/**
 * Migration orchestrator: coordinates the data migration from
 * an external accounting system directly via provider APIs into gnubok.
 *
 * Bookkeeping data (accounts, balances, vouchers) is imported
 * via SIE files through the core SIE import engine. This orchestrator
 * handles only entity-level imports:
 *   1. Company info → pre-fill company_settings
 *   2. Customers → needed before sales invoices
 *   3. Suppliers → needed before supplier invoices
 *   4. Sales invoices (all statuses, duplicates skipped)
 *   5. Supplier invoices (all statuses, duplicates skipped)
 *   6. Asset register (Fortnox only) → asset register rows, no journal entries
 *
 * Performance note: All steps use bulk reads + chunked inserts to
 * avoid N+1 round-trips that would exhaust the Vercel function
 * timeout (300s hard cap). A typical import with a few thousand
 * entities completes in a handful of Supabase requests per step.
 */

import { chunk } from '@/lib/utils'
import type { SupabaseClient } from '@supabase/supabase-js'
import type { MigrationProgress, MigrationResults, MigrationStepError, SkipReasons } from '../types'
import type { ProviderName } from '@/lib/providers/types'
import { classifyProviderError } from '@/lib/providers/with-provider-call'
import { fortnoxErrorMessage } from '@/lib/providers/fortnox/client'
import { getErrorEntry } from '@/lib/errors/structured-errors'
import { getProviderResourceForbiddenMessage } from '@/lib/errors/get-error-message'
import type { CustomerDto, SupplierDto, SalesInvoiceDto, SupplierInvoiceDto, PartyDto } from '@/lib/providers/dto'
import { resolveConsent } from '@/lib/providers/resolve-consent'
import { normalizeVatNumber, isValidSwedishVatNumber } from '@/lib/vat/vat-number'
import {
  fetchCompanyInfoDirect,
  fetchCustomersDirect,
  fetchSuppliersDirect,
  fetchSalesInvoicesHydrated,
  fetchSupplierInvoicesHydrated,
} from '@/lib/providers/provider-data-fetcher'
import { fetchAllRows } from '@/lib/supabase/fetch-all'
import { createLogger } from '@/lib/logger'
import { reconcileSupplierInvoiceVouchers } from '@/lib/invoices/bulk-reconcile-supplier-vouchers'
import {
  linkMigratedRegistrationVouchers,
  type MigratedInvoiceLinkInput,
} from '@/lib/invoices/link-migrated-registration-vouchers'
import {
  buildCustomerMetadataEnrichment,
  type CustomerMetadataEnrichment,
  type ExistingCustomerMetadata,
} from './customer-metadata'
import { insertWithPerRowFallback } from './insert-fallback'
import { importProviderAssets, FortnoxAssetScopesRequiredError } from './import-assets'
import {
  mapCustomer,
  mapSupplier,
  mapSalesInvoice,
  mapSupplierInvoice,
  mapCompanyInfo,
  inferTypeFromParty,
  buildFxRateIndex,
  type FxUnresolved,
} from './entity-mapper'

const log = createLogger('extensions/arcim-migration/migration-orchestrator')

export interface MigrationOptions {
  consentId: string
  companyId: string
  userId: string
  supabase: SupabaseClient
  importCompanyInfo?: boolean
  importCustomers?: boolean
  importSuppliers?: boolean
  importSalesInvoices?: boolean
  importSupplierInvoices?: boolean
  /** Import the provider's asset register (Fortnox only). Default true. */
  importAssets?: boolean
  /** Auto-link imported supplier invoices to GL payment vouchers. Default true. */
  reconcileVouchers?: boolean
  onProgress?: (progress: MigrationProgress) => void
}

/**
 * Chunk size for bulk inserts. 500 rows/request keeps payloads below
 * PostgREST's practical size limit while minimising round-trips.
 */
const INSERT_CHUNK_SIZE = 500
const ENRICHMENT_CONCURRENCY = 10

function emitProgress(options: MigrationOptions, progress: MigrationProgress) {
  options.onProgress?.(progress)
}

/**
 * Codes that doom every remaining provider call in this run: dead/expired
 * grant, missing integration license, API module not activated. Continuing
 * would fail four more times with the same cause and then report a
 * "successful" migration with zero rows (the failure mode that sent a real
 * config issue to the bug tracker). Rethrow so /migrate answers with the
 * structured code and the wizard shows the actual remediation.
 *
 * PROVIDER_RESOURCE_FORBIDDEN is deliberately NOT here: it means the grant
 * answered other calls in this same run and only one register is closed, so
 * the remaining steps have every chance of succeeding.
 */
const FATAL_STEP_ERROR_CODES = new Set([
  'PROVIDER_AUTH_EXPIRED',
  'PROVIDER_LICENSE_MISSING',
  'PROVIDER_API_MODULE_INACTIVE',
])

/**
 * What this run has learned about the grant, threaded through the steps so a
 * later failure can be read in context.
 */
interface ProviderRunState {
  /**
   * True once any provider fetch in this run has returned data: the access
   * token provably works, so a 403 after that point is the provider closing
   * one register, not the grant dying.
   *
   * Set it from rows actually returned, never from a fetch that merely
   * resolved. fetchCustomersDirect and friends answer [] without issuing any
   * request when the provider needs a company id this consent has none of
   * (Bokio, Björn Lundén) or does not expose the register at all (WINT
   * suppliers), and a step that never spoke to the provider proves nothing
   * about the grant. Reading it as proof would downgrade a genuine auth
   * expiry on the NEXT step to a non-fatal per-register denial, and the run
   * would report success with empty sections: exactly what
   * FATAL_STEP_ERROR_CODES exists to prevent. An empty but real answer only
   * costs the better message on a later 403, so under-claiming is the safe
   * direction.
   */
  grantProven: boolean
}

