using Avalonia_Services.Core;
using Microsoft.AspNetCore.Authorization;
using AspNetCoreFilterContext = Microsoft.AspNetCore.Http.EndpointFilterInvocationContext;
using AspNetCoreFilterDelegate = Microsoft.AspNetCore.Http.EndpointFilterDelegate;
// 解决与 ASP.NET Core 同名类型的冲突
using UnifiedFilter = Avalonia_Services.Core.IEndpointFilter;

namespace Avalonia_API.Extensions
{
    /// <summary>
    /// 将 Avalonia-Services 的统一端点映射到 ASP.NET Core Minimal API。
    /// 支持鉴权、过滤器、中间件的完整 ASP.NET Core 管道。
    /// </summary>
    public static class UnifiedEndpointExtensions
    {
        /// <summary>
        /// 将 ServiceEndpointCollection 中的所有端点注册到 ASP.NET Core 路由。
        /// </summary>
        public static IEndpointRouteBuilder MapUnifiedEndpoints(
            this IEndpointRouteBuilder routeBuilder,
            ServiceEndpointCollection endpoints,
            IServiceProvider serviceProvider)
        {
            var apiGroup = routeBuilder.MapGroup("/");

            foreach (var endpoint in endpoints.ForHost(EndpointHostTarget.Api))
            {
                var routeHandlerBuilder = MapEndpoint(apiGroup, endpoint, serviceProvider);

                // 全局过滤器 → ASP.NET Core Endpoint Filters
                foreach (var globalFilter in endpoints.GlobalFilters)
                {
                    routeHandlerBuilder.AddEndpointFilter(
                        async (context, next) => await ConvertFilterAsync(globalFilter, context, next));
                }

                // 端点专属过滤器
                foreach (var filter in endpoint.Filters)
                {
                    routeHandlerBuilder.AddEndpointFilter(
                        async (context, next) => await ConvertFilterAsync(filter, context, next));
                }

                // 鉴权（使用 ASP.NET Core 原生鉴权机制）
                if (endpoint.RequireAuthorization)
                {
                    if (endpoint.Roles.Count > 0)
                    {
                        routeHandlerBuilder.RequireAuthorization(new AuthorizeAttribute
                        {
                            Roles = string.Join(',', endpoint.Roles),
                        });
                    }
                    else if (!string.IsNullOrEmpty(endpoint.Policy))
                    {
                        routeHandlerBuilder.RequireAuthorization(endpoint.Policy);
                    }
                    else
                    {
                        routeHandlerBuilder.RequireAuthorization();
                    }
                }

                if (!string.IsNullOrEmpty(endpoint.Name))
                {
                    routeHandlerBuilder.WithName(endpoint.Name);
                }

                if (!string.IsNullOrEmpty(endpoint.OpenApiTag))
                {
                    routeHandlerBuilder.WithTags(endpoint.OpenApiTag);
                }

                if (!string.IsNullOrEmpty(endpoint.OpenApiDescription))
                {
                    routeHandlerBuilder.WithDescription(endpoint.OpenApiDescription);
                }

                if (!string.IsNullOrWhiteSpace(endpoint.OpenApiSummary))
                {
                    routeHandlerBuilder.WithSummary(endpoint.OpenApiSummary);
                }

                if (endpoint.OpenApiRequestType is not null)
                {
                    routeHandlerBuilder.Accepts(endpoint.OpenApiRequestType, "application/json");
                }

                if (endpoint.OpenApiResponseType is not null)
                {
                    routeHandlerBuilder.Produces(200, endpoint.OpenApiResponseType, "application/json");
                }
            }

            return routeBuilder;
        }

        /// <summary>
        /// 根据端点的 HTTP 方法（GET/POST/PUT/DELETE）将其映射到 ASP.NET Core 路由。
        /// </summary>
        /// <param name="group">路由组。</param>
        /// <param name="endpoint">统一端点定义。</param>
        /// <param name="serviceProvider">服务提供程序。</param>
        /// <returns>路由处理器构建器，用于叠加过滤器等配置。</returns>
        private static RouteHandlerBuilder MapEndpoint(
            IEndpointRouteBuilder group,
            ServiceEndpoint endpoint,
            IServiceProvider serviceProvider)
        {
            var handler = CreateAspNetCoreHandler(endpoint.Handler, serviceProvider);

            return endpoint.HttpMethod.ToUpperInvariant() switch
            {
                "GET" => group.MapGet(endpoint.Pattern, handler),
                "POST" => group.MapPost(endpoint.Pattern, handler),
                "PUT" => group.MapPut(endpoint.Pattern, handler),
                "DELETE" => group.MapDelete(endpoint.Pattern, handler),
                _ => group.MapGet(endpoint.Pattern, handler),
            };
        }

