import si from 'systeminformation';

interface SystemMetrics {
  cpu: {
    usage: number;
    cores: number;
    model: string;
  };
  memory: {
    total: number;
    used: number;
    free: number;
    usagePercent: number;
  };
  disk: {
    total: number;
    used: number;
    free: number;
    usagePercent: number;
  };
  uptime: string;
  processes: {
    total: number;
    running: number;
    sleeping: number;
  };
}

// Cache system metrics to avoid excessive system calls
let metricsCache: SystemMetrics | null = null;
let lastCacheTime = 0;
const CACHE_DURATION = 30000; // 30 seconds

export async function getSystemMetrics(): Promise<SystemMetrics> {
  const now = Date.now();
  
  // Return cached data if still valid
  if (metricsCache && (now - lastCacheTime) < CACHE_DURATION) {
    return metricsCache;
  }

  try {
    console.log('🔄 Fetching fresh system metrics...');
    
    // Get all metrics in parallel for better performance
    const [cpuData, memData, fsData, currentLoad, processData, uptimeData] = await Promise.all([
      si.cpu(),
      si.mem(),
      si.fsSize(),
      si.currentLoad(),
      si.processes(),
      si.time()
    ]);

    // Calculate disk totals across all mounted filesystems
    const diskTotals = fsData.reduce((acc, fs) => {
      // Skip special filesystems and focus on main storage
      if (fs.type && !['tmpfs', 'devtmpfs', 'proc', 'sysfs'].includes(fs.type.toLowerCase())) {
        acc.total += fs.size || 0;
        acc.used += fs.used || 0;
      }
      return acc;
    }, { total: 0, used: 0 });

    const diskFree = diskTotals.total - diskTotals.used;
    const diskUsagePercent = diskTotals.total > 0 ? Math.round((diskTotals.used / diskTotals.total) * 100) : 0;

    // Format uptime
    const formatUptime = (seconds: number): string => {
      const days = Math.floor(seconds / 86400);
      const hours = Math.floor((seconds % 86400) / 3600);
      const minutes = Math.floor((seconds % 3600) / 60);
      
      if (days > 0) {
        return `${days}d ${hours}h ${minutes}m`;
      } else if (hours > 0) {
        return `${hours}h ${minutes}m`;
      } else {
        return `${minutes}m`;
      }
    };

    // Build metrics object
    const metrics: SystemMetrics = {
      cpu: {
        usage: Math.round(currentLoad.currentLoad || 0),
        cores: cpuData.cores || 0,
        model: cpuData.brand || 'Unknown'
      },
      memory: {
        total: memData.total || 0,
        used: memData.used || 0,
        free: memData.free || 0,
        usagePercent: memData.total > 0 ? Math.round((memData.used / memData.total) * 100) : 0
      },
      disk: {
        total: diskTotals.total,
        used: diskTotals.used,
        free: diskFree,
        usagePercent: diskUsagePercent
      },
      uptime: formatUptime(uptimeData.uptime || 0),
      processes: {
        total: processData.all || 0,
        running: processData.running || 0,
        sleeping: processData.sleeping || 0
      }
    };

    // Cache the results
    metricsCache = metrics;
    lastCacheTime = now;

    console.log('✅ System metrics fetched successfully:', {
      cpu: `${metrics.cpu.usage}%`,
      memory: `${metrics.memory.usagePercent}%`,
      disk: `${metrics.disk.usagePercent}%`,
      uptime: metrics.uptime
    });

    return metrics;

  } catch (error) {
    console.error('❌ Failed to fetch system metrics:', error);
    
    // Return fallback metrics on error
    const fallbackMetrics: SystemMetrics = {
      cpu: { usage: 0, cores: 0, model: 'Unknown' },
      memory: { total: 0, used: 0, free: 0, usagePercent: 0 },
      disk: { total: 0, used: 0, free: 0, usagePercent: 0 },
      uptime: '0m',
      processes: { total: 0, running: 0, sleeping: 0 }
    };

    return fallbackMetrics;
  }
}

// Helper function to format bytes to human readable format
export function formatBytes(bytes: number): string {
  if (bytes === 0) return '0 B';
  
  const k = 1024;
  const sizes = ['B', 'KB', 'MB', 'GB', 'TB'];
  const i = Math.floor(Math.log(bytes) / Math.log(k));
  
  return parseFloat((bytes / Math.pow(k, i)).toFixed(1)) + ' ' + sizes[i];
}

// Helper function to get system health status
export function getSystemHealthStatus(metrics: SystemMetrics): 'healthy' | 'degraded' | 'unhealthy' {
  const { cpu, memory, disk } = metrics;
  
  // Define thresholds
  const criticalThresholds = { cpu: 90, memory: 95, disk: 95 };
  const warningThresholds = { cpu: 70, memory: 80, disk: 85 };
  
  // Check for critical issues
  if (cpu.usage > criticalThresholds.cpu || 
      memory.usagePercent > criticalThresholds.memory || 
      disk.usagePercent > criticalThresholds.disk) {
    return 'unhealthy';
  }
  
  // Check for warning issues
  if (cpu.usage > warningThresholds.cpu || 
      memory.usagePercent > warningThresholds.memory || 
      disk.usagePercent > warningThresholds.disk) {
    return 'degraded';
  }
  
  return 'healthy';
}