/**
 * Record a failed step on the results so the UI can render it. Non-fatal
 * failures keep the log-and-continue behavior (one bad step must not discard
 * the others' already-persisted rows); fatal connection-level failures
 * rethrow, see FATAL_STEP_ERROR_CODES.
 */
function recordStepError(
  results: MigrationResults,
  step: MigrationStepError['step'],
  err: unknown,
  runState: ProviderRunState,
): void {
  // Company information is step 1, so grantProven is false there by
  // definition. Its 403 is still no proof of a dead grant: the fetch used to
  // swallow every error and return null, and a grant that really is dead says
  // so on the next step, which stays fatal. Letting the opening call abort the
  // run would turn a partial import into no import at all.
  const grantProven = runState.grantProven || step === 'companyInfo'
  const code = classifyProviderError(err, { grantProven })
  if (code && FATAL_STEP_ERROR_CODES.has(code)) throw err

  const rawMessage = err instanceof Error ? err.message : String(err)
  const entry = code ? getErrorEntry(code) : undefined
  let message: string
  if (code === 'PROVIDER_RESOURCE_FORBIDDEN') {
    // The registry cannot hold this copy: the useful half is the provider's
    // own sentence naming the register, which only the error carries. Fortnox
    // is the one provider that sends it (fortnoxErrorMessage caps it at 300
    // chars); the others send an opaque body and get the base message alone.
    message = getProviderResourceForbiddenMessage(fortnoxErrorMessage(err))
  } else {
    message = entry?.message_sv ?? `Leverantören svarade med ett fel: ${rawMessage}`
  }

  results.stepErrors = results.stepErrors ?? []
  results.stepErrors.push({ step, code, message })
}

function getOrgNumberFromParty(party: PartyDto): string | null {
  return (
    party.legalEntity?.companyId ||
    party.identifications?.find((i) => i.schemeId === 'SE:ORGNR')?.id ||
    null
  )
}

/**
 * Log a foreign-currency document that was imported WITHOUT a SEK conversion.
 *
 * It is still imported (dropping it would lose räkenskapsinformation), but it
 * carries exchange_rate = null, so every booking path refuses it loudly rather
 * than posting it as if 1 unit = 1 SEK. Counted into the step's result so the
 * migration reports it instead of passing it off as an ordinary import.
 */
function logFxUnresolved(kind: string, invoiceNumber: string, fx: FxUnresolved): void {
  // Structured logger, not console.error: the record passes the observability
  // redaction pipeline (lib/observability/redact.ts) before it can reach any
  // sink, so invoice identifiers in log output stay inside the same PII
  // controls as every other server log line.
  log.error('document imported without a SEK conversion; set an exchange rate before booking it', {
    entityType: kind,
    entityId: invoiceNumber,
    currency: fx.currency,
    documentDate: fx.date || null,
    reason: fx.reason,
  })
}

// ── Main orchestrator ─────────────────────────────────────────────

export async function executeMigration(options: MigrationOptions): Promise<MigrationResults> {
  const { consentId, companyId, userId, supabase } = options
  const results: MigrationResults = {}
  // What this run has proven about the grant, read by recordStepError: a 403
  // once a call has already succeeded is one closed register, not a dead token.
  const runState: ProviderRunState = { grantProven: false }
  // Every invoice this run inserted, with the booking voucher the provider
  // named for it. Linked to the SIE-imported registration verifikat after both
  // invoice steps (see the registration-link step below).
  const registrationLinkInputs: MigratedInvoiceLinkInput[] = []

  // Resolve consent to get access token and provider
  const resolved = await resolveConsent(companyId, consentId)
  const provider = resolved.consent.provider as ProviderName
  const accessToken = resolved.accessToken
  const providerCompanyId = resolved.providerCompanyId

  try {
    // ── Step 1: Company information ───────────────────────────────
    if (options.importCompanyInfo !== false) {
      emitProgress(options, { status: 'fetching', currentStep: 'Hämtar företagsinformation...', progress: 5 })
      try {
        const companyInfo = await fetchCompanyInfoDirect(provider, accessToken, providerCompanyId)
        if (companyInfo) {
          // A DTO means the provider answered on this token. A null does not:
          // it also means "no company-information resource for this provider",
          // which is decided before any request goes out.
          runState.grantProven = true
          const mapped = mapCompanyInfo(companyInfo)
          const { data: existing } = await supabase
            .from('company_settings')
            .select('company_name, org_number, vat_number')
            .eq('company_id', companyId)
            .single()

          const updates: Record<string, unknown> = {}
          if (!existing?.company_name && mapped.company_name) updates.company_name = mapped.company_name
          if (!existing?.org_number && mapped.org_number) updates.org_number = mapped.org_number
          if (!existing?.vat_number && mapped.vat_number) {
            // Normalise provider input; only persist a structurally valid
            // SE+12 momsregistreringsnummer so a malformed value from an
            // external API can't enter company_settings unchecked.
            const normalizedVat = normalizeVatNumber(mapped.vat_number)
            if (isValidSwedishVatNumber(normalizedVat)) {
              updates.vat_number = normalizedVat
              updates.vat_registered = true
            } else {
              // Observability: a provider sent a VAT number we can't normalise
              // to a valid SE+12 momsregistreringsnummer. We drop it (above),
              // but surface the anomaly so consistently-bad provider data is
              // visible. Don't log the raw value: it can embed a personnummer.
              console.warn(
                `[migration] Dropped malformed VAT number from ${provider} for company ${companyId} (normalized length ${normalizedVat.length})`,
              )
            }
          }
          if (mapped.fiscal_year_start_month !== 1) {
            updates.fiscal_year_start_month = mapped.fiscal_year_start_month
          }
          if (mapped.address_line1) updates.address_line1 = mapped.address_line1
          if (mapped.postal_code) updates.postal_code = mapped.postal_code
          if (mapped.city) updates.city = mapped.city
          if (mapped.phone) updates.phone = mapped.phone
          if (mapped.email) updates.email = mapped.email

          if (Object.keys(updates).length > 0) {
            await supabase.from('company_settings').update(updates).eq('company_id', companyId)
          }
          results.companyInfo = { imported: true }
        }
      } catch (err) {
        console.error('Failed to import company info:', err)
        results.companyInfo = { imported: false }
        recordStepError(results, 'companyInfo', err, runState)
      }
    }

