using System;
using System.Collections.Generic;
using Steamworks;
using UnityEngine;

namespace MegaKoop.Game.Networking
{
    /// <summary>
    /// High level orchestrator for Steam lobby + P2P messaging. Keeps track of handlers per message type.
    /// </summary>
    [DisallowMultipleComponent]
    public class SteamCoopNetworkManager : MonoBehaviour
    {
        public static SteamCoopNetworkManager Instance { get; private set; }

        [SerializeField] private SteamLobbyManager lobbyManager;
        [SerializeField] private SteamP2PTransport p2pTransport;

        private readonly Dictionary<NetworkMessageType, Action<NetworkMessage>> handlers = new();
        private readonly HashSet<ulong> lobbyMembers = new();
        private readonly Dictionary<ulong, string> memberNames = new();
        private readonly List<OnScreenMessage> onScreenMessages = new();
        private bool isHost;
        private bool isConnected;
        private ulong lobbyOwnerSteamId;

        public bool IsHost => isHost;
        public bool IsConnected => isConnected;
        public CSteamID ActiveLobby => lobbyManager != null ? lobbyManager.GetActiveLobby() : CSteamID.Nil;

        public event Action HostClosed;
        public event Action<ulong> PlayerDisconnected;

        private void Awake()
        {
            if (Instance != null)
            {
                Destroy(gameObject);
                return;
            }

            Instance = this;
            DontDestroyOnLoad(gameObject);

            if (lobbyManager == null)
            {
                lobbyManager = GetComponentInChildren<SteamLobbyManager>();
            }

            if (p2pTransport == null)
            {
                p2pTransport = GetComponentInChildren<SteamP2PTransport>();
            }

            if (lobbyManager != null)
            {
                lobbyManager.LobbyCreated += HandleLobbyCreated;
                lobbyManager.LobbyJoined += HandleLobbyJoined;
                lobbyManager.LobbyMemberJoined += HandleLobbyMemberJoined;
                lobbyManager.LobbyMemberLeft += HandleLobbyMemberLeft;
            }

            if (p2pTransport != null)
            {
                p2pTransport.MessageReceived += DispatchMessage;
            }
        }

        private void OnDestroy()
        {
            if (Instance == this)
            {
                Instance = null;
            }

            if (lobbyManager != null)
            {
                lobbyManager.LobbyCreated -= HandleLobbyCreated;
                lobbyManager.LobbyJoined -= HandleLobbyJoined;
                lobbyManager.LobbyMemberJoined -= HandleLobbyMemberJoined;
                lobbyManager.LobbyMemberLeft -= HandleLobbyMemberLeft;
            }

            if (p2pTransport != null)
            {
                p2pTransport.MessageReceived -= DispatchMessage;
            }
        }

        public void RegisterHandler(NetworkMessageType type, Action<NetworkMessage> handler)
        {
            if (handlers.TryGetValue(type, out Action<NetworkMessage> existing))
            {
                existing += handler;
                handlers[type] = existing;
            }
            else
            {
                handlers[type] = handler;
            }
        }

        public void UnregisterHandler(NetworkMessageType type, Action<NetworkMessage> handler)
        {
            if (!handlers.TryGetValue(type, out Action<NetworkMessage> existing))
            {
                return;
            }

            existing -= handler;
            if (existing == null)
            {
                handlers.Remove(type);
            }
            else
            {
                handlers[type] = existing;
            }
        }

        public void SendToAll(NetworkMessageType type, byte[] payload, EP2PSend sendType = EP2PSend.k_EP2PSendReliable)
        {
            p2pTransport?.Broadcast(type, payload, sendType);
        }

        public void SendToPlayer(CSteamID target, NetworkMessageType type, byte[] payload, EP2PSend sendType = EP2PSend.k_EP2PSendReliable)
        {
            p2pTransport?.Send(target, type, payload, sendType);
        }

        public void SynchronizeWithLobby(MegaKoop.Steam.SteamLobbyService steamService)
        {
            if (steamService == null)
            {
                return;
            }

            isConnected = steamService.IsInLobby;
            isHost = steamService.IsHost;

            if (steamService.IsInLobby)
            {
                lobbyMembers.Clear();
                memberNames.Clear();
                lobbyOwnerSteamId = 0;

                var members = steamService.GetMembers();
                if (members != null)
                {
                    foreach (var member in members)
                    {
                        if (!ulong.TryParse(member.steamId, out ulong steamId))
                        {
                            continue;
                        }

