namespace OASystem.API.Middlewares
{
    /// <summary>
    /// 全局异常捕获中间件
    /// </summary>
    public class ExceptionHandlingMiddleware
    {
        private readonly RequestDelegate _next;  // 用来处理上下文请求
        private readonly ILogger<ExceptionHandlingMiddleware> _logger;

        /// <summary>
        /// 初始化
        /// </summary>
        /// <param name="next"></param>
        /// <param name="logger"></param>
        public ExceptionHandlingMiddleware(RequestDelegate next, ILogger<ExceptionHandlingMiddleware> logger)
        {
            _next = next;
            _logger = logger;
        }

        /// <summary>
        /// 执行中间件
        /// </summary>
        /// <param name="httpContext"></param>
        /// <returns></returns>
        public async Task InvokeAsync(HttpContext httpContext, SqlSugarClient db)
        {
            try
            {
                await _next(httpContext); //要么在中间件中处理，要么被传递到下一个中间件中去
            }
            catch (Exception ex)
            {
                await HandleExceptionAsync(httpContext, ex, db); // 捕获异常了 在HandleExceptionAsync中处理
            }
        }

        /// <summary>
        /// 异步处理异常
        /// </summary>
        /// <param name="context"></param>
        /// <param name="exception"></param>
        /// <returns></returns>
        private async Task HandleExceptionAsync(HttpContext context, Exception exception, SqlSugarClient db)
        {
            if (db.Ado != null && db.Ado.Transaction != null)
            {
                db.Ado.RollbackTran();
            }

            context.Response.ContentType = "application/json";  // 返回json 类型
            var response = context.Response;
            var errorResponse = new JsonView
            {
                Code = StatusCodes.Status500InternalServerError,
                Data = ""
            };  
            
            // 自定义的异常错误信息类型
            switch (exception)
            {
                case ApplicationException ex:
                    if (ex.Message.Contains("Invalid token"))
                    {
                        response.StatusCode = StatusCodes.Status403Forbidden;
                        errorResponse.Msg = ex.Message;
                        break;
                    }
                    response.StatusCode = StatusCodes.Status400BadRequest;
                    errorResponse.Msg = ex.Message;
                    break;
                case KeyNotFoundException ex:
                    response.StatusCode = StatusCodes.Status404NotFound;
                    errorResponse.Msg = ex.Message;
                    break;
                case SqlSugarException ex:
                    response.StatusCode = StatusCodes.Status204NoContent;
                    if (ex.Message.Contains("timeout")) errorResponse.Msg = $"数据库连接超时，请稍后重试。";
                    else errorResponse.Msg = ex.Message;
                    break;
                default:
                    response.StatusCode = StatusCodes.Status500InternalServerError;
                    errorResponse.Msg = exception.Message;
                    break;
            }
            _logger.LogError(exception.Message);
            var result = JsonConvert.SerializeObject(errorResponse);
            await context.Response.WriteAsync(result);
        }
    }
}