using System;
using System.Collections.Generic;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Security.Claims;
using System.Threading.Tasks;
using Microsoft.Owin;
using Microsoft.Owin.Infrastructure;
using Microsoft.Owin.Logging;
using Microsoft.Owin.Security;
using Microsoft.Owin.Security.Infrastructure;
using Newtonsoft.Json;
using Newtonsoft.Json.Linq;

namespace Owin.Security.Providers.VisualStudio {
	public class VisualStudioAuthenticationHandler : AuthenticationHandler<VisualStudioAuthenticationOptions> {
		private const string XmlSchemaString = "http://www.w3.org/2001/XMLSchema#string";

		private readonly ILogger logger;
		private readonly HttpClient httpClient;

		public VisualStudioAuthenticationHandler(HttpClient httpClient, ILogger logger) {
            this.httpClient = httpClient;
            this.logger = logger;
        }

		protected override async Task<AuthenticationTicket> AuthenticateCoreAsync() {
			AuthenticationProperties properties = null;

			try {
				string code = null;
				string state = null;

				IReadableStringCollection query = Request.Query;
				IList<string> values = query.GetValues("code");
				if (values != null && values.Count == 1) {
					code = values[0];
				}
				values = query.GetValues("state");
				if (values != null && values.Count == 1) {
					state = values[0];
				}

				properties = Options.StateDataFormat.Unprotect(state);
				if (properties == null) {
					return null;
				}

				// OAuth2 10.12 CSRF
				if (!ValidateCorrelationId(properties, logger)) {
					return new AuthenticationTicket(null, properties);
				}

				string requestPrefix = "https://" + Request.Host; // Schema must be HTTPS
				string redirectUri = requestPrefix + Request.PathBase + Options.CallbackPath;

				// Build up the body for the token request
				var body = new List<KeyValuePair<string, string>>();
				body.Add(new KeyValuePair<string, string>("client_assertion_type", "urn:ietf:params:oauth:client-assertion-type:jwt-bearer"));
				body.Add(new KeyValuePair<string, string>("client_assertion", Options.AppSecret));
				body.Add(new KeyValuePair<string, string>("grant_type", "urn:ietf:params:oauth:grant-type:jwt-bearer"));
				body.Add(new KeyValuePair<string, string>("assertion", code));
				body.Add(new KeyValuePair<string, string>("redirect_uri", redirectUri));

				// Request the token
				var requestMessage = new HttpRequestMessage(HttpMethod.Post, Options.Endpoints.TokenEndpoint);
				requestMessage.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
				requestMessage.Content = new FormUrlEncodedContent(body);
				HttpResponseMessage tokenResponse = await httpClient.SendAsync(requestMessage);
				tokenResponse.EnsureSuccessStatusCode();
				string text = await tokenResponse.Content.ReadAsStringAsync();

				// Deserializes the token response
				dynamic response = JsonConvert.DeserializeObject<dynamic>(text);
				string accessToken = (string)response.access_token;
				string refreshToken = (string)response.refresh_token;
				int expiresIn = (int)response.expires_in;

				// Get the Visual Studio Online user
				HttpRequestMessage userRequest = new HttpRequestMessage(HttpMethod.Get, Options.Endpoints.UserInfoEndpoint);
				userRequest.Headers.Authorization = new AuthenticationHeaderValue("Bearer", accessToken);
				userRequest.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
				HttpResponseMessage userResponse = await httpClient.SendAsync(userRequest, Request.CallCancelled);
				userResponse.EnsureSuccessStatusCode();
				text = await userResponse.Content.ReadAsStringAsync();
				JObject user = JObject.Parse(text);

