const { spawn, exec } = require('child_process');
const fs = require('fs').promises;
const fsSync = require('fs');
const path = require('path');
const EventEmitter = require('events');
const paths = require('./paths');

class ServerManager extends EventEmitter {
  constructor() {
    super();
    this.serverProcess = null;
    this.isRunning = false;
    this.isReady = false; // Track if server is actually ready to accept connections
    this.startTime = null;
    this.logBuffer = [];
    this.maxLogLines = 1000;
    this.serverStats = {
      players: 0,
      uptime: 0,
      memoryUsage: 0,
      cpuUsage: 0
    };
    this.debugFileWatcher = null;
    this.lastDebugFilePosition = 0;
  }

  async getServerStatus() {
    // Double-check if process is actually running when we think it is
    if (this.isRunning && this.serverProcess && this.serverProcess.pid) {
      try {
        // Use kill(pid, 0) to check if process exists without sending a signal
        process.kill(this.serverProcess.pid, 0);
      } catch (error) {
        // Process doesn't exist anymore - it was killed externally
        this.addLogLine('warning', 'Server process was terminated externally');
        this.isRunning = false;
        this.isReady = false;
        this.serverProcess = null;
        this.startTime = null;
        
        // Reset player stats when server stops
        this.serverStats.players = 0;
        this.serverStats.memoryUsage = 0;
        this.serverStats.cpuUsage = 0;
        
        this.emit('exit', { code: null, signal: 'external' });
        // Emit status change immediately
        this.emit('status', {
          isRunning: this.isRunning,
          isReady: this.isReady,
          uptime: 0,
          startTime: null,
          players: 0,
          memoryUsage: 0,
          cpuUsage: 0,
          processId: null
        });
      }
    }

    // Always check for externally running Luanti servers if we don't have a running one
    if (!this.isRunning) {
      const externalServer = await this.detectExternalLuantiServer();
      if (externalServer) {
        this.isRunning = true;
        this.isReady = true;
        this.startTime = externalServer.startTime;
        
        // Try to get player data from debug log for external servers
        const playerData = await this.getExternalServerPlayerData();
        this.serverStats.players = playerData.count;
        
        this.addLogLine('info', `Detected external Luanti server (PID: ${externalServer.pid}, World: ${externalServer.world})`);
        // Create a mock server process object for tracking
        this.serverProcess = { pid: externalServer.pid, external: true };
        console.log('ServerManager: Set serverProcess.external = true');
        
        // Start monitoring debug file for external server
        this.startDebugFileMonitoring();
      }
    }

    return {
      isRunning: this.isRunning,
      isReady: this.isReady,
      uptime: this.isRunning && this.startTime ? Date.now() - this.startTime : 0,
      startTime: this.startTime,
      players: this.serverStats.players,
      memoryUsage: this.serverStats.memoryUsage,
      cpuUsage: this.serverStats.cpuUsage,
      processId: this.serverProcess?.pid || null
    };
  }

  async startServer(worldName = null) {
    if (this.isRunning) {
      throw new Error('Server is already running');
    }

    try {
      // Ensure minetest directory exists
      paths.ensureDirectories();

      // Build command arguments
      const args = [
        '--server',
        '--config', paths.configFile
      ];

      if (worldName && worldName.trim() !== '') {
        if (!paths.isValidWorldName(worldName)) {
          throw new Error('Invalid world name');
        }
        
        // Check if world exists
        const worldPath = paths.getWorldPath(worldName);
        try {
          await fs.access(worldPath);
        } catch (error) {
          throw new Error(`World "${worldName}" does not exist. Please create it first in the Worlds section.`);
        }
        
