using Sarand.Net.Standard.Base.App;
using Sarand.Net.Standard.Base.Core;
using Sarand.Net.Standard.Base.Tasks;
using Sarand.Net.Standard.Base.Utils;
using System;
using System.Collections.Generic;
using System.IO;
using System.Net;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace Sarand.Net.Standard.Base.Net
{
	//=======================================================================
	public class SacsHttpRequestData : SacsTaskData
	{
		public SacsHttpRequestData (CancellationToken? cancellationToken) : base(cancellationToken) { }
		/// <summary>URL to send request to.</summary>
		public String Url { get; set; }
		/// <summary>
		/// Request timeout. Default: 5 secs.
		/// <para>NB Not currently supported as can only be changed when static HTTP Client not in use.</para>
		/// </summary>
		public int TimeoutSecs { get; set; } = SacsHttpClient.RequestTimeoutSecs_Default;
		/// <summary>
		/// Headers to send with request.
		/// <para>Accept, Accept-Charset, Accept-Encoding, Accept-Language, User-Agent, Transfer-Encoding, Pragma, Expect etc.</para>
		/// </summary>
		public Dictionary<String, List<String>> RequestHeaders { get; } = new Dictionary<String, List<String>>();
		/// <summary>
		/// Content Headers to send with request.
		/// <para>Content-Length (bytes), Content-Type (media type), Content-Encoding (compression algorithm), Content-Language etc.</para>
		/// <para>Content-Type header is defaulted for POST request if not specified.</para>
		/// </summary>
		public Dictionary<String, List<String>> ContentHeaders { get; } = new Dictionary<String, List<String>>();
		/// <summary>
		/// Form values to post as 'URL Encoded'.
		/// <para>Content-Type defaults to 'application/x-www-form-urlencoded; charset=utf-8'.</para>
		/// </summary>
		public List<KeyValuePair<string, string>> FormData { get; } = new List<KeyValuePair<string, string>>();
		/// <summary>
		/// Data to POST. Ignored if FormData populated.
		/// <para>Content-Type defaults to 'text/plain; charset=utf-8'.</para>
		/// </summary>
		public String PostData { get; set; }
		/// <summary>Use POST request rather than GET even if no data to post.</summary>
		public bool ForcePost { get; set; }
	}

	//=======================================================================
	public class SacsHttpResponseData
	{
		public DateTime RequestStarted { get; set; }
		public DateTime RequestCompleted { get; set; }
		/// <summary>Response headers.</summary>
		public Dictionary<String, IEnumerable<String>> ResponseHeaders { get; } = new Dictionary<String, IEnumerable<String>>();
		/// <summary>Response content headers.</summary>
		public Dictionary<String, IEnumerable<String>> ContentHeaders { get; } = new Dictionary<String, IEnumerable<String>>();
		/// <summary>Indicates whether Status Code represents success.</summary>
		public bool Success { get; set; }
		/// <summary>HTTP Status Code.</summary>
		public HttpStatusCode StatusCode { get; set; }
		/// <summary>HTTP Reason Code.</summary>
		public String ReasonPhrase { get; set; } = "";
		/// <summary>Response data.</summary>
		public String Data { get; set; } = "";
		/// <summary>Elapsed time for request.</summary>
		public TimeSpan Elapsed { get; set; }
		/// <summary>Exception thrown during handling of request.</summary>
		public Exception Exception { get; set; }
		/// <summary>Error state message - generally exception type and message.</summary>
		public String ErrorStateMessage { get; set; }
	}

	//=======================================================================
	public static class SacsHttpClient
	{
		//-------------------------------------------------------------------
		// Data members.
		private static readonly HttpClient client;

		//-------------------------------------------------------------------
		// Static initialisation.
		static SacsHttpClient ()
		{
			// Configure client.
			client = new HttpClient();
			client.Timeout = new TimeSpan(0, 0, RequestTimeoutSecs_Default);
		}

		//-------------------------------------------------------------------
		// Properties.
		public static int RequestTimeoutSecs_Default { get; } = 5;
		public static String HeaderName_ContentType { get; } = "Content-Type";

		//-------------------------------------------------------------------
		public static async Task<SacsHttpResponseData> DoRequest (SacsHttpRequestData requestData)
		{
			String fn = "SacsHttpClient.DoRequest";
			SacsHttpResponseData responseData = new SacsHttpResponseData();
			requestData.ThrowIfCancellationRequested();

			// Construct content to post.
			HttpContent postContent = null;
			if (requestData.FormData.Count > 0)
			{
				postContent = new FormUrlEncodedContent(requestData.FormData);
				if (!requestData.ContentHeaders.ContainsKey(HeaderName_ContentType))
					requestData.ContentHeaders.Add(HeaderName_ContentType,"application/x-www-form-urlencoded; charset=utf-8");
			}
			else if (!StringUtil.IsEmpty(requestData.PostData) || requestData.ForcePost)
			{
				postContent = new StringContent(StringUtil.EmptyOnNull(requestData.PostData), Encoding.UTF8);
				if (!requestData.ContentHeaders.ContainsKey(HeaderName_ContentType))
					requestData.ContentHeaders.Add(HeaderName_ContentType,"text/plain; charset=utf-8");
			}
			requestData.ThrowIfCancellationRequested();