    // ── Step 2: Customers (bulk) ──────────────────────────────────
    // customerIdMap: provider customer id → Accounted customer id.
    // orgNumberToCustomerId / nameToCustomerId speed up invoice lookup
    // without extra queries later.
    const customerIdMap = new Map<string, string>()
    const orgNumberToCustomerId = new Map<string, string>()
    const nameToCustomerId = new Map<string, string>()

    if (options.importCustomers !== false) {
      emitProgress(options, { status: 'importing', currentStep: 'Importerar kunder...', progress: 20 })
      try {
        const customers = await fetchCustomersDirect(provider, accessToken, providerCompanyId)
        // Rows, not a resolved promise: see ProviderRunState.grantProven.
        if (customers.length > 0) runState.grantProven = true

        // One bulk read instead of N `.eq('org_number', ...)` lookups.
        type ExistingCustomer = ExistingCustomerMetadata & {
          id: string
          org_number: string | null
          name: string | null
        }
        const existingCustomers = await fetchAllRows<ExistingCustomer>(
          ({ from, to }) =>
            supabase
              .from('customers')
              .select('id, org_number, name, contact_person, invoice_email_cc_addresses, invoice_email_bcc_addresses')
              .eq('company_id', companyId)
              .range(from, to)
        )
        const existingCustomerById = new Map(existingCustomers.map((row) => [row.id, row]))
        for (const row of existingCustomers) {
          if (row.org_number) orgNumberToCustomerId.set(row.org_number, row.id)
          if (row.name) nameToCustomerId.set(row.name, row.id)
        }

        let imported = 0
        let updated = 0
        let skipped = 0
        const skipReasons: SkipReasons = {}
        let errorSample: string | null = null

        type PendingCustomer = {
          dto: CustomerDto
          row: Record<string, unknown>
        }
        const pending: PendingCustomer[] = []
        const pendingEnrichments: { id: string; changes: CustomerMetadataEnrichment }[] = []
        // Providers can hand back the same record more than once (a paging
        // fault upstream, or genuine source duplicates). The DB-backed maps
        // above only know rows that existed BEFORE this run, so without an
        // in-run key set every repeat would be inserted again.
        const pendingCustomerKeys = new Set<string>()

        for (const customer of customers) {
          if (!customer.active) {
            skipReasons.inactive = (skipReasons.inactive ?? 0) + 1
            skipped++
            continue
          }

          // Dedup against already-imported records: prefer org-number, but fall
          // back to name when the party has no org-number. Otherwise org-less
          // customers (private persons) are re-created on every re-sync, since
          // the org-number map can never match them.
          const orgNumber = getOrgNumberFromParty(customer.party)
          const existingCustomerId = orgNumber
            ? orgNumberToCustomerId.get(orgNumber)
            : customer.party.name
              ? nameToCustomerId.get(customer.party.name)
              : undefined
          if (existingCustomerId) {
            customerIdMap.set(customer.id, existingCustomerId)
            const existingCustomer = existingCustomerById.get(existingCustomerId)
            const mapped = mapCustomer(customer, userId, companyId)
            const changes = existingCustomer
              ? buildCustomerMetadataEnrichment(existingCustomer, mapped)
              : null
            if (changes) {
              pendingEnrichments.push({ id: existingCustomerId, changes })
            } else {
              skipReasons.duplicate = (skipReasons.duplicate ?? 0) + 1
              skipped++
            }
            continue
          }

          const pendingKey = (orgNumber ?? `name:${customer.party.name?.toLowerCase() ?? ''}`).trim()
          if (pendingCustomerKeys.has(pendingKey)) {
            skipReasons.duplicate = (skipReasons.duplicate ?? 0) + 1
            skipped++
            continue
          }
          pendingCustomerKeys.add(pendingKey)

          pending.push({ dto: customer, row: mapCustomer(customer, userId, companyId) })
        }

        for (const batch of chunk(pending, INSERT_CHUNK_SIZE)) {
          const outcome = await insertWithPerRowFallback(
            supabase, 'customers', batch.map((p) => p.row), 'id, org_number, name'
          )

          if (outcome.failedCount > 0) {
            console.error(
              `[migration] Customer insert failed for ${outcome.failedCount} of ${batch.length} rows:`,
              outcome.firstError
            )
            skipReasons.failed = (skipReasons.failed ?? 0) + outcome.failedCount
            skipped += outcome.failedCount
            errorSample ??= outcome.firstError
          }

          for (let i = 0; i < batch.length; i++) {
            const insertedRow = outcome.returned[i]
            if (!insertedRow) continue
            const providerId = batch[i].dto.id
            const newId = insertedRow.id as string
            customerIdMap.set(providerId, newId)
            if (insertedRow.org_number) orgNumberToCustomerId.set(insertedRow.org_number as string, newId)
            if (insertedRow.name) nameToCustomerId.set(insertedRow.name as string, newId)
            imported++
          }
        }

