/**
 * 系统状态 API 路由
 * 返回 MongoDB 数据库真实状态
 */

import { NextResponse } from "next/server"
import { getDatabaseStats, healthCheck } from "@/lib/mongodb"

/**
 * GET /api/system-status
 * 获取系统状态
 */
export async function GET() {
  try {
    // 健康检查
    const health = await healthCheck()
    
    if (!health.mongodb) {
      return NextResponse.json({
        status: 'error',
        connected: false,
        latencyMs: health.latencyMs,
        error: health.error || 'MongoDB 连接失败',
        databases: [],
        totalDocuments: 0,
        totalSizeGB: 0,
        lastCheck: new Date().toISOString()
      }, { status: 503 })
    }
    
    // 获取数据库统计
    const stats = await getDatabaseStats()
    
    return NextResponse.json({
      status: 'healthy',
      connected: stats.connected,
      latencyMs: health.latencyMs,
      databases: stats.databases,
      totalDocuments: stats.totalDocuments,
      totalSizeGB: stats.totalSizeGB,
      lastCheck: new Date().toISOString(),
      // 格式化显示
      summary: {
        userCount: formatNumber(stats.totalDocuments),
        dataSize: `${stats.totalSizeGB} GB`,
        dbCount: stats.databases.length,
        responseTime: `${health.latencyMs}ms`
      }
    }, {
      headers: { 'Cache-Control': 'no-store, max-age=0' }
    })
    
  } catch (error) {
    console.error('System status error:', error)
    return NextResponse.json({
      status: 'error',
      connected: false,
      error: error instanceof Error ? error.message : 'Unknown error',
      lastCheck: new Date().toISOString()
    }, { status: 500 })
  }
}

/**
 * 格式化数字显示
 */
function formatNumber(num: number): string {
  if (num >= 1000000000) {
    return `${(num / 1000000000).toFixed(2)}B`
  }
  if (num >= 1000000) {
    return `${(num / 1000000).toFixed(1)}M`
  }
  if (num >= 1000) {
    return `${(num / 1000).toFixed(1)}K`
  }
  return num.toString()
}