        // Read the world's game configuration
        const worldConfigPath = path.join(worldPath, 'world.mt');
        try {
          const worldConfig = await fs.readFile(worldConfigPath, 'utf8');
          const gameMatch = worldConfig.match(/gameid\s*=\s*(.+)/);
          if (gameMatch) {
            const gameId = gameMatch[1].trim();
            
            args.push('--gameid', gameId);
            this.addLogLine('info', `Using game: ${gameId} for world: ${worldName}`);
          }
        } catch (error) {
          this.addLogLine('warning', `Could not read world config, using default game: ${error.message}`);
        }
        
        args.push('--world', worldPath);
      } else {
        // If no world specified, we need to create a default world or let the server create one
        this.addLogLine('info', 'Starting server without specifying a world. Server will use default world settings.');
      }

      // Check if minetest/luanti executable exists
      const executable = await this.findMinetestExecutable();
      
      this.serverProcess = spawn(executable, args, {
        cwd: paths.minetestDir,
        stdio: ['pipe', 'pipe', 'pipe']
      });

      this.isRunning = true;
      this.isReady = false; // Server started but not ready yet
      this.startTime = Date.now();

      // Handle process events
      this.serverProcess.on('error', (error) => {
        this.emit('error', error);
        this.isRunning = false;
        this.isReady = false;
        this.serverProcess = null;
      });

      this.serverProcess.on('exit', (code, signal) => {
        this.emit('exit', { code, signal });
        this.isRunning = false;
        this.isReady = false;
        this.serverProcess = null;
        this.startTime = null;
        this.stopDebugFileMonitoring();
      });

      // Handle output streams
      this.serverProcess.stdout.on('data', (data) => {
        const lines = data.toString().split('\n').filter(line => line.trim());
        lines.forEach(line => this.addLogLine('stdout', line));
        this.parseServerStats(data.toString());
      });

      this.serverProcess.stderr.on('data', (data) => {
        const lines = data.toString().split('\n').filter(line => line.trim());
        lines.forEach(line => this.addLogLine('stderr', line));
      });

      this.emit('started', { pid: this.serverProcess.pid });
      
      // Start monitoring debug.txt file for server ready messages
      this.startDebugFileMonitoring();
      
      return {
        success: true,
        pid: this.serverProcess.pid,
        message: `Server started successfully with PID ${this.serverProcess.pid}`
      };

    } catch (error) {
      this.isRunning = false;
      this.isReady = false;
      this.serverProcess = null;
      throw error;
    }
  }

  async stopServer(force = false) {
    if (!this.isRunning || !this.serverProcess) {
      throw new Error('Server is not running');
    }

    return new Promise((resolve, reject) => {
      const timeout = setTimeout(() => {
        if (this.serverProcess && this.isRunning) {
          // Force kill if graceful shutdown failed
          this.serverProcess.kill('SIGKILL');
          resolve({ success: true, message: 'Server force-stopped' });
        }
      }, 10000); // 10 second timeout

      this.serverProcess.on('exit', () => {
        clearTimeout(timeout);
        resolve({ success: true, message: 'Server stopped gracefully' });
      });

      // Try graceful shutdown first
      if (force) {
        this.serverProcess.kill('SIGTERM');
      } else {
        // Send shutdown command to server
        try {
          this.serverProcess.stdin.write('/shutdown\n');
        } catch (error) {
          // If stdin fails, use SIGTERM
          this.serverProcess.kill('SIGTERM');
        }
      }
    });
  }

  async restartServer(worldName = null) {
    if (this.isRunning) {
      await this.stopServer();
      // Wait a moment for clean shutdown
      await new Promise(resolve => setTimeout(resolve, 2000));
    }
    return await this.startServer(worldName);
  }

  async findGamePath(gameId) {
    try {
      // Use the paths utility to find installed games
      const games = await paths.getInstalledGames();
      const game = games.find(g => g.name === gameId);
      
      if (game) {
        return game.path;
      }
      
      return null;
    } catch (error) {
      this.addLogLine('warning', `Error finding game path for "${gameId}": ${error.message}`);
      return null;
    }
  }

  async findMinetestExecutable() {
    // Whitelist of allowed executable names to prevent command injection
    const allowedExecutables = ['luanti', 'minetest', 'minetestserver'];
    const foundExecutables = [];
    
