/**
 * Maps Arcim Sync canonical DTOs to Accounted internal types.
 *
 * These mappers transform the normalized data from any Swedish accounting
 * provider into the exact shapes Accounted expects for database insertion.
 */

import type { SupabaseClient } from '@supabase/supabase-js'
import { fetchExchangeRate } from '@/lib/currency/riksbanken'
import { encryptCustomerPersonalNumber } from '@/lib/customers/protect-personal-number'
import { normalizeVatRateToFraction } from '@/lib/vat/vat-rate-unit'
import { sumLineVat, lineVatFromPercent } from '@/lib/providers/amounts'
import type { Currency, CustomerType, ExchangeRate, SupplierType, VatTreatment } from '@/types'
import type {
  AmountType,
  CustomerDto,
  SupplierDto,
  SalesInvoiceDto,
  SalesInvoiceLineDto,
  SupplierInvoiceDto,
  SupplierInvoiceLineDto,
  CompanyInformationDto,
  PostalAddress,
  PartyDto,
} from '@/lib/providers/dto'

// ── Helpers ─────────────────────────────────────────────────────────

function round2(n: number): number {
  return Math.round(n * 100) / 100
}

function formatAddress(addr?: PostalAddress): {
  address_line1: string | null
  address_line2: string | null
  postal_code: string | null
  city: string | null
  country: string | null
} {
  if (!addr) {
    return { address_line1: null, address_line2: null, postal_code: null, city: null, country: null }
  }
  const line1 = [addr.streetName, addr.buildingNumber].filter(Boolean).join(' ') || null
  return {
    address_line1: line1,
    address_line2: addr.additionalStreetName || null,
    postal_code: addr.postalZone || null,
    city: addr.cityName || null,
    country: addr.countryCode || null,
  }
}

function getOrgNumber(party: PartyDto): string | null {
  // Look for SE:ORGNR scheme first, then companyId in legalEntity
  const seOrg = party.identifications?.find(i => i.schemeId === 'SE:ORGNR')
  if (seOrg) return seOrg.id
  return party.legalEntity?.companyId || null
}

const EU_COUNTRIES = ['AT', 'BE', 'BG', 'CY', 'CZ', 'DE', 'DK', 'EE', 'EL', 'ES', 'FI', 'FR', 'GR', 'HR', 'HU', 'IE', 'IT', 'LT', 'LU', 'LV', 'MT', 'NL', 'PL', 'PT', 'RO', 'SI', 'SK']

/**
 * Check if a string looks like a Swedish org number (XXXXXX-XXXX or 10 digits).
 * Swedish org numbers are 10 digits where the third digit is >= 2 (to distinguish
 * from personal numbers where month 01-12 appears in positions 3-4).
 */
function looksLikeSwedishOrgNumber(orgNumber: string | null | undefined): boolean {
  if (!orgNumber) return false
  const digits = orgNumber.replace(/[-\s]/g, '')
  if (digits.length !== 10 || !/^\d+$/.test(digits)) return false
  // Third digit >= 2 distinguishes org numbers from personal numbers
  const thirdDigit = parseInt(digits[2], 10)
  return thirdDigit >= 2
}

/**
 * Check if a string looks like a Swedish identity number: an organisation
 * number or personnummer in 10-digit form, or a personnummer in the 12-digit
 * century-prefixed form (19xx / 20xx). Used to avoid misclassifying a domestic
 * party as foreign just because its number isn't exactly 10 digits: a 12-digit
 * personnummer like 19700616-7113 is Swedish, not an unknown foreign org number.
 */
function looksLikeSwedishIdNumber(orgNumber: string | null | undefined): boolean {
  if (!orgNumber) return false
  const digits = orgNumber.replace(/[-+\s]/g, '')
  if (!/^\d+$/.test(digits)) return false
  if (digits.length === 10) return true
  return digits.length === 12 && /^(19|20)/.test(digits)
}

