import { NextRequest, NextResponse } from 'next/server'
import { getServerSession } from 'next-auth'
import { authOptions } from '@/lib/auth'
import { prisma } from '@/lib/prisma'
import {
  createShopifyProduct,
  updateShopifyProduct,
  deactivateShopifyProduct,
  getFirstVariantId,
} from '@/lib/shopifySync'
import type { SyncChange, SyncLogEntry, SyncStreamEvent } from '@/types/sync'

export async function POST(req: NextRequest) {
  const session = await getServerSession(authOptions)
  if (!session?.user) {
    return NextResponse.json({ error: 'Non authentifié' }, { status: 401 })
  }

  let changes: SyncChange[]
  try {
    const body = await req.json()
    changes = body.changes
  } catch {
    return NextResponse.json({ error: 'Corps JSON invalide' }, { status: 400 })
  }

  if (!Array.isArray(changes) || changes.length === 0) {
    return NextResponse.json({ error: 'Aucun changement à appliquer' }, { status: 400 })
  }

  const userId = (session.user as { id: string }).id
  const encoder = new TextEncoder()

  const stream = new ReadableStream({
    async start(controller) {
      const send = (event: SyncStreamEvent) => {
        controller.enqueue(encoder.encode(JSON.stringify(event) + '\n'))
      }

      const log: SyncLogEntry[] = []
      let created = 0, updated = 0, deactivated = 0, errors = 0
      const total = changes.filter((c) => c.type !== 'unchanged').length
      let current = 0

      for (const change of changes) {
        if (change.type === 'unchanged') continue
        current++

        try {
          if (change.type === 'create') {
            await createShopifyProduct(change.sheetProduct!)
            created++
            const msg = `✓ ${change.ref} créé`
            log.push({ ref: change.ref, action: 'create', status: 'success', message: msg })
            send({ type: 'progress', current, total, message: msg })

          } else if (change.type === 'update') {
            const variantId = await getFirstVariantId(change.shopifyProduct!.shopifyId)
            await updateShopifyProduct(
              change.shopifyProduct!.shopifyId,
              change.sheetProduct!,
              variantId,
            )
            updated++
            const fields = change.changedFields?.map((f) => f.field).join(', ') ?? ''
            const msg = `✓ ${change.ref} mis à jour (${fields})`
            log.push({ ref: change.ref, action: 'update', status: 'success', message: msg })
            send({ type: 'progress', current, total, message: msg })

          } else if (change.type === 'deactivate') {
            await deactivateShopifyProduct(change.shopifyProduct!.shopifyId)
            deactivated++
            const msg = `✓ ${change.ref} désactivé`
            log.push({ ref: change.ref, action: 'deactivate', status: 'success', message: msg })
            send({ type: 'progress', current, total, message: msg })
          }
        } catch (err) {
          errors++
          const msg = `✗ ${change.ref} : ${(err as Error).message}`
          log.push({ ref: change.ref, action: change.type as SyncLogEntry['action'], status: 'error', message: msg })
          send({ type: 'progress', current, total, message: msg })
        }
      }

      const syncStatus = errors === 0 ? 'success' : errors === total ? 'error' : 'partial'
      try {
        await prisma.syncRun.create({
          data: {
            userId,
            status: syncStatus,
            created,
            updated,
            deactivated,
            errors,
            log: JSON.stringify(log),
          },
        })
      } catch (dbErr) {
        console.error('Erreur sauvegarde SyncRun:', dbErr)
      }

      send({
        type: 'done',
        summary: { created, updated, deactivated, errors, status: syncStatus },
      })
      controller.close()
    },
  })

  return new Response(stream, {
    headers: { 'Content-Type': 'application/x-ndjson; charset=utf-8' },
  })
}