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 * modification, are permitted provided that the following conditions are met:
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 *       derived from this software without specific prior written permission.
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 * THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY
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using System;
using System.Collections.Generic;
using System.Reflection;
using System.Threading.Tasks;

using OpenSim.Region.Framework.Scenes;
using OpenSim.Region.Framework.Interfaces;
using OpenSim.Server.Base;

using OpenMetaverse;
using OpenMetaverse.StructuredData;

using Mono.Addins;

using log4net;
using Nini.Config;
using System.Linq;

[assembly: Addin("WebRtcVoiceServiceModule", "1.0")]
[assembly: AddinDependency("OpenSim.Region.Framework", OpenSim.VersionInfo.VersionNumber)]

namespace osWebRtcVoice
{
    /// <summary>
    /// Interface for the WebRtcVoiceService.
    /// An instance of this is registered as the IWebRtcVoiceService for this region.
    /// The function here is to direct the capability requests to the appropriate voice service.
    /// For the moment, there are separate voice services for spatial and non-spatial voice
    /// with the idea that a region could have a pre-region spatial voice service while
    /// the grid could have a non-spatial voice service for group chat, etc.
    /// Fancier configurations are possible.
    /// </summary>
    [Extension(Path = "/OpenSim/RegionModules", NodeName = "RegionModule", Id = "WebRtcVoiceServiceModule")]
    public class WebRtcVoiceServiceModule : IWebRtcVoiceService
    {
        private static readonly ILog m_log = LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);
        private static string LogHeader = "[WEBRTC VOICE SERVICE MODULE]";

        private static bool m_Enabled = false;
        private IConfigSource m_Config;

        private IWebRtcVoiceService m_spatialVoiceService;
        private IWebRtcVoiceService m_nonSpatialVoiceService;

        // =====================================================================

        public WebRtcVoiceServiceModule(IConfigSource pConfig)
        {
            m_Config = pConfig;
            IConfig moduleConfig = m_Config.Configs["WebRtcVoice"];

            if (moduleConfig is not null)
            {
                m_Enabled = moduleConfig.GetBoolean("Enabled", false);
                if (m_Enabled)
                {
                    // Get the DLLs for the two voice services
                    // TODO: spacial/nonspacial names are wrong
                    // spacial here means service for region parcels, that can be spacial or not
                    // non spacial means for other uses like IMs, that just happen to be non spacial
                    // in fact this needs more consideration than just this 2 options

                    string spatialDllName = moduleConfig.GetString("SpatialVoiceService", string.Empty);
                    string nonSpatialDllName = moduleConfig.GetString("NonSpatialVoiceService", string.Empty);
                    if (string.IsNullOrEmpty(spatialDllName) && string.IsNullOrEmpty(nonSpatialDllName))
                    {
                        m_log.Error($"{LogHeader} No VoiceService specified in configuration");
                        m_Enabled = false;
                        return;
                    }

                    // Default non-spatial to spatial if not specified
                    if (string.IsNullOrEmpty(nonSpatialDllName))
                    {
                        m_log.Debug($"{LogHeader} nonSpatialDllName not specified. Defaulting to spatialDllName");
                        nonSpatialDllName = spatialDllName;
                    }

                    // Load the two voice services
                    m_log.Debug($"{LogHeader} Loading SpatialVoiceService from {spatialDllName}");
                    m_spatialVoiceService = ServerUtils.LoadPlugin<IWebRtcVoiceService>(spatialDllName, [m_Config]);
                    if (m_spatialVoiceService is null)
                    {
                        m_log.Error($"{LogHeader} Could not load SpatialVoiceService from {spatialDllName}, module disabled");
                        m_Enabled = false;
                        return;
                    }

                    m_log.Debug($"{LogHeader} Loading NonSpatialVoiceService from {nonSpatialDllName}");
                    if (spatialDllName != nonSpatialDllName)
                    {
                        m_nonSpatialVoiceService = ServerUtils.LoadPlugin<IWebRtcVoiceService>(nonSpatialDllName, [ m_Config ]);
                        if (m_nonSpatialVoiceService is null)
                        {
                            m_log.Error($"{LogHeader} Could not load NonSpatialVoiceService from {nonSpatialDllName}");
                            m_Enabled = false;
                        }
                    }

                    if (m_Enabled)
                    {
                        m_log.Info($"{LogHeader} WebRtcVoiceService enabled");
                    }
                }
            }
        }


         private static void CleanupDuplicateSessions(UUID pAgentID, UUID pSceneID, string pKeepViewerSessionId)
        {
            if(VoiceViewerSession.TryGetViewerSessionsByAgentAndRegion(pAgentID, pSceneID, out IEnumerable<KeyValuePair<string, IVoiceViewerSession>> candidates))
            {
                bool noskip = string.IsNullOrEmpty(pKeepViewerSessionId);
                foreach (KeyValuePair<string, IVoiceViewerSession> candidate in candidates)
                {
                    if (noskip && candidate.Key == pKeepViewerSessionId)
                        continue;

                    m_log.Warn(
                        $"{LogHeader} CleanupDuplicateSessions: removing stale viewer_session {candidate.Key} for agent {pAgentID}, scene {pSceneID}");

                    VoiceViewerSession.RemoveViewerSession(candidate.Key);
                    _ = Task.Run(async () =>
                    {
                        try
                        {
                            await candidate.Value.Shutdown();
                        }
                        catch (Exception ex)
                        {
                            m_log.Debug(
                                $"{LogHeader} CleanupDuplicateSessions: shutdown failed for viewer_session {candidate.Key}: {ex.Message}");
                        }
                    });
                }
            }
        }

