using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using System.Net.Sockets;
using System.Threading;
using System.Threading.Tasks;
using Newtonsoft.Json;
using Newtonsoft.Json.Linq;
using UnityEditor;
using UnityEngine;
using UnityMcpBridge.Editor.Helpers;
using UnityMcpBridge.Editor.Models;
using UnityMcpBridge.Editor.Tools;

namespace UnityMcpBridge.Editor
{
    [InitializeOnLoad]
    public static partial class UnityMcpBridge
    {
        private static TcpListener listener;
        private static bool isRunning = false;
        private static readonly object lockObj = new();
        private static readonly object startStopLock = new();
        private static bool initScheduled = false;
        private static bool ensureUpdateHooked = false;
        private static bool isStarting = false;
        private static double nextStartAt = 0.0f;
        private static double nextHeartbeatAt = 0.0f;
        private static int heartbeatSeq = 0;
        private static Dictionary<
            string,
            (string commandJson, TaskCompletionSource<string> tcs)
        > commandQueue = new();
        private static int currentUnityPort = 6400; // Dynamic port, starts with default
        private static bool isAutoConnectMode = false;
        
        // Debug helpers
        private static bool IsDebugEnabled()
        {
            try { return EditorPrefs.GetBool("UnityMCP.DebugLogs", false); } catch { return false; }
        }
        
        private static void LogBreadcrumb(string stage)
        {
            if (IsDebugEnabled())
            {
                Debug.Log($"<b><color=#2EA3FF>UNITY-MCP</color></b>: [{stage}]");
            }
        }

        public static bool IsRunning => isRunning;
        public static int GetCurrentPort() => currentUnityPort;
        public static bool IsAutoConnectMode() => isAutoConnectMode;

        /// <summary>
        /// Start with Auto-Connect mode - discovers new port and saves it
        /// </summary>
        public static void StartAutoConnect()
        {
            Stop(); // Stop current connection
            
            try
            {
                // Prefer stored project port and start using the robust Start() path (with retries/options)
                currentUnityPort = PortManager.GetPortWithFallback();
                Start();
                isAutoConnectMode = true;
            }
            catch (Exception ex)
            {
                Debug.LogError($"Auto-connect failed: {ex.Message}");
                throw;
            }
        }

        public static bool FolderExists(string path)
        {
            if (string.IsNullOrEmpty(path))
            {
                return false;
            }

            if (path.Equals("Assets", StringComparison.OrdinalIgnoreCase))
            {
                return true;
            }

            string fullPath = Path.Combine(
                Application.dataPath,
                path.StartsWith("Assets/") ? path[7..] : path
            );
            return Directory.Exists(fullPath);
        }

        static UnityMcpBridge()
        {
            // Skip bridge in headless/batch environments (CI/builds)
            if (Application.isBatchMode)
            {
                return;
            }
            // Defer start until the editor is idle and not compiling
            ScheduleInitRetry();
            // Add a safety net update hook in case delayCall is missed during reload churn
            if (!ensureUpdateHooked)
            {
                ensureUpdateHooked = true;
                EditorApplication.update += EnsureStartedOnEditorIdle;
            }
            EditorApplication.quitting += Stop;
            AssemblyReloadEvents.beforeAssemblyReload += OnBeforeAssemblyReload;
            AssemblyReloadEvents.afterAssemblyReload += OnAfterAssemblyReload;
            // Also coalesce play mode transitions into a deferred init
            EditorApplication.playModeStateChanged += _ => ScheduleInitRetry();
        }

        /// <summary>
        /// Initialize the MCP bridge after Unity is fully loaded and compilation is complete.
        /// This prevents repeated restarts during script compilation that cause port hopping.
        /// </summary>
        private static void InitializeAfterCompilation()
        {
            initScheduled = false;

            // Play-mode friendly: allow starting in play mode; only defer while compiling
            if (IsCompiling())
            {
                ScheduleInitRetry();
                return;
            }

            if (!isRunning)
            {
                Start();
                if (!isRunning)
                {
                    // If a race prevented start, retry later
                    ScheduleInitRetry();
                }
            }
        }

        private static void ScheduleInitRetry()
        {
            if (initScheduled)
            {
                return;
            }
            initScheduled = true;
            // Debounce: start ~200ms after the last trigger
            nextStartAt = EditorApplication.timeSinceStartup + 0.20f;
            // Ensure the update pump is active
            if (!ensureUpdateHooked)
            {
                ensureUpdateHooked = true;
                EditorApplication.update += EnsureStartedOnEditorIdle;
            }
            // Keep the original delayCall as a secondary path
            EditorApplication.delayCall += InitializeAfterCompilation;
        }

