using Serilog;
using StackExchange.Redis;
using System;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace RunRedis.Services
{
    public class RedisProcessManager
    {
        private readonly RedisSetting _settings;
        private Process _redisProcess;
        private int _restartAttempts = 0;

        public RedisProcessManager(RedisSetting settings)
        {
            _settings = settings ?? throw new ArgumentNullException(nameof(settings));
        }

        public bool IsRedisRunning()
        {
            try
            {
                // First check if process is running
                if (!IsRedisProcessRunning())
                    return false;

                // Then check if Redis is responding on the configured port
                using (var tcpClient = new TcpClient())
                {
                    var connectTask = tcpClient.ConnectAsync(_settings.Host, int.Parse(_settings.Port));
                    var timeoutTask = Task.Delay(_settings.ConnectionTimeoutSeconds * 1000);
                    
                    var completedTask = Task.WaitAny(connectTask, timeoutTask);
                    
                    if (completedTask == 0 && tcpClient.Connected)
                    {
                        return true;
                    }
                }
                return false;
            }
            catch (Exception ex)
            {
                Log.Debug("Error checking Redis status: {Error}", ex.Message);
                return false;
            }
        }
      
        public bool IsRedisProcessRunning()
        {
            try
            {
                var processes = Process.GetProcessesByName("redis-server");
                return processes.Length > 0;
            }
            catch
            {
                return false;
            }
        }

        public async Task<bool> StartRedisAsync()
        {
            try
            {
                if (IsRedisRunning())
                {
                    Log.Information("Redis is already running");
                    return true;
                }

                // Prepare for startup
                await PrepareForStartupAsync();

                // Determine Redis executable path
                string redisExecutable = GetRedisExecutablePath();
                if (!File.Exists(redisExecutable))
                {
                    Log.Error("Redis executable not found at: {Path}", redisExecutable);
                    return false;
                }

                // Create process start info
                var startInfo = new ProcessStartInfo
                {
                    FileName = redisExecutable,
                    WorkingDirectory = Path.GetDirectoryName(redisExecutable),
                    CreateNoWindow = true,
                    UseShellExecute = false,
                    RedirectStandardOutput = true,
                    RedirectStandardError = true
                };

                // Add configuration file if exists
                string configPath = GetRedisConfigPath();
                if (File.Exists(configPath))
                {
                    startInfo.Arguments = $"\"{configPath}\"";
                    Log.Information("Starting Redis with config file: {ConfigPath}", configPath);
                }
                else
                {
                    // Use command line arguments
                    startInfo.Arguments = BuildRedisArguments();
                    Log.Information("Starting Redis with command line arguments");
                }

                _redisProcess = Process.Start(startInfo);
                
                if (_redisProcess != null)
                {
                    Log.Information("Redis process started with PID: {ProcessId}", _redisProcess.Id);
                    
                    // Wait a moment for the process to initialize
                    await Task.Delay(5000);
                    
                    // Verify the process is still running and Redis is responding
                    if (!_redisProcess.HasExited && IsRedisRunning())
                    {
                        _restartAttempts = 0; // Reset restart attempts on successful start
                        Log.Information("Redis started successfully");
                        return true;
                    }
                    else
                    {
                        Log.Error("Redis process exited immediately after start or is not responding");
                        return false;
                    }
                }
                else
                {
                    Log.Error("Failed to start Redis process");
                    return false;
                }
            }
            catch (Exception ex)
            {
                Log.Error("Error starting Redis: {Error}", ex.Message);
                return false;
            }
        }

        public async Task<bool> StopRedisAsync(bool graceful = true)
        {
            try
            {
                if (!IsRedisProcessRunning())
                {
                    Log.Information("Redis is not running");
                    return true;
                }

                if (graceful)
                {
                    // Try graceful shutdown using redis-cli
                    using var cts = new CancellationTokenSource(TimeSpan.FromSeconds(5));

                    await ExecuteRedisCliCommandAsync("SHUTDOWN SAVE", cts.Token);
                    await Task.Delay(5000); // Wait for graceful shutdown
                }