        /// <summary>
        /// 创建适配 ASP.NET Core 的委托处理器，将统一处理器包装为 ASP.NET Core 可识别的委托。
        /// </summary>
        /// <param name="unifiedHandler">统一端点处理器。</param>
        /// <param name="serviceProvider">服务提供程序。</param>
        /// <returns>ASP.NET Core 兼容的委托。</returns>
        private static Delegate CreateAspNetCoreHandler(
            Func<ServiceEndpointContext, Task<object?>> unifiedHandler,
            IServiceProvider serviceProvider)
        {
            return async (HttpContext httpContext) =>
            {
                var ctx = httpContext.Items["UnifiedContext"] as ServiceEndpointContext
                    ?? await BuildContextFromHttpContext(httpContext);
                ctx.Items["ServiceProvider"] = serviceProvider;
                ctx.Items["User"] = httpContext.User;
                httpContext.Items["UnifiedContext"] = ctx;

                var result = await unifiedHandler(ctx);

                // 同步响应状态
                httpContext.Response.StatusCode = ctx.StatusCode;
                foreach (var kvp in ctx.ResponseHeaders)
                {
                    httpContext.Response.Headers[kvp.Key] = kvp.Value;
                }

                return result is not null ? Results.Json(result) : Results.Ok();
            };
        }

        /// <summary>
        /// 从 ASP.NET Core 的 HttpContext 构建统一的 ServiceEndpointContext，
        /// 提取路径、方法、请求头、查询参数和请求体。
        /// </summary>
        /// <param name="httpContext">ASP.NET Core 的 HttpContext。</param>
        /// <returns>构建好的统一端点上下文。</returns>
        private static async Task<ServiceEndpointContext> BuildContextFromHttpContext(HttpContext httpContext)
        {
            var ctx = new ServiceEndpointContext
            {
                Path = httpContext.Request.Path.Value ?? "/",
                Method = httpContext.Request.Method,
                StatusCode = 200,
            };

            foreach (var header in httpContext.Request.Headers)
            {
                ctx.Headers[header.Key] = header.Value.ToString();
            }

            foreach (var query in httpContext.Request.Query)
            {
                ctx.Query[query.Key] = query.Value.ToString();
            }

            if (httpContext.Request.ContentLength > 0)
            {
                using var reader = new StreamReader(httpContext.Request.Body);
                ctx.Body = await reader.ReadToEndAsync();
            }

            ctx.Items["HttpContext"] = httpContext;
            ctx.Items["User"] = httpContext.User;

            return ctx;
        }

        /// <summary>
        /// 将统一过滤器转换为 ASP.NET Core 端点过滤器，
        /// 在调用统一过滤器前后桥接上下文和状态。
        /// </summary>
        /// <param name="unifiedFilter">统一过滤器。</param>
        /// <param name="aspContext">ASP.NET Core 过滤器调用上下文。</param>
        /// <param name="aspNext">ASP.NET Core 过滤器管道中的下一个委托。</param>
        /// <returns>过滤器执行结果，可能包含短路响应体。</returns>
        private static async ValueTask<object?> ConvertFilterAsync(
            UnifiedFilter unifiedFilter,
            AspNetCoreFilterContext aspContext,
            AspNetCoreFilterDelegate aspNext)
        {
            var httpContext = aspContext.HttpContext;
            var ctx = httpContext.Items["UnifiedContext"] as ServiceEndpointContext
                ?? await BuildContextFromHttpContext(httpContext);

            httpContext.Items["UnifiedContext"] = ctx;

            object? nextResult = null;
            await unifiedFilter.InvokeAsync(ctx, async (c) =>
            {
                httpContext.Response.StatusCode = c.StatusCode;
                foreach (var kvp in c.ResponseHeaders)
                {
                    httpContext.Response.Headers[kvp.Key] = kvp.Value;
                }
                nextResult = await aspNext(aspContext);
            });

            if (ctx.ResponseBody is not null)
            {
                return Results.Json(ctx.ResponseBody, statusCode: ctx.StatusCode);
            }

            return nextResult;
        }
    }
}