        // Safety net: ensure the bridge starts shortly after domain reload when editor is idle
        private static void EnsureStartedOnEditorIdle()
        {
            // Do nothing while compiling
            if (IsCompiling())
            {
                return;
            }

            // If already running, remove the hook
            if (isRunning)
            {
                EditorApplication.update -= EnsureStartedOnEditorIdle;
                ensureUpdateHooked = false;
                return;
            }

            // Debounced start: wait until the scheduled time
            if (nextStartAt > 0 && EditorApplication.timeSinceStartup < nextStartAt)
            {
                return;
            }

            if (isStarting)
            {
                return;
            }

            isStarting = true;
            // Attempt start; if it succeeds, remove the hook to avoid overhead
            Start();
            isStarting = false;
            if (isRunning)
            {
                EditorApplication.update -= EnsureStartedOnEditorIdle;
                ensureUpdateHooked = false;
            }
        }

        // Helper to check compilation status across Unity versions
        private static bool IsCompiling()
        {
            if (EditorApplication.isCompiling)
            {
                return true;
            }
            try
            {
                System.Type pipeline = System.Type.GetType("UnityEditor.Compilation.CompilationPipeline, UnityEditor");
                var prop = pipeline?.GetProperty("isCompiling", System.Reflection.BindingFlags.Public | System.Reflection.BindingFlags.Static);
                if (prop != null)
                {
                    return (bool)prop.GetValue(null);
                }
            }
            catch { }
            return false;
        }

        public static void Start()
        {
            lock (startStopLock)
            {
                // Don't restart if already running on a working port
                if (isRunning && listener != null)
                {
                    Debug.Log($"<b><color=#2EA3FF>UNITY-MCP</color></b>: UnityMcpBridge already running on port {currentUnityPort}");
                    return;
                }

                Stop();

                // Attempt fast bind with stored-port preference (sticky per-project)
                try
                {
                    // Always consult PortManager first so we prefer the persisted project port
                    currentUnityPort = PortManager.GetPortWithFallback();

                    // Breadcrumb: Start
                    LogBreadcrumb("Start");

                    const int maxImmediateRetries = 3;
                    const int retrySleepMs = 75;
                    int attempt = 0;
                    for (;;)
                    {
                        try
                        {
                            listener = new TcpListener(IPAddress.Loopback, currentUnityPort);
                            listener.Server.SetSocketOption(
                                SocketOptionLevel.Socket,
                                SocketOptionName.ReuseAddress,
                                true
                            );
#if UNITY_EDITOR_WIN
                            try
                            {
                                listener.ExclusiveAddressUse = false;
                            }
                            catch { }
#endif
                            // Minimize TIME_WAIT by sending RST on close
                            try
                            {
                                listener.Server.LingerState = new LingerOption(true, 0);
                            }
                            catch (Exception)
                            {
                                // Ignore if not supported on platform
                            }
                            listener.Start();
                            break;
                        }
                        catch (SocketException se) when (se.SocketErrorCode == SocketError.AddressAlreadyInUse && attempt < maxImmediateRetries)
                        {
                            attempt++;
                            Thread.Sleep(retrySleepMs);
                            continue;
                        }
                        catch (SocketException se) when (se.SocketErrorCode == SocketError.AddressAlreadyInUse && attempt >= maxImmediateRetries)
                        {
                            currentUnityPort = PortManager.GetPortWithFallback();
                            listener = new TcpListener(IPAddress.Loopback, currentUnityPort);
                            listener.Server.SetSocketOption(
                                SocketOptionLevel.Socket,
                                SocketOptionName.ReuseAddress,
                                true
                            );
#if UNITY_EDITOR_WIN
                            try
                            {
                                listener.ExclusiveAddressUse = false;
                            }
                            catch { }
#endif
                            try
                            {
                                listener.Server.LingerState = new LingerOption(true, 0);
                            }
                            catch (Exception)
                            {
                            }
                            listener.Start();
                            break;
                        }
                    }

