastModified = DateTime.UtcNow.Subtract(response.Headers.Age.Value);
            }

            var expires = response.Content.Headers.Expires;

            if (expires.HasValue)
            {
                cachedInfo.Expires = expires.Value.UtcDateTime;
            }
            else
            {
                var cacheControl = response.Headers.CacheControl;

                if (cacheControl != null)
                {
                    if (cacheControl.MaxAge.HasValue)
                    {
                        var baseline = cachedInfo.LastModified ?? DateTime.UtcNow;
                        cachedInfo.Expires = baseline.Add(cacheControl.MaxAge.Value);
                    }

                    cachedInfo.MustRevalidate = cacheControl.MustRevalidate;
                }
            }

            if (string.IsNullOrEmpty(cachedInfo.Etag) && !cachedInfo.Expires.HasValue && !cachedInfo.LastModified.HasValue)
            {
                // Nothing to cache
                if (fileExists)
                {
                    File.Delete(path);
                }
            }
            else
            {
                _jsonSerializer.SerializeToFile(cachedInfo, path);
            }

            return cachedInfo;
        }

        /// <summary>
        /// Updates the response cache.
        /// </summary>
        /// <param name="response">The response.</param>
        /// <param name="path">The path.</param>
        /// <returns>Task.</returns>
        private async Task UpdateResponseCache(HttpResponseMessage response, string path)
        {
            using (var stream = await response.Content.ReadAsStreamAsync().ConfigureAwait(false))
            {
                using (var fs = new FileStream(path, FileMode.Create, FileAccess.Write, FileShare.Read, StreamDefaults.DefaultFileStreamBufferSize, FileOptions.Asynchronous))
                {
                    await stream.CopyToAsync(fs).ConfigureAwait(false);
                }
            }
        }

        /// <summary>
        /// Performs a POST request
        /// </summary>
        /// <param name="url">The URL.</param>
        /// <param name="postData">Params to add to the POST data.</param>
        /// <param name="resourcePool">The resource pool.</param>
        /// <param name="cancellationToken">The cancellation token.</param>
        /// <returns>stream on success, null on failure</returns>
        /// <exception cref="System.ArgumentNullException">postData</exception>
        /// <exception cref="MediaBrowser.Model.Net.HttpException"></exception>
        public async Task<Stream> Post(string url, Dictionary<string, string> postData, SemaphoreSlim resourcePool, CancellationToken cancellationToken)
        {
            ValidateParams(url, cancellationToken);

            if (postData == null)
            {
                throw new ArgumentNullException("postData");
            }

            cancellationToken.ThrowIfCancellationRequested();

            var strings = postData.Keys.Select(key => string.Format("{0}={1}", key, postData[key]));
            var postContent = string.Join("&", strings.ToArray());
            var content = new StringContent(postContent, Encoding.UTF8, "application/x-www-form-urlencoded");

            if (resourcePool != null)
            {
                await resourcePool.WaitAsync(cancellationToken).ConfigureAwait(false);
            }

            _logger.Info("HttpClientManager.Post url: {0}", url);

            try
            {
                cancellationToken.ThrowIfCancellationRequested();

                var msg = await GetHttpClient(GetHostFromUrl(url)).PostAsync(url, content, cancellationToken).ConfigureAwait(false);

                EnsureSuccessStatusCode(msg);

                return await msg.Content.ReadAsStreamAsync().ConfigureAwait(false);
            }
            catch (OperationCanceledException ex)
            {
                throw GetCancellationException(url, cancellationToken, ex);
            }
            catch (HttpRequestException ex)
            {
                _logger.ErrorException("Error getting response from " + url, ex);

                throw new HttpException(ex.Message, ex);
            }
            finally
            {
                if (resourcePool != null)
                {
                    resourcePool.Release();
                }
            }
        }