                // If still running, force kill
                var processes = Process.GetProcessesByName("redis-server");
                foreach (var process in processes)
                {
                    try
                    {
                        if (!process.HasExited)
                        {
                            process.Kill();
                            await process.WaitForExitAsync();
                            Log.Information("Redis process {ProcessId} terminated", process.Id);
                        }
                    }
                    finally
                    {
                        process.Dispose();
                    }
                }

                return true;
            }
            catch (Exception ex)
            {
                Log.Error("Error stopping Redis: {Error}", ex.Message);
                return false;
            }
        }

        public async Task<bool> RestartRedisAsync()
        {
            try
            {

                // 2. 优雅关闭Redis
                Log.Information("🛑 Gracefully stopping Redis...");
                await StopRedisAsync(graceful: true);

                // 3. 清理可能的锁文件和临时文件
                await CleanupStaleFilesAsync();

                // 4. 验证数据文件完整性
                await ValidateDataFilesAsync();

                // 5. 等待系统稳定
                Log.Information("⏳ Waiting {Delay} seconds before restart...", _settings.RestartDelaySeconds);
                await Task.Delay(_settings.RestartDelaySeconds * 1000);

                // 6. 启动Redis
                Log.Information("🚀 Starting Redis...");
                var startResult = await StartRedisAsync();

                if (startResult)
                {
                    // 7. 验证重启后的状态
                    await Task.Delay(3000); // 等待Redis完全启动
                    var isHealthy = await VerifyRedisHealthAfterRestartAsync();

                    if (isHealthy)
                    {
                        Log.Information("✅ Redis restart successful and healthy");
                        _restartAttempts = 0; // 重置重启计数
                        return true;
                    }
                    else
                    {
                        Log.Warning("⚠️ Redis started but health check failed");
                        return false;
                    }
                }
                else
                {
                    Log.Error("❌ Failed to start Redis after restart attempt");
                    return false;
                }
            }
            catch (Exception ex)
            {
                Log.Error("❌ Error during Redis restart: {Error}", ex.Message);
                return false;
            }
        }

        private async Task PrepareForStartupAsync()
        {
            try
            {
                // Ensure data directory exists
                if (!string.IsNullOrEmpty(_settings.DataDirectory))
                {
                    Directory.CreateDirectory(_settings.DataDirectory);
                }

                // Ensure log directory exists
                if (!string.IsNullOrEmpty(_settings.LogDirectory))
                {
                    Directory.CreateDirectory(_settings.LogDirectory);
                }

                // Clean up any stale lock files or temporary files
                await CleanupStaleFilesAsync();
            }
            catch (Exception ex)
            {
                Log.Warning("Error during startup preparation: {Error}", ex.Message);
            }
        }

        private Task CleanupStaleFilesAsync()
        {
            try
            {
                // Remove Redis dump.rdb lock files if they exist
                var lockFiles = new[] { "dump.rdb.lock", "redis.pid" };

                foreach (var lockFile in lockFiles)
                {
                    var lockPath = Path.Combine(_settings.DataDirectory, lockFile);
                    if (File.Exists(lockPath))
                    {
                        File.Delete(lockPath);
                        Log.Information("Removed stale lock file: {LockFile}", lockPath);
                    }
                }
            }
            catch (Exception ex)
            {
                Log.Warning("Error cleaning up stale files: {Error}", ex.Message);
            }

            return Task.CompletedTask;
        }

        private string GetRedisExecutablePath()
        {
            // Try configured path first
            if (!string.IsNullOrEmpty(_settings.RedisExecutablePath) && File.Exists(_settings.RedisExecutablePath))
            {
                return _settings.RedisExecutablePath;
            }

            // Try current directory
            var currentDirPath = Path.Combine(Directory.GetCurrentDirectory(), "redis-server.exe");
            if (File.Exists(currentDirPath))
            {
                return currentDirPath;
            }

            // Try PATH environment variable
            return "redis-server.exe"; // Let the system find it
        }

        private string GetRedisConfigPath()
        {
            // Try configured path first
            if (!string.IsNullOrEmpty(_settings.RedisConfigPath) && File.Exists(_settings.RedisConfigPath))
            {
                return _settings.RedisConfigPath;
            }

            // Try current directory
            var currentDirPath = Path.Combine(Directory.GetCurrentDirectory(), "redis.conf");
            if (File.Exists(currentDirPath))
            {
                return currentDirPath;
            }

            return null; // No config file found
        }

        private string BuildRedisArguments()
        {
            var args = new System.Collections.Generic.List<string>();

