import { NextRequest, NextResponse } from 'next/server'
import { prisma } from '@/lib/prisma'
import { verifyJWT } from '@/lib/auth'

// ─────────────────────────────────────────────
// Greeting pools — tiered by engagement level
// ─────────────────────────────────────────────

const DAILY_GREETINGS = [
  `Assalamu alaikum! I was thinking of you this morning. How is your heart today?`,
  `Assalamu alaikum! A new day, a new opportunity to draw closer to Allah. How are you, my friend?`,
  `Peace be upon you. I felt a gentle nudge to check in with you. How has your journey been?`,
  `Assalamu alaikum! The sun rises again, and so does Allah's mercy. How are you doing today?`,
  `Peace be with you. I was wondering how you've been — we don't need to talk about anything heavy. Just checking in.`,
  `Assalamu alaikum! Every breath is a gift we didn't earn. How are you spending yours today?`,
  `Peace upon you. No pressure, no expectations — just wanted you to know someone is here when you're ready.`,
]

// For users who haven't checked in for 2+ days — gentler, warmer
const NURTURE_GREETINGS = [
  `Assalamu alaikum. I noticed it's been a little while. Just wanted you to know — there's no guilt here, no judgment. Only welcome. How have you been, truly?`,
  `Peace be upon you. Life gets busy, I know. But I wanted to check in because you matter. How is your heart these days?`,
  `Assalamu alaikum. Whether you've been distant from Allah or just busy with the world — His door is always open. So is this conversation. How are you?`,
  `Peace be with you. They say the journey back begins with a single step. You're here — that's your step. How can I lighten your load today?`,
  `Assalamu alaikum. No matter how many days have passed, you are always welcome here. The Prophet ﷺ said the one who returns to good is like one who never left. How can I support you today?`,
  `Peace be upon you. Silence between friends is not a wall — it's a pause. I'm still here. What's on your mind?`,
]

// For first-time users with no history — the warmest welcome
const FIRST_GREETINGS = [
  `Assalamu alaikum! I'm so glad you're here. This is a space for you — for your questions, your struggles, your quiet thoughts. There is nothing too small or too big to bring here. How are you feeling today?`,
  `Peace be upon you. Welcome. Think of me as a friend who loves the Quran and the Sunnah, and who is simply here to walk alongside you. Where would you like to start?`,
  `Assalamu alaikum! The Prophet ﷺ said, "Whoever Allah desires good for, He gives him understanding of the religion." You seeking knowledge is a sign of goodness. How can I help you grow today?`,
]

function daysSince(date: Date): number {
  const now = new Date()
  const diff = now.getTime() - date.getTime()
  return Math.floor(diff / (1000 * 60 * 60 * 24))
}

function pickRandom<T>(pool: T[]): T {
  return pool[Math.floor(Math.random() * pool.length)]
}

export async function POST(req: NextRequest) {
  try {
    const authHeader = req.headers.get('authorization')
    if (!authHeader?.startsWith('Bearer ')) {
      return NextResponse.json({ error: 'Unauthorized' }, { status: 401 })
    }
    const payload = await verifyJWT(authHeader.slice(7))
    if (!payload) {
      return NextResponse.json({ error: 'Invalid token' }, { status: 401 })
    }
    const userId = payload.id

    const user = await prisma.user.findUnique({ where: { id: userId } })
    if (!user) {
      return NextResponse.json({ error: 'User not found' }, { status: 404 })
    }

    // Check last bot message
    const lastBotMessage = await prisma.chatHistory.findFirst({
      where: { userId, role: 'assistant' },
      orderBy: { createdAt: 'desc' },
    })

    // If bot already messaged today, skip
    if (lastBotMessage) {
      const lastDate = new Date(lastBotMessage.createdAt)
      const now = new Date()
      const sameDay = lastDate.getDate() === now.getDate()
        && lastDate.getMonth() === now.getMonth()
        && lastDate.getFullYear() === now.getFullYear()
      if (sameDay) {
        return NextResponse.json({
          needsGreeting: false,
          message: null,
          lastSeen: lastBotMessage.createdAt,
        })
      }
    }

    // Check last user message for idle detection
    const lastUserMessage = await prisma.chatHistory.findFirst({
      where: { userId, role: 'user' },
      orderBy: { createdAt: 'desc' },
    })

    // Check if this is a first-time user (no history at all)
    const totalMessages = await prisma.chatHistory.count({ where: { userId } })

    // Determine greeting tier
    let greeting: string

    if (totalMessages === 0) {
      // First visit ever — warm welcome
      greeting = pickRandom(FIRST_GREETINGS)
    } else if (lastUserMessage && daysSince(new Date(lastUserMessage.createdAt)) >= 2) {
      // Been away 2+ days — nurture/re-engagement message
      greeting = pickRandom(NURTURE_GREETINGS)
    } else {
      // Regular daily check-in
      let lastTopic: string | undefined
      if (lastUserMessage) {
        const words = lastUserMessage.content.split(/\s+/).slice(0, 8).join(' ')
        lastTopic = words.length > 60 ? words.slice(0, 60) + '...' : words
      }
      const base = pickRandom(DAILY_GREETINGS)
      greeting = lastTopic
        ? `${base} Last time we spoke about ${lastTopic}. Want to continue, or something new?`
        : base
    }

    // Save the greeting
    await prisma.chatHistory.create({
      data: {
        userId,
        role: 'assistant',
        content: greeting,
        metadata: JSON.stringify({
          command: '_daily',
          summary: 'Daily check-in',
          actionItems: [],
          topics: ['daily-check-in'],
        }),
      },
    })

    // Update lastCoachedAt
    await prisma.user.update({
      where: { id: userId },
      data: { lastCoachedAt: new Date() },
    })

    return NextResponse.json({
      needsGreeting: true,
      message: greeting,
      lastSeen: lastBotMessage?.createdAt || null,
    })
  } catch (e) {
    console.error('Daily check-in error:', e)
    return NextResponse.json({ error: 'Internal server error' }, { status: 500 })
  }
}