                    isRunning = true;
                    isAutoConnectMode = false;
                    Debug.Log($"<b><color=#2EA3FF>UNITY-MCP</color></b>: UnityMcpBridge started on port {currentUnityPort}.");
                    Task.Run(ListenerLoop);
                    EditorApplication.update += ProcessCommands;
                    // Write initial heartbeat immediately
                    heartbeatSeq++;
                    WriteHeartbeat(false, "ready");
                    nextHeartbeatAt = EditorApplication.timeSinceStartup + 0.5f;
                }
                catch (SocketException ex)
                {
                    Debug.LogError($"Failed to start TCP listener: {ex.Message}");
                }
            }
        }

        public static void Stop()
        {
            lock (startStopLock)
            {
                if (!isRunning)
                {
                    return;
                }

                try
                {
                    // Mark as stopping early to avoid accept logging during disposal
                    isRunning = false;
                    // Mark heartbeat one last time before stopping
                    WriteHeartbeat(false);
                    listener?.Stop();
                    listener = null;
                    EditorApplication.update -= ProcessCommands;
                    Debug.Log("<b><color=#2EA3FF>UNITY-MCP</color></b>: UnityMcpBridge stopped.");
                }
                catch (Exception ex)
                {
                    Debug.LogError($"Error stopping UnityMcpBridge: {ex.Message}");
                }
            }
        }

        private static async Task ListenerLoop()
        {
            while (isRunning)
            {
                try
                {
                    TcpClient client = await listener.AcceptTcpClientAsync();
                    // Enable basic socket keepalive
                    client.Client.SetSocketOption(
                        SocketOptionLevel.Socket,
                        SocketOptionName.KeepAlive,
                        true
                    );

                    // Set longer receive timeout to prevent quick disconnections
                    client.ReceiveTimeout = 60000; // 60 seconds

                    // Fire and forget each client connection
                    _ = HandleClientAsync(client);
                }
                catch (ObjectDisposedException)
                {
                    // Listener was disposed during stop/reload; exit quietly
                    if (!isRunning)
                    {
                        break;
                    }
                }
                catch (Exception ex)
                {
                    if (isRunning)
                    {
                        Debug.LogError($"Listener error: {ex.Message}");
                    }
                }
            }
        }

        private static async Task HandleClientAsync(TcpClient client)
        {
            using (client)
            using (NetworkStream stream = client.GetStream())
            {
                const int MaxMessageBytes = 64 * 1024 * 1024; // 64 MB safety cap
                byte[] buffer = new byte[8192];
                while (isRunning)
                {
                    try
                    {
                        // Read message with optional length prefix (8-byte big-endian)
                        bool usedFraming = false;
                        string commandText = null;

                        // First, attempt to read an 8-byte header
                        byte[] header = new byte[8];
                        int headerFilled = 0;
                        while (headerFilled < 8)
                        {
                            int r = await stream.ReadAsync(header, headerFilled, 8 - headerFilled);
                            if (r == 0)
                            {
                                // Disconnected
                                return;
                            }
                            headerFilled += r;
                        }

                        // Interpret header as big-endian payload length, with plausibility check
                        ulong payloadLen = ReadUInt64BigEndian(header);
                        if (payloadLen > 0 && payloadLen <= (ulong)MaxMessageBytes)
                        {
                            // Framed message path
                            usedFraming = true;
                            byte[] payload = await ReadExactAsync(stream, (int)payloadLen);
                            commandText = System.Text.Encoding.UTF8.GetString(payload);
                        }
                        else
                        {
                            // Legacy path: treat header bytes as the beginning of a JSON/plain message and read until we have a full JSON
                            usedFraming = false;
                            using var ms = new MemoryStream();
                            ms.Write(header, 0, header.Length);

                            // Read available data in chunks; stop when we have valid JSON or ping, or when no more data available for now
                            while (true)
                            {
                                // If we already have enough text, try to interpret
                                string currentText = System.Text.Encoding.UTF8.GetString(ms.ToArray());
                                string trimmed = currentText.Trim();
                                if (trimmed == "ping")
                                {
                                    commandText = trimmed;
                                    break;
                                }
                                if (IsValidJson(trimmed))
                                {
                                    commandText = trimmed;
                                    break;
                                }