            // Basic configuration
            args.Add($"--port {_settings.Port}");
            args.Add($"--bind {_settings.Host}");

            if (!string.IsNullOrEmpty(_settings.Auth))
            {
                args.Add($"--requirepass {_settings.Auth}");
            }

            if (!string.IsNullOrEmpty(_settings.DataDirectory))
            {
                args.Add($"--dir \"{_settings.DataDirectory}\"");
            }

            // Memory settings
            if (_settings.MaxMemoryUsageMB > 0)
            {
                args.Add($"--maxmemory {_settings.MaxMemoryUsageMB}mb");
                args.Add($"--maxmemory-policy {_settings.MaxMemoryPolicy}");
            }

            // Persistence settings
            if (_settings.EnablePersistence)
            {
                args.Add($"--save {_settings.SaveConfiguration}");
            }
            else
            {
                args.Add("--save \"\"");
            }

            // Database settings
            args.Add($"--databases {_settings.DatabaseCount}");
            args.Add($"--timeout {_settings.ClientTimeoutSeconds}");

            // Slow log settings
            if (_settings.EnableSlowLog)
            {
                args.Add($"--slowlog-max-len {_settings.SlowLogMaxLength}");
                args.Add($"--slowlog-log-slower-than {_settings.SlowLogSlowerThanMicroseconds}");
            }

            return string.Join(" ", args);
        }

        public async Task<string> ExecuteRedisCliCommandAsync(string command, CancellationToken token =default)
        {
            Process process = null;
            try
            {
                if (token == default)
                {
                    using var cts = new CancellationTokenSource(TimeSpan.FromSeconds(5));
                    token = cts.Token;
                }
                string redisCliPath = GetRedisCliPath();

                var processStartInfo = new ProcessStartInfo
                {
                    FileName = redisCliPath,
                    Arguments = BuildRedisCliArguments(command),
                    CreateNoWindow = true,
                    UseShellExecute = false,
                    RedirectStandardOutput = true,
                    RedirectStandardError = true,
                    RedirectStandardInput = true
                };

                process = Process.Start(processStartInfo);
                var outputBuilder = new StringBuilder();
                var errorBuilder = new StringBuilder();

                // 异步读取输出和错误
                var outputTask = ReadStreamAsync(process.StandardOutput, outputBuilder);
                var errorTask = ReadStreamAsync(process.StandardError, errorBuilder);

                // 创建超时监控任务
                var processExitTask = process.WaitForExitAsync();
                var timeoutTask = Task.Delay(Timeout.Infinite, token);

                // 等待任意任务完成
                var completedTask = await Task.WhenAny(processExitTask, timeoutTask);

                if (completedTask == timeoutTask)
                {
                    // 超时处理
                    try
                    {
                        if (!process.HasExited)
                        {
                            process.Kill();
                            Log.Warning("Redis CLI command timed out and was killed: {Command}", command);
                        }
                    }
                    catch (InvalidOperationException) { /* 进程已退出 */ }

                    token.ThrowIfCancellationRequested();
                }

                // 确保获取退出代码
                await processExitTask;
                await Task.WhenAll(outputTask, errorTask);

                var output = outputBuilder.ToString().Trim();
                var error = errorBuilder.ToString().Trim();

                if (process.ExitCode == 0)
                {
                    Log.Debug("Redis CLI command executed successfully: {Command}", command);
                    return output;
                }

                Log.Warning("Redis CLI command failed (Exit {ExitCode}): {Command}, Error: {Error}",
                           process.ExitCode, command, error);
                return null;
            }
            catch (OperationCanceledException)
            {
                Log.Warning("Redis CLI command canceled: {Command}", command);
                throw;  // 重新抛出让调用方处理
            }
            catch (Exception ex)
            {
                Log.Error(ex, "Error executing Redis CLI command: {Command}", command);
                return null;
            }
            finally
            {
                process?.Dispose();
            }
        }

