using System;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Security.Principal;
using System.Threading;
using System.Web;
using System.Web.Security;
using Newtonsoft.Json;
using Umbraco.Core.Configuration;

namespace Umbraco.Core.Security
{
    /// <summary>
    /// Extensions to create and renew and remove authentication tickets for the Umbraco back office
    /// </summary>
    internal static class AuthenticationExtensions
    {
        /// <summary>
        /// This will check the ticket to see if it is valid, if it is it will set the current thread's user and culture
        /// </summary>
        /// <param name="http"></param>
        /// <param name="ticket"></param>
        /// <param name="renewTicket">If true will attempt to renew the ticket</param>
        public static bool AuthenticateCurrentRequest(this HttpContextBase http, FormsAuthenticationTicket ticket, bool renewTicket)
        {
            if (http == null) throw new ArgumentNullException("http");

            //if there was a ticket, it's not expired, - it should not be renewed or its renewable
            if (ticket != null && ticket.Expired == false && (renewTicket == false || http.RenewUmbracoAuthTicket()))
            {
                try
                {
                    //create the Umbraco user identity 
                    var identity = new UmbracoBackOfficeIdentity(ticket);

                    //set the principal object
                    var principal = new GenericPrincipal(identity, identity.Roles);

                    //It is actually not good enough to set this on the current app Context and the thread, it also needs
                    // to be set explicitly on the HttpContext.Current !! This is a strange web api thing that is actually 
                    // an underlying fault of asp.net not propogating the User correctly.
                    if (HttpContext.Current != null)
                    {
                        HttpContext.Current.User = principal;
                    }
                    http.User = principal;
                    Thread.CurrentPrincipal = principal;

                    //This is a back office request, we will also set the culture/ui culture
                    Thread.CurrentThread.CurrentCulture =
                        Thread.CurrentThread.CurrentUICulture =
                        new System.Globalization.CultureInfo(identity.Culture);

                    return true;
                }
                catch (Exception ex)
                {
                    if (ex is FormatException || ex is JsonReaderException)
                    {
                        //this will occur if the cookie data is invalid
                        http.UmbracoLogout();
                    }
                    else
                    {
                        throw;
                    }

                }
            }

            return false;
        }


        /// <summary>
        /// This will return the current back office identity. 
        /// </summary>
        /// <param name="http"></param>
        /// <param name="authenticateRequestIfNotFound">
        /// If set to true and a back office identity is not found and not authenticated, this will attempt to authenticate the 
        /// request just as is done in the Umbraco module and then set the current identity if it is valid
        /// </param>
        /// <returns>
        /// Returns the current back office identity if an admin is authenticated otherwise null
        /// </returns>
        public static UmbracoBackOfficeIdentity GetCurrentIdentity(this HttpContextBase http, bool authenticateRequestIfNotFound)
        {
            if (http == null) throw new ArgumentNullException("http");
            var identity = http.User.Identity as UmbracoBackOfficeIdentity;
            if (identity != null) return identity;
            if (authenticateRequestIfNotFound == false) return null;
            //even if authenticateRequestIfNotFound is true we cannot continue if the request is actually authenticated 
            // which would mean something strange is going on that it is not an umbraco identity.
            if (http.User.Identity.IsAuthenticated) return null;
            
            //now we just need to try to authenticate the current request
            var ticket = http.GetUmbracoAuthTicket();
            if (http.AuthenticateCurrentRequest(ticket, true))
            {
                //now we 'should have an umbraco identity
                return http.User.Identity as UmbracoBackOfficeIdentity;
            }
            return null;
        }

        /// <summary>
        /// This will return the current back office identity. 
        /// </summary>
        /// <param name="http"></param>
        /// <param name="authenticateRequestIfNotFound">
        /// If set to true and a back office identity is not found and not authenticated, this will attempt to authenticate the 
        /// request just as is done in the Umbraco module and then set the current identity if it is valid
        /// </param>
        /// <returns>
        /// Returns the current back office identity if an admin is authenticated otherwise null
        /// </returns>
        internal static UmbracoBackOfficeIdentity GetCurrentIdentity(this HttpContext http, bool authenticateRequestIfNotFound)
        {
            if (http == null) throw new ArgumentNullException("http");
            return new HttpContextWrapper(http).GetCurrentIdentity(authenticateRequestIfNotFound);
        }

        /// <summary>
        /// This clears the forms authentication cookie
        /// </summary>
        public static void UmbracoLogout(this HttpContextBase http)
        {
            if (http == null) throw new ArgumentNullException("http");
            Logout(http, UmbracoConfig.For.UmbracoSettings().Security.AuthCookieName);
        }