                                // Read next chunk
                                int r = await stream.ReadAsync(buffer, 0, buffer.Length);
                                if (r == 0)
                                {
                                    // Disconnected mid-message; fall back to whatever we have
                                    commandText = currentText;
                                    break;
                                }
                                ms.Write(buffer, 0, r);

                                if (ms.Length > MaxMessageBytes)
                                {
                                    throw new IOException($"Incoming message exceeded {MaxMessageBytes} bytes cap");
                                }
                            }
                        }

                        string commandId = Guid.NewGuid().ToString();
                        TaskCompletionSource<string> tcs = new();

                        // Special handling for ping command to avoid JSON parsing
                        if (commandText.Trim() == "ping")
                        {
                            // Direct response to ping without going through JSON parsing
                            byte[] pingResponseBytes = System.Text.Encoding.UTF8.GetBytes(
                                /*lang=json,strict*/
                                "{\"status\":\"success\",\"result\":{\"message\":\"pong\"}}"
                            );

                            if (usedFraming)
                            {
                                // Mirror framing for response
                                byte[] outHeader = new byte[8];
                                WriteUInt64BigEndian(outHeader, (ulong)pingResponseBytes.Length);
                                await stream.WriteAsync(outHeader, 0, outHeader.Length);
                            }
                            await stream.WriteAsync(pingResponseBytes, 0, pingResponseBytes.Length);
                            continue;
                        }

                        lock (lockObj)
                        {
                            commandQueue[commandId] = (commandText, tcs);
                        }

                        string response = await tcs.Task;
                        byte[] responseBytes = System.Text.Encoding.UTF8.GetBytes(response);
                        if (usedFraming)
                        {
                            byte[] outHeader = new byte[8];
                            WriteUInt64BigEndian(outHeader, (ulong)responseBytes.Length);
                            await stream.WriteAsync(outHeader, 0, outHeader.Length);
                        }
                        await stream.WriteAsync(responseBytes, 0, responseBytes.Length);
                    }
                    catch (Exception ex)
                    {
                        Debug.LogError($"Client handler error: {ex.Message}");
                        break;
                    }
                }
            }
        }

        // Read exactly count bytes or throw if stream closes prematurely
        private static async Task<byte[]> ReadExactAsync(NetworkStream stream, int count)
        {
            byte[] data = new byte[count];
            int offset = 0;
            while (offset < count)
            {
                int r = await stream.ReadAsync(data, offset, count - offset);
                if (r == 0)
                {
                    throw new IOException("Connection closed before reading expected bytes");
                }
                offset += r;
            }
            return data;
        }

        private static ulong ReadUInt64BigEndian(byte[] buffer)
        {
            if (buffer == null || buffer.Length < 8)
            {
                return 0UL;
            }
            return ((ulong)buffer[0] << 56)
                 | ((ulong)buffer[1] << 48)
                 | ((ulong)buffer[2] << 40)
                 | ((ulong)buffer[3] << 32)
                 | ((ulong)buffer[4] << 24)
                 | ((ulong)buffer[5] << 16)
                 | ((ulong)buffer[6] << 8)
                 | buffer[7];
        }

        private static void WriteUInt64BigEndian(byte[] dest, ulong value)
        {
            if (dest == null || dest.Length < 8)
            {
                throw new ArgumentException("Destination buffer too small for UInt64");
            }
            dest[0] = (byte)(value >> 56);
            dest[1] = (byte)(value >> 48);
            dest[2] = (byte)(value >> 40);
            dest[3] = (byte)(value >> 32);
            dest[4] = (byte)(value >> 24);
            dest[5] = (byte)(value >> 16);
            dest[6] = (byte)(value >> 8);
            dest[7] = (byte)(value);
        }

        private static void ProcessCommands()
        {
            List<string> processedIds = new();
            lock (lockObj)
            {
                // Periodic heartbeat while editor is idle/processing
                double now = EditorApplication.timeSinceStartup;
                if (now >= nextHeartbeatAt)
                {
                    WriteHeartbeat(false);
                    nextHeartbeatAt = now + 0.5f;
                }