        /// <summary>
        /// Downloads the contents of a given url into a temporary location
        /// </summary>
        /// <param name="options">The options.</param>
        /// <returns>Task{System.String}.</returns>
        /// <exception cref="System.ArgumentNullException">progress</exception>
        /// <exception cref="HttpException"></exception>
        /// <exception cref="MediaBrowser.Model.Net.HttpException"></exception>
        public async Task<string> GetTempFile(HttpRequestOptions options)
        {
            ValidateParams(options.Url, options.CancellationToken);

            var tempFile = Path.Combine(_appPaths.TempDirectory, Guid.NewGuid() + ".tmp");

            if (options.Progress == null)
            {
                throw new ArgumentNullException("progress");
            }

            options.CancellationToken.ThrowIfCancellationRequested();

            if (options.ResourcePool != null)
            {
                await options.ResourcePool.WaitAsync(options.CancellationToken).ConfigureAwait(false);
            }

            options.Progress.Report(0);

            _logger.Info("HttpClientManager.GetTempFile url: {0}, temp file: {1}", options.Url, tempFile);

            try
            {
                options.CancellationToken.ThrowIfCancellationRequested();

                using (var response = await GetHttpClient(GetHostFromUrl(options.Url)).SendAsync(GetHttpRequestMessage(options), HttpCompletionOption.ResponseHeadersRead, options.CancellationToken).ConfigureAwait(false))
                {
                    EnsureSuccessStatusCode(response);

                    options.CancellationToken.ThrowIfCancellationRequested();

                    var contentLength = GetContentLength(response);

                    if (!contentLength.HasValue)
                    {
                        // We're not able to track progress
                        using (var stream = await response.Content.ReadAsStreamAsync().ConfigureAwait(false))
                        {
                            using (var fs = new FileStream(tempFile, FileMode.Create, FileAccess.Write, FileShare.Read, StreamDefaults.DefaultFileStreamBufferSize, FileOptions.Asynchronous))
                            {
                                await stream.CopyToAsync(fs, StreamDefaults.DefaultCopyToBufferSize, options.CancellationToken).ConfigureAwait(false);
                            }
                        }
                    }
                    else
                    {
                        using (var stream = ProgressStream.CreateReadProgressStream(await response.Content.ReadAsStreamAsync().ConfigureAwait(false), options.Progress.Report, contentLength.Value))
                        {
                            using (var fs = new FileStream(tempFile, FileMode.Create, FileAccess.Write, FileShare.Read, StreamDefaults.DefaultFileStreamBufferSize, FileOptions.Asynchronous))
                            {
                                await stream.CopyToAsync(fs, StreamDefaults.DefaultCopyToBufferSize, options.CancellationToken).ConfigureAwait(false);
                            }
                        }
                    }

                    options.Progress.Report(100);

                    options.CancellationToken.ThrowIfCancellationRequested();
                }
            }
            catch (Exception ex)
            {
                HandleTempFileException(ex, options, tempFile);
            }
            finally
            {
                if (options.ResourcePool != null)
                {
                    options.ResourcePool.Release();
                }
            }

            return tempFile;
        }

        /// <summary>
        /// Gets the message.
        /// </summary>
        /// <param name="options">The options.</param>
        /// <returns>HttpResponseMessage.</returns>
        private HttpRequestMessage GetHttpRequestMessage(HttpRequestOptions options)
        {
            var message = new HttpRequestMessage(HttpMethod.Get, options.Url);

            if (!string.IsNullOrEmpty(options.UserAgent))
            {
                message.Headers.Add("User-Agent", options.UserAgent);
            }

            if (!string.IsNullOrEmpty(options.AcceptHeader))
            {
                message.Headers.Add("Accept", options.AcceptHeader);
            }

            return message;
        }

        /// <summary>
        /// Gets the length of the content.
        /// </summary>
        /// <param name="response">The response.</param>
        /// <returns>System.Nullable{System.Int64}.</returns>
        private long? GetContentLength(HttpResponseMessage response)
        {
            IEnumerable<string> lengthValues;

            if (!response.Headers.TryGetValues("content-length", out lengthValues) && !response.Content.Headers.TryGetValues("content-length", out lengthValues))
            {
                return null;
            }

            return long.Parse(string.Join(string.Empty, lengthValues.ToArray()), UsCulture);
        }

        protected static readonly CultureInfo UsCulture = new CultureInfo("en-US");

