using Avalonia_Services.Core;

namespace Avalonia_Services.Extensions
{
    /// <summary>
    /// Desktop (Avalonia-PC) 端点适配器。
    /// 将统一端点转换为桌面端可用的路由处理器，支持过滤器和鉴权管道。
    /// </summary>
    public class DesktopEndpointAdapter
    {
        /// <summary>
        /// 统一端点集合。
        /// </summary>
        private readonly ServiceEndpointCollection _endpoints;
        /// <summary>
        /// 鉴权服务。
        /// </summary>
        private readonly IAuthService _authService;
        /// <summary>
        /// DI 服务提供程序。
        /// </summary>
        private readonly IServiceProvider _serviceProvider;

        /// <summary>
        /// 匹配后的路由结果（与原有 RouteDispatchResult 兼容）。
        /// </summary>
        public class RouteResult
        {
            /// <summary>
            /// 获取是否匹配到路由。
            /// </summary>
            public bool IsMatched { get; init; }
            /// <summary>
            /// 获取 HTTP 状态码。
            /// </summary>
            public int StatusCode { get; init; } = 200;
            /// <summary>
            /// 获取状态描述文本。
            /// </summary>
            public string StatusMessage { get; init; } = "";
            /// <summary>
            /// 获取响应数据。
            /// </summary>
            public object? Data { get; init; }
            /// <summary>
            /// 获取响应头字典。
            /// </summary>
            public Dictionary<string, string> ResponseHeaders { get; init; } = new();

            /// <summary>
            /// 创建成功响应结果。
            /// </summary>
            /// <param name="data">响应数据。</param>
            /// <param name="ctx">端点上下文。</param>
            /// <returns>路由结果。</returns>
            public static RouteResult Success(object? data, ServiceEndpointContext ctx)
            {
                return new RouteResult
                {
                    IsMatched = true,
                    StatusCode = ctx.StatusCode,
                    StatusMessage = ctx.StatusMessage,
                    Data = data,
                    ResponseHeaders = new Dictionary<string, string>(ctx.ResponseHeaders, StringComparer.OrdinalIgnoreCase),
                };
            }

            /// <summary>
            /// 创建 404 未找到响应。
            /// </summary>
            /// <returns>表示未匹配的路由结果。</returns>
            public static RouteResult NotFound() => new()
            {
                IsMatched = false,
                StatusCode = 404,
                StatusMessage = "Not Found",
            };
        }

        /// <summary>
        /// 初始化桌面端点适配器。
        /// </summary>
        /// <param name="endpoints">端点集合。</param>
        /// <param name="authService">鉴权服务。</param>
        /// <param name="serviceProvider">DI 服务提供程序。</param>
        public DesktopEndpointAdapter(
            ServiceEndpointCollection endpoints,
            IAuthService authService,
            IServiceProvider serviceProvider)
        {
            _endpoints = endpoints;
            _authService = authService;
            _serviceProvider = serviceProvider;
        }

        /// <summary>
        /// 处理来自前端（WebView2 Bridge）的请求。
        /// </summary>
        /// <param name="path">规范化路径，如 "api/wData"</param>
        /// <param name="method">HTTP 方法</param>
        /// <param name="body">请求体字符串</param>
        /// <param name="headers">请求头字典</param>
        /// <param name="query">查询参数字典</param>
        public async Task<RouteResult> HandleRequestAsync(
            string path,
            string method,
            string? body,
            Dictionary<string, string>? headers = null,
            Dictionary<string, string>? query = null)
        {
            // 查找匹配的端点（忽略大小写 + 方法匹配）
            var endpoint = _endpoints.Endpoints.FirstOrDefault(e =>
                e.SupportsHost(EndpointHostTarget.Pc) &&
                string.Equals(e.Pattern, path, StringComparison.OrdinalIgnoreCase) &&
                string.Equals(e.HttpMethod, method, StringComparison.OrdinalIgnoreCase));

            if (endpoint is null)
            {
                return RouteResult.NotFound();
            }