			// Make request.
			DateTime startedAt = DateTime.Now;
			try
			{
				// Request.
				using (HttpRequestMessage request = new HttpRequestMessage())
				{
					request.RequestUri = new Uri(requestData.Url);

					// Request headers.
					foreach (String headerName in requestData.RequestHeaders.Keys)
					{
						if (request.Headers.Contains(headerName))
							request.Headers.Remove(headerName);
						request.Headers.Add(headerName, requestData.RequestHeaders[headerName]);
					}

					// Default request headers.
					if (client.DefaultRequestHeaders.Accept.Count == 0 && request.Headers.Accept.Count == 0)
						request.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue("text/*"));

					// Configure request.
					HttpResponseMessage response = null;
					// Send request.
					if (postContent != null)
					{
						// POST.
						request.Method = HttpMethod.Post;
						request.Content = postContent;
						// Content headers.
						foreach (String headerName in requestData.ContentHeaders.Keys)
						{
							if (request.Content.Headers.Contains(headerName))
								request.Content.Headers.Remove(headerName);
							request.Content.Headers.Add(headerName, requestData.ContentHeaders[headerName]);
						}
						// Send request.
						responseData.RequestStarted = DateTime.Now;
						response = await client.SendAsync(request, requestData.CancellationToken);
						responseData.RequestCompleted = DateTime.Now;
					}
					else
					{
						// GET.
						request.Method = HttpMethod.Get;
						responseData.RequestStarted = DateTime.Now;
						response = await client.SendAsync(request, requestData.CancellationToken);
						responseData.RequestCompleted = DateTime.Now;
					}

					// Extract resopnse data.
					responseData.Success = response.IsSuccessStatusCode;
					responseData.StatusCode = response.StatusCode;
					responseData.ReasonPhrase = response.ReasonPhrase;
					if (response.Headers != null)
					{
						foreach (var header in response.Headers)
							responseData.ResponseHeaders[header.Key] = new List<String>(header.Value);
					}
					if (response.Content != null && response.Content.Headers != null)
					{
						foreach (var header in response.Content.Headers)
							responseData.ContentHeaders[header.Key] = new List<String>(header.Value);
					}
					responseData.Data = await response.Content.ReadAsStringAsync();
					if (response != null) response.Dispose();
				}
			}
			catch (Exception exc)
			{
				// Ignore if task has been cancelled.
				if (requestData.IsCancellationRequested) throw exc;
				// Record exception.
				responseData.Exception = exc;
				if (exc.InnerException != null)
				{
					exc = exc.InnerException;
				}
				String msg = exc.GetType().Name + ": " + exc.Message;
				SaLogger.Warn(fn + " " + msg + ExceptionUtil.GetStackEntries(exc, 6).Concat("", "\n\t"));
				responseData.ErrorStateMessage = msg;
			}
			requestData.ThrowIfCancellationRequested();

			// Complete response data.
			responseData.Elapsed = DateTime.Now - startedAt;
			return responseData;
		}

		//-------------------------------------------------------------------
		//       R e s p o n s e   S t a t u s   D e s c r i p t i o n
		//-------------------------------------------------------------------
		public static String GetResponseStatusDescription (HttpStatusCode httpStatus)
		{
			// Ref. https://www.iana.org/assignments/http-status-codes/http-status-codes.xhtml
			switch (httpStatus)
			{
				// 1xx: Informational - Request received, continuing process.
				case HttpStatusCode.Continue: return "Continue";
				// 2xx: Success - The action was successfully received, understood, and accepted.
				case HttpStatusCode.OK: return "OK";
				case HttpStatusCode.Created: return "Created";
				case HttpStatusCode.Accepted: return "Accepted";
				// 3xx: Redirection - Further action must be taken in order to complete the request.
				case HttpStatusCode.MultipleChoices: return "Multiple choices";
				case HttpStatusCode.MovedPermanently: return "Moved permanently";
				case HttpStatusCode.Found: return "Found";
				// 4xx: Client Error -The request contains bad syntax or cannot be fulfilled.
				case HttpStatusCode.BadRequest: return "Bad request";
				case HttpStatusCode.Unauthorized: return "Unauthorized";
				case HttpStatusCode.PaymentRequired: return "Payment required";
				case HttpStatusCode.Forbidden: return "Forbidden";
				case HttpStatusCode.NotFound: return "Not found";
				case HttpStatusCode.MethodNotAllowed: return "Method not allowed";
				case HttpStatusCode.NotAcceptable: return "Not acceptable";
				// 5xx: Server Error -The server failed to fulfill an apparently valid request.
				case HttpStatusCode.InternalServerError: return "Internal server error";
			}
			return httpStatus.ToString();
		}

		//-------------------------------------------------------------------
	}
	//=======================================================================
}