        // A rerun can match hundreds of legacy customers. Update only rows
        // that actually have new provider metadata, with bounded concurrency,
        // so enrichment neither overwrites edits nor serializes the migration.
        for (const batch of chunk(pendingEnrichments, ENRICHMENT_CONCURRENCY)) {
          const outcomes = await Promise.all(batch.map(async ({ id, changes }) => {
            const { data, error } = await supabase
              .from('customers')
              // Object literal, not the record itself: absent keys serialize
              // away, and the phantom-column guard can resolve the columns.
              .update({
                contact_person: changes.contact_person,
                invoice_email_cc_addresses: changes.invoice_email_cc_addresses,
                invoice_email_bcc_addresses: changes.invoice_email_bcc_addresses,
              })
              .eq('id', id)
              .eq('company_id', companyId)
              .select('id')
              .maybeSingle()
            return { data, error }
          }))

          for (const outcome of outcomes) {
            if (outcome.error || !outcome.data) {
              if (outcome.error) {
                console.error('[migration] Customer metadata enrichment failed:', outcome.error.message)
                errorSample ??= outcome.error.message
              }
              skipReasons.failed = (skipReasons.failed ?? 0) + 1
              skipped++
            } else {
              updated++
            }
          }
        }

        results.customers = { total: customers.length, imported, updated, skipped, skipReasons, errorSample: errorSample ?? undefined }
      } catch (err) {
        console.error('Failed to import customers:', err)
        recordStepError(results, 'customers', err, runState)
      }
    }

    // ── Step 3: Suppliers (bulk) ──────────────────────────────────
    const supplierIdMap = new Map<string, string>()
    const orgNumberToSupplierId = new Map<string, string>()
    const nameToSupplierId = new Map<string, string>()

    if (options.importSuppliers !== false) {
      emitProgress(options, { status: 'importing', currentStep: 'Importerar leverantörer...', progress: 40 })
      try {
        const suppliers = await fetchSuppliersDirect(provider, accessToken, providerCompanyId)
        if (suppliers.length > 0) runState.grantProven = true

        const existingSuppliers = await fetchAllRows<{ id: string; org_number: string | null; name: string | null }>(
          ({ from, to }) =>
            supabase
              .from('suppliers')
              .select('id, org_number, name')
              .eq('company_id', companyId)
              .range(from, to)
        )
        for (const row of existingSuppliers) {
          if (row.org_number) orgNumberToSupplierId.set(row.org_number, row.id)
          if (row.name) nameToSupplierId.set(row.name, row.id)
        }

        let imported = 0
        let skipped = 0
        const skipReasons: SkipReasons = {}
        let errorSample: string | null = null

        type PendingSupplier = { dto: SupplierDto; row: Record<string, unknown> }
        const pending: PendingSupplier[] = []
        // Same in-run repeat guard as customers.
        const pendingSupplierKeys = new Set<string>()

        for (const supplier of suppliers) {
          if (!supplier.active) {
            skipReasons.inactive = (skipReasons.inactive ?? 0) + 1
            skipped++
            continue
          }

          // Same org-number-then-name dedup as customers, so org-less suppliers
          // (e.g. PostNord, IKANO BANK) aren't duplicated on every re-sync.
          const orgNumber = getOrgNumberFromParty(supplier.party)
          const existingSupplierId = orgNumber
            ? orgNumberToSupplierId.get(orgNumber)
            : supplier.party.name
              ? nameToSupplierId.get(supplier.party.name)
              : undefined
          if (existingSupplierId) {
            supplierIdMap.set(supplier.id, existingSupplierId)
            skipReasons.duplicate = (skipReasons.duplicate ?? 0) + 1
            skipped++
            continue
          }

          const pendingKey = (orgNumber ?? `name:${supplier.party.name?.toLowerCase() ?? ''}`).trim()
          if (pendingSupplierKeys.has(pendingKey)) {
            skipReasons.duplicate = (skipReasons.duplicate ?? 0) + 1
            skipped++
            continue
          }
          pendingSupplierKeys.add(pendingKey)

          pending.push({ dto: supplier, row: mapSupplier(supplier, userId, companyId) })
        }

        for (const batch of chunk(pending, INSERT_CHUNK_SIZE)) {
          const outcome = await insertWithPerRowFallback(
            supabase, 'suppliers', batch.map((p) => p.row), 'id, org_number, name'
          )

          if (outcome.failedCount > 0) {
            console.error(
              `[migration] Supplier insert failed for ${outcome.failedCount} of ${batch.length} rows:`,
              outcome.firstError
            )
            skipReasons.failed = (skipReasons.failed ?? 0) + outcome.failedCount
            skipped += outcome.failedCount
            errorSample ??= outcome.firstError
          }

          for (let i = 0; i < batch.length; i++) {
            const insertedRow = outcome.returned[i]
            if (!insertedRow) continue
            const providerId = batch[i].dto.id
            const newId = insertedRow.id as string
            supplierIdMap.set(providerId, newId)
            if (insertedRow.org_number) orgNumberToSupplierId.set(insertedRow.org_number as string, newId)
            if (insertedRow.name) nameToSupplierId.set(insertedRow.name as string, newId)
            imported++
          }
        }

        results.suppliers = { total: suppliers.length, imported, skipped, skipReasons, errorSample: errorSample ?? undefined }
      } catch (err) {
        console.error('Failed to import suppliers:', err)
        recordStepError(results, 'suppliers', err, runState)
      }
    }

    // ── Step 4: Sales invoices (bulk) ─────────────────────────────
    if (options.importSalesInvoices !== false) {
      emitProgress(options, { status: 'importing', currentStep: 'Importerar kundfakturor...', progress: 60 })
      try {
        // Hydrated, not the bare list: the list payload omits VAT, the net
        // and the line items for most providers (see provider-data-fetcher).
        const { invoices, hydration, unhydratedIds } = await fetchSalesInvoicesHydrated(
          provider, accessToken, providerCompanyId,
        )
        if (invoices.length > 0) runState.grantProven = true
        console.log(`[migration] Sales invoices: ${invoices.length} total`)