    for (const name of allowedExecutables) {
      try {
        // Validate executable name against whitelist
        if (!/^[a-zA-Z0-9_-]+$/.test(name)) {
          continue;
        }
        
        const execPath = await new Promise((resolve, reject) => {
          // Use spawn instead of exec to avoid command injection
          const { spawn } = require('child_process');
          const whichProcess = spawn('which', [name], { stdio: ['ignore', 'pipe', 'pipe'] });
          
          let stdout = '';
          let stderr = '';
          
          whichProcess.stdout.on('data', (data) => {
            stdout += data.toString();
          });
          
          whichProcess.stderr.on('data', (data) => {
            stderr += data.toString();
          });
          
          whichProcess.on('close', (code) => {
            if (code === 0) {
              resolve(stdout.trim());
            } else {
              reject(new Error(`which command failed: ${stderr}`));
            }
          });
          
          whichProcess.on('error', (error) => {
            reject(error);
          });
        });
        
        // Validate that the returned path is safe
        if (execPath && path.isAbsolute(execPath)) {
          foundExecutables.push({ name, path: execPath });
          this.addLogLine('info', `Found executable: ${name} at ${execPath}`);
          return execPath; // Return the full path for security
        }
      } catch (error) {
        // Continue to next possibility
      }
    }
    
    // Provide detailed error message
    const errorMsg = `Minetest/Luanti executable not found. Please install Luanti or add it to your PATH.\n` +
                    `Searched for: ${allowedExecutables.join(', ')}\n` +
                    `Try: sudo apt install luanti (Ubuntu/Debian) or your system's package manager`;
    
    this.addLogLine('error', errorMsg);
    throw new Error(errorMsg);
  }

  addLogLine(type, content) {
    const timestamp = new Date().toISOString();
    const logEntry = {
      timestamp,
      type,
      content: content.trim()
    };

    this.logBuffer.push(logEntry);
    
    // Keep only the last N lines
    if (this.logBuffer.length > this.maxLogLines) {
      this.logBuffer = this.logBuffer.slice(-this.maxLogLines);
    }

    this.emit('log', logEntry);
  }

  parseServerStats(output) {
    // Parse server output for statistics and ready state
    const lines = output.split('\n');
    
    for (const line of lines) {
      // Look for player count
      const playerMatch = line.match(/(\d+) players? online/i);
      if (playerMatch) {
        this.serverStats.players = parseInt(playerMatch[1]);
      }

      // Look for performance stats if available
      const memMatch = line.match(/Memory usage: ([\d.]+)MB/i);
      if (memMatch) {
        this.serverStats.memoryUsage = parseFloat(memMatch[1]);
      }
      
      // Check if server is ready - look for common Luanti server ready messages
      if (!this.isReady && this.isRunning) {
        const readyIndicators = [
          /Server for gameid=".*?" listening on/i,
          /listening on \[::\]:\d+/i,
          /listening on 0\.0\.0\.0:\d+/i,
          /World at \[.*?\]/i,
          /Server started/i,
          /Loading environment/i
        ];
        
        for (const indicator of readyIndicators) {
          if (indicator.test(line)) {
            this.isReady = true;
            this.addLogLine('info', 'Server is now ready to accept connections');
            console.log(`Server ready detected from line: ${line}`); // Debug log
            // Emit status change when server becomes ready
            this.emit('status', {
              isRunning: this.isRunning,
              isReady: this.isReady,
              uptime: this.startTime ? Date.now() - this.startTime : 0,
              startTime: this.startTime,
              players: this.serverStats.players,
              memoryUsage: this.serverStats.memoryUsage,
              cpuUsage: this.serverStats.cpuUsage,
              processId: this.serverProcess?.pid || null
            });
            break;
          }
        }
        