        /// <summary>
        /// Handles the temp file exception.
        /// </summary>
        /// <param name="ex">The ex.</param>
        /// <param name="options">The options.</param>
        /// <param name="tempFile">The temp file.</param>
        /// <returns>Task.</returns>
        /// <exception cref="HttpException"></exception>
        private void HandleTempFileException(Exception ex, HttpRequestOptions options, string tempFile)
        {
            var operationCanceledException = ex as OperationCanceledException;

            if (operationCanceledException != null)
            {
                // Cleanup
                if (File.Exists(tempFile))
                {
                    File.Delete(tempFile);
                }

                throw GetCancellationException(options.Url, options.CancellationToken, operationCanceledException);
            }

            _logger.ErrorException("Error getting response from " + options.Url, ex);

            var httpRequestException = ex as HttpRequestException;

            // Cleanup
            if (File.Exists(tempFile))
            {
                File.Delete(tempFile);
            }

            if (httpRequestException != null)
            {
                throw new HttpException(ex.Message, ex);
            }

            throw ex;
        }

        /// <summary>
        /// Validates the params.
        /// </summary>
        /// <param name="url">The URL.</param>
        /// <param name="cancellationToken">The cancellation token.</param>
        /// <exception cref="System.ArgumentNullException">url</exception>
        private void ValidateParams(string url, CancellationToken cancellationToken)
        {
            if (string.IsNullOrEmpty(url))
            {
                throw new ArgumentNullException("url");
            }

            if (cancellationToken == null)
            {
                throw new ArgumentNullException("cancellationToken");
            }
        }

        /// <summary>
        /// Gets the host from URL.
        /// </summary>
        /// <param name="url">The URL.</param>
        /// <returns>System.String.</returns>
        private string GetHostFromUrl(string url)
        {
            var start = url.IndexOf("://", StringComparison.OrdinalIgnoreCase) + 3;
            var len = url.IndexOf('/', start) - start;
            return url.Substring(start, len);
        }

        /// <summary>
        /// Performs application-defined tasks associated with freeing, releasing, or resetting unmanaged resources.
        /// </summary>
        public void Dispose()
        {
            Dispose(true);
            GC.SuppressFinalize(this);
        }

        /// <summary>
        /// Releases unmanaged and - optionally - managed resources.
        /// </summary>
        /// <param name="dispose"><c>true</c> to release both managed and unmanaged resources; <c>false</c> to release only unmanaged resources.</param>
        protected virtual void Dispose(bool dispose)
        {
            if (dispose)
            {
                foreach (var client in _httpClients.Values.ToList())
                {
                    client.Dispose();
                }

                _httpClients.Clear();
            }
        }

        /// <summary>
        /// Throws the cancellation exception.
        /// </summary>
        /// <param name="url">The URL.</param>
        /// <param name="cancellationToken">The cancellation token.</param>
        /// <param name="exception">The exception.</param>
        /// <returns>Exception.</returns>
        private Exception GetCancellationException(string url, CancellationToken cancellationToken, OperationCanceledException exception)
        {
            // If the HttpClient's timeout is reached, it will cancel the Task internally
            if (!cancellationToken.IsCancellationRequested)
            {
                var msg = string.Format("Connection to {0} timed out", url);

                _logger.Error(msg);

                // Throw an HttpException so that the caller doesn't think it was cancelled by user code
                return new HttpException(msg, exception) { IsTimedOut = true };
            }

            return exception;
        }

        /// <summary>
        /// Ensures the success status code.
        /// </summary>
        /// <param name="response">The response.</param>
        /// <exception cref="MediaBrowser.Model.Net.HttpException"></exception>
        private void EnsureSuccessStatusCode(HttpResponseMessage response)
        {
            if (!response.IsSuccessStatusCode)
            {
                throw new HttpException(response.ReasonPhrase) { StatusCode = response.StatusCode };
            }
        }

        /// <summary>
        /// Posts the specified URL.
        /// </summary>
        /// <param name="url">The URL.</param>
        /// <param name="postData">The post data.</param>
        /// <param name="cancellationToken">The cancellation token.</param>
        /// <returns>Task{Stream}.</returns>
        public Task<Stream> Post(string url, Dictionary<string, string> postData, CancellationToken cancellationToken)
        {
            return Post(url, postData, null, cancellationToken);
        }
    }
}