using System;
using System.Net.Http.Headers;
using System.Security.Claims;
using System.Text;
using System.Text.Encodings.Web;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Authentication;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;

namespace EqidManager.Services
{
  public static class BasicAuthenticationScheme
  {
    public const string DefaultScheme = "Basic";
  }

  public class BasicAuthenticationOption:AuthenticationSchemeOptions
  {
    public string Realm { get; set; }
    public string UserName { get; set; }
    public string UserPwd { get; set; }
  }

  public class BasicAuthenticationHandler : AuthenticationHandler<BasicAuthenticationOption>
  {
    private readonly BasicAuthenticationOption authOptions;
    public BasicAuthenticationHandler(
      IOptionsMonitor<BasicAuthenticationOption> options,
      ILoggerFactory logger,
      UrlEncoder encoder,
      ISystemClock clock)
      : base(options, logger, encoder, clock)
    {
      authOptions = options.CurrentValue;
    }

    /// <summary>
    /// 認(rèn)證
    /// </summary>
    /// <returns></returns>
    protected override async Task<AuthenticateResult> HandleAuthenticateAsync()
    {
      if (!Request.Headers.ContainsKey("Authorization"))
        return AuthenticateResult.Fail("Missing Authorization Header");
      string username, password;
      try
      {
        var authHeader = AuthenticationHeaderValue.Parse(Request.Headers["Authorization"]);
        var credentialBytes = Convert.FromBase64String(authHeader.Parameter);
        var credentials = Encoding.UTF8.GetString(credentialBytes).Split(':');
         username = credentials[0];
         password = credentials[1];
         var isValidUser= IsAuthorized(username,password);
        if(isValidUser== false)
        {
          return AuthenticateResult.Fail("Invalid username or password");
        }
      }
      catch
      {
        return AuthenticateResult.Fail("Invalid Authorization Header");
      }

      var claims = new[] {
        new Claim(ClaimTypes.NameIdentifier,username),
        new Claim(ClaimTypes.Name,username),
      };
      var identity = new ClaimsIdentity(claims, Scheme.Name);
      var principal = new ClaimsPrincipal(identity);
      var ticket = new AuthenticationTicket(principal, Scheme.Name);
      return await Task.FromResult(AuthenticateResult.Success(ticket));
    }

    /// <summary>
    /// 質(zhì)詢(xún)
    /// </summary>
    /// <param name="properties"></param>
    /// <returns></returns>
    protected override async Task HandleChallengeAsync(AuthenticationProperties properties)
    {
      Response.Headers["WWW-Authenticate"] = $"Basic realm=\"{Options.Realm}\"";
      await base.HandleChallengeAsync(properties);
    }

    /// <summary>
    /// 認(rèn)證失敗
    /// </summary>
    /// <param name="properties"></param>
    /// <returns></returns>
    protected override async Task HandleForbiddenAsync(AuthenticationProperties properties)
    {
      await base.HandleForbiddenAsync(properties); 
    }

    private bool IsAuthorized(string username, string password)
    {
      return username.Equals(authOptions.UserName, StringComparison.InvariantCultureIgnoreCase)
          && password.Equals(authOptions.UserPwd);
    }
  }
}

// HTTP基本認(rèn)證Middleware public static class BasicAuthentication
 {
    public static void UseBasicAuthentication(this IApplicationBuilder app)
    {
      app.UseMiddleware<BasicAuthenticationMiddleware>();
    }
 }

public class BasicAuthenticationMiddleware
{
   private readonly RequestDelegate _next;
   private readonly ILogger _logger;

   public BasicAuthenticationMiddleware(RequestDelegate next, ILoggerFactory LoggerFactory)
   {
    _next = next;    _logger = LoggerFactory.CreateLogger<BasicAuthenticationMiddleware>();
   }
   public async Task Invoke(HttpContext httpContext, IAuthenticationService authenticationService)
   {
    var authenticated = await authenticationService.AuthenticateAsync(httpContext, BasicAuthenticationScheme.DefaultScheme);
    _logger.LogInformation("Access Status：" + authenticated.Succeeded);
    if (!authenticated.Succeeded)
    {
      await authenticationService.ChallengeAsync(httpContext, BasicAuthenticationScheme.DefaultScheme, new AuthenticationProperties { });
      return;
    }
    await _next(httpContext);
   }
}

// HTTP基本認(rèn)證Middleware public static class BasicAuthentication
 {
    public static void UseBasicAuthentication(this IApplicationBuilder app)
    {
      app.UseMiddleware<BasicAuthenticationMiddleware>();
    }
 }

public class BasicAuthenticationMiddleware
{
   private readonly RequestDelegate _next;
   private readonly ILogger _logger;

   public BasicAuthenticationMiddleware(RequestDelegate next, ILoggerFactory LoggerFactory)
   {
    _next = next;    _logger = LoggerFactory.CreateLogger<BasicAuthenticationMiddleware>();
   }
   public async Task Invoke(HttpContext httpContext, IAuthenticationService authenticationService)
   {
    var authenticated = await authenticationService.AuthenticateAsync(httpContext, BasicAuthenticationScheme.DefaultScheme);
    _logger.LogInformation("Access Status：" + authenticated.Succeeded);
    if (!authenticated.Succeeded)
    {
      await authenticationService.ChallengeAsync(httpContext, BasicAuthenticationScheme.DefaultScheme, new AuthenticationProperties { });
      return;
    }
    await _next(httpContext);
   }
}

services.AddAuthentication(BasicAuthenticationScheme.DefaultScheme)
        .AddScheme<BasicAuthenticationOption, BasicAuthenticationHandler>(BasicAuthenticationScheme.DefaultScheme,null);
app.UseWhen(
      predicate:x => x.Request.Path.StartsWithSegments(new PathString(_protectedResourceOption.Path)),
      configuration:appBuilder => { appBuilder.UseBasicAuthentication()； }
  );

/// <summary>
  /// BA認(rèn)證請(qǐng)求Handler
  /// </summary>
  public class BasicAuthenticationClientHandler : HttpClientHandler
  {
    public static string BAHeaderNames = "authorization";
    private RemoteBasicAuth _remoteAccount;

    public BasicAuthenticationClientHandler(RemoteBasicAuth remoteAccount)
    {
      _remoteAccount = remoteAccount;
      AllowAutoRedirect = false;
      UseCookies = true;
    }

    protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
    {
      var authorization = $"{_remoteAccount.UserName}:{_remoteAccount.Password}";
      var authorizationBased64 = "Basic " + Convert.ToBase64String(new ASCIIEncoding().GetBytes(authorization));
      request.Headers.Remove(BAHeaderNames);
      request.Headers.Add(BAHeaderNames, authorizationBased64);
      return base.SendAsync(request, cancellationToken);
    }
  }


 // 生成basic Authentication請(qǐng)求
      services.AddHttpClient("eqid-ba-request", x =>
          x.BaseAddress = new Uri(_proxyOption.Scheme +"://"+ _proxyOption.Host+":"+_proxyOption.Port ) )
        .ConfigurePrimaryHttpMessageHandler(y => new BasicAuthenticationClientHandler(_remoteAccount){} )
        .SetHandlerLifetime(TimeSpan.FromMinutes(2));

仿BA認(rèn)證協(xié)議中的瀏覽器行為