using System;
using System.Collections.Generic;
using System.Linq;
using System.Net.Http;
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.LinkedIn
{
    public class LinkedInAuthenticationHandler : AuthenticationHandler<LinkedInAuthenticationOptions>
    {
        private const string XmlSchemaString = "http://www.w3.org/2001/XMLSchema#string";
        private const string TokenEndpoint = "https://www.linkedin.com/uas/oauth2/accessToken";
        private const string UserInfoEndpoint = "https://api.linkedin.com/v1/people/";

        private readonly ILogger logger;
        private readonly HttpClient httpClient;

        public LinkedInAuthenticationHandler(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 = Request.Scheme + "://" + Request.Host;
                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>("grant_type", "authorization_code"));
                body.Add(new KeyValuePair<string, string>("code", code));
                body.Add(new KeyValuePair<string, string>("redirect_uri", redirectUri));
                body.Add(new KeyValuePair<string, string>("client_id", Options.ClientId));
                body.Add(new KeyValuePair<string, string>("client_secret", Options.ClientSecret));

                // Request the token
                HttpResponseMessage tokenResponse =
                    await httpClient.PostAsync(TokenEndpoint, new FormUrlEncodedContent(body));
                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 expires = (string) response.expires_in;

                // Get the LinkedIn user
                string userInfoEndpoint = UserInfoEndpoint
                                          + "~:("+ string.Join(",", Options.ProfileFields.Distinct().ToArray()) +")"
                                          + "?oauth2_access_token=" + Uri.EscapeDataString(accessToken);
                HttpRequestMessage userRequest = new HttpRequestMessage(HttpMethod.Get, userInfoEndpoint);
                userRequest.Headers.Add("x-li-format", "json");
                HttpResponseMessage graphResponse = await httpClient.SendAsync(userRequest, Request.CallCancelled);
                graphResponse.EnsureSuccessStatusCode();
                text = await graphResponse.Content.ReadAsStringAsync();
                JObject user = JObject.Parse(text);

                var context = new LinkedInAuthenticatedContext(Context, user, accessToken, expires);
                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.Email))
                {
                    context.Identity.AddClaim(new Claim(ClaimTypes.Email, context.Email, XmlSchemaString, Options.AuthenticationType));
                }
                if (!string.IsNullOrEmpty(context.GivenName))
                {
                    context.Identity.AddClaim(new Claim(ClaimTypes.GivenName, context.GivenName, XmlSchemaString, Options.AuthenticationType));
                }
                if (!string.IsNullOrEmpty(context.FamilyName))
                {
                    context.Identity.AddClaim(new Claim(ClaimTypes.Surname, context.FamilyName, XmlSchemaString, Options.AuthenticationType));
                }
                if (!string.IsNullOrEmpty(context.Name))
                {
                    context.Identity.AddClaim(new Claim(ClaimTypes.Name, context.Name, XmlSchemaString, Options.AuthenticationType));
                    context.Identity.AddClaim(new Claim("urn:linkedin:name", context.Name, XmlSchemaString, Options.AuthenticationType));
                }
                if (!string.IsNullOrEmpty(context.Link))
                {
                    context.Identity.AddClaim(new Claim("urn:linkedin:url", context.Link, XmlSchemaString, Options.AuthenticationType));
                }
                if (!string.IsNullOrEmpty(context.AccessToken))
                {
                    context.Identity.AddClaim(new Claim("urn:linkedin:accesstoken", context.AccessToken, 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 =
                    Request.Scheme +
                    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);

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

                // allow scopes to be specified via the authentication properties for this request, when specified they will already be comma separated
                if (properties.Dictionary.ContainsKey("scope"))
                {
                    scope = properties.Dictionary["scope"];
                }
                
                string state = Options.StateDataFormat.Protect(properties);

                string authorizationEndpoint =
                    "https://www.linkedin.com/uas/oauth2/authorization" +
                        "?response_type=code" +
                        "&client_id=" + Uri.EscapeDataString(Options.ClientId) +
                        "&redirect_uri=" + Uri.EscapeDataString(redirectUri) +
                        "&scope=" + Uri.EscapeDataString(scope) +
                        "&state=" + Uri.EscapeDataString(state);

                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 LinkedInReturnEndpointContext(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;
        }
    }
}