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.Infrastructure;
using Microsoft.Owin.Logging;
using Microsoft.Owin.Security;
using Microsoft.Owin.Security.Infrastructure;
using Newtonsoft.Json;

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

        private readonly ILogger _logger;
        private readonly HttpClient _httpClient;

        public AsanaAuthenticationHandler(HttpClient httpClient, ILogger logger)
        {
            _httpClient = httpClient;
            _logger = logger;
        }

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

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

                var query = Request.Query;
                var 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);
                }

                var requestPrefix = Request.Scheme + "://" + Request.Host;
                var redirectUri = requestPrefix + Request.PathBase + Options.CallbackPath;

                // Build up the body for the token request
                var body = new List<KeyValuePair<string, string>>
                {
                    new KeyValuePair<string, string>("grant_type", "authorization_code"),
                    new KeyValuePair<string, string>("client_id", Options.ClientId),
                    new KeyValuePair<string, string>("client_secret", Options.ClientSecret),
                    new KeyValuePair<string, string>("redirect_uri", redirectUri),
                    new KeyValuePair<string, string>("code", code)
                };

                /*Your app makes a POST request to https://app.asana.com/-/oauth_token, passing the parameters as part of a standard form-encoded post body.
                        grant_type - required Must be authorization_code
                        client_id - required The Client ID uniquely identifies the application making the request.
                        client_secret - required The Client Secret belonging to the app, found in the details pane of the developer view
                        redirect_uri - required Must match the redirect_uri specified in the original request
                        code - required The code you are exchanging for an auth token
                 */ 

                // 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);
                var tokenResponse = await _httpClient.SendAsync(requestMessage);
                tokenResponse.EnsureSuccessStatusCode();
                var text = await tokenResponse.Content.ReadAsStringAsync();

                // Deserializes the token response
                dynamic response = JsonConvert.DeserializeObject<dynamic>(text);
                var accessToken = (string)response.access_token;

                /*
                 * In the response, you will receive a JSON payload with the following parameters:
                    access_token - The token to use in future requests against the API
                    expires_in - The number of seconds the token is valid, typically 3600 (one hour)
                    token_type - The type of token, in our case, bearer
                    refresh_token - If exchanging a code, a long-lived token that can be used to get new access tokens when old ones expire.
                    data - A JSON object encoding a few key fields about the logged-in user, currently id, name, and email.
                 */

                // Get the Asana user

                var context = new AsanaAuthenticatedContext(Context, response.data, accessToken)
                {
                    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.Name))
                {
                    context.Identity.AddClaim(new Claim("urn:asana:name", context.Name, 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);
            }

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

            if (challenge == null) return Task.FromResult<object>(null);
            var baseUri =
                Request.Scheme +
                Uri.SchemeDelimiter +
                Request.Host +
                Request.PathBase;

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

            var redirectUri =
                baseUri +
                Options.CallbackPath;

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

            // OAuth2 10.12 CSRF
            GenerateCorrelationId(properties);

            var state = Options.StateDataFormat.Protect(properties);
            var authorizationEndpoint =
                Options.Endpoints.AuthorizationEndpoint +
                "?response_type=code" +
                "&client_id=" + Uri.EscapeDataString(Options.ClientId) +
                "&redirect_uri=" + Uri.EscapeDataString(redirectUri) +
                "&state=" + Uri.EscapeDataString(state)
                ;


            /*Your app redirects the user to https://app.asana.com/-/oauth_authorize, passing parameters along as a standard query string:

                    client_id - required The Client ID uniquely identifies the application making the request.
                    redirect_uri - required The URI to redirect to on success or error. This must match the Redirect URL specified in the application settings.
                    response_type - required Must be one of either code (if using the Authorization Code Grant flow) or token (if using the Implicit Grant flow). Other flows are currently not supported.
                    state - optional Encodes state of the app, which will be returned verbatim in the response and can be used to match the response up to a given request.
                 */ 

            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) return false;
            // TODO: error responses

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

            var context = new AsanaReturnEndpointContext(Context, ticket)
            {
                SignInAsAuthenticationType = Options.SignInAsAuthenticationType,
                RedirectUri = ticket.Properties.RedirectUri
            };

            await Options.Provider.ReturnEndpoint(context);

            if (context.SignInAsAuthenticationType != null &&
                context.Identity != null)
            {
                var 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) return context.IsRequestCompleted;
            var 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;
        }
    }
}