using System;
using System.Collections.Generic;
using System.Threading.Tasks;
using Microsoft.Extensions.DependencyInjection;

namespace Avalonia_Services.Core
{
    /// <summary>
    /// 端点挂载的宿主目标。
    /// </summary>
    [Flags]
    public enum EndpointHostTarget
    {
        /// <summary>挂载到 Avalonia-API（ASP.NET Core Web API）。</summary>
        Api = 1,
        /// <summary>挂载到 Avalonia-PC（桌面 WebView）。</summary>
        Pc = 2,
        /// <summary>同时挂载到 API 和 PC。</summary>
        All = Api | Pc,
    }

    /// <summary>
    /// 单个端点定义。
    /// </summary>
    public class ServiceEndpoint
    {
        /// <summary>路由路径，如 "api/wData"</summary>
        public string Pattern { get; init; } = string.Empty;

        /// <summary>HTTP 方法（GET/POST/PUT/DELETE）</summary>
        public string HttpMethod { get; init; } = "GET";

        /// <summary>端点名称（用于 OpenAPI / 日志）</summary>
        public string? Name { get; set; }

        /// <summary>OpenAPI 分组标签。</summary>
        public string? OpenApiTag { get; set; }

        /// <summary>OpenAPI 摘要。</summary>
        public string? OpenApiSummary { get; set; }

        /// <summary>OpenAPI 描述。</summary>
        public string? OpenApiDescription { get; set; }

        /// <summary>OpenAPI 请求体类型。</summary>
        public Type? OpenApiRequestType { get; set; }

        /// <summary>OpenAPI 200 响应数据类型。</summary>
        public Type? OpenApiResponseType { get; set; }

        /// <summary>端点处理器</summary>
        public Func<ServiceEndpointContext, Task<object?>> Handler { get; init; } = _ => Task.FromResult<object?>(null);

        /// <summary>该端点专属的过滤器（按顺序执行）</summary>
        public List<IEndpointFilter> Filters { get; init; } = new();

        /// <summary>是否需要鉴权</summary>
        public bool RequireAuthorization { get; set; }

        /// <summary>鉴权策略名</summary>
        public string? Policy { get; set; }

        /// <summary>允许访问该端点的角色。多个角色满足任意一个即可。</summary>
        public List<string> Roles { get; } = new();

        /// <summary>端点挂载的宿主。默认 API 和 PC 都挂载。</summary>
        public EndpointHostTarget HostTarget { get; set; } = EndpointHostTarget.All;

        /// <summary>
        /// 设置端点名称（Fluent API）。
        /// </summary>
        public ServiceEndpoint WithName(string name)
        {
            Name = name;
            return this;
        }

        /// <summary>
        /// 设置端点的 OpenAPI 元数据（标签、摘要、描述、请求/响应类型）。
        /// </summary>
        /// <param name="tag">OpenAPI 分组标签。</param>
        /// <param name="summary">简要摘要。</param>
        /// <param name="description">详细描述。</param>
        /// <param name="requestType">请求体类型。</param>
        /// <param name="responseType">成功响应类型。</param>
        /// <returns>当前端点实例（Fluent API）。</returns>
        public ServiceEndpoint WithOpenApi(
            string tag,
            string summary,
            string? description = null,
            Type? requestType = null,
            Type? responseType = null)
        {
            OpenApiTag = tag;
            OpenApiSummary = summary;
            OpenApiDescription = description;
            OpenApiRequestType = requestType;
            OpenApiResponseType = responseType;
            return this;
        }

        /// <summary>
        /// 标记端点需要登录。
        /// </summary>
        public ServiceEndpoint RequireAuth()
        {
            RequireAuthorization = true;
            return this;
        }

        /// <summary>
        /// 标记端点需要指定角色。多个角色满足任意一个即可。
        /// </summary>
        public ServiceEndpoint RequireRoles(params string[] roles)
        {
            RequireAuthorization = true;
            Roles.Clear();
            Roles.AddRange(roles.Where(role => !string.IsNullOrWhiteSpace(role)).Select(role => role.Trim()));
            return this;
        }

