using System;
using System.IO;
using System.Text;
using Best.HTTP;
using Cysharp.Threading.Tasks;
using IchniOnline.Online.Network.Models;
using UnityEngine;

namespace IchniOnline.Online.Network
{
    /// <summary>
    /// BestHTTP-based API client singleton for IchniOnline backend communication.
    /// Pure HTTP layer — no business logic.
    /// </summary>
    public class IchniOnlineApiClient
    {
        private static IchniOnlineApiClient _instance;
        public static IchniOnlineApiClient Instance => _instance ??= new IchniOnlineApiClient();

        public string BaseUrl { get; set; } = "http://localhost:5308";
        public string JwtToken { get; set; }

        private IchniOnlineApiClient() { }

        public async UniTask<ApiResult<T>> GetAsync<T>(string endpoint)
        {
            string url = BuildUrl(endpoint);
            var request = new HTTPRequest(new Uri(url), HTTPMethods.Get);
            AddAuthHeader(request);

            try
            {
                var resp = await SendAsync(request);
                return ProcessResponse<T>(resp);
            }
            catch (Exception ex)
            {
                return ApiResult<T>.Fail(ResponseCode.InternalServerError, "Network error", ex.Message);
            }
        }

        public async UniTask<ApiResult<T>> PostAsync<T>(string endpoint, object body)
        {
            string url = BuildUrl(endpoint);
            var request = new HTTPRequest(new Uri(url), HTTPMethods.Post);
            request.SetHeader("Content-Type", "application/json");
            AddAuthHeader(request);

            if (body != null)
            {
                string jsonBody = JsonUtility.ToJson(body);
                request.UploadSettings.UploadStream = new MemoryStream(Encoding.UTF8.GetBytes(jsonBody));
            }

            try
            {
                var resp = await SendAsync(request);
                return ProcessResponse<T>(resp);
            }
            catch (Exception ex)
            {
                return ApiResult<T>.Fail(ResponseCode.InternalServerError, "Network error", ex.Message);
            }
        }

        private string BuildUrl(string endpoint)
        {
            if (string.IsNullOrEmpty(BaseUrl))
                throw new InvalidOperationException("BaseUrl is not configured.");

            string baseUrl = BaseUrl.TrimEnd('/');
            string path = endpoint.StartsWith("/") ? endpoint : $"/{endpoint}";
            return baseUrl + path;
        }

        private void AddAuthHeader(HTTPRequest request)
        {
            if (!string.IsNullOrEmpty(JwtToken))
            {
                request.SetHeader("Authorization", $"Bearer {JwtToken}");
            }
        }

        private UniTask<HTTPResponse> SendAsync(HTTPRequest request)
        {
            var completionSource = new UniTaskCompletionSource<HTTPResponse>();

            request.Callback = (req, resp) =>
            {
                switch (req.State)
                {
                    case HTTPRequestStates.Finished:
                        completionSource.TrySetResult(resp);
                        break;
                    case HTTPRequestStates.Aborted:
                        completionSource.TrySetCanceled();
                        break;
                    default:
                        completionSource.TrySetException(req.Exception ?? new Exception($"HTTP request failed: {req.State}"));
                        break;
                }
            };

            request.Send();
            return completionSource.Task;
        }

        private ApiResult<T> ProcessResponse<T>(HTTPResponse resp)
        {
            string json = resp.DataAsText;

            if (resp.StatusCode >= 200 && resp.StatusCode < 300)
            {
                if (string.IsNullOrEmpty(json))
                {
                    return ApiResult<T>.Fail(ResponseCode.InternalServerError, "Empty response body");
                }

                var response = JsonUtility.FromJson(json, typeof(GlobalResponse<T>)) as GlobalResponse<T>;
                if (response == null)
                {
                    return ApiResult<T>.Fail(ResponseCode.InternalServerError, "Failed to parse response JSON");
                }

                if (response.code == ResponseCode.Ok)
                {
                    return ApiResult<T>.Ok(response.data);
                }

                return ApiResult<T>.Fail(response.code, response.message);
            }

            // Non-2xx: try to parse server error body
            if (!string.IsNullOrEmpty(json))
            {
                var errorResponse = JsonUtility.FromJson(json, typeof(GlobalResponseBase)) as GlobalResponseBase;
                if (errorResponse != null)
                {
                    return ApiResult<T>.Fail(errorResponse.code, errorResponse.message);
                }
            }

            return ApiResult<T>.Fail(ResponseCode.InternalServerError, $"HTTP error {resp.StatusCode}");
        }
    }
}