/*
 * Copyright (c) Contributors, http://opensimulator.org/
 * See CONTRIBUTORS.TXT for a full list of copyright holders.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *     * Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *     * Neither the name of the OpenSimulator Project nor the
 *       names of its contributors may be used to endorse or promote products
 *       derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

using System;
using System.Collections.Generic;
using System.Net;
using System.Reflection;
using System.Text.RegularExpressions;

using OpenSim.Framework;
using OpenSim.Services.Interfaces;
using GridRegion = OpenSim.Services.Interfaces.GridRegion;
using OpenSim.Server.Base;
using OpenSim.Services.Connectors.Hypergrid;

using OpenMetaverse;

using Nini.Config;
using log4net;

namespace OpenSim.Services.HypergridService
{
    public class GatekeeperService : IGatekeeperService
    {
        private static readonly ILog m_log =
                LogManager.GetLogger(
                MethodBase.GetCurrentMethod().DeclaringType);

        private static bool m_Initialized = false;

        private static IGridService m_GridService;
        private static IPresenceService m_PresenceService;
        private static IUserAccountService m_UserAccountService;
        private static IUserAgentService m_UserAgentService;
        private static ISimulationService m_SimulationService;

        protected string m_AllowedClients = string.Empty;
        protected string m_DeniedClients = string.Empty;

        private static UUID m_ScopeID;
        private static bool m_AllowTeleportsToAnyRegion;
        private static string m_ExternalName;
        private static GridRegion m_DefaultGatewayRegion;

        public GatekeeperService(IConfigSource config, ISimulationService simService)
        {
            if (!m_Initialized)
            {
                m_Initialized = true;

                IConfig serverConfig = config.Configs["GatekeeperService"];
                if (serverConfig == null)
                    throw new Exception(String.Format("No section GatekeeperService in config file"));

                string accountService = serverConfig.GetString("UserAccountService", String.Empty);
                string homeUsersService = serverConfig.GetString("UserAgentService", string.Empty);
                string gridService = serverConfig.GetString("GridService", String.Empty);
                string presenceService = serverConfig.GetString("PresenceService", String.Empty);
                string simulationService = serverConfig.GetString("SimulationService", String.Empty);

                // These 3 are mandatory, the others aren't
                if (gridService == string.Empty || presenceService == string.Empty)
                    throw new Exception("Incomplete specifications, Gatekeeper Service cannot function.");
                
                string scope = serverConfig.GetString("ScopeID", UUID.Zero.ToString());
                UUID.TryParse(scope, out m_ScopeID);
                //m_WelcomeMessage = serverConfig.GetString("WelcomeMessage", "Welcome to OpenSim!");
                m_AllowTeleportsToAnyRegion = serverConfig.GetBoolean("AllowTeleportsToAnyRegion", true);
                m_ExternalName = serverConfig.GetString("ExternalName", string.Empty);
                if (m_ExternalName != string.Empty && !m_ExternalName.EndsWith("/"))
                    m_ExternalName = m_ExternalName + "/";

                Object[] args = new Object[] { config };
                m_GridService = ServerUtils.LoadPlugin<IGridService>(gridService, args);
                m_PresenceService = ServerUtils.LoadPlugin<IPresenceService>(presenceService, args);

                if (accountService != string.Empty)
                    m_UserAccountService = ServerUtils.LoadPlugin<IUserAccountService>(accountService, args);
                if (homeUsersService != string.Empty)
                    m_UserAgentService = ServerUtils.LoadPlugin<IUserAgentService>(homeUsersService, args);

                if (simService != null)
                    m_SimulationService = simService;
                else if (simulationService != string.Empty)
                        m_SimulationService = ServerUtils.LoadPlugin<ISimulationService>(simulationService, args);

                m_AllowedClients = serverConfig.GetString("AllowedClients", string.Empty);
                m_DeniedClients = serverConfig.GetString("DeniedClients", string.Empty);

                if (m_GridService == null || m_PresenceService == null || m_SimulationService == null)
                    throw new Exception("Unable to load a required plugin, Gatekeeper Service cannot function.");

                m_log.Debug("[GATEKEEPER SERVICE]: Starting...");
            }
        }

        public GatekeeperService(IConfigSource config)
            : this(config, null)
        {
        }

        public bool LinkRegion(string regionName, out UUID regionID, out ulong regionHandle, out string externalName, out string imageURL, out string reason)
        {
            regionID = UUID.Zero;
            regionHandle = 0;
            externalName = m_ExternalName + ((regionName != string.Empty) ? " " + regionName : "");
            imageURL = string.Empty;
            reason = string.Empty;
            GridRegion region = null;