        // Also check for error conditions that indicate startup failure
        const errorIndicators = [
          /ERROR\[Main\]:/i,
          /FATAL ERROR/i,
          /Could not find or load game/i,
          /Failed to/i
        ];
        
        for (const errorIndicator of errorIndicators) {
          if (errorIndicator.test(line)) {
            // Don't mark as ready if we see critical errors
            this.addLogLine('warning', 'Server startup may have failed - check logs for errors');
            break;
          }
        }
      }
    }

    this.emit('stats', this.serverStats);
  }

  getLogs(lines = 100) {
    return this.logBuffer.slice(-lines);
  }

  getRecentLogs(since = null) {
    if (!since) {
      return this.logBuffer.slice(-50);
    }
    
    const sinceTime = new Date(since);
    return this.logBuffer.filter(log => 
      new Date(log.timestamp) > sinceTime
    );
  }

  async sendCommand(command) {
    if (!this.isRunning || !this.serverProcess) {
      throw new Error('Server is not running');
    }

    // Check if this is an external server
    if (this.serverProcess.external) {
      throw new Error('Cannot send commands to external servers. Commands can only be sent to servers started through this dashboard.');
    }

    // Validate and sanitize command
    const sanitizedCommand = this.validateServerCommand(command);
    
    return new Promise((resolve, reject) => {
      try {
        this.serverProcess.stdin.write(sanitizedCommand + '\n');
        this.addLogLine('info', `Command sent: ${sanitizedCommand}`);
        resolve({ success: true, message: 'Command sent successfully' });
      } catch (error) {
        reject(error);
      }
    });
  }

  validateServerCommand(command) {
    if (!command || typeof command !== 'string') {
      throw new Error('Command must be a non-empty string');
    }

    // Remove any control characters and limit length
    const sanitized = command.replace(/[\x00-\x1F\x7F]/g, '').trim();
    
    if (sanitized.length === 0) {
      throw new Error('Command cannot be empty after sanitization');
    }

    if (sanitized.length > 500) {
      throw new Error('Command too long (max 500 characters)');
    }

    // Whitelist of allowed command prefixes for safety
    const allowedCommands = [
      '/say', '/tell', '/kick', '/ban', '/unban', '/status', '/time', '/weather',
      '/give', '/teleport', '/tp', '/spawn', '/help', '/list', '/who', '/shutdown',
      '/stop', '/save-all', '/whitelist', '/op', '/deop', '/gamemode', '/difficulty',
      '/seed', '/defaultgamemode', '/gamerule', '/reload', '/clear', '/experience',
      '/xp', '/effect', '/enchant', '/summon', '/kill', '/scoreboard', '/team',
      '/trigger', '/clone', '/execute', '/fill', '/setblock', '/testforblock',
      '/blockdata', '/entitydata', '/testfor', '/stats', '/worldborder'
    ];

    // Check if command starts with allowed prefix or is a direct server command
    const isAllowed = allowedCommands.some(prefix => 
      sanitized.toLowerCase().startsWith(prefix.toLowerCase())
    ) || /^[a-zA-Z0-9_-]+(\s+[a-zA-Z0-9_.-]+)*$/.test(sanitized);

    if (!isAllowed) {
      throw new Error('Command not allowed or contains invalid characters');
    }

    return sanitized;
  }

  async getServerInfo() {
    try {
      const configExists = await fs.access(paths.configFile).then(() => true).catch(() => false);
      const debugLogExists = await fs.access(paths.debugFile).then(() => true).catch(() => false);
      
      let configMtime = null;
      if (configExists) {
        const stats = await fs.stat(paths.configFile);
        configMtime = stats.mtime;
      }

      return {
        configFile: {
          exists: configExists,
          path: paths.configFile,
          lastModified: configMtime
        },
        debugLog: {
          exists: debugLogExists,
          path: paths.debugFile
        },
        directories: {
          minetest: paths.minetestDir,
          worlds: paths.worldsDir,
          mods: paths.modsDir
        }
      };
    } catch (error) {
      throw new Error(`Failed to get server info: ${error.message}`);
    }
  }

  startDebugFileMonitoring() {
    const debugFilePath = path.join(paths.minetestDir, 'debug.txt');
    
    try {
      // Get initial file size to start monitoring from the end
      const stats = fsSync.existsSync(debugFilePath) ? fsSync.statSync(debugFilePath) : null;
      this.lastDebugFilePosition = stats ? stats.size : 0;
      
