using Maki.Structures.Rest;
using Newtonsoft.Json;
using System;
using System.IO;
using System.Linq;
using System.Net;
using System.Text;

namespace Maki.Rest
{
    /// <summary>
    /// Handles requests to Discord's REST API
    /// </summary>
    internal class RestClient
    {
        /// <summary>
        /// User agent that is send alongside requests
        /// </summary>
        private const string USER_AGENT = @"DiscordBot (https://github.com/flashwave/maki, 1.0.0.0)";

        /// <summary>
        /// Container for parent DiscordClient instance
        /// </summary>
        private readonly Discord client;

        /// <summary>
        /// Request types that should be handled as data requests
        /// </summary>
        private readonly RestRequestMethod[] dataRequestTypes = new RestRequestMethod[] {
            RestRequestMethod.POST,
            RestRequestMethod.PUT,
            RestRequestMethod.PATCH,
        };

        /// <summary>
        /// Constructor
        /// </summary>
        /// <param name="c">Parent DiscordClient instance</param>
        public RestClient(Discord c)
        {
            client = c;
        }

        /// <summary>
        /// Creates a base HttpWebRequest
        /// </summary>
        /// <param name="method">Request method</param>
        /// <param name="url">Endpoint url</param>
        /// <returns>Prepared HttpWebRequest</returns>
        private HttpWebRequest BaseRequest(RestRequestMethod method, string url)
        {
            Uri uri = new Uri(RestEndpoints.BASE_URL + RestEndpoints.BASE_PATH + url);
            HttpWebRequest request = WebRequest.Create(uri) as HttpWebRequest;

            request.Method = method.ToString();
            request.UserAgent = USER_AGENT;

            if (!string.IsNullOrEmpty(client.Token))
                request.Headers[HttpRequestHeader.Authorization] = (client.IsBot ? "Bot " : string.Empty) + client.Token;

            return request;
        }

        /// <summary>
        /// Gets a response string from HttpWebRequest
        /// </summary>
        /// <param name="request">HttpWebRequest instance</param>
        /// <returns>string output</returns>
        private RestResponse<T> HandleResponse<T>(HttpWebRequest request)
        {
            HttpWebResponse webResponse;
            RestResponse<T> response = new RestResponse<T>();

            try
            {
                webResponse = request.GetResponse() as HttpWebResponse;
            }
            catch (WebException ex)
            {
                webResponse = ex.Response as HttpWebResponse;
            }

            Enum.TryParse(webResponse.Method, out response.Method);
            response.Uri = webResponse.ResponseUri;
            response.Status = (ushort)webResponse.StatusCode;

            using (Stream httpResponseStream = webResponse.GetResponseStream())
            using (StreamReader streamReader = new StreamReader(httpResponseStream))
                response.RawResponse = streamReader.ReadToEnd();

            webResponse.Close();

            Error error = default(Error);

            try
            {
                error = JsonConvert.DeserializeObject<Error>(response.RawResponse);
            }
            catch
            {
            }

            if (error.Equals(default(Error)))
            {
                response.ErrorCode = RestErrorCode.Ok;
                response.ErrorMessage = string.Empty;
            }
            else
            {
                response.ErrorCode = (RestErrorCode)error.Code;
                response.ErrorMessage = error.Message;
            }

            if (client.LogRest)
                Console.WriteLine(response.RawResponse);

            if (response.Status == 200)
                response.Response = JsonConvert.DeserializeObject<T>(response.RawResponse);

            return response;
        }

        /// <summary>
        /// Make a json request
        /// </summary>
        /// <typeparam name="T">Type to use when deserialising the JSON object</typeparam>
        /// <param name="method">Request method</param>
        /// <param name="url">Endpoint url</param>
        /// <param name="data">Request data</param>
        /// <returns>Deserialised JSON object</returns>
        public RestResponse<T> Request<T>(RestRequestMethod method, string url, object data = null)
        {
            HttpWebRequest request = BaseRequest(method, url);

            request.ContentType = "application/json;charset=utf-8";
            request.ContentLength = 0;

            if (dataRequestTypes.Contains(method) && data != null)
            {
                byte[] bytes = Encoding.UTF8.GetBytes(JsonConvert.SerializeObject(data));
                request.ContentLength = bytes.LongLength;

                using (Stream requestStream = request.GetRequestStream())
                    requestStream.Write(bytes, 0, bytes.Length);
            }

            return HandleResponse<T>(request);
        }
    }
}