        /// <summary>
        /// 只挂载到 Avalonia-API。
        /// </summary>
        public ServiceEndpoint ApiOnly()
        {
            HostTarget = EndpointHostTarget.Api;
            return this;
        }

        /// <summary>
        /// 只挂载到 Avalonia-PC。
        /// </summary>
        public ServiceEndpoint PcOnly()
        {
            HostTarget = EndpointHostTarget.Pc;
            return this;
        }

        /// <summary>
        /// 判断端点是否支持指定的宿主目标。
        /// </summary>
        /// <param name="host">要检查的宿主目标。</param>
        /// <returns>是否支持。</returns>
        public bool SupportsHost(EndpointHostTarget host)
        {
            return (HostTarget & host) != 0;
        }
    }

    /// <summary>
    /// 端点集合 —— 所有端点的注册中心。在 Avalonia-Services 中统一配置。
    /// </summary>
    public class ServiceEndpointCollection
    {
        /// <summary>所有已注册的端点</summary>
        public List<ServiceEndpoint> Endpoints { get; } = new();

        /// <summary>
        /// 获取指定宿主目标的所有端点。
        /// </summary>
        /// <param name="host">宿主目标。</param>
        /// <returns>匹配的端点集合。</returns>
        public IEnumerable<ServiceEndpoint> ForHost(EndpointHostTarget host)
        {
            return Endpoints.Where(endpoint => endpoint.SupportsHost(host));
        }

        /// <summary>作用于所有端点的全局过滤器</summary>
        public List<IEndpointFilter> GlobalFilters { get; } = new();

        /// <summary>
        /// 注册一个端点。
        /// </summary>
        public ServiceEndpoint MapGet(string pattern, Func<ServiceEndpointContext, Task<object?>> handler)
        {
            return AddEndpoint(pattern, "GET", handler);
        }

        /// <summary>
        /// 注册一个带服务依赖注入的 GET 端点。
        /// </summary>
        /// <typeparam name="TService">服务类型。</typeparam>
        /// <param name="pattern">路由路径。</param>
        /// <param name="handler">接受服务实例和上下文的处理器。</param>
        /// <returns>已注册的端点实例。</returns>
        public ServiceEndpoint MapGet<TService>(
            string pattern,
            Func<TService, ServiceEndpointContext, Task<object?>> handler)
            where TService : notnull
        {
            return MapGet(pattern, CreateServiceHandler(handler));
        }

        /// <summary>
        /// 注册一个 POST 端点。
        /// </summary>
        public ServiceEndpoint MapPost(string pattern, Func<ServiceEndpointContext, Task<object?>> handler)
        {
            return AddEndpoint(pattern, "POST", handler);
        }

        /// <summary>
        /// 注册一个带服务依赖注入的 POST 端点。
        /// </summary>
        /// <typeparam name="TService">服务类型。</typeparam>
        /// <param name="pattern">路由路径。</param>
        /// <param name="handler">接受服务实例和上下文的处理器。</param>
        /// <returns>已注册的端点实例。</returns>
        public ServiceEndpoint MapPost<TService>(
            string pattern,
            Func<TService, ServiceEndpointContext, Task<object?>> handler)
            where TService : notnull
        {
            return MapPost(pattern, CreateServiceHandler(handler));
        }

        /// <summary>
        /// 注册一个 PUT 端点。
        /// </summary>
        public ServiceEndpoint MapPut(string pattern, Func<ServiceEndpointContext, Task<object?>> handler)
        {
            return AddEndpoint(pattern, "PUT", handler);
        }

        /// <summary>
        /// 注册一个带服务依赖注入的 PUT 端点。
        /// </summary>
        /// <typeparam name="TService">服务类型。</typeparam>
        /// <param name="pattern">路由路径。</param>
        /// <param name="handler">接受服务实例和上下文的处理器。</param>
        /// <returns>已注册的端点实例。</returns>
        public ServiceEndpoint MapPut<TService>(
            string pattern,
            Func<TService, ServiceEndpointContext, Task<object?>> handler)
            where TService : notnull
        {
            return MapPut(pattern, CreateServiceHandler(handler));
        }

