using System.Collections.Generic;
using System.Linq;
using UnityEngine;

namespace Unity.RenderStreaming
{
    /// <summary>
    /// Host模式的连接处理器
    /// 适用于私有模式下Unity作为Host（第一个加入房间的客户端）
    /// 支持多个Participant连接，每个Participant拥有独立的PeerConnection
    /// 
    /// 工作原理：
    /// - Host通过CreateConnection(connectionId)创建房间连接
    /// - 当Participant加入时，服务器发送participant-joined通知
    /// - WebSocketSignaling将participantId作为内部connectionId使用，
    ///   因此每个Participant会自动创建独立的PeerConnection
    /// - 当收到Participant的offer时，自动添加Stream并发送answer
    /// - 当Participant离开时，自动清理对应的连接资源
    /// </summary>
    [AddComponentMenu("Render Streaming/Host Connection")]
    public class HostConnection : SignalingHandlerBase,
        IOfferHandler, IAddChannelHandler, IDisconnectHandler, IDeletedConnectionHandler,
        IAddReceiverHandler, IParticipantJoinedHandler, IParticipantLeftHandler,
        ICallRequestHandler, IMessageHandler
    {
        [SerializeField] private List<Component> streams = new List<Component>();

        /// <summary>
        /// 当前连接的所有Participant的participantId列表
        /// </summary>
        private List<string> participantIds = new List<string>();

        /// <summary>
        /// 房间的connectionId（Host创建连接时使用的ID）
        /// </summary>
        private string roomConnectionId;

        public override IEnumerable<Component> Streams => streams;

        public void AddComponent(Component component)
        {
            streams.Add(component);
        }

        public void RemoveComponent(Component component)
        {
            streams.Remove(component);
        }

        /// <summary>
        /// 创建Host连接（即创建房间）
        /// Unity作为第一个连接的客户端，服务器会分配host角色(polite=false)
        /// </summary>
        /// <param name="connectionId">房间ID</param>
        public override void CreateConnection(string connectionId)
        {
            roomConnectionId = connectionId;
            base.CreateConnection(connectionId);
        }

        /// <summary>
        /// 删除Host连接（关闭房间）
        /// Host离开时，服务器会自动断开所有Participant
        /// </summary>
        public override void DeleteConnection(string connectionId)
        {
            // 清理所有Participant连接
            foreach (var participantId in participantIds.ToList())
            {
                DisconnectParticipant(participantId);
            }
            participantIds.Clear();

            if (connectionId == roomConnectionId)
            {
                base.DeleteConnection(connectionId);
                roomConnectionId = null;
            }
            else
            {
                base.DeleteConnection(connectionId);
            }
        }

        public void OnDeletedConnection(SignalingEventData eventData)
        {
            Disconnect(eventData.connectionId);
        }

        public void OnDisconnect(SignalingEventData eventData)
        {
            Disconnect(eventData.connectionId);
        }

        private void Disconnect(string connectionId)
        {
            if (!participantIds.Contains(connectionId) && connectionId != roomConnectionId)
                return;

            participantIds.Remove(connectionId);

            foreach (var sender in streams.OfType<IStreamSender>())
            {
                RemoveSender(connectionId, sender);
            }
            foreach (var receiver in streams.OfType<IStreamReceiver>())
            {
                RemoveReceiver(connectionId, receiver);
            }
            foreach (var channel in streams.OfType<IDataChannel>().Where(c => c.ConnectionId == connectionId))
            {
                RemoveChannel(connectionId, channel);
            }
        }

        /// <summary>
        /// 断开指定Participant的连接资源
        /// </summary>
        private void DisconnectParticipant(string participantId)
        {
            foreach (var sender in streams.OfType<IStreamSender>())
            {
                RemoveSender(participantId, sender);
            }
            foreach (var receiver in streams.OfType<IStreamReceiver>())
            {
                RemoveReceiver(participantId, receiver);
            }
            foreach (var channel in streams.OfType<IDataChannel>().Where(c => c.ConnectionId == participantId))
            {
                RemoveChannel(participantId, channel);
            }
        }

