using System;
using System.Collections.Generic;
using System.Net;
using System.Text;
using System.Threading.Tasks;
using Amazon.Lambda.APIGatewayEvents;
using Amazon.Lambda.AspNetCoreServer;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Logging;

namespace WebApi
{
	public class ProxyPathMiddleware
	{
		readonly RequestDelegate _next;
		readonly ILogger _logger;

		public ProxyPathMiddleware(RequestDelegate next, ILoggerFactory loggerFactory)
		{
			_next = next;
			_logger = loggerFactory.CreateLogger<ProxyPathMiddleware>();
		}

		public Task Invoke(HttpContext context)
		{
			if (!context.Items.TryGetValue(APIGatewayProxyFunction.APIGATEWAY_REQUEST, out var apiGatewayRequestObject))
				return _next(context);      //This was not an API Gateway request. Move on.

			var apiGatewayRequest = apiGatewayRequestObject as APIGatewayProxyRequest;
			if (apiGatewayRequest == null)
				throw new InvalidOperationException("An API Gateway Request was set but was an invalid type");

			if (apiGatewayRequest.PathParameters == null || !apiGatewayRequest.PathParameters.TryGetValue("proxy", out var proxyPath))
				return _next(context);      //This was an API Gateway request but was not proxied. Move on.

			var newPath = WebUtility.UrlDecode("/" + proxyPath);
			_logger.LogDebug($"Rewriting request path. Original={context.Request.Path} New={newPath}");

			context.Request.Path = newPath;
			return _next(context);
		}
	}

	public static class ProxyPathMiddlewareExtensions
	{
		public static IApplicationBuilder UseProxyPath(this IApplicationBuilder builder)
		{
			return builder.UseMiddleware<ProxyPathMiddleware>();
		}
	}
}