        // 辅助方法：构建Redis CLI参数
        private string BuildRedisCliArguments(string command)
        {
            var args = new StringBuilder($"-h {_settings.Host} -p {_settings.Port}");

            if (!string.IsNullOrEmpty(_settings.Auth))
            {
                args.Append($" -a {_settings.Auth}");
            }

            args.Append($" {command}");
            return args.ToString();
        }

        // 辅助方法：异步读取流
        private async Task ReadStreamAsync(StreamReader reader, StringBuilder builder)
        {
            char[] buffer = new char[4096];
            int bytesRead;

            while ((bytesRead = await reader.ReadAsync(buffer, 0, buffer.Length)) > 0)
            {
                builder.Append(buffer, 0, bytesRead);
            }
        }


        private string GetRedisCliPath()
        {
            // Try configured path first
            if (!string.IsNullOrEmpty(_settings.RedisCliPath) && File.Exists(_settings.RedisCliPath))
            {
                return _settings.RedisCliPath;
            }

            // Try current directory
            var currentDirPath = Path.Combine(Directory.GetCurrentDirectory(), "redis-cli.exe");
            if (File.Exists(currentDirPath))
            {
                return currentDirPath;
            }

            // Try PATH environment variable
            return "redis-cli.exe"; // Let the system find it
        }

        private async Task CreateEmergencyBackupAsync()
        {
            try
            {
                if (!_settings.EnableAutoBackup)
                    return;

                Log.Information("💾 Creating emergency backup before restart...");

                // 确保备份目录存在
                if (!Directory.Exists(_settings.BackupDirectory))
                {
                    Directory.CreateDirectory(_settings.BackupDirectory);
                }

                // 尝试触发BGSAVE（如果Redis还在运行）
                if (IsRedisRunning())
                {
                    using var cts = new CancellationTokenSource(TimeSpan.FromSeconds(5));

                    var saveResult = await ExecuteRedisCliCommandAsync("BGSAVE", cts.Token);
                    if (!string.IsNullOrEmpty(saveResult) && !saveResult.Contains("ERR"))
                    {
                        Log.Information("✅ Background save triggered successfully");
                        await Task.Delay(2000); // 等待保存完成
                    }
                }

                // 复制现有的数据文件
                var dataFiles = new[] { "dump.rdb", "appendonly.aof" };
                var timestamp = DateTime.Now.ToString("yyyyMMdd_HHmmss");

                foreach (var dataFile in dataFiles)
                {
                    var sourcePath = Path.Combine(_settings.DataDirectory, dataFile);
                    if (File.Exists(sourcePath))
                    {
                        var backupPath = Path.Combine(_settings.BackupDirectory, $"emergency_{dataFile}_{timestamp}");
                        File.Copy(sourcePath, backupPath, true);
                        Log.Information("📁 Backed up {DataFile} to {BackupPath}", dataFile, backupPath);
                    }
                }
            }
            catch (Exception ex)
            {
                Log.Warning("⚠️ Failed to create emergency backup: {Error}", ex.Message);
            }
        }

        private async Task ValidateDataFilesAsync()
        {
            try
            {
                Log.Information("🔍 Validating Redis data files...");

                var dumpFile = Path.Combine(_settings.DataDirectory, "dump.rdb");
                var aofFile = Path.Combine(_settings.DataDirectory, "appendonly.aof");

                // 检查RDB文件
                if (File.Exists(dumpFile))
                {
                    var fileInfo = new FileInfo(dumpFile);
                    if (fileInfo.Length == 0)
                    {
                        Log.Warning("⚠️ RDB file is empty, may be corrupted");
                    }
                    else
                    {
                        Log.Information("✅ RDB file exists and has data ({Size} bytes)", fileInfo.Length);
                    }
                }

                // 检查AOF文件
                if (File.Exists(aofFile))
                {
                    var fileInfo = new FileInfo(aofFile);
                    Log.Information("✅ AOF file exists ({Size} bytes)", fileInfo.Length);
                }

                // 检查并修复可能的权限问题
                await EnsureDataDirectoryPermissionsAsync();
            }
            catch (Exception ex)
            {
                Log.Warning("⚠️ Error validating data files: {Error}", ex.Message);
            }
        }

        private Task EnsureDataDirectoryPermissionsAsync()
        {
            try
            {
                if (!Directory.Exists(_settings.DataDirectory))
                {
                    Directory.CreateDirectory(_settings.DataDirectory);
                    Log.Information("📁 Created data directory: {DataDirectory}", _settings.DataDirectory);
                }