        // Bulk-load existing invoice numbers once.
        const existingInvoices = await fetchAllRows<{ invoice_number: string }>(({ from, to }) =>
          supabase
            .from('invoices')
            .select('invoice_number')
            .eq('company_id', companyId)
            .range(from, to)
        )
        const existingInvoiceNumbers = new Set(existingInvoices.map((r) => r.invoice_number))

        let imported = 0
        let skipped = 0
        const skipReasons: SkipReasons = {}
        let errorSample: string | null = null
        // invoice_number carries a UNIQUE (company_id, invoice_number) index,
        // so a repeated number WITHIN the fetched set (paging fault or source
        // duplicate) must be skipped here: inside one insert statement it
        // would reject the whole chunk. Empty numbers are exempt: they are
        // stored as NULL, which the partial index does not cover.
        const seenInvoiceNumbers = new Set<string>()

        // Phase A: resolve customer for each invoice; collect those that
        // need a minimal customer record to be created on-the-fly.
        type ResolvedInvoice = { dto: SalesInvoiceDto; customerId: string }
        const resolved: ResolvedInvoice[] = []

        type NewCustomerStub = {
          key: string // dedupe key (orgNumber or lowercased name)
          row: Record<string, unknown>
          // invoices waiting for this stub's id
          waitingInvoiceIndices: number[]
        }
        const stubByKey = new Map<string, NewCustomerStub>()
        const stubsForThisBatch: { orgNumber: string | null; name: string }[] = []

        for (const inv of invoices) {
          if (existingInvoiceNumbers.has(inv.invoiceNumber)) {
            skipReasons.duplicate = (skipReasons.duplicate ?? 0) + 1
            skipped++
            continue
          }
          if (inv.invoiceNumber) {
            if (seenInvoiceNumbers.has(inv.invoiceNumber)) {
              skipReasons.duplicate = (skipReasons.duplicate ?? 0) + 1
              skipped++
              continue
            }
            seenInvoiceNumbers.add(inv.invoiceNumber)
          }

          const customerOrgNumber = getOrgNumberFromParty(inv.customer)
          let customerId: string | null = null

          if (customerOrgNumber && orgNumberToCustomerId.has(customerOrgNumber)) {
            customerId = orgNumberToCustomerId.get(customerOrgNumber)!
          } else if (nameToCustomerId.has(inv.customer.name)) {
            customerId = nameToCustomerId.get(inv.customer.name)!
          }

          if (customerId) {
            resolved.push({ dto: inv, customerId })
            continue
          }

          // Need to create a minimal customer: dedupe by org number first,
          // then by name, so invoices sharing a missing party only create
          // one stub row.
          const key = (customerOrgNumber ?? `name:${inv.customer.name.toLowerCase()}`).trim()
          let stub = stubByKey.get(key)
          if (!stub) {
            const customerType = inferTypeFromParty(inv.customer)
            const minimalCustomer = {
              user_id: userId,
              company_id: companyId,
              name: inv.customer.name,
              customer_type: customerType,
              default_payment_terms: 30,
              country:
                inv.customer.postalAddress?.countryCode ||
                (customerType === 'swedish_business' ? 'SE' : null),
              vat_number_validated: false,
              org_number: customerOrgNumber,
            }
            stub = { key, row: minimalCustomer, waitingInvoiceIndices: [] }
            stubByKey.set(key, stub)
            stubsForThisBatch.push({ orgNumber: customerOrgNumber, name: inv.customer.name })
          }
          // reserve slot; we'll backfill customerId after stubs insert
          const placeholderIndex = resolved.length
          resolved.push({ dto: inv, customerId: '' })
          stub.waitingInvoiceIndices.push(placeholderIndex)
        }

        // Phase B: insert any missing customer stubs in chunks.
        if (stubByKey.size > 0) {
          const stubList = [...stubByKey.values()]
          for (const batch of chunk(stubList, INSERT_CHUNK_SIZE)) {
            const outcome = await insertWithPerRowFallback(
              supabase, 'customers', batch.map((s) => s.row), 'id, org_number, name'
            )

            if (outcome.failedCount > 0) {
              console.error(
                `[migration] Sales invoice customer stub insert failed for ${outcome.failedCount} of ${batch.length} rows:`,
                outcome.firstError
              )
              errorSample ??= outcome.firstError
            }

            for (let i = 0; i < batch.length; i++) {
              const insertedRow = outcome.returned[i]
              if (!insertedRow) {
                // Mark invoices waiting on this failed stub as no-match
                for (const idx of batch[i].waitingInvoiceIndices) {
                  resolved[idx] = { ...resolved[idx], customerId: '__FAILED__' }
                }
                continue
              }
              const newId = insertedRow.id as string
              if (insertedRow.org_number) orgNumberToCustomerId.set(insertedRow.org_number as string, newId)
              if (insertedRow.name) nameToCustomerId.set(insertedRow.name as string, newId)
              for (const idx of batch[i].waitingInvoiceIndices) {
                resolved[idx] = { ...resolved[idx], customerId: newId }
              }
            }
          }
        }

        // Drop invoices whose customer couldn't be created. That is a DB
        // failure (the stub insert errored, errorSample carries it), not a
        // matching miss: counting it as noMatch would render a green result
        // row with the database error hidden.
        const ready = resolved.filter((r) => {
          if (r.customerId === '__FAILED__') {
            skipReasons.failed = (skipReasons.failed ?? 0) + 1
            skipped++
            return false
          }
          return !!r.customerId
        })

        // Phase B2: resolve the SEK conversion for every foreign-currency
        // invoice, at the rate valid on its OWN issue date. The provider DTO
        // carries no rate and no SEK amount, so without this every foreign
        // invoice lands unconverted. One pass over the whole step (not per
        // chunk) so repeat (currency, date) pairs are fetched once.
        const fxRates = await buildFxRateIndex(
          supabase,
          ready.map((r) => ({ currencyCode: r.dto.currencyCode, issueDate: r.dto.issueDate }))
        )
        let fxUnresolved = 0
        let vatUnresolved = 0
        let creditNotesUnlinked = 0

