// ==========================================================================
//  Squidex Headless CMS
// ==========================================================================
//  Copyright (c) Squidex UG (haftungsbeschränkt)
//  All rights reserved. Licensed under the MIT license.
// ==========================================================================

using System;
using System.Collections.Generic;
using System.Linq;
using System.Security;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.Filters;
using Squidex.Infrastructure;

namespace Squidex.Web
{
    public sealed class ApiExceptionFilterAttribute : ActionFilterAttribute, IExceptionFilter
    {
        private static readonly List<Func<Exception, IActionResult>> Handlers = new List<Func<Exception, IActionResult>>();

        private static void AddHandler<T>(Func<T, IActionResult> handler) where T : Exception
        {
            Handlers.Add(ex => ex is T typed ? handler(typed) : null);
        }

        static ApiExceptionFilterAttribute()
        {
            AddHandler<ValidationException>(OnValidationException);
            AddHandler<DomainObjectNotFoundException>(OnDomainObjectNotFoundException);
            AddHandler<DomainObjectVersionException>(OnDomainObjectVersionException);
            AddHandler<DomainForbiddenException>(OnDomainForbiddenException);
            AddHandler<DomainException>(OnDomainException);
            AddHandler<SecurityException>(OnSecurityException);
        }

        private static IActionResult OnDomainObjectNotFoundException(DomainObjectNotFoundException ex)
        {
            return new NotFoundResult();
        }

        private static IActionResult OnDomainObjectVersionException(DomainObjectVersionException ex)
        {
            return ErrorResult(412, new ErrorDto { Message = ex.Message });
        }

        private static IActionResult OnDomainException(DomainException ex)
        {
            return ErrorResult(400, new ErrorDto { Message = ex.Message });
        }

        private static IActionResult OnDomainForbiddenException(DomainForbiddenException ex)
        {
            return ErrorResult(403, new ErrorDto { Message = ex.Message });
        }

        private static IActionResult OnSecurityException(SecurityException ex)
        {
            return ErrorResult(403, new ErrorDto { Message = ex.Message });
        }

        private static IActionResult OnValidationException(ValidationException ex)
        {
            return ErrorResult(400, new ErrorDto { Message = ex.Summary, Details = ToDetails(ex) });
        }

        private static IActionResult ErrorResult(int statusCode, ErrorDto error)
        {
            error.StatusCode = statusCode;

            return new ObjectResult(error) { StatusCode = statusCode };
        }

        public void OnException(ExceptionContext context)
        {
            IActionResult result = null;

            foreach (var handler in Handlers)
            {
                result = handler(context.Exception);

                if (result != null)
                {
                    break;
                }
            }

            if (result != null)
            {
                context.Result = result;
            }
        }

        private static string[] ToDetails(ValidationException ex)
        {
            return ex.Errors?.ToArray(e =>
            {
                if (e.PropertyNames?.Any() == true)
                {
                    return $"{string.Join(", ", e.PropertyNames)}: {e.Message}";
                }
                else
                {
                    return e.Message;
                }
            });
        }
    }
}