// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.

using System;
using System.Globalization;
using System.Net.Http;
using System.Text.Encodings.Web;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.DataProtection;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;

namespace Microsoft.AspNetCore.Authentication.OAuth
{
    /// <summary>
    /// An ASP.NET Core middleware for authenticating users using OAuth services.
    /// </summary>
    public class OAuthMiddleware<TOptions> : AuthenticationMiddleware<TOptions> where TOptions : OAuthOptions, new()
    {
        /// <summary>
        /// Initializes a new <see cref="OAuthMiddleware{T}"/>.
        /// </summary>
        /// <param name="next">The next middleware in the HTTP pipeline to invoke.</param>
        /// <param name="dataProtectionProvider"></param>
        /// <param name="loggerFactory"></param>
        /// <param name="encoder">The <see cref="UrlEncoder"/>.</param>
        /// <param name="sharedOptions">The <see cref="SharedAuthenticationOptions"/> configuration options for this middleware.</param>
        /// <param name="options">Configuration options for the middleware.</param>
        public OAuthMiddleware(
            RequestDelegate next,
            IDataProtectionProvider dataProtectionProvider,
            ILoggerFactory loggerFactory,
            UrlEncoder encoder,
            IOptions<SharedAuthenticationOptions> sharedOptions,
            IOptions<TOptions> options)
            : base(next, options, loggerFactory, encoder)
        {
            if (next == null)
            {
                throw new ArgumentNullException(nameof(next));
            }

            if (dataProtectionProvider == null)
            {
                throw new ArgumentNullException(nameof(dataProtectionProvider));
            }

            if (loggerFactory == null)
            {
                throw new ArgumentNullException(nameof(loggerFactory));
            }

            if (encoder == null)
            {
                throw new ArgumentNullException(nameof(encoder));
            }

            if (sharedOptions == null)
            {
                throw new ArgumentNullException(nameof(sharedOptions));
            }

            if (options == null)
            {
                throw new ArgumentNullException(nameof(options));
            }

            // todo: review error handling
            if (string.IsNullOrEmpty(Options.AuthenticationScheme))
            {
                throw new ArgumentException(string.Format(CultureInfo.CurrentCulture, Resources.Exception_OptionMustBeProvided, nameof(Options.AuthenticationScheme)));
            }

            if (string.IsNullOrEmpty(Options.ClientId))
            {
                throw new ArgumentException(string.Format(CultureInfo.CurrentCulture, Resources.Exception_OptionMustBeProvided, nameof(Options.ClientId)));
            }

            if (string.IsNullOrEmpty(Options.ClientSecret))
            {
                throw new ArgumentException(string.Format(CultureInfo.CurrentCulture, Resources.Exception_OptionMustBeProvided, nameof(Options.ClientSecret)));
            }

            if (string.IsNullOrEmpty(Options.AuthorizationEndpoint))
            {
                throw new ArgumentException(string.Format(CultureInfo.CurrentCulture, Resources.Exception_OptionMustBeProvided, nameof(Options.AuthorizationEndpoint)));
            }

            if (string.IsNullOrEmpty(Options.TokenEndpoint))
            {
                throw new ArgumentException(string.Format(CultureInfo.CurrentCulture, Resources.Exception_OptionMustBeProvided, nameof(Options.TokenEndpoint)));
            }

            if (!Options.CallbackPath.HasValue)
            {
                throw new ArgumentException(string.Format(CultureInfo.CurrentCulture, Resources.Exception_OptionMustBeProvided, nameof(Options.CallbackPath)));
            }

            if (Options.Events == null)
            {
                Options.Events = new OAuthEvents();
            }

            if (Options.StateDataFormat == null)
            {
                var dataProtector = dataProtectionProvider.CreateProtector(
                    GetType().FullName, Options.AuthenticationScheme, "v1");
                Options.StateDataFormat = new PropertiesDataFormat(dataProtector);
            }

            Backchannel = new HttpClient(Options.BackchannelHttpHandler ?? new HttpClientHandler());
            Backchannel.DefaultRequestHeaders.UserAgent.ParseAdd("Microsoft ASP.NET Core OAuth middleware");
            Backchannel.Timeout = Options.BackchannelTimeout;
            Backchannel.MaxResponseContentBufferSize = 1024 * 1024 * 10; // 10 MB

            if (string.IsNullOrEmpty(Options.SignInScheme))
            {
                Options.SignInScheme = sharedOptions.Value.SignInScheme;
            }
            if (string.IsNullOrEmpty(Options.SignInScheme))
            {
                throw new ArgumentException(string.Format(CultureInfo.CurrentCulture, Resources.Exception_OptionMustBeProvided, nameof(Options.SignInScheme)));
            }
        }

        protected HttpClient Backchannel { get; private set; }

        /// <summary>
        /// Provides the <see cref="AuthenticationHandler{T}"/> object for processing authentication-related requests.
        /// </summary>
        /// <returns>An <see cref="AuthenticationHandler{T}"/> configured with the <see cref="OAuthOptions"/> supplied to the constructor.</returns>
        protected override AuthenticationHandler<TOptions> CreateHandler()
        {
            return new OAuthHandler<TOptions>(Backchannel);
        }
    }
}