        // Phase C: chunk-insert invoices + their line items.
        for (const batch of chunk(ready, INSERT_CHUNK_SIZE)) {
          const mappedBatch = batch.map((r) => ({
            ...mapSalesInvoice(r.dto, userId, companyId, r.customerId, fxRates),
            dto: r.dto,
          }))

          const outcome = await insertWithPerRowFallback(
            supabase, 'invoices', mappedBatch.map((m) => m.invoice), 'id'
          )

          if (outcome.failedCount > 0) {
            console.error(
              `[migration] Sales invoice insert failed for ${outcome.failedCount} of ${batch.length} rows:`,
              outcome.firstError
            )
            skipReasons.failed = (skipReasons.failed ?? 0) + outcome.failedCount
            skipped += outcome.failedCount
            errorSample ??= outcome.firstError
          }

          const allItems: Record<string, unknown>[] = []
          for (let i = 0; i < mappedBatch.length; i++) {
            const insertedRow = outcome.returned[i]
            if (!insertedRow) continue
            const invoiceId = insertedRow.id
            for (const item of mappedBatch[i].items) {
              allItems.push({ ...item, invoice_id: invoiceId })
            }
            registrationLinkInputs.push({
              invoiceId: String(invoiceId),
              kind: 'customer',
              sourceVoucher: mappedBatch[i].dto.sourceVoucher ?? null,
              refNotFetched: unhydratedIds.has(mappedBatch[i].dto.id),
              invoiceDate: mappedBatch[i].dto.issueDate,
              totalSek: mappedBatch[i].invoice.total_sek as number | null,
              currencyCode: mappedBatch[i].dto.currencyCode || 'SEK',
              invoiceNumber: mappedBatch[i].dto.invoiceNumber || null,
            })
            const fx = mappedBatch[i].fxUnresolved
            if (fx) {
              fxUnresolved++
              logFxUnresolved('Sales invoice', mappedBatch[i].dto.invoiceNumber, fx)
            }
            if (mappedBatch[i].vatUnresolved) {
              vatUnresolved++
              console.warn(
                `[migration] Sales invoice ${mappedBatch[i].dto.invoiceNumber}: no VAT in provider payload; `
                + 'imported with gross as subtotal and a null rate.'
              )
            }
            if (mappedBatch[i].creditNoteUnlinked) {
              creditNotesUnlinked++
            }
            imported++
          }

          if (allItems.length > 0) {
            for (const itemBatch of chunk(allItems, INSERT_CHUNK_SIZE)) {
              const { error: itemErr } = await supabase.from('invoice_items').insert(itemBatch)
              if (itemErr) {
                console.error(`[migration] Sales invoice items insert failed (${itemBatch.length}):`, itemErr.message)
              }
            }
          }
        }

        results.salesInvoices = { total: invoices.length, imported, skipped, skipReasons, fxUnresolved, vatUnresolved, creditNotesUnlinked, hydration, errorSample: errorSample ?? undefined }
      } catch (err) {
        console.error('Failed to import sales invoices:', err)
        recordStepError(results, 'salesInvoices', err, runState)
      }
    }

    // ── Step 5: Supplier invoices (bulk) ──────────────────────────
    if (options.importSupplierInvoices !== false) {
      emitProgress(options, { status: 'importing', currentStep: 'Importerar leverantörsfakturor...', progress: 80 })
      try {
        const { invoices, hydration, unhydratedIds } = await fetchSupplierInvoicesHydrated(
          provider, accessToken, providerCompanyId,
        )
        if (invoices.length > 0) runState.grantProven = true
        console.log(`[migration] Supplier invoices: ${invoices.length} total`)

        // Load existing (supplier_invoice_number, supplier_id) pairs once.
        const existingSuppInv = await fetchAllRows<{
          supplier_invoice_number: string | null
          supplier_id: string | null
        }>(({ from, to }) =>
          supabase
            .from('supplier_invoices')
            .select('supplier_invoice_number, supplier_id')
            .eq('company_id', companyId)
            .range(from, to)
        )
        const existingSuppInvKeys = new Set(
          existingSuppInv
            .filter((r) => r.supplier_invoice_number && r.supplier_id)
            .map((r) => `${r.supplier_id}::${r.supplier_invoice_number}`)
        )

        // Compute next arrival number locally. Unique index is
        // (company_id, arrival_number); we're the only writer during
        // migration so incrementing in-memory is safe.
        const { data: maxRow } = await supabase
          .from('supplier_invoices')
          .select('arrival_number')
          .eq('company_id', companyId)
          .order('arrival_number', { ascending: false })
          .limit(1)
          .maybeSingle()
        let nextArrivalNumber = ((maxRow?.arrival_number as number | undefined) ?? 0) + 1

        let imported = 0
        let skipped = 0
        const skipReasons: SkipReasons = {}
        let errorSample: string | null = null

        type ResolvedSupplierInvoice = { dto: SupplierInvoiceDto; supplierId: string }
        const resolved: ResolvedSupplierInvoice[] = []

        type NewSupplierStub = {
          key: string
          row: Record<string, unknown>
          waitingInvoiceIndices: number[]
        }
        const stubByKey = new Map<string, NewSupplierStub>()

        for (const inv of invoices) {
          const supplierOrgNumber = getOrgNumberFromParty(inv.supplier)
          let supplierId: string | null = null

          if (supplierOrgNumber && orgNumberToSupplierId.has(supplierOrgNumber)) {
            supplierId = orgNumberToSupplierId.get(supplierOrgNumber)!
          } else if (nameToSupplierId.has(inv.supplier.name)) {
            supplierId = nameToSupplierId.get(inv.supplier.name)!
          }

          if (supplierId) {
            const dupKey = `${supplierId}::${inv.invoiceNumber}`
            if (existingSuppInvKeys.has(dupKey)) {
              skipReasons.duplicate = (skipReasons.duplicate ?? 0) + 1
              skipped++
              continue
            }
            resolved.push({ dto: inv, supplierId })
            continue
          }