        // =====================================================================
        // IWebRtcVoiceService

        // IWebRtcVoiceService.ProvisionVoiceAccountRequest
        public OSDMap ProvisionVoiceAccountRequest(OSDMap pRequest, UUID pUserID, UUID pSceneID)
        {
            IVoiceViewerSession vSession = null;
            if (pRequest.TryGetString("viewer_session", out string viewerSessionId))
            {
                if(pRequest.TryGetBool("logout", out bool islog) && islog)
                {
                    if(UUID.ZeroString.Equals(viewerSessionId, StringComparison.OrdinalIgnoreCase))
                    {
                        if (VoiceViewerSession.TryGetViewerSessionsByAgentId(pUserID, out IEnumerable<KeyValuePair<string, IVoiceViewerSession>> vSessions))
                        {
                            m_log.Info(
                                $"{LogHeader} ProvisionVoiceAccountRequest: doing logout for {vSessions.Count()} stall sessions");

                            OSDMap vreq = new() {{ "logout" , true} };

                            foreach(KeyValuePair<string, IVoiceViewerSession> kvp in vSessions)
                            {
                                IVoiceViewerSession v = kvp.Value;
                                if(v is null)
                                    continue;
                                vreq["viewer_session"] = v.ViewerSessionID;

                                VoiceViewerSession.RemoveViewerSession(v.ViewerSessionID);
                                v.VoiceService.ProvisionVoiceAccountRequest(v, vreq , pUserID, pSceneID);
                            }
                        }

                        return new OSDMap {{ "response", "closed" }};
                    }

                    OSDMap resp = null;
                    if (VoiceViewerSession.TryGetViewerSession(viewerSessionId, out vSession))
                    {
                        VoiceViewerSession.RemoveViewerSession(viewerSessionId);
                        resp = vSession.VoiceService.ProvisionVoiceAccountRequest(vSession, pRequest, pUserID, pSceneID);
                    }
                    return resp ?? new OSDMap() {
                        { "response", "error" },
                        { "message", "Logout session not found" } };
                }

                // request has a viewer session. Use that to find the voice service
                if (VoiceViewerSession.TryGetViewerSession(viewerSessionId, out vSession))
                {
                    CleanupDuplicateSessions(pUserID, pSceneID, viewerSessionId);
                }
            }
            else
            {
                // the request does not have a viewer session. See if it's an initial request
                if (pRequest.TryGetString("channel_type", out string channelType))
                {
                    // Ensure stale sessions are cleared before creating a new one.
                    CleanupDuplicateSessions(pUserID, pSceneID, null);
                    if (channelType == "local")
                    {
                        // TODO: check if this userId is making a new session (case that user is reconnecting)
                        vSession = m_spatialVoiceService.CreateViewerSession(pRequest, pUserID, pSceneID);
                        if(vSession != null)
                        {
                            if(pRequest.TryGetInt("parcel_local_id", out int parcelID))
                                vSession.Flags = IVoiceViewerSession.VFlags.IsParcel;
                            else
                                vSession.Flags = IVoiceViewerSession.VFlags.IsEstate;
                            VoiceViewerSession.AddViewerSession(vSession);
                        }
                    }
                    else
                    {
                        // TODO: check if this userId is making a new session (case that user is reconnecting)
                        vSession = m_nonSpatialVoiceService.CreateViewerSession(pRequest, pUserID, pSceneID);
                        if(vSession != null) VoiceViewerSession.AddViewerSession(vSession);
                    }
                }
            }

            OSDMap response = null;

            if (vSession is not null)
            {
                response = vSession.VoiceService.ProvisionVoiceAccountRequest(vSession, pRequest, pUserID, pSceneID);
            }

            if (response is null)
            {
                return new OSDMap
                {
                    { "response", "error" },
                    { "message", "Unable to provision voice session (missing viewer_session/channel_type or session not found)" }
                };
             }

            return response;
        }

        // IWebRtcVoiceService.VoiceSignalingRequest
        public OSDMap VoiceSignalingRequest(OSDMap pRequest, UUID pUserID, UUID pSceneID)
        {
            OSDMap response = null;
            IVoiceViewerSession vSession = null;
            if (pRequest.TryGetString("viewer_session", out string viewerSessionId))
            {
                // request has a viewer session. Use that to find the voice service
                if (VoiceViewerSession.TryGetViewerSession(viewerSessionId, out vSession))
                {
                    response = vSession.VoiceService.VoiceSignalingRequest(vSession, pRequest, pUserID, pSceneID);
                }
                else
                {
                    m_log.Error($"{LogHeader} VoiceSignalingRequest: viewer session {viewerSessionId} not found");
                }
            }
            else
            {
                m_log.Error($"{LogHeader} VoiceSignalingRequest: no viewer_session in request");
            }
            return response;
        }

        // This module should never be called with this signature
        public OSDMap ProvisionVoiceAccountRequest(IVoiceViewerSession pVSession, OSDMap pRequest, UUID pUserID, UUID pSceneID)
        {
            throw new NotImplementedException();
        }

        // This module should never be called with this signature
        public OSDMap VoiceSignalingRequest(IVoiceViewerSession pVSession, OSDMap pRequest, UUID pUserID, UUID pSceneID)
        {
            throw new NotImplementedException();
        }

        public IVoiceViewerSession CreateViewerSession(OSDMap pRequest, UUID pUserID, UUID pSceneID)
        {
            throw new NotImplementedException();
        }
    }
}