// SSE endpoint for the backlog 3-pane (PBI / story / task changes).
// Simpler than /api/realtime/solo — no sprint or user scoping, just product_id filter.
// Auth: iron-session cookie. Demo users may read (no 403 for demo).

import { NextRequest } from 'next/server'
import { Client } from 'pg'
import { getSession } from '@/lib/auth'
import { getAccessibleProduct } from '@/lib/product-access'
import { closePgClientSafely } from '@/lib/realtime/pg-client-cleanup'

export const runtime = 'nodejs'
export const dynamic = 'force-dynamic'
export const maxDuration = 300

const CHANNEL = 'scrum4me_changes'
const HEARTBEAT_MS = 25_000
const HARD_CLOSE_MS = 240_000

type NotifyPayload = Record<string, unknown>

function shouldEmit(payload: NotifyPayload, productId: string): boolean {
  if ('type' in payload) return false // job / worker events — not relevant here
  const entity = payload.entity as string | undefined
  if (!entity || !['pbi', 'story', 'task'].includes(entity)) return false
  return payload.product_id === productId
}

export async function GET(request: NextRequest) {
  const session = await getSession()
  if (!session.userId) {
    return Response.json({ error: 'Niet ingelogd' }, { status: 401 })
  }

  const productId = request.nextUrl.searchParams.get('product_id')
  if (!productId) {
    return Response.json({ error: 'product_id is verplicht' }, { status: 400 })
  }

  const product = await getAccessibleProduct(productId, session.userId)
  if (!product) {
    return Response.json({ error: 'Geen toegang tot dit product' }, { status: 403 })
  }

  const directUrl = process.env.DIRECT_URL ?? process.env.DATABASE_URL
  if (!directUrl) {
    return Response.json({ error: 'DIRECT_URL/DATABASE_URL niet geconfigureerd' }, { status: 500 })
  }

  const encoder = new TextEncoder()
  const pgClient = new Client({ connectionString: directUrl })

  let heartbeatTimer: ReturnType<typeof setInterval> | null = null
  let hardCloseTimer: ReturnType<typeof setTimeout> | null = null
  let closed = false

  const stream = new ReadableStream({
    async start(controller) {
      const enqueue = (chunk: string) => {
        if (closed) return
        try {
          controller.enqueue(encoder.encode(chunk))
        } catch {
          // stream already closed
        }
      }

      const cleanup = async (reason: string) => {
        if (closed) return
        closed = true
        if (heartbeatTimer) clearInterval(heartbeatTimer)
        if (hardCloseTimer) clearTimeout(hardCloseTimer)
        await closePgClientSafely(pgClient, 'realtime/backlog')
        try { controller.close() } catch { /* already closed */ }
        if (process.env.NODE_ENV !== 'production') {
          console.log(`[realtime/backlog] closed: ${reason}`)
        }
      }

      try {
        await pgClient.connect()
        await pgClient.query(`LISTEN ${CHANNEL}`)
      } catch (err) {
        console.error('[realtime/backlog] pg connect/listen failed:', err)
        enqueue(`event: error\ndata: ${JSON.stringify({ message: 'pg connect failed' })}\n\n`)
        await cleanup('pg connect failed')
        return
      }

      pgClient.on('notification', (msg) => {
        if (!msg.payload) return
        let payload: NotifyPayload
        try {
          payload = JSON.parse(msg.payload) as NotifyPayload
        } catch {
          return
        }
        if (!shouldEmit(payload, productId)) return
        enqueue(`data: ${msg.payload}\n\n`)
      })

      pgClient.on('error', async (err) => {
        console.error('[realtime/backlog] pg client error:', err)
        await cleanup('pg error')
      })

      enqueue(`event: ready\ndata: ${JSON.stringify({ product_id: productId })}\n\n`)

      heartbeatTimer = setInterval(() => {
        enqueue(`: heartbeat\n\n`)
      }, HEARTBEAT_MS)

      hardCloseTimer = setTimeout(() => {
        cleanup('hard close 240s')
      }, HARD_CLOSE_MS)

      request.signal.addEventListener('abort', () => {
        cleanup('client aborted')
      })
    },
  })

  return new Response(stream, {
    headers: {
      'Content-Type': 'text/event-stream; charset=utf-8',
      'Cache-Control': 'no-cache, no-transform',
      Connection: 'keep-alive',
      'X-Accel-Buffering': 'no',
    },
  })
}