      // Watch for changes to debug.txt
      this.debugFileWatcher = fsSync.watchFile(debugFilePath, { interval: 500 }, (current, previous) => {
        if (current.mtime > previous.mtime) {
          this.readDebugFileChanges(debugFilePath);
        }
      });
    } catch (error) {
      this.addLogLine('warning', `Could not monitor debug.txt: ${error.message}`);
    }
  }

  stopDebugFileMonitoring() {
    if (this.debugFileWatcher) {
      const debugFilePath = path.join(paths.minetestDir, 'debug.txt');
      fsSync.unwatchFile(debugFilePath);
      this.debugFileWatcher = null;
    }
  }

  async readDebugFileChanges(debugFilePath) {
    try {
      const stats = fsSync.statSync(debugFilePath);
      if (stats.size > this.lastDebugFilePosition) {
        const stream = fsSync.createReadStream(debugFilePath, {
          start: this.lastDebugFilePosition,
          end: stats.size - 1
        });
        
        let buffer = '';
        stream.on('data', (chunk) => {
          buffer += chunk.toString();
        });
        
        stream.on('end', () => {
          const lines = buffer.split('\n').filter(line => line.trim());
          lines.forEach(line => {
            this.addLogLine('debug-file', line);
            this.parseServerStats(line); // Parse each line for ready indicators
            
            // For external servers, also update player count from new log entries
            if (this.serverProcess?.external) {
              this.updatePlayerCountFromLogLine(line);
            }
          });
        });
        
        this.lastDebugFilePosition = stats.size;
      }
    } catch (error) {
      // Ignore errors when reading debug file changes
    }
  }

  updatePlayerCountFromLogLine(line) {
    // Update player count based on join/leave messages in log
    const joinMatch = line.match(/\[Server\]: (\w+) joined the game/);
    const leaveMatch = line.match(/\[Server\]: (\w+) left the game/);
    
    if (joinMatch || leaveMatch) {
      // Player joined or left - update player data
      this.getExternalServerPlayerData().then(playerData => {
        this.serverStats.players = playerData.count;
      });
    }
  }
  async detectExternalLuantiServer() {
    try {
      const { spawn } = require('child_process');
      
      return new Promise((resolve) => {
        const psProcess = spawn('ps', ['aux'], { stdio: ['ignore', 'pipe', 'pipe'] });
        let stdout = '';
        
        psProcess.stdout.on('data', (data) => {
          stdout += data.toString();
        });
        
        psProcess.on('close', (code) => {
          if (code === 0) {
            const lines = stdout.split('\n');
            for (const line of lines) {
              // Look for luanti or minetest server processes (exclude this dashboard process)
              if ((line.includes('luanti') || line.includes('minetest')) && 
                  (line.includes('--server') || line.includes('--worldname')) &&
                  !line.includes('node app.js')) {
                
                const parts = line.trim().split(/\s+/);
                const pid = parseInt(parts[1]);
                
                if (pid && !isNaN(pid)) {
                  // Extract world name from command line
                  let world = 'unknown';
                  const worldNameMatch = line.match(/--worldname\s+(\S+)/);
                  const worldPathMatch = line.match(/--world\s+(\S+)/);
                  
                  if (worldNameMatch) {
                    world = worldNameMatch[1];
                  } else if (worldPathMatch) {
                    world = path.basename(worldPathMatch[1]);
                  }
                  
                  // Estimate start time (this is rough, but better than nothing)
                  const startTime = Date.now() - 60000; // Assume started 1 minute ago
                  
                  resolve({
                    pid: pid,
                    world: world,
                    startTime: startTime
                  });
                  return;
                }
              }
            }
          }
          resolve(null);
        });
        
        psProcess.on('error', () => {
          resolve(null);
        });
      });
    } catch (error) {
      return null;
    }
  }

  async getExternalServerPlayerData() {
    try {
      const fs = require('fs').promises;
      const debugFilePath = path.join(paths.minetestDir, 'debug.txt');
      