                foreach (
                    KeyValuePair<
                        string,
                        (string commandJson, TaskCompletionSource<string> tcs)
                    > kvp in commandQueue.ToList()
                )
                {
                    string id = kvp.Key;
                    string commandText = kvp.Value.commandJson;
                    TaskCompletionSource<string> tcs = kvp.Value.tcs;

                    try
                    {
                        // Special case handling
                        if (string.IsNullOrEmpty(commandText))
                        {
                            var emptyResponse = new
                            {
                                status = "error",
                                error = "Empty command received",
                            };
                            tcs.SetResult(JsonConvert.SerializeObject(emptyResponse));
                            processedIds.Add(id);
                            continue;
                        }

                        // Trim the command text to remove any whitespace
                        commandText = commandText.Trim();

                        // Non-JSON direct commands handling (like ping)
                        if (commandText == "ping")
                        {
                            var pingResponse = new
                            {
                                status = "success",
                                result = new { message = "pong" },
                            };
                            tcs.SetResult(JsonConvert.SerializeObject(pingResponse));
                            processedIds.Add(id);
                            continue;
                        }

                        // Check if the command is valid JSON before attempting to deserialize
                        if (!IsValidJson(commandText))
                        {
                            var invalidJsonResponse = new
                            {
                                status = "error",
                                error = "Invalid JSON format",
                                receivedText = commandText.Length > 50
                                    ? commandText[..50] + "..."
                                    : commandText,
                            };
                            tcs.SetResult(JsonConvert.SerializeObject(invalidJsonResponse));
                            processedIds.Add(id);
                            continue;
                        }

                        // Normal JSON command processing
                        Command command = JsonConvert.DeserializeObject<Command>(commandText);
                        
                        if (command == null)
                        {
                            var nullCommandResponse = new
                            {
                                status = "error",
                                error = "Command deserialized to null",
                                details = "The command was valid JSON but could not be deserialized to a Command object",
                            };
                            tcs.SetResult(JsonConvert.SerializeObject(nullCommandResponse));
                        }
                        else
                        {
                            string responseJson = ExecuteCommand(command);
                            tcs.SetResult(responseJson);
                        }
                    }
                    catch (Exception ex)
                    {
                        Debug.LogError($"Error processing command: {ex.Message}\n{ex.StackTrace}");

                        var response = new
                        {
                            status = "error",
                            error = ex.Message,
                            commandType = "Unknown (error during processing)",
                            receivedText = commandText?.Length > 50
                                ? commandText[..50] + "..."
                                : commandText,
                        };
                        string responseJson = JsonConvert.SerializeObject(response);
                        tcs.SetResult(responseJson);
                    }

                    processedIds.Add(id);
                }

                foreach (string id in processedIds)
                {
                    commandQueue.Remove(id);
                }
            }
        }

        // Helper method to check if a string is valid JSON
        private static bool IsValidJson(string text)
        {
            if (string.IsNullOrWhiteSpace(text))
            {
                return false;
            }

            text = text.Trim();
            if (
                (text.StartsWith("{") && text.EndsWith("}"))
                || // Object
                (text.StartsWith("[") && text.EndsWith("]"))
            ) // Array
            {
                try
                {
                    JToken.Parse(text);
                    return true;
                }
                catch
                {
                    return false;
                }
            }

            return false;
        }

        private static string ExecuteCommand(Command command)
        {
            try
            {
                if (string.IsNullOrEmpty(command.type))
                {
                    var errorResponse = new
                    {
                        status = "error",
                        error = "Command type cannot be empty",
                        details = "A valid command type is required for processing",
                    };
                    return JsonConvert.SerializeObject(errorResponse);
                }

                // Handle ping command for connection verification
                if (command.type.Equals("ping", StringComparison.OrdinalIgnoreCase))
                {
                    var pingResponse = new
                    {
                        status = "success",
                        result = new { message = "pong" },
                    };
                    return JsonConvert.SerializeObject(pingResponse);
                }

                // Use JObject for parameters as the new handlers likely expect this
                JObject paramsObject = command.@params ?? new JObject();