        /// <summary>
        /// 注册一个 DELETE 端点。
        /// </summary>
        public ServiceEndpoint MapDelete(string pattern, Func<ServiceEndpointContext, Task<object?>> handler)
        {
            return AddEndpoint(pattern, "DELETE", handler);
        }

        /// <summary>
        /// 注册一个带服务依赖注入的 DELETE 端点。
        /// </summary>
        /// <typeparam name="TService">服务类型。</typeparam>
        /// <param name="pattern">路由路径。</param>
        /// <param name="handler">接受服务实例和上下文的处理器。</param>
        /// <returns>已注册的端点实例。</returns>
        public ServiceEndpoint MapDelete<TService>(
            string pattern,
            Func<TService, ServiceEndpointContext, Task<object?>> handler)
            where TService : notnull
        {
            return MapDelete(pattern, CreateServiceHandler(handler));
        }

        /// <summary>
        /// 添加全局过滤器（作用于所有端点）。
        /// </summary>
        public ServiceEndpointCollection AddGlobalFilter(IEndpointFilter filter)
        {
            GlobalFilters.Add(filter);
            return this;
        }

        /// <summary>
        /// 通过匿名函数添加全局过滤器。
        /// </summary>
        public ServiceEndpointCollection AddGlobalFilter(Func<ServiceEndpointContext, EndpointFilterDelegate, Task> filter)
        {
            GlobalFilters.Add(new AnonymousEndpointFilter(filter));
            return this;
        }

        /// <summary>
        /// 内部方法，创建端点并添加到集合。
        /// </summary>
        /// <param name="pattern">路由路径。</param>
        /// <param name="method">HTTP 方法。</param>
        /// <param name="handler">端点处理器。</param>
        /// <returns>已创建的端点实例。</returns>
        private ServiceEndpoint AddEndpoint(string pattern, string method, Func<ServiceEndpointContext, Task<object?>> handler)
        {
            var endpoint = new ServiceEndpoint
            {
                Pattern = pattern,
                HttpMethod = method,
                Handler = handler,
            };
            Endpoints.Add(endpoint);
            return endpoint;
        }

        /// <summary>
        /// 创建自动从 DI 解析服务实例并调用处理器的委托包装。
        /// </summary>
        /// <typeparam name="TService">服务类型。</typeparam>
        /// <param name="handler">接受服务实例和上下文的处理器。</param>
        /// <returns>包装后的处理器委托。</returns>
        private static Func<ServiceEndpointContext, Task<object?>> CreateServiceHandler<TService>(
            Func<TService, ServiceEndpointContext, Task<object?>> handler)
            where TService : notnull
        {
            return async ctx =>
            {
                var serviceProvider = ctx.Items["ServiceProvider"] as IServiceProvider
                    ?? throw new InvalidOperationException("ServiceProvider 未注入。");

                await using var scope = serviceProvider.CreateAsyncScope();
                var service = scope.ServiceProvider.GetRequiredService<TService>();
                return await handler(service, ctx);
            };
        }
    }

    /// <summary>
    /// 构建器 —— 提供 Fluent API 来配置所有端点。
    /// </summary>
    public class ServiceEndpointBuilder
    {
        /// <summary>
        /// 端点集合
        /// </summary>
        public ServiceEndpointCollection Endpoints { get; } = new();

        /// <summary>
        /// 鉴权服务（默认匿名）
        /// </summary>
        public IAuthService AuthService { get; set; } = new AnonymousAuthService();

        /// <summary>
        /// 配置端点（在此方法中调用 endpoints.MapGet 等）。
        /// </summary>
        public ServiceEndpointBuilder ConfigureEndpoints(Action<ServiceEndpointCollection> configure)
        {
            configure(Endpoints);
            return this;
        }

        /// <summary>
        /// 设置鉴权服务。
        /// </summary>
        public ServiceEndpointBuilder UseAuthService(IAuthService authService)
        {
            AuthService = authService;
            return this;
        }

        /// <summary>
        /// 构建最终的端点集合。
        /// </summary>
        public ServiceEndpointCollection Build()
        {
            return Endpoints;
        }
    }
}