/**
 * Company name suffixes that indicate a foreign (non-Swedish) entity.
 * These override the default swedish_business assumption when no other
 * signals (VAT, country code, org number) are available.
 */
const FOREIGN_SUFFIXES: { suffix: string; region: 'eu' | 'non_eu' }[] = [
  // German
  { suffix: 'gmbh', region: 'eu' },
  { suffix: 'ag', region: 'eu' },
  { suffix: 'e.v.', region: 'eu' },
  { suffix: 'ohg', region: 'eu' },
  { suffix: 'kg', region: 'eu' },
  { suffix: 'ug', region: 'eu' },
  // French
  { suffix: 'sarl', region: 'eu' },
  { suffix: 's.a.r.l.', region: 'eu' },
  { suffix: 'sas', region: 'eu' },
  // Dutch/Belgian
  { suffix: 'b.v.', region: 'eu' },
  { suffix: 'n.v.', region: 'eu' },
  { suffix: 'bv', region: 'eu' },
  { suffix: 'nv', region: 'eu' },
  // Spanish/Italian
  { suffix: 's.l.', region: 'eu' },
  { suffix: 's.r.l.', region: 'eu' },
  // Finnish
  { suffix: 'oy', region: 'eu' },
  { suffix: 'oyj', region: 'eu' },
  // Danish/Norwegian
  { suffix: 'a/s', region: 'eu' },
  { suffix: 'aps', region: 'eu' },
  // Anglo (could be UK, US, etc.: treat as non-EU since UK left)
  { suffix: 'ltd', region: 'non_eu' },
  { suffix: 'limited', region: 'non_eu' },
  { suffix: 'llc', region: 'non_eu' },
  { suffix: 'inc', region: 'non_eu' },
  { suffix: 'corp', region: 'non_eu' },
  { suffix: 'plc', region: 'non_eu' },
  // Irish (EU)
  { suffix: 'dac', region: 'eu' },
]

function inferRegionFromName(name: string | undefined): 'eu' | 'non_eu' | null {
  if (!name) return null
  const lower = name.toLowerCase().trim()
  for (const { suffix, region } of FOREIGN_SUFFIXES) {
    // Match as a word boundary at the end: "Acme GmbH" but not "Gmbhsson"
    if (lower.endsWith(suffix) || lower.endsWith(suffix + '.')) {
      // Check that there's a space or start before the suffix
      const pos = lower.lastIndexOf(suffix)
      if (pos === 0 || lower[pos - 1] === ' ') {
        return region
      }
    }
  }
  return null
}

function inferTypeFromVatOrCountry(
  vatNumber: string | undefined,
  countryCode: string | undefined,
  orgNumber?: string | null,
  companyName?: string
): 'swedish_business' | 'eu_business' | 'non_eu_business' {
  // 1. VAT number prefix is the strongest signal
  if (vatNumber) {
    const prefix = vatNumber.substring(0, 2).toUpperCase()
    if (prefix === 'SE') return 'swedish_business'
    if (EU_COUNTRIES.includes(prefix)) return 'eu_business'
    return 'non_eu_business'
  }

  // 2. Explicit country code
  const country = countryCode?.toUpperCase()
  if (country === 'SE') return 'swedish_business'
  if (country && EU_COUNTRIES.includes(country)) return 'eu_business'
  if (country) return 'non_eu_business'

  // 3. Swedish-format org number is strong evidence of domestic entity
  if (looksLikeSwedishOrgNumber(orgNumber)) return 'swedish_business'

  // 4. A number that isn't a Swedish-format identity number → foreign entity.
  //    Accepts both 10-digit and 12-digit (century-prefixed) Swedish numbers so
  //    a domestic personnummer like 19700616-7113 isn't treated as foreign.
  if (orgNumber) {
    const digits = orgNumber.replace(/[-+\s]/g, '')
    if (digits.length > 0 && !looksLikeSwedishIdNumber(orgNumber)) {
      // Not a Swedish number: use name heuristic or default to non_eu
      const nameRegion = inferRegionFromName(companyName)
      if (nameRegion === 'eu') return 'eu_business'
      return 'non_eu_business'
    }
  }