        /// <summary>
        /// This clears the forms authentication cookie
        /// </summary>
        /// <param name="response"></param>
        public static void UmbracoLogout(this HttpResponseMessage response)
        {
            if (response == null) throw new ArgumentNullException("response");
            //remove the cookie
            var authCookie = new CookieHeaderValue(UmbracoConfig.For.UmbracoSettings().Security.AuthCookieName, "")
            {
                Expires = DateTime.Now.AddYears(-1),                
                Path = "/"
            };
            //remove the preview cookie too
            var prevCookie = new CookieHeaderValue(Constants.Web.PreviewCookieName, "")
            {
                Expires = DateTime.Now.AddYears(-1),
                Path = "/"
            };

            response.Headers.AddCookies(new[] { authCookie, prevCookie });
        }

        /// <summary>
        /// This clears the forms authentication cookie
        /// </summary>
        /// <param name="http"></param>
        internal static void UmbracoLogout(this HttpContext http)
        {
            if (http == null) throw new ArgumentNullException("http");
            new HttpContextWrapper(http).UmbracoLogout();
        }

        /// <summary>
        /// Renews the Umbraco authentication ticket
        /// </summary>
        /// <param name="http"></param>
        /// <returns></returns>
        public static bool RenewUmbracoAuthTicket(this HttpContextBase http)
        {
            if (http == null) throw new ArgumentNullException("http");
            return RenewAuthTicket(http,
                UmbracoConfig.For.UmbracoSettings().Security.AuthCookieName,
                UmbracoConfig.For.UmbracoSettings().Security.AuthCookieDomain,
                //Umbraco has always persisted it's original cookie for 1 day so we'll keep it that way
                1440);
        }

        internal static bool RenewUmbracoAuthTicket(this HttpContext http)
        {
            if (http == null) throw new ArgumentNullException("http");
            return new HttpContextWrapper(http).RenewUmbracoAuthTicket();
        }

        /// <summary>
        /// Creates the umbraco authentication ticket
        /// </summary>
        /// <param name="http"></param>
        /// <param name="userdata"></param>
        public static FormsAuthenticationTicket CreateUmbracoAuthTicket(this HttpContextBase http, UserData userdata)
        {
            if (http == null) throw new ArgumentNullException("http");
            if (userdata == null) throw new ArgumentNullException("userdata");
            var userDataString = JsonConvert.SerializeObject(userdata);
            return CreateAuthTicketAndCookie(
                http, 
                userdata.Username, 
                userDataString, 
                //use the configuration timeout - this is the same timeout that will be used when renewing the ticket.
                GlobalSettings.TimeOutInMinutes, 
                //Umbraco has always persisted it's original cookie for 1 day so we'll keep it that way
                1440, 
                "/",
                UmbracoConfig.For.UmbracoSettings().Security.AuthCookieName,
                UmbracoConfig.For.UmbracoSettings().Security.AuthCookieDomain);
        }

        internal static FormsAuthenticationTicket CreateUmbracoAuthTicket(this HttpContext http, UserData userdata)
        {
            if (http == null) throw new ArgumentNullException("http");
            if (userdata == null) throw new ArgumentNullException("userdata");
            return new HttpContextWrapper(http).CreateUmbracoAuthTicket(userdata);
        }

        /// <summary>
        /// returns the number of seconds the user has until their auth session times out
        /// </summary>
        /// <param name="http"></param>
        /// <returns></returns>
        public static double GetRemainingAuthSeconds(this HttpContextBase http)
        {
            if (http == null) throw new ArgumentNullException("http");
            var ticket = http.GetUmbracoAuthTicket();
            return ticket.GetRemainingAuthSeconds();
        }

        /// <summary>
        /// returns the number of seconds the user has until their auth session times out
        /// </summary>
        /// <param name="ticket"></param>
        /// <returns></returns>
        public static double GetRemainingAuthSeconds(this FormsAuthenticationTicket ticket)
        {
            if (ticket == null)
            {
                return 0;
            }
            var utcExpired = ticket.Expiration.ToUniversalTime();
            var secondsRemaining = utcExpired.Subtract(DateTime.UtcNow).TotalSeconds;
            return secondsRemaining;
        }

        /// <summary>
        /// Gets the umbraco auth ticket
        /// </summary>
        /// <param name="http"></param>
        /// <returns></returns>
        public static FormsAuthenticationTicket GetUmbracoAuthTicket(this HttpContextBase http)
        {
            if (http == null) throw new ArgumentNullException("http");
            return GetAuthTicket(http, UmbracoConfig.For.UmbracoSettings().Security.AuthCookieName);
        }

        internal static FormsAuthenticationTicket GetUmbracoAuthTicket(this HttpContext http)
        {
            if (http == null) throw new ArgumentNullException("http");
            return new HttpContextWrapper(http).GetUmbracoAuthTicket();
        }