                // 确保目录可写
                var testFile = Path.Combine(_settings.DataDirectory, "test_write.tmp");
                File.WriteAllText(testFile, "test");
                File.Delete(testFile);

                Log.Debug("✅ Data directory permissions verified");
            }
            catch (Exception ex)
            {
                Log.Error("❌ Data directory permission issue: {Error}", ex.Message);
            }

            return Task.CompletedTask;
        }

        private async Task<bool> VerifyRedisHealthAfterRestartAsync()
        {
            try
            {
                Log.Information("🏥 Verifying Redis health after restart...");

                // 等待Redis完全启动
                for (int i = 0; i < 10; i++)
                {
                    if (IsRedisRunning())
                    {
                        using var cts = new CancellationTokenSource(TimeSpan.FromSeconds(5));

                        // 测试基本连接
                        var pingResult = await ExecuteRedisCliCommandAsync("PING", cts.Token);
                        if (!string.IsNullOrEmpty(pingResult) && pingResult.Contains("PONG"))
                        {
                            Log.Information("✅ Redis is responding to PING");

                            // 测试基本操作
                            var setResult = await ExecuteRedisCliCommandAsync("SET health_check_key test_value");
                            var getResult = await ExecuteRedisCliCommandAsync("GET health_check_key");
                            var delResult = await ExecuteRedisCliCommandAsync("DEL health_check_key");

                            if (!string.IsNullOrEmpty(getResult) && getResult.Contains("test_value"))
                            {
                                Log.Information("✅ Redis basic operations working correctly");
                                return true;
                            }
                        }
                    }

                    await Task.Delay(1000);
                }

                Log.Warning("⚠️ Redis health verification failed after restart");
                return false;
            }
            catch (Exception ex)
            {
                Log.Error("❌ Error verifying Redis health: {Error}", ex.Message);
                return false;
            }
        }

        public async Task<bool> RecoverFromBackupAsync(string backupPath = null)
        {
            try
            {
                Log.Information("🔄 Starting Redis data recovery...");

                // 停止Redis
                await StopRedisAsync(graceful: false);

                // 如果没有指定备份路径，寻找最新的备份
                if (string.IsNullOrEmpty(backupPath))
                {
                    backupPath = FindLatestBackup();
                }

                if (string.IsNullOrEmpty(backupPath) || !File.Exists(backupPath))
                {
                    Log.Error("❌ No valid backup found for recovery");
                    return false;
                }

                Log.Information("📁 Recovering from backup: {BackupPath}", backupPath);

                // 备份当前损坏的文件
                var corruptedBackupDir = Path.Combine(_settings.BackupDirectory, $"corrupted_{DateTime.Now:yyyyMMdd_HHmmss}");
                Directory.CreateDirectory(corruptedBackupDir);

                var currentDumpFile = Path.Combine(_settings.DataDirectory, "dump.rdb");
                if (File.Exists(currentDumpFile))
                {
                    File.Move(currentDumpFile, Path.Combine(corruptedBackupDir, "dump.rdb"));
                }

                // 恢复备份文件
                File.Copy(backupPath, currentDumpFile, true);
                Log.Information("✅ Backup file restored");

                // 重启Redis
                var startResult = await StartRedisAsync();
                if (startResult)
                {
                    Log.Information("✅ Redis recovery completed successfully");
                    return true;
                }
                else
                {
                    Log.Error("❌ Failed to start Redis after recovery");
                    return false;
                }
            }
            catch (Exception ex)
            {
                Log.Error("❌ Error during Redis recovery: {Error}", ex.Message);
                return false;
            }
        }

        private string FindLatestBackup()
        {
            try
            {
                if (!Directory.Exists(_settings.BackupDirectory))
                    return null;

                var backupFiles = Directory.GetFiles(_settings.BackupDirectory, "*.rdb")
                    .OrderByDescending(f => new FileInfo(f).CreationTime)
                    .ToArray();

                return backupFiles.FirstOrDefault();
            }
            catch
            {
                return null;
            }
        }

        public void Dispose()
        {
            _redisProcess?.Dispose();
        }
    }
}