  // 5. Company name suffix heuristic (GmbH, Ltd, etc.)
  const nameRegion = inferRegionFromName(companyName)
  if (nameRegion === 'eu') return 'eu_business'
  if (nameRegion === 'non_eu') return 'non_eu_business'

  // 6. No signal at all: default to swedish_business (most common in Swedish systems)
  return 'swedish_business'
}

function inferCustomerType(dto: CustomerDto): CustomerType {
  if (dto.type === 'private') return 'individual'
  return inferTypeFromVatOrCountry(
    dto.vatNumber,
    dto.party.postalAddress?.countryCode,
    getOrgNumber(dto.party),
    dto.party.name
  )
}

function inferSupplierType(dto: SupplierDto): SupplierType {
  return inferTypeFromVatOrCountry(
    dto.vatNumber,
    dto.party.postalAddress?.countryCode,
    getOrgNumber(dto.party),
    dto.party.name
  )
}

/**
 * Infer customer/supplier type from a PartyDto (used by orchestrator for
 * minimal entity creation from invoice data).
 */
export function inferTypeFromParty(
  party: PartyDto,
  vatNumber?: string
): 'swedish_business' | 'eu_business' | 'non_eu_business' {
  return inferTypeFromVatOrCountry(
    vatNumber,
    party.postalAddress?.countryCode,
    getOrgNumber(party),
    party.name
  )
}

/**
 * The VAT figures for one imported invoice, and whether they were observed.
 *
 * `rate` is null when nothing in the payload established one. That is the
 * difference this type exists to carry: the old code answered "25" to that
 * question and the record then read "25 % moms" beside "0 kr", which is not a
 * rounding artefact but a claim the source never made.
 */
interface InvoiceVatResolution {
  subtotal: number
  vatAmount: number
  /** Percent (25 / 12 / 6 / 0), or null when no evidence established it. */
  rate: number | null
  treatment: VatTreatment
  /** True when neither a VAT total, line VAT, nor a net could be found. */
  unresolved: boolean
}

/** Swedish statutory rates, most common first. */
const SWEDISH_VAT_RATES = [25, 12, 6, 0] as const

/**
 * Snap an observed ratio to a statutory Swedish rate.
 *
 * Providers hand back both units (25 and 0.25) and their own rounding, so an
 * invoice whose VAT divided by its net comes to 0.2499 is a 25 % invoice.
 * A ratio matching none of the statutory rates returns null rather than the
 * nearest one: an unrecognised rate is a fact worth surfacing, and a foreign
 * invoice may legitimately carry 19 % or 24 %.
 */
function snapToSwedishRate(ratio: number): number | null {
  const percent = ratio > 1 ? ratio : ratio * 100
  return SWEDISH_VAT_RATES.find((rate) => Math.abs(percent - rate) < 0.5) ?? null
}

/**
 * Treatment implied by an observed rate.
 *
 * A 0 % rate is genuinely ambiguous in the source data: it could be momsfritt,
 * omvänd skattskyldighet or an export. Currency is the only signal available
 * here, so a non-SEK invoice reads as export and a SEK one as exempt. Both
 * post to a 0 % revenue account, which is what the numbers say; calling it
 * `standard_25` (the old fallback) would have put a momsfri sale on 3001 and
 * into ruta 05 of the momsdeklaration.
 */
function treatmentForRate(rate: number, currencyCode?: string): VatTreatment {
  if (rate === 25) return 'standard_25'
  if (rate === 12) return 'reduced_12'
  if (rate === 6) return 'reduced_6'
  return currencyCode && currencyCode !== 'SEK' ? 'export' : 'exempt'
}