        /// <summary>
        /// This clears the forms authentication cookie
        /// </summary>
        /// <param name="http"></param>
        /// <param name="cookieName"></param>
        private static void Logout(this HttpContextBase http, string cookieName)
        {
            if (http == null) throw new ArgumentNullException("http");
            //clear the preview cookie too
            var cookies = new[] { cookieName, Constants.Web.PreviewCookieName };
            foreach (var c in cookies)
            {
                //remove from the request
                http.Request.Cookies.Remove(c);

                //expire from the response
                var formsCookie = http.Response.Cookies[c];
                if (formsCookie != null)
                {
                    //this will expire immediately and be removed from the browser
                    formsCookie.Expires = DateTime.Now.AddYears(-1);
                }
                else
                {
                    //ensure there's def an expired cookie
                    http.Response.Cookies.Add(new HttpCookie(c) { Expires = DateTime.Now.AddYears(-1) });
                }               
            }            

        }

        private static FormsAuthenticationTicket GetAuthTicket(this HttpContextBase http, string cookieName)
        {
            if (http == null) throw new ArgumentNullException("http");
            var formsCookie = http.Request.Cookies[cookieName];
            if (formsCookie == null)
            {
                return null;
            }
            //get the ticket
            try
            {
                return FormsAuthentication.Decrypt(formsCookie.Value);
            }
            catch (Exception)
            {
                //occurs when decryption fails
                http.Logout(cookieName);
                return null;
            }
        }

        /// <summary>
        /// Renews the forms authentication ticket & cookie
        /// </summary>
        /// <param name="http"></param>
        /// <param name="cookieName"></param>
        /// <param name="cookieDomain"></param>
        /// <param name="minutesPersisted"></param>
        /// <returns>true if there was a ticket to renew otherwise false if there was no ticket</returns>
        private static bool RenewAuthTicket(this HttpContextBase http, string cookieName, string cookieDomain, int minutesPersisted)
        {
            if (http == null) throw new ArgumentNullException("http");
            //get the ticket
            var ticket = GetAuthTicket(http, cookieName);
            //renew the ticket
            var renewed = FormsAuthentication.RenewTicketIfOld(ticket);
            if (renewed == null)
            {
                return false;
            }

            //get the request cookie to get it's expiry date, 
            //NOTE: this will never be null becaues we already do this
            // check in teh GetAuthTicket.
            var formsCookie = http.Request.Cookies[cookieName];
            
            //encrypt it
            var hash = FormsAuthentication.Encrypt(renewed);
            //write it to the response
            var cookie = new HttpCookie(cookieName, hash)
                {                    
                    Expires = DateTime.Now.AddMinutes(minutesPersisted),
                    Domain = cookieDomain
                };

            if (GlobalSettings.UseSSL)
                cookie.Secure = true;

            //ensure http only, this should only be able to be accessed via the server
            cookie.HttpOnly = true;

            //rewrite the cooke
            http.Response.Cookies.Set(cookie);
            return true;
        }

        /// <summary>
        /// Creates a custom FormsAuthentication ticket with the data specified
        /// </summary>
        /// <param name="http">The HTTP.</param>
        /// <param name="username">The username.</param>
        /// <param name="userData">The user data.</param>
        /// <param name="loginTimeoutMins">The login timeout mins.</param>
        /// <param name="minutesPersisted">The minutes persisted.</param>
        /// <param name="cookiePath">The cookie path.</param>
        /// <param name="cookieName">Name of the cookie.</param>
        /// <param name="cookieDomain">The cookie domain.</param>
        private static FormsAuthenticationTicket CreateAuthTicketAndCookie(this HttpContextBase http,
                                            string username,
                                            string userData,
                                            int loginTimeoutMins,
                                            int minutesPersisted,
                                            string cookiePath,
                                            string cookieName,
                                            string cookieDomain)
        {
            if (http == null) throw new ArgumentNullException("http");
            // Create a new ticket used for authentication
            var ticket = new FormsAuthenticationTicket(
                4,
                username,
                DateTime.Now,
                DateTime.Now.AddMinutes(loginTimeoutMins),
                true,
                userData,
                cookiePath
                );
	
            // Encrypt the cookie using the machine key for secure transport
            var hash = FormsAuthentication.Encrypt(ticket);
            var cookie = new HttpCookie(
                cookieName,
                hash)
                {
                    Expires = DateTime.Now.AddMinutes(minutesPersisted),
                    Domain = cookieDomain
                };

			if (GlobalSettings.UseSSL)
                cookie.Secure = true;

            //ensure http only, this should only be able to be accessed via the server
            cookie.HttpOnly = true;
				
            http.Response.Cookies.Set(cookie);

            return ticket;
        }
    }
}