          // Need to create a minimal supplier: dedupe the same way as customers.
          const key = (supplierOrgNumber ?? `name:${inv.supplier.name.toLowerCase()}`).trim()
          let stub = stubByKey.get(key)
          if (!stub) {
            const supplierType = inferTypeFromParty(inv.supplier)
            const minimalSupplier = {
              user_id: userId,
              company_id: companyId,
              name: inv.supplier.name,
              supplier_type: supplierType,
              default_payment_terms: 30,
              default_currency: 'SEK',
              country:
                inv.supplier.postalAddress?.countryCode ||
                (supplierType === 'swedish_business' ? 'SE' : null),
              org_number: supplierOrgNumber,
            }
            stub = { key, row: minimalSupplier, waitingInvoiceIndices: [] }
            stubByKey.set(key, stub)
          }
          const placeholderIndex = resolved.length
          resolved.push({ dto: inv, supplierId: '' })
          stub.waitingInvoiceIndices.push(placeholderIndex)
        }

        if (stubByKey.size > 0) {
          const stubList = [...stubByKey.values()]
          for (const batch of chunk(stubList, INSERT_CHUNK_SIZE)) {
            const outcome = await insertWithPerRowFallback(
              supabase, 'suppliers', batch.map((s) => s.row), 'id, org_number, name'
            )

            if (outcome.failedCount > 0) {
              console.error(
                `[migration] Supplier invoice supplier stub insert failed for ${outcome.failedCount} of ${batch.length} rows:`,
                outcome.firstError
              )
              errorSample ??= outcome.firstError
            }

            for (let i = 0; i < batch.length; i++) {
              const insertedRow = outcome.returned[i]
              if (!insertedRow) {
                for (const idx of batch[i].waitingInvoiceIndices) {
                  resolved[idx] = { ...resolved[idx], supplierId: '__FAILED__' }
                }
                continue
              }
              const newId = insertedRow.id as string
              if (insertedRow.org_number) orgNumberToSupplierId.set(insertedRow.org_number as string, newId)
              if (insertedRow.name) nameToSupplierId.set(insertedRow.name as string, newId)
              for (const idx of batch[i].waitingInvoiceIndices) {
                resolved[idx] = { ...resolved[idx], supplierId: newId }
              }
            }
          }
        }

        // After stubs, do a final dedupe pass against existing supplier invoices
        // using the now-resolved supplierId. The in-run key set catches the
        // same (supplier, number) pair appearing twice in the fetched data,
        // which the UNIQUE (company_id, supplier_id, supplier_invoice_number)
        // index would otherwise reject mid-insert. NULL/empty numbers are
        // exempt: the index treats NULLs as distinct.
        const seenSuppInvKeys = new Set<string>()
        const ready = resolved.filter((r) => {
          if (r.supplierId === '__FAILED__' || !r.supplierId) {
            // Failed stub insert = DB failure with errorSample set, so count
            // it as failed; noMatch would hide the error in the result row.
            if (r.supplierId === '__FAILED__') {
              skipReasons.failed = (skipReasons.failed ?? 0) + 1
              skipped++
            }
            return false
          }
          if (r.dto.invoiceNumber) {
            const dupKey = `${r.supplierId}::${r.dto.invoiceNumber}`
            if (existingSuppInvKeys.has(dupKey) || seenSuppInvKeys.has(dupKey)) {
              skipReasons.duplicate = (skipReasons.duplicate ?? 0) + 1
              skipped++
              return false
            }
            seenSuppInvKeys.add(dupKey)
          }
          return true
        })

        // Resolve the SEK conversion for every foreign-currency invoice at the
        // rate valid on its OWN issue date (see the sales-invoice step).
        const fxRates = await buildFxRateIndex(
          supabase,
          ready.map((r) => ({ currencyCode: r.dto.currencyCode, issueDate: r.dto.issueDate }))
        )
        let fxUnresolved = 0
        let vatUnresolved = 0

        for (const batch of chunk(ready, INSERT_CHUNK_SIZE)) {
          const mappedBatch = batch.map((r) => {
            const { invoice, items, fxUnresolved: fx, vatUnresolved: vatMissing } = mapSupplierInvoice(
              r.dto, userId, companyId, r.supplierId, fxRates
            )
            invoice.arrival_number = nextArrivalNumber++
            return { invoice, items, fxUnresolved: fx, vatUnresolved: vatMissing, dto: r.dto }
          })

          const outcome = await insertWithPerRowFallback(
            supabase, 'supplier_invoices', mappedBatch.map((m) => m.invoice), 'id'
          )

          if (outcome.failedCount > 0) {
            console.error(
              `[migration] Supplier invoice insert failed for ${outcome.failedCount} of ${batch.length} rows:`,
              outcome.firstError
            )
            skipReasons.failed = (skipReasons.failed ?? 0) + outcome.failedCount
            skipped += outcome.failedCount
            errorSample ??= outcome.firstError
            // A failed row leaves a hole in the arrival numbering. That is
            // acceptable: ankomstnummer is an internal sequence, not a
            // verifikationsnummer, and rewinding the counter after a PARTIAL
            // success would hand out numbers that already landed.
          }

