// PBI-76: User-scoped SSE stream voor user-settings cross-tab/cross-device sync.
//
// Wordt door <UserSettingsBridge /> in app/(app)/layout.tsx geopend zodra de
// gebruiker is ingelogd. Filtert pg_notify-payloads op
// `kind === 'user_settings' && userId === session.userId`. Settings worden
// via prop al gehydrateerd; deze route levert alleen incrementele patches.
//
// Auth: iron-session cookie. Demo-tokens openen geen subscription (bridge
// skipt voor isDemo).
// Output: text/event-stream — `data:` met de patch (Partial<UserSettings>).
// Sluit zelf na 240s als safety-net; client herconnect.

import { NextRequest } from 'next/server'
import { Client } from 'pg'
import { getSession } from '@/lib/auth'
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

interface UserSettingsPayload {
  kind: 'user_settings'
  userId: string
  patch: Record<string, unknown>
}

function isUserSettingsPayload(p: unknown): p is UserSettingsPayload {
  if (typeof p !== 'object' || p === null) return false
  const obj = p as Record<string, unknown>
  return (
    obj.kind === 'user_settings' &&
    typeof obj.userId === 'string' &&
    typeof obj.patch === 'object' &&
    obj.patch !== null
  )
}

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 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 {
          // controller already closed
        }
      }

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

      try {
        await pgClient.connect()
        await pgClient.query(`LISTEN ${CHANNEL}`)
      } catch (err) {
        console.error('[realtime/user-settings] 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: unknown
        try {
          payload = JSON.parse(msg.payload)
        } catch {
          return
        }
        if (!isUserSettingsPayload(payload)) return
        if (payload.userId !== userId) return
        enqueue(`data: ${JSON.stringify(payload.patch)}\n\n`)
      })

      pgClient.on('error', (err) => {
        console.error('[realtime/user-settings] pg client error:', err)
        cleanup('pg error')
      })

      enqueue(`: connected\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',
    },
  })
}