using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.OpenApi.Models;
using System.Collections.Generic;
using System.Linq;

namespace IdentityServer.Api.Swagger
{
    public static class SwaggerExtensions
    {
        public static IServiceCollection AddSwagger(this IServiceCollection services)
        {
            services.AddSwaggerGen(c =>
            {
                c.SwaggerDoc("v1",
                    new OpenApiInfo
                    {
                        Title = "Identity Server API",
                        Version = "v1"
                    });

                c.OperationFilter<PathParamsOperationFilter>();
                c.SchemaFilter<DtoSchemaFilter>();
                c.CustomSchemaIds(type => type.ToString());
            });

            return services;
        }

        public static IApplicationBuilder ConfigureSwagger(this IApplicationBuilder applicationBuilder)
        {
            applicationBuilder.UseSwagger(c =>
            {
                c.PreSerializeFilters.Add((swagger, httpRequest) =>
                {
                    var (host, basePath, scheme) = GetUrlComponents(httpRequest);

                    swagger.Servers = new List<OpenApiServer>
                    {
                        new OpenApiServer {Url = $"{scheme}://{host}{basePath}"}
                    };
                });
                c.RouteTemplate = "swagger/{documentName}/swagger.json";
            });

            applicationBuilder.UseSwaggerUI(c =>
            {
                c.SwaggerEndpoint("v1/swagger.json", "IdentityServer API");
                c.RoutePrefix = $"swagger";
            });

            return applicationBuilder;
        }

        private static (string host, string basePath, string scheme) GetUrlComponents(HttpRequest request)
        {
            var host = ExtractHost(request);
            var basePath = ExtractBasePath(request);
            var scheme = ExtractScheme(request);

            return (host, basePath, scheme);
        }

        private static string ExtractHost(HttpRequest request)
        {
            if (request.Headers.ContainsKey("X-Forwarded-Host"))
                return request.Headers["X-Forwarded-Host"].First();

            return request.Host.Value;
        }

        private static string ExtractBasePath(HttpRequest request)
        {
            if (request.Headers.ContainsKey("X-Forwarded-PathBase"))
                return request.Headers["X-Forwarded-PathBase"].First();

            return string.Empty;
        }

        private static string ExtractScheme(HttpRequest request)
        {
            return request.Headers["X-Forwarded-Proto"].FirstOrDefault() ?? request.Scheme;
        }
    }
}