// ST-802: Server-Sent Events stream voor het Solo Paneel.
//
// Opent een dedicated pg-verbinding (DIRECT_URL) en LISTEN't op het
// `scrum4me_changes`-kanaal. Filtert events server-side op product
// (uit query-param), sprint (actieve sprint van het product), en
// persoonlijke relevantie (assignee_id == userId, of assignee_id IS NULL
// voor stories — claim-lijst).
//
// Auth: iron-session cookie. Demo-tokens mogen lezen.
// Output: text/event-stream met JSON-payloads + heartbeat-comments.
// Sluit zelf na 240s als safety-net; client herconnect.

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

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

interface NotifyPayload {
  op: 'I' | 'U' | 'D'
  entity: 'task' | 'story'
  id: string
  story_id?: string
  product_id: string
  sprint_id: string | null
  assignee_id: string | null
  changed_fields?: string[]
}

function shouldEmit(
  payload: NotifyPayload,
  productId: string,
  activeSprintId: string | null,
  userId: string,
): boolean {
  if (payload.product_id !== productId) return false

  // Sprint scope: alleen events binnen de actieve sprint (of zonder sprint
  // voor unassigned-story claims die in de claim-sheet horen).
  if (payload.entity === 'story' && payload.assignee_id === null) {
    // Unassigned story (claim-lijst) — toon altijd, ongeacht sprint
    return payload.sprint_id === activeSprintId || payload.sprint_id === null
  }
  if (payload.sprint_id !== activeSprintId) return false

  // Persoonlijke relevantie
  return payload.assignee_id === userId
}

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

  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, 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 al gesloten — controller throwt, negeren
        }
      }

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

      // Resolve actieve sprint éénmalig per connectie
      const sprint = await prisma_sprint_findActive(productId)
      const activeSprintId = sprint?.id ?? null

      try {
        await pgClient.connect()
        await pgClient.query(`LISTEN ${CHANNEL}`)
      } catch (err) {
        console.error('[realtime/solo] 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, activeSprintId, userId)) return
        enqueue(`data: ${msg.payload}\n\n`)
      })

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

      // Stuur eerst een "ready"-event zodat de client weet dat de connectie staat
      enqueue(
        `event: ready\ndata: ${JSON.stringify({
          product_id: productId,
          sprint_id: activeSprintId,
        })}\n\n`,
      )

      // Heartbeat als SSE-comment — voorkomt proxy-timeouts
      heartbeatTimer = setInterval(() => {
        enqueue(`: heartbeat\n\n`)
      }, HEARTBEAT_MS)

      // Hard-close safety: Vercel kapt na maxDuration; we sluiten zelf eerder
      hardCloseTimer = setTimeout(() => {
        cleanup('hard close 240s')
      }, HARD_CLOSE_MS)

      // Client trekt de stekker (tab dicht, refresh, etc.)
      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',
    },
  })
}

// Lokaal helper — Prisma vermijden voor deze ene query om de pg-only flow
// schoon te houden. Geeft de actieve sprint van een product, of null.
async function prisma_sprint_findActive(productId: string): Promise<{ id: string } | null> {
  const { prisma } = await import('@/lib/prisma')
  return prisma.sprint.findFirst({
    where: { product_id: productId, status: 'ACTIVE' },
    select: { id: true },
    orderBy: { created_at: 'desc' },
  })
}