                        lobbyMembers.Add(steamId);
                        memberNames[steamId] = string.IsNullOrWhiteSpace(member.name) ? steamId.ToString() : member.name;

                        if (member.isHost)
                        {
                            lobbyOwnerSteamId = steamId;
                        }
                    }
                }

                if (lobbyOwnerSteamId == 0 && steamService.IsHost && SteamBootstrap.IsInitialized)
                {
                    lobbyOwnerSteamId = SteamUser.GetSteamID().m_SteamID;
                }
            }
            else
            {
                lobbyMembers.Clear();
                memberNames.Clear();
                lobbyOwnerSteamId = 0;
            }

#if STEAMWORKSNET
            if (p2pTransport != null)
            {
                if (steamService.IsInLobby)
                {
                    CSteamID lobbyId = steamService.LobbyId;
                    if (lobbyId != CSteamID.Nil)
                    {
                        p2pTransport.SetActiveLobby(lobbyId);
                    }
                    else if (ulong.TryParse(steamService.LobbyIdString, out ulong lobbyValue) && lobbyValue != 0)
                    {
                        p2pTransport.SetActiveLobby(new CSteamID(lobbyValue));
                    }
                }
                else
                {
                    p2pTransport.SetActiveLobby(CSteamID.Nil);
                }
            }
#endif
        }

        private void DispatchMessage(NetworkMessage message)
        {
            if (handlers.TryGetValue(message.Type, out Action<NetworkMessage> handler))
            {
                handler?.Invoke(message);
            }
        }

        private void HandleLobbyCreated(CSteamID lobbyId)
        {
            isHost = true;
            isConnected = true;
            p2pTransport?.SetActiveLobby(lobbyId);
            lobbyOwnerSteamId = SteamUser.GetSteamID().m_SteamID;
            lobbyMembers.Clear();
            memberNames.Clear();
            RegisterMember(lobbyOwnerSteamId);
        }

        private void HandleLobbyJoined(CSteamID lobbyId)
        {
            isConnected = true;
            p2pTransport?.SetActiveLobby(lobbyId);

            string ownerId = SteamMatchmaking.GetLobbyData(lobbyId, "owner");
            if (!string.IsNullOrEmpty(ownerId) && ulong.TryParse(ownerId, out ulong ownerSteamId))
            {
                lobbyOwnerSteamId = ownerSteamId;
                isHost = ownerSteamId == SteamUser.GetSteamID().m_SteamID;
            }
            else
            {
                CSteamID owner = SteamMatchmaking.GetLobbyOwner(lobbyId);
                lobbyOwnerSteamId = owner.m_SteamID;
                isHost = owner == SteamUser.GetSteamID();
            }

            RegisterExistingMembers(lobbyId);
        }

        private void HandleLobbyMemberJoined(CSteamID member)
        {
            RegisterMember(member.m_SteamID);

            if (ActiveLobby != CSteamID.Nil)
            {
                CSteamID owner = SteamMatchmaking.GetLobbyOwner(ActiveLobby);
                if (owner != CSteamID.Nil)
                {
                    lobbyOwnerSteamId = owner.m_SteamID;
                }
            }

