using Microsoft.AspNetCore.Http.Features;
using Microsoft.AspNetCore.Http;
using Microsoft.Net.Http.Headers;
using System.Net;
using System.Text.Encodings.Web;
using System.Text.Json;
using System.Text.Unicode;
using System;
using System.Threading.Tasks;
using Microsoft.IdentityModel.Logging;

namespace Shentun.Peis
{
    public class ErrorHandlerMiddleWare
    {
        //请求委托
        private readonly RequestDelegate _next;

       // private readonly LogHelper _nlogger;

        public ErrorHandlerMiddleWare(RequestDelegate next
            //, LogHelper nlogger
            )
        {
            this._next = next;
           // this._nlogger = nlogger;
        }

        public async Task Invoke(HttpContext context)
        {
            try
            {
                await this._next.Invoke(context);
            }
            catch (Exception ex)
            {
                await HandleExceptionAsync(context, ex);
            }
        }

        private async Task HandleExceptionAsync(HttpContext context, Exception exception)
        {
            if (exception == null) return;
            await HandleErrorResultAsync(context, exception).ConfigureAwait(false);
        }

        private async Task HandleErrorResultAsync(HttpContext context, Exception exception)
        {
            //记录日志
           // _nlogger.LogError(exception);
            //返回友好的提示
            var response = context.Response;
            //清除原有HTTP上下文信息，为了明确指定程序出现异常，防止异常未被处理而后续当做正常操作执行
            ClearHttpContext(context);
            //状态码
            if (exception is UnauthorizedAccessException)
                response.StatusCode = (int)HttpStatusCode.Unauthorized;
            else if (exception is BadHttpRequestException)
                response.StatusCode = (int)HttpStatusCode.BadRequest;
            else if (response.StatusCode == 403 || response.StatusCode == 404) { }
            else response.StatusCode = (int)HttpStatusCode.InternalServerError;

            response.ContentType = context.Request.Headers["Accept"];
            var result = new ApiResult
            {
                Code = 500,
                Message = exception.GetBaseException().Message
            };
            if (response.ContentType.ToLower() != "application/x-www-form-urlencoded")
            {
                response.ContentType = "application/json";
            }
            await response.WriteAsync(JsonSerializer.Serialize(result
            , new JsonSerializerOptions()
            {
                Encoder = JavaScriptEncoder.Create(UnicodeRanges.All),
                PropertyNameCaseInsensitive = true,
                PropertyNamingPolicy = JsonNamingPolicy.CamelCase
            })).ConfigureAwait(false);
        }

        private static void ClearHttpContext(HttpContext context)
        {
            context.Response.Clear();
            //因为可能创建了新的终结点，所以执行管道会有所调整，所以需要重新计算
            context.SetEndpoint(endpoint: null);
            var routeValuesFeature = context.Features.Get<IRouteValuesFeature>();
            routeValuesFeature?.RouteValues?.Clear();
        }

        private static Task ClearCacheHeaders(object state)
        {
            //清除输出缓存相关
            var headers = ((HttpResponse)state).Headers;
            headers[HeaderNames.CacheControl] = "no-cache";
            headers[HeaderNames.Pragma] = "no-cache";
            headers[HeaderNames.Expires] = "-1";
            headers.Remove(HeaderNames.ETag);
            return Task.CompletedTask;
        }
    }
}