            m_log.DebugFormat("[GATEKEEPER SERVICE]: Request to link to {0}", (regionName == string.Empty)? "default region" : regionName);
            if (!m_AllowTeleportsToAnyRegion || regionName == string.Empty)
            {
                List<GridRegion> defs = m_GridService.GetDefaultRegions(m_ScopeID);
                if (defs != null && defs.Count > 0)
                {
                    region = defs[0];
                    m_DefaultGatewayRegion = region;
                }
                else
                {
                    reason = "Grid setup problem. Try specifying a particular region here.";
                    m_log.DebugFormat("[GATEKEEPER SERVICE]: Unable to send information. Please specify a default region for this grid!");
                    return false;
                }
            }
            else
            {
                region = m_GridService.GetRegionByName(m_ScopeID, regionName);
                if (region == null)
                {
                    reason = "Region not found";
                    return false;
                }
            }

            regionID = region.RegionID;
            regionHandle = region.RegionHandle;

            string regionimage = "regionImage" + regionID.ToString();
            regionimage = regionimage.Replace("-", "");
            imageURL = region.ServerURI + "index.php?method=" + regionimage;

            return true;
        }

        public GridRegion GetHyperlinkRegion(UUID regionID)
        {
            m_log.DebugFormat("[GATEKEEPER SERVICE]: Request to get hyperlink region {0}", regionID);

            if (!m_AllowTeleportsToAnyRegion)
                // Don't even check the given regionID
                return m_DefaultGatewayRegion;

            GridRegion region = m_GridService.GetRegionByUUID(m_ScopeID, regionID);
            return region;
        }

        #region Login Agent
        public bool LoginAgent(AgentCircuitData aCircuit, GridRegion destination, out string reason)
        {
            reason = string.Empty;

            string authURL = string.Empty;
            if (aCircuit.ServiceURLs.ContainsKey("HomeURI"))
                authURL = aCircuit.ServiceURLs["HomeURI"].ToString();
            m_log.InfoFormat("[GATEKEEPER SERVICE]: Login request for {0} {1} @ {2} ({3}) at {4} using viewer {5}, channel {6}, IP {7}, Mac {8}, Id0 {9}",
                aCircuit.firstname, aCircuit.lastname, authURL, aCircuit.AgentID, destination.RegionName,
                aCircuit.Viewer, aCircuit.Channel, aCircuit.IPAddress, aCircuit.Mac, aCircuit.Id0);
            
            //
            // Check client
            //
            if (m_AllowedClients != string.Empty)
            {
                Regex arx = new Regex(m_AllowedClients);
                Match am = arx.Match(aCircuit.Viewer);

                if (!am.Success)
                {
                    m_log.InfoFormat("[GATEKEEPER SERVICE]: Login failed, reason: client {0} is not allowed", aCircuit.Viewer);
                    return false;
                }
            }

            if (m_DeniedClients != string.Empty)
            {
                Regex drx = new Regex(m_DeniedClients);
                Match dm = drx.Match(aCircuit.Viewer);

                if (dm.Success)
                {
                    m_log.InfoFormat("[GATEKEEPER SERVICE]: Login failed, reason: client {0} is denied", aCircuit.Viewer);
                    return false;
                }
            }

            //
            // Authenticate the user
            //
            if (!Authenticate(aCircuit))
            {
                reason = "Unable to verify identity";
                m_log.InfoFormat("[GATEKEEPER SERVICE]: Unable to verify identity of agent {0} {1}. Refusing service.", aCircuit.firstname, aCircuit.lastname);
                return false;
            }
            m_log.DebugFormat("[GATEKEEPER SERVICE]: Identity verified for {0} {1} @ {2}", aCircuit.firstname, aCircuit.lastname, authURL);
            
            //
            // Check for impersonations
            //
            UserAccount account = null;
            if (m_UserAccountService != null)
            {
                // Check to see if we have a local user with that UUID
                account = m_UserAccountService.GetUserAccount(m_ScopeID, aCircuit.AgentID);
                if (account != null)
                {
                    // Make sure this is the user coming home, and not a foreign user with same UUID as a local user
                    if (m_UserAgentService != null)
                    {
                        if (!m_UserAgentService.AgentIsComingHome(aCircuit.SessionID, m_ExternalName))
                        {
                            // Can't do, sorry
                            reason = "Unauthorized";
                            m_log.InfoFormat("[GATEKEEPER SERVICE]: Foreign agent {0} {1} has same ID as local user. Refusing service.",
                                aCircuit.firstname, aCircuit.lastname);
                            return false;