				var context = new VisualStudioAuthenticatedContext(Context, user, accessToken, expiresIn, refreshToken);
				context.Identity = new ClaimsIdentity(
					Options.AuthenticationType,
					ClaimsIdentity.DefaultNameClaimType,
					ClaimsIdentity.DefaultRoleClaimType);
				if (!string.IsNullOrEmpty(context.Id)) {
					context.Identity.AddClaim(new Claim(ClaimTypes.NameIdentifier, context.Id, XmlSchemaString, Options.AuthenticationType));
				}
				if (!string.IsNullOrEmpty(context.Name)) {
					context.Identity.AddClaim(new Claim(ClaimsIdentity.DefaultNameClaimType, context.Name, XmlSchemaString, Options.AuthenticationType));
				}
				if (!string.IsNullOrEmpty(context.Email)) {
					context.Identity.AddClaim(new Claim(ClaimTypes.Email, context.Email, XmlSchemaString, Options.AuthenticationType));
				}
				if (!string.IsNullOrEmpty(context.Alias)) {
					context.Identity.AddClaim(new Claim("urn:vso:alias", context.Alias, XmlSchemaString, Options.AuthenticationType));
				}
				context.Properties = properties;

				await Options.Provider.Authenticated(context);

				return new AuthenticationTicket(context.Identity, context.Properties);
			} catch (Exception ex) {
				logger.WriteError(ex.Message);
			}
			return new AuthenticationTicket(null, properties);
		}

		protected override Task ApplyResponseChallengeAsync() {
			if (Response.StatusCode != 401) {
				return Task.FromResult<object>(null);
			}

			AuthenticationResponseChallenge challenge = Helper.LookupChallenge(Options.AuthenticationType, Options.AuthenticationMode);

			if (challenge != null) {
				string baseUri =
					"https" + //Schema must be HTTPS
					Uri.SchemeDelimiter +
					Request.Host +
					Request.PathBase;

				string currentUri =
					baseUri +
					Request.Path +
					Request.QueryString;

				string redirectUri =
					baseUri +
					Options.CallbackPath;

				AuthenticationProperties properties = challenge.Properties;
				if (string.IsNullOrEmpty(properties.RedirectUri)) {
					properties.RedirectUri = currentUri;
				}

				// OAuth2 10.12 CSRF
				GenerateCorrelationId(properties);

				// space separated
				string scope = string.Join(" ", Options.Scope);

				string state = Options.StateDataFormat.Protect(properties);

				string authorizationEndpoint =
					Options.Endpoints.AuthorizationEndpoint +
						"?client_id=" + Uri.EscapeDataString(Options.AppId) +
						"&response_type=Assertion" +
						"&state=" + Uri.EscapeDataString(state) +
						"&scope=" + Uri.EscapeDataString(scope) +
						"&redirect_uri=" + Uri.EscapeDataString(redirectUri);

				Response.Redirect(authorizationEndpoint);
			}

			return Task.FromResult<object>(null);
		}

		public override async Task<bool> InvokeAsync() {
			return await InvokeReplyPathAsync();
		}

		private async Task<bool> InvokeReplyPathAsync() {
			if (Options.CallbackPath.HasValue && Options.CallbackPath == Request.Path) {
				// TODO: error responses

				AuthenticationTicket ticket = await AuthenticateAsync();
				if (ticket == null) {
					logger.WriteWarning("Invalid return state, unable to redirect.");
					Response.StatusCode = 500;
					return true;
				}

				var context = new VisualStudioReturnEndpointContext(Context, ticket);
				context.SignInAsAuthenticationType = Options.SignInAsAuthenticationType;
				context.RedirectUri = ticket.Properties.RedirectUri;

				await Options.Provider.ReturnEndpoint(context);

				if (context.SignInAsAuthenticationType != null &&
					context.Identity != null) {
					ClaimsIdentity grantIdentity = context.Identity;
					if (!string.Equals(grantIdentity.AuthenticationType, context.SignInAsAuthenticationType, StringComparison.Ordinal)) {
						grantIdentity = new ClaimsIdentity(grantIdentity.Claims, context.SignInAsAuthenticationType, grantIdentity.NameClaimType, grantIdentity.RoleClaimType);
					}
					Context.Authentication.SignIn(context.Properties, grantIdentity);
				}

				if (!context.IsRequestCompleted && context.RedirectUri != null) {
					string redirectUri = context.RedirectUri;
					if (context.Identity == null) {
						// add a redirect hint that sign-in failed in some way
						redirectUri = WebUtilities.AddQueryString(redirectUri, "error", "access_denied");
					}
					Response.Redirect(redirectUri);
					context.RequestCompleted();
				}

				return context.IsRequestCompleted;
			}
			return false;
		}
	}
}