                // Route command based on the new tool structure from the refactor plan
                object result = command.type switch
                {
                    // Maps the command type (tool name) to the corresponding handler's static HandleCommand method
                    // Assumes each handler class has a static method named 'HandleCommand' that takes JObject parameters
                    "manage_script" => ManageScript.HandleCommand(paramsObject),
                    "manage_scene" => ManageScene.HandleCommand(paramsObject),
                    "manage_editor" => ManageEditor.HandleCommand(paramsObject),
                    "manage_gameobject" => ManageGameObject.HandleCommand(paramsObject),
                    "manage_asset" => ManageAsset.HandleCommand(paramsObject),
                    "manage_shader" => ManageShader.HandleCommand(paramsObject),
                    "read_console" => ReadConsole.HandleCommand(paramsObject),
                    "execute_menu_item" => ExecuteMenuItem.HandleCommand(paramsObject),
                    _ => throw new ArgumentException(
                        $"Unknown or unsupported command type: {command.type}"
                    ),
                };

                // Standard success response format
                var response = new { status = "success", result };
                return JsonConvert.SerializeObject(response);
            }
            catch (Exception ex)
            {
                // Log the detailed error in Unity for debugging
                Debug.LogError(
                    $"Error executing command '{command?.type ?? "Unknown"}': {ex.Message}\n{ex.StackTrace}"
                );

                // Standard error response format
                var response = new
                {
                    status = "error",
                    error = ex.Message, // Provide the specific error message
                    command = command?.type ?? "Unknown", // Include the command type if available
                    stackTrace = ex.StackTrace, // Include stack trace for detailed debugging
                    paramsSummary = command?.@params != null
                        ? GetParamsSummary(command.@params)
                        : "No parameters", // Summarize parameters for context
                };
                return JsonConvert.SerializeObject(response);
            }
        }

        // Helper method to get a summary of parameters for error reporting
        private static string GetParamsSummary(JObject @params)
        {
            try
            {
                return @params == null || !@params.HasValues
                    ? "No parameters"
                    : string.Join(
                        ", ",
                        @params
                            .Properties()
                            .Select(static p =>
                                $"{p.Name}: {p.Value?.ToString()?[..Math.Min(20, p.Value?.ToString()?.Length ?? 0)]}"
                            )
                    );
            }
            catch
            {
                return "Could not summarize parameters";
            }
        }

        // Heartbeat/status helpers
        private static void OnBeforeAssemblyReload()
        {
            // Stop cleanly before reload so sockets close and clients see 'reloading'
            try { Stop(); } catch { }
            WriteHeartbeat(true, "reloading");
            LogBreadcrumb("Reload");
        }

        private static void OnAfterAssemblyReload()
        {
            // Will be overwritten by Start(), but mark as alive quickly
            WriteHeartbeat(false, "idle");
            LogBreadcrumb("Idle");
            // Schedule a safe restart after reload to avoid races during compilation
            ScheduleInitRetry();
        }

        private static void WriteHeartbeat(bool reloading, string reason = null)
        {
            try
            {
                string dir = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.UserProfile), ".unity-mcp");
                Directory.CreateDirectory(dir);
                string filePath = Path.Combine(dir, $"unity-mcp-status-{ComputeProjectHash(Application.dataPath)}.json");
                var payload = new
                {
                    unity_port = currentUnityPort,
                    reloading,
                    reason = reason ?? (reloading ? "reloading" : "ready"),
                    seq = heartbeatSeq,
                    project_path = Application.dataPath,
                    last_heartbeat = DateTime.UtcNow.ToString("O")
                };
                File.WriteAllText(filePath, JsonConvert.SerializeObject(payload));
            }
            catch (Exception)
            {
                // Best-effort only
            }
        }

        private static string ComputeProjectHash(string input)
        {
            try
            {
                using var sha1 = System.Security.Cryptography.SHA1.Create();
                byte[] bytes = System.Text.Encoding.UTF8.GetBytes(input ?? string.Empty);
                byte[] hashBytes = sha1.ComputeHash(bytes);
                var sb = new System.Text.StringBuilder();
                foreach (byte b in hashBytes)
                {
                    sb.Append(b.ToString("x2"));
                }
                return sb.ToString()[..8];
            }
            catch
            {
                return "default";
            }
        }
    }
}