                        }
                    }
                }
            }
            m_log.DebugFormat("[GATEKEEPER SERVICE]: User is ok");

            // May want to authorize

            bool isFirstLogin = false;
            //
            // Login the presence, if it's not there yet (by the login service)
            //
            PresenceInfo presence = m_PresenceService.GetAgent(aCircuit.SessionID);
            if (presence != null) // it has been placed there by the login service
                isFirstLogin = true;

            else 
                if (!m_PresenceService.LoginAgent(aCircuit.AgentID.ToString(), aCircuit.SessionID, aCircuit.SecureSessionID))
                {
                    reason = "Unable to login presence";
                    m_log.InfoFormat("[GATEKEEPER SERVICE]: Presence login failed for foreign agent {0} {1}. Refusing service.",
                        aCircuit.firstname, aCircuit.lastname);
                    return false;
                }
                m_log.DebugFormat("[GATEKEEPER SERVICE]: Login presence ok");

            //
            // Get the region
            //
            destination = m_GridService.GetRegionByUUID(m_ScopeID, destination.RegionID);
            if (destination == null)
            {
                reason = "Destination region not found";
                return false;
            }
            m_log.DebugFormat("[GATEKEEPER SERVICE]: destination ok: {0}", destination.RegionName);

            //
            // Adjust the visible name
            //
            if (account != null)
            {
                aCircuit.firstname = account.FirstName;
                aCircuit.lastname = account.LastName;
            }
            if (account == null && !aCircuit.lastname.StartsWith("@"))
            {
                aCircuit.firstname = aCircuit.firstname + "." + aCircuit.lastname;
                try
                {
                    Uri uri = new Uri(aCircuit.ServiceURLs["HomeURI"].ToString());
                    aCircuit.lastname = "@" + uri.Host; // + ":" + uri.Port;
                }
                catch
                {
                    m_log.WarnFormat("[GATEKEEPER SERVICE]: Malformed HomeURI (this should never happen): {0}", aCircuit.ServiceURLs["HomeURI"]);
                    aCircuit.lastname = "@" + aCircuit.ServiceURLs["HomeURI"].ToString();
                }
            }

            //
            // Finally launch the agent at the destination
            //
            Constants.TeleportFlags loginFlag = isFirstLogin ? Constants.TeleportFlags.ViaLogin : Constants.TeleportFlags.ViaHGLogin;
            m_log.DebugFormat("[GATEKEEPER SERVICE]: launching agent {0}", loginFlag);
            return m_SimulationService.CreateAgent(destination, aCircuit, (uint)loginFlag, out reason);
        }

        protected bool Authenticate(AgentCircuitData aCircuit)
        {
            if (!CheckAddress(aCircuit.ServiceSessionID))
                return false;

            string userURL = string.Empty;
            if (aCircuit.ServiceURLs.ContainsKey("HomeURI"))
                userURL = aCircuit.ServiceURLs["HomeURI"].ToString();

            if (userURL == string.Empty)
            {
                m_log.DebugFormat("[GATEKEEPER SERVICE]: Agent did not provide an authentication server URL");
                return false;
            }

            if (userURL == m_ExternalName)
                return m_UserAgentService.VerifyAgent(aCircuit.SessionID, aCircuit.ServiceSessionID);
            else
            {
//                Object[] args = new Object[] { userURL };
                IUserAgentService userAgentService = new UserAgentServiceConnector(userURL); 
                if (userAgentService != null)
                {
                    try
                    {
                        return userAgentService.VerifyAgent(aCircuit.SessionID, aCircuit.ServiceSessionID);
                    }
                    catch
                    {
                        m_log.DebugFormat("[GATEKEEPER SERVICE]: Unable to contact authentication service at {0}", userURL);
                        return false;
                    }
                }
            }

            return false;
        }

        // Check that the service token was generated for *this* grid.
        // If it wasn't then that's a fake agent.
        protected bool CheckAddress(string serviceToken)
        {
            string[] parts = serviceToken.Split(new char[] { ';' });
            if (parts.Length < 2)
                return false;

            char[] trailing_slash = new char[] { '/' };
            string addressee = parts[0].TrimEnd(trailing_slash);
            string externalname = m_ExternalName.TrimEnd(trailing_slash);
            m_log.DebugFormat("[GATEKEEPER SERVICE]: Verifying {0} against {1}", addressee, externalname);

            return string.Equals(addressee, externalname, StringComparison.OrdinalIgnoreCase);
        }

        #endregion


        #region Misc


        #endregion
    }
}