            Debug.Log("[SteamCoopNetworkManager] Member joined: " + member);
        }

        private void HandleLobbyMemberLeft(CSteamID member)
        {
            ulong steamId = member.m_SteamID;
            string displayName = ResolveMemberName(steamId);

            bool hostLeft = lobbyOwnerSteamId != 0 && steamId == lobbyOwnerSteamId;
            lobbyMembers.Remove(steamId);
            memberNames.Remove(steamId);

            if (hostLeft)
            {
                Debug.Log("[SteamCoopNetworkManager] Host left lobby: " + member);
                ShowOnScreenMessage("Host closed the game.", 6f);
                HostClosed?.Invoke();

                if (!isHost)
                {
                    ForceDisconnectFromLobby();
                }
            }
            else
            {
                Debug.Log("[SteamCoopNetworkManager] Member left: " + member);
                string message = string.IsNullOrEmpty(displayName) ? "A player disconnected." : $"{displayName} disconnected.";
                ShowOnScreenMessage(message, 4f);
                PlayerDisconnected?.Invoke(steamId);
            }
        }

        private void Update()
        {
            if (onScreenMessages.Count == 0)
            {
                return;
            }

            float now = Time.unscaledTime;
            for (int i = onScreenMessages.Count - 1; i >= 0; i--)
            {
                if (onScreenMessages[i].ExpiresAt <= now)
                {
                    onScreenMessages.RemoveAt(i);
                }
            }
        }

        private void OnGUI()
        {
            if (onScreenMessages.Count == 0)
            {
                return;
            }

            float y = 20f;
            foreach (var entry in onScreenMessages)
            {
                if (entry.ExpiresAt <= Time.unscaledTime)
                {
                    continue;
                }

                GUIContent content = new(entry.Text);
                Vector2 size = GUI.skin.box.CalcSize(content);
                Rect rect = new(20f, y, Mathf.Max(220f, size.x + 20f), size.y + 10f);
                GUI.Box(rect, content);
                y += rect.height + 6f;
            }
        }

        private void RegisterExistingMembers(CSteamID lobbyId)
        {
            lobbyMembers.Clear();
            memberNames.Clear();

            int count = SteamMatchmaking.GetNumLobbyMembers(lobbyId);
            for (int i = 0; i < count; i++)
            {
                CSteamID member = SteamMatchmaking.GetLobbyMemberByIndex(lobbyId, i);
                RegisterMember(member.m_SteamID);
            }
        }

        private void RegisterMember(ulong steamId)
        {
            if (steamId == 0)
            {
                return;
            }

            lobbyMembers.Add(steamId);
            memberNames[steamId] = ResolveMemberNameInternal(steamId);
        }

        private string ResolveMemberName(ulong steamId)
        {
            if (memberNames.TryGetValue(steamId, out string cached) && !string.IsNullOrEmpty(cached))
            {
                return cached;
            }

            return ResolveMemberNameInternal(steamId);
        }

        private string ResolveMemberNameInternal(ulong steamId)
        {
#if STEAMWORKSNET
            if (steamId != 0 && SteamBootstrap.IsInitialized)
            {
                try
                {
                    return SteamFriends.GetFriendPersonaName(new CSteamID(steamId));
                }
                catch
                {
                    // Ignore Steam API hiccups and fall back to id string.
                }
            }
#endif
            return steamId != 0 ? steamId.ToString() : string.Empty;
        }

        private void ShowOnScreenMessage(string message, float lifetimeSeconds)
        {
            if (string.IsNullOrWhiteSpace(message))
            {
                return;
            }

            float expiry = Time.unscaledTime + Mathf.Max(0.5f, lifetimeSeconds);
            onScreenMessages.Add(new OnScreenMessage
            {
                Text = message,
                ExpiresAt = expiry
            });
        }

        private void ForceDisconnectFromLobby()
        {
            if (ActiveLobby != CSteamID.Nil && SteamBootstrap.IsInitialized)
            {
                SteamMatchmaking.LeaveLobby(ActiveLobby);
            }

            lobbyMembers.Clear();
            memberNames.Clear();
            lobbyOwnerSteamId = 0;
            isConnected = false;
            p2pTransport?.SetActiveLobby(CSteamID.Nil);
        }

        private struct OnScreenMessage
        {
            public string Text;
            public float ExpiresAt;
        }
    }
}