        /// <summary>
        /// 收到Participant的offer时触发
        /// WebSocketSignaling已经将participantId作为内部connectionId
        /// 所以每个Participant的offer会自动创建独立的PeerConnection
        /// </summary>
        public void OnOffer(SignalingEventData data)
        {
            // 记录新的Participant连接
            if (!participantIds.Contains(data.connectionId))
            {
                participantIds.Add(data.connectionId);
                Debug.Log($"[HostConnection] Participant offer received: {data.connectionId}");
            }

            // 为该Participant添加所有Stream
            foreach (var source in streams.OfType<IStreamSender>())
            {
                AddSender(data.connectionId, source);
            }
            foreach (var channel in streams.OfType<IDataChannel>().Where(c => c.IsLocal))
            {
                AddChannel(data.connectionId, channel);
            }

            // 发送answer给该Participant
            SendAnswer(data.connectionId);
        }

        /// <summary>
        /// 收到远程Track时触发
        /// </summary>
        public void OnAddReceiver(SignalingEventData data)
        {
            var track = data.transceiver.Receiver.Track;
            IStreamReceiver receiver = GetReceiver(track.Kind);
            SetReceiver(data.connectionId, receiver, data.transceiver);
        }

        /// <summary>
        /// 收到远程DataChannel时触发
        /// </summary>
        public void OnAddChannel(SignalingEventData data)
        {
            var channel = streams.OfType<IDataChannel>().
                FirstOrDefault(r => !r.IsConnected && !r.IsLocal);
            channel?.SetChannel(data.connectionId, data.channel);
        }

        /// <summary>
        /// 新Participant加入房间通知
        /// 在私有模式下，服务器会通知Host有新的Participant加入
        /// 此时不做额外处理，等收到Participant的offer时再建立连接
        /// </summary>
        public void OnParticipantJoined(SignalingEventData eventData)
        {
            Debug.Log($"[HostConnection] Participant joined: connectionId={eventData.connectionId}, participantId={eventData.participantId}");
        }

        /// <summary>
        /// Participant离开房间通知
        /// 清理该Participant的连接资源
        /// </summary>
        public void OnParticipantLeft(SignalingEventData eventData)
        {
            string participantId = eventData.participantId;
            if (!string.IsNullOrEmpty(participantId))
            {
                Debug.Log($"[HostConnection] Participant left: connectionId={eventData.connectionId}, participantId={participantId}");
                DisconnectParticipant(participantId);
                participantIds.Remove(participantId);
            }
        }

        /// <summary>
        /// 收到呼叫请求
        /// </summary>
        public void OnCallRequest(SignalingEventData eventData)
        {
            Debug.Log($"[HostConnection] Call request from: {eventData.connectionId}, data: {eventData.message}");
        }

        /// <summary>
        /// 收到自定义消息
        /// </summary>
        public void OnMessage(SignalingEventData eventData)
        {
            Debug.Log($"[HostConnection] Message from: {eventData.connectionId}, participantId: {eventData.participantId}, message: {eventData.message}");
        }

        /// <summary>
        /// 获取当前连接的Participant数量
        /// </summary>
        public int ParticipantCount => participantIds.Count;

        /// <summary>
        /// 获取所有Participant的ID列表
        /// </summary>
        public IReadOnlyList<string> ParticipantIds => participantIds.AsReadOnly();

        IStreamReceiver GetReceiver(WebRTC.TrackKind kind)
        {
            if (kind == WebRTC.TrackKind.Audio)
                return streams.OfType<AudioStreamReceiver>().FirstOrDefault();
            if (kind == WebRTC.TrackKind.Video)
                return streams.OfType<VideoStreamReceiver>().FirstOrDefault();
            throw new System.ArgumentException();
        }
    }
}