            // 构建上下文
            var ctx = new ServiceEndpointContext
            {
                Path = path,
                Method = method,
                Body = body,
                Headers = headers ?? new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase),
                Query = query ?? new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase),
                Items = { ["ServiceProvider"] = _serviceProvider },
            };

            try
            {
                // 1. 鉴权检查
                if (endpoint.RequireAuthorization)
                {
                    var user = await _authService.AuthenticateAsync(ctx);
                    if (user is null)
                    {
                        ctx.StatusCode = 401;
                        ctx.StatusMessage = "Unauthorized";
                        ctx.ResponseBody = new { success = false, error = "Unauthorized" };
                        return RouteResult.Success(ctx.ResponseBody, ctx);
                    }

                    if (endpoint.Roles.Count > 0)
                    {
                        var authorized = await _authService.AuthorizeAsync(user, $"roles:{string.Join(',', endpoint.Roles)}");
                        if (!authorized)
                        {
                            ctx.StatusCode = 403;
                            ctx.StatusMessage = "Forbidden";
                            ctx.ResponseBody = new { success = false, error = "Forbidden" };
                            return RouteResult.Success(ctx.ResponseBody, ctx);
                        }
                    }
                    else if (!string.IsNullOrEmpty(endpoint.Policy))
                    {
                        var authorized = await _authService.AuthorizeAsync(user, endpoint.Policy);
                        if (!authorized)
                        {
                            ctx.StatusCode = 403;
                            ctx.StatusMessage = "Forbidden";
                            ctx.ResponseBody = new { success = false, error = "Forbidden" };
                            return RouteResult.Success(ctx.ResponseBody, ctx);
                        }
                    }

                    ctx.Items["User"] = user;
                }

                // 2. 构建过滤管道：全局过滤器 → 端点过滤器 → 处理器
                var pipeline = BuildPipeline(endpoint);

                // 3. 执行管道
                await pipeline(ctx);

                return RouteResult.Success(ctx.ResponseBody, ctx);
            }
            catch (Exception ex)
            {
                ctx.StatusCode = 500;
                ctx.StatusMessage = "Internal Server Error";
                ctx.ResponseBody = new { success = false, error = ex.Message };
                return RouteResult.Success(ctx.ResponseBody, ctx);
            }
        }

        /// <summary>
        /// 构建过滤管道（全局过滤器 + 端点过滤器 → 端点处理器）。
        /// </summary>
        private EndpointFilterDelegate BuildPipeline(ServiceEndpoint endpoint)
        {
            // 最内层：端点处理器
            EndpointFilterDelegate handler = async (ctx) =>
            {
                ctx.ResponseBody = await endpoint.Handler(ctx);
            };

            // 先包裹端点专属过滤器（后注册的先执行）
            var filters = new List<IEndpointFilter>();
            filters.AddRange(_endpoints.GlobalFilters);
            filters.AddRange(endpoint.Filters);

            for (int i = filters.Count - 1; i >= 0; i--)
            {
                var filter = filters[i];
                var next = handler;
                handler = (ctx) => filter.InvokeAsync(ctx, next);
            }

            return handler;
        }
    }

    /// <summary>
    /// Desktop 端的辅助扩展。不依赖 IServiceCollection（由宿主项目自行完成 DI 注册）。
    /// </summary>
    public static class DesktopServiceExtensions
    {
        /// <summary>
        /// 快速构建 DesktopEndpointAdapter（用于非 DI 场景如 MainWindow）。
        /// </summary>
        public static DesktopEndpointAdapter CreateAdapter(
            this ServiceEndpointCollection endpoints,
            IServiceProvider serviceProvider)
        {
            var auth = (serviceProvider.GetService(typeof(IAuthService)) as IAuthService) ?? new AnonymousAuthService();
            return new DesktopEndpointAdapter(endpoints, auth, serviceProvider);
        }
    }
}