      // Read the last 100 lines of debug.txt to find recent player activity
      const data = await fs.readFile(debugFilePath, 'utf8');
      const lines = data.split('\n').slice(-100);
      
      // Look for recent player actions to determine who's online
      const playerData = new Map(); // Map to store player name -> player info
      const cutoffTime = new Date(Date.now() - 10 * 60 * 1000); // 10 minutes ago (extended from 5)
      
      console.log('DEBUG: Looking for players active since:', cutoffTime.toISOString());
      
      for (const line of lines.reverse()) {
        // Parse timestamp from log line
        const timestampMatch = line.match(/^(\d{4}-\d{2}-\d{2} \d{2}:\d{2}:\d{2}):/);
        if (timestampMatch) {
          const logTime = new Date(timestampMatch[1]);
          if (logTime < cutoffTime) break; // Stop looking at older entries
          
          // Look for player actions with more detail
          const actionPatterns = [
            { pattern: /ACTION\[Server\]: (\w+) (.+)/, type: 'action' },
            { pattern: /\[Server\]: (\w+) joined the game/, type: 'joined' },
            { pattern: /\[Server\]: (\w+) left the game/, type: 'left' }
          ];
          
          for (const { pattern, type } of actionPatterns) {
            const match = line.match(pattern);
            if (match && match[1]) {
              const playerName = match[1];
              const actionDescription = match[2] || type;
              
              console.log('DEBUG: Found potential player:', playerName, 'action:', actionDescription);
              
              // Filter out obvious non-player names and false positives
              if (!playerName.includes('Entity') && 
                  !playerName.includes('SAO') && 
                  !playerName.includes('Explosion') &&
                  playerName !== 'Player' && // Generic "Player" is not a real username
                  playerName !== 'Server' &&
                  playerName !== 'Main' &&
                  playerName.length > 2 && // Too short usernames are likely false positives
                  playerName.length < 20 && 
                  /^[a-zA-Z0-9_]+$/.test(playerName)) {
                
                console.log('DEBUG: Player passed filters:', playerName);
                
                // Update player data with most recent activity
                if (!playerData.has(playerName) || logTime > playerData.get(playerName).lastSeen) {
                  let lastAction = actionDescription;
                  
                  // Simplify common actions for display
                  if (lastAction.includes('digs ')) {
                    lastAction = 'Mining';
                  } else if (lastAction.includes('places ') || lastAction.includes('puts ')) {
                    lastAction = 'Building';
                  } else if (lastAction.includes('uses ') || lastAction.includes('activates ')) {
                    lastAction = 'Using items';
                  } else if (lastAction.includes('punched ') || lastAction.includes('damage')) {
                    lastAction = 'Combat';
                  } else if (type === 'joined') {
                    lastAction = 'Just joined';
                  } else if (type === 'left') {
                    lastAction = 'Left game';
                  } else {
                    lastAction = 'Active';
                  }
                  
                  // Count activities for this player
                  const existingData = playerData.get(playerName) || { activityCount: 0 };
                  
                  playerData.set(playerName, {
                    name: playerName,
                    lastSeen: logTime,
                    lastAction: lastAction,
                    activityCount: existingData.activityCount + 1,
                    online: type !== 'left' // Mark as offline if they left
                  });
                }
              } else {
                console.log('DEBUG: Player filtered out:', playerName, 'reason: failed validation');
              }
            }
          }
        }
      }
      
      // Convert to array of player objects, filtering out players who left
      const players = Array.from(playerData.values())
        .filter(player => player.online)
        .map(player => ({
          name: player.name,
          lastSeen: player.lastSeen,
          lastAction: player.lastAction,
          activityCount: player.activityCount,
          online: true
        }));
      
      return {
        count: players.length,
        players: players
      };
    } catch (error) {
      console.error('Error reading debug file for player data:', error);
      return { count: 0, players: [] };
    }
  }
}

module.exports = ServerManager;