          const allItems: Record<string, unknown>[] = []
          for (let i = 0; i < mappedBatch.length; i++) {
            const insertedRow = outcome.returned[i]
            if (!insertedRow) continue
            const invoiceId = insertedRow.id
            for (const item of mappedBatch[i].items) {
              allItems.push({ ...item, supplier_invoice_id: invoiceId })
            }
            registrationLinkInputs.push({
              invoiceId: String(invoiceId),
              kind: 'supplier',
              sourceVoucher: mappedBatch[i].dto.sourceVoucher ?? null,
              refNotFetched: unhydratedIds.has(mappedBatch[i].dto.id),
              invoiceDate: mappedBatch[i].dto.issueDate,
              totalSek: mappedBatch[i].invoice.total_sek as number | null,
              currencyCode: mappedBatch[i].dto.currencyCode || 'SEK',
              invoiceNumber: mappedBatch[i].dto.invoiceNumber || null,
            })
            const fx = mappedBatch[i].fxUnresolved
            if (fx) {
              fxUnresolved++
              logFxUnresolved('Supplier invoice', mappedBatch[i].dto.invoiceNumber, fx)
            }
            if (mappedBatch[i].vatUnresolved) {
              vatUnresolved++
              console.warn(
                `[migration] Supplier invoice ${mappedBatch[i].dto.invoiceNumber}: no VAT in provider payload; `
                + 'imported with gross as subtotal.'
              )
            }
            imported++
          }

          if (allItems.length > 0) {
            for (const itemBatch of chunk(allItems, INSERT_CHUNK_SIZE)) {
              const { error: itemErr } = await supabase.from('supplier_invoice_items').insert(itemBatch)
              if (itemErr) {
                console.error(`[migration] Supplier invoice items insert failed (${itemBatch.length}):`, itemErr.message)
              }
            }
          }
        }

        results.supplierInvoices = { total: invoices.length, imported, skipped, skipReasons, fxUnresolved, vatUnresolved, hydration, errorSample: errorSample ?? undefined }
      } catch (err) {
        console.error('Failed to import supplier invoices:', err)
        recordStepError(results, 'supplierInvoices', err, runState)
      }
    }

    // ── Step 5b: Link imported invoices to their registration vouchers ──
    // The provider named the verifikat that booked each invoice ("A329");
    // the SIE import preserved that source ref on the entry it created. Link
    // the two where the match is exact and amount-corroborated, so migrated
    // invoices stop reading as unbooked. Writes only the invoice-side FK from
    // NULL; never touches journal entries. Best-effort like step 6: the
    // invoices are already persisted, and /reconcile can re-run this.
    if (registrationLinkInputs.length > 0) {
      emitProgress(options, { status: 'importing', currentStep: 'Kopplar fakturor till verifikationer...', progress: 90 })
      try {
        const links = await linkMigratedRegistrationVouchers({
          supabase,
          companyId,
          invoices: registrationLinkInputs,
        })
        results.registrationLinks = {
          scanned: links.scanned,
          linked: links.linked,
          noRef: links.noRef,
          refNotFetched: links.refNotFetched,
          unresolved: links.unresolved,
          ambiguous: links.ambiguous,
          amountMismatch: links.amountMismatch,
          alreadyLinked: links.alreadyLinked,
        }
        console.log(
          `[migration] Registration vouchers: ${links.linked} linked, ${links.noRef} without ref, ${links.refNotFetched} ref not fetched, ${links.unresolved} unresolved, `
          + `${links.ambiguous} ambiguous, ${links.amountMismatch} amount mismatch, ${links.alreadyLinked} already linked (${links.scanned} scanned)`,
        )
      } catch (err) {
        console.error('Failed to link registration vouchers:', err)
        recordStepError(results, 'registrationLinks', err, runState)
      }
    }

    // ── Step 5c: Asset register (Fortnox only) ─────────────────────
    // Register metadata only: the bookkeeping values (12xx anskaffning and
    // ackumulerade avskrivningar) already arrived via SIE, so this step never
    // writes journal entries. A consent without the Fortnox assets scope
    // reports scopesMissing instead of failing the migration.
    if (options.importAssets !== false) {
      emitProgress(options, { status: 'importing', currentStep: 'Importerar anläggningstillgångar...', progress: 92 })
      try {
        const assets = await importProviderAssets({ supabase, companyId, userId, consentId })
        if (assets) results.assets = assets
      } catch (err) {
        if (err instanceof FortnoxAssetScopesRequiredError) {
          log.warn('asset register skipped: consent lacks the Fortnox assets scope')
          results.assets = { total: 0, imported: 0, skipped: 0, scopesMissing: true }
        } else {
          console.error('Failed to import assets:', err)
          recordStepError(results, 'assets', err, runState)
        }
      }
    }

    // ── Step 6: Reconcile supplier invoices to GL payment vouchers ────
    // The GL (incl. the Dr 2440 / Cr 1930 bank-payment vouchers) is imported
    // separately via SIE. Supplier invoices arrive (via ?filter=unpaid) as open
    // payables with no link to those vouchers, so settled invoices would surface
    // as overdue. Auto-link the unambiguous matches. Best-effort: a failure here
    // must never fail the migration: the imported data is already persisted.
    if (options.reconcileVouchers !== false) {
      emitProgress(options, { status: 'importing', currentStep: 'Stämmer av betalningar mot verifikationer...', progress: 95 })
      try {
        const recon = await reconcileSupplierInvoiceVouchers({ supabase, companyId, userId })
        results.reconciliation = {
          scanned: recon.scanned,
          autoLinked: recon.autoLinked,
          ambiguous: recon.ambiguous,
          unmatched: recon.unmatched,
        }
        console.log(
          `[migration] Reconcile: ${recon.autoLinked} auto-linked, ${recon.ambiguous} need review, ${recon.unmatched} unmatched (${recon.scanned} scanned)`,
        )
      } catch (err) {
        console.error('Failed to reconcile supplier invoice payments:', err)
        recordStepError(results, 'reconciliation', err, runState)
      }
    }

    emitProgress(options, { status: 'completed', progress: 100, results })
    return results
  } catch (error) {
    const message = error instanceof Error ? error.message : 'Migration failed'
    emitProgress(options, { status: 'failed', progress: 0, error: message })
    throw error
  }
}