/**
 * NextAuth 4 API Route Handler with Redis Session Storage
 *
 * 架構說明:
 * 1. Keycloak SSO - 統一認證入口
 * 2. Redis - 集中式 session storage (解決 Cookie 4KB 限制)
 * 3. Cookie - 只存 session_key (64 bytes)
 *
 * 多系統共享:
 * - hr.ease.taipei, mail.ease.taipei, calendar.ease.taipei 等
 * - 共用同一個 Redis session (透過 Keycloak user_id)
 * - Token refresh 自動同步到所有系統
 */
import NextAuth, { NextAuthOptions } from 'next-auth'
import KeycloakProvider from 'next-auth/providers/keycloak'
import Redis from 'ioredis'

// Redis 客戶端 (DB 0 專用於 Session Storage)
const redis = new Redis({
  host: process.env.REDIS_HOST || '10.1.0.20',
  port: parseInt(process.env.REDIS_PORT || '6379'),
  password: process.env.REDIS_PASSWORD,
  db: 0, // Session Storage 專用
  retryStrategy: (times) => {
    const delay = Math.min(times * 50, 2000)
    return delay
  },
})

// Redis 連線錯誤處理
redis.on('error', (err) => {
  console.error('[Redis] Connection error:', err)
})

redis.on('connect', () => {
  console.log('[Redis] Connected to session storage')
})

const authOptions: NextAuthOptions = {
  providers: [
    KeycloakProvider({
      clientId: process.env.NEXT_PUBLIC_KEYCLOAK_CLIENT_ID!,
      clientSecret: process.env.KEYCLOAK_CLIENT_SECRET!,
      issuer: `${process.env.NEXT_PUBLIC_KEYCLOAK_URL}/realms/${process.env.NEXT_PUBLIC_KEYCLOAK_REALM}`,
    }),
  ],
  session: {
    strategy: 'jwt',
    maxAge: 8 * 60 * 60, // 8 小時
    updateAge: 60 * 60,  // 每 1 小時檢查一次
  },
  events: {
    // 登出時清除 Redis session (所有系統同步登出)
    async signOut({ token }) {
      if (token?.sub) {
        const sessionKey = `session:${token.sub}`
        await redis.del(sessionKey)
        console.log('[EVENT] Signed out, Redis session deleted:', sessionKey)
      }
    },
  },
  callbacks: {
    async jwt({ token, account, profile, trigger }) {
      const userId = token.sub || profile?.sub
      if (!userId) return token

      console.log('[JWT CALLBACK]', { trigger, userId: userId.substring(0, 8) })

      // 初次登入 - 儲存 Keycloak tokens 到 Redis
      if (account && profile) {
        const sessionData = {
          sub: profile.sub,
          email: profile.email,
          name: profile.name,
          accessToken: account.access_token,
          refreshToken: account.refresh_token,
          expiresAt: account.expires_at,
          createdAt: Math.floor(Date.now() / 1000),
        }

        // 存入 Redis (Key: session:{user_id})
        const sessionKey = `session:${userId}`
        await redis.setex(
          sessionKey,
          8 * 60 * 60, // TTL: 8 hours
          JSON.stringify(sessionData)
        )

        console.log('[JWT CALLBACK] Stored session to Redis:', sessionKey)

        // Cookie 只存輕量資料 (user_id)
        return {
          sub: userId,
          email: profile.email,
          name: profile.name,
          sessionKey, // 引用 Redis 的 key
        }
      }

      // 後續請求 - 從 Redis 讀取 tokens
      const sessionKey = token.sessionKey as string || `session:${userId}`
      const sessionDataStr = await redis.get(sessionKey)

      if (!sessionDataStr) {
        console.error('[JWT CALLBACK] Session not found in Redis:', sessionKey)
        return { ...token, error: 'SessionNotFound' }
      }

      const sessionData = JSON.parse(sessionDataStr)

      // 檢查 access_token 是否即將過期 (提前 1 分鐘刷新)
      const now = Math.floor(Date.now() / 1000)
      const expiresAt = sessionData.expiresAt as number

      if (now < expiresAt - 60) {
        // Token 仍有效 - 更新 Redis TTL (Sliding Expiration)
        await redis.expire(sessionKey, 8 * 60 * 60)
        console.log('[JWT CALLBACK] Token valid, TTL refreshed')
        return token
      }

      // Token 即將過期 - 使用 refresh_token 更新
      console.log('[JWT CALLBACK] Refreshing token...')
      try {
        const response = await fetch(
          `${process.env.NEXT_PUBLIC_KEYCLOAK_URL}/realms/${process.env.NEXT_PUBLIC_KEYCLOAK_REALM}/protocol/openid-connect/token`,
          {
            method: 'POST',
            headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
            body: new URLSearchParams({
              client_id: process.env.NEXT_PUBLIC_KEYCLOAK_CLIENT_ID!,
              client_secret: process.env.KEYCLOAK_CLIENT_SECRET!,
              grant_type: 'refresh_token',
              refresh_token: sessionData.refreshToken,
            }),
          }
        )

        if (!response.ok) {
          console.error('[JWT CALLBACK] Refresh failed:', response.status)
          await redis.del(sessionKey) // 刪除無效 session
          return { ...token, error: 'RefreshTokenError' }
        }

        const refreshedTokens = await response.json()

        // 更新 Redis session
        const updatedSessionData = {
          ...sessionData,
          accessToken: refreshedTokens.access_token,
          refreshToken: refreshedTokens.refresh_token ?? sessionData.refreshToken,
          expiresAt: now + refreshedTokens.expires_in,
        }

        await redis.setex(sessionKey, 8 * 60 * 60, JSON.stringify(updatedSessionData))
        console.log('[JWT CALLBACK] Token refreshed and updated in Redis')

        return token
      } catch (error) {
        console.error('[JWT CALLBACK] Refresh error:', error)
        await redis.del(sessionKey)
        return { ...token, error: 'RefreshTokenError' }
      }
    },
    async session({ session, token }) {
      console.log('[SESSION CALLBACK] Called')

      // 處理錯誤狀態
      if (token?.error) {
        console.error('[SESSION CALLBACK] Session error:', token.error)
        return { ...session, error: token.error }
      }

      if (!token.sub) {
        return { ...session, error: 'InvalidSession' }
      }

      // 從 Redis 讀取完整 session 資料
      const sessionKey = token.sessionKey as string || `session:${token.sub}`
      const sessionDataStr = await redis.get(sessionKey)

      if (!sessionDataStr) {
        console.error('[SESSION CALLBACK] Session expired or not found')
        return { ...session, error: 'SessionExpired' }
      }

      const sessionData = JSON.parse(sessionDataStr)

      // 填充 session 物件 (前端可用)
      if (session.user) {
        session.user.id = sessionData.sub
        session.user.email = sessionData.email
        session.user.name = sessionData.name
        session.accessToken = sessionData.accessToken // ← 從 Redis 取得!

        // Tenant 資訊 (如果需要可以存在 Redis)
        if (sessionData.tenant) {
          ;(session.user as any).tenant = sessionData.tenant
        }

        console.log('[SESSION CALLBACK] Session loaded from Redis')
      }

      return session
    },
  },
  secret: process.env.NEXTAUTH_SECRET,
  debug: true,
}

const handler = NextAuth(authOptions)

export { handler as GET, handler as POST }