/**
 * Establish subtotal / VAT / rate for an imported invoice from evidence only.
 *
 * Evidence is taken in descending order of authority: the provider's own VAT
 * total, then the sum of per-line VAT, then the gap between a stated net and
 * the gross. When none of the three exists the invoice is marked unresolved
 * and keeps only the figure that IS known, the gross the customer owes; the
 * rate goes to null so no downstream reader can mistake silence for 25 %.
 */
function resolveInvoiceVat(
  dto: { currencyCode: string; lines: readonly { taxPercent?: number; taxAmount?: { value: number } }[]; taxTotal?: { taxAmount: { value: number } }; legalMonetaryTotal: { lineExtensionAmount?: { value: number }; payableAmount: { value: number } } },
): InvoiceVatResolution {
  const total = round2(dto.legalMonetaryTotal.payableAmount.value)
  const statedNet = dto.legalMonetaryTotal.lineExtensionAmount?.value
  const net = statedNet !== undefined ? round2(statedNet) : undefined

  const vatAmount = dto.taxTotal !== undefined
    ? round2(dto.taxTotal.taxAmount.value)
    : sumLineVat(dto.lines) ?? (net !== undefined ? round2(total - net) : undefined)

  if (vatAmount === undefined) {
    return {
      subtotal: total,
      vatAmount: 0,
      rate: null,
      // Nothing was observed, so nothing is asserted: `vat_rate: null` is the
      // signal the UI and the repair query read. The treatment column is NOT
      // NULL-typed across the codebase, so it keeps the schema default rather
      // than widening `Invoice['vat_treatment']` through 90 call sites.
      treatment: 'standard_25',
      unresolved: true,
    }
  }

  const subtotal = net ?? round2(total - vatAmount)

  // A rate stated on a line beats one divided out of the totals: mixed-rate
  // invoices divide out to a blended figure that matches no statutory rate.
  // Distinct rates actually stated on the lines. A rate stated on a line beats
  // one divided out of the totals, because a mixed-rate invoice divides out to
  // a blended figure matching no statutory rate at all (25 % goods plus 6 %
  // books lands near 21 %).
  const statedRates = [...new Set(
    dto.lines
      .filter((line) => line.taxPercent != null)
      .map((line) => snapToSwedishRate(line.taxPercent as number) ?? (line.taxPercent as number)),
  )]

  // Mixed rates store `vat_rate: null` while keeping a treatment, matching what
  // buildInvoiceWriteData does for a natively created mixed invoice
  // (`isMixedRate ? null : theRate`). Labelling the whole invoice with its
  // first line's rate would assert 25 % on an invoice that is 25 % and 6 %.
  // The money is unaffected: the booking engine groups per ITEM rate, which is
  // why the per-line vat_rate/vat_amount above have to be right.
  const isMixed = statedRates.length > 1
  const rate = isMixed
    ? null
    : statedRates.length === 1
      ? snapToSwedishRate(statedRates[0])
      : subtotal > 0
        ? snapToSwedishRate(vatAmount / subtotal)
        : null

  // A mixed invoice still needs a treatment for the non-null column; the
  // highest stated rate is the one that decides which revenue account the
  // no-items fallback would reach for, and it is the safest of the set.
  const treatmentRate = isMixed ? Math.max(...statedRates) : rate

  return {
    subtotal,
    vatAmount,
    rate,
    treatment: treatmentRate !== null
      ? treatmentForRate(treatmentRate, dto.currencyCode)
      : 'standard_25',
    // A VAT amount was established; only its rate could not be classified.
    unresolved: false,
  }
}

// ── Currency conversion ─────────────────────────────────────────────
//
// The provider DTOs (lib/providers/dto.ts) carry NO exchange rate and NO SEK
// amount: an invoice exposes only `currencyCode` plus amounts already expressed
// in that currency. So for a foreign-currency document the SEK value has to be
// established here, at import, from the rate that was valid on the document's
// OWN date. An imported invoice is räkenskapsinformation (BFL 7 kap): its SEK
// value is part of the record, and stamping it with today's rate, or with a
// fabricated 1:1, would misstate it.
//
// Same pattern as lib/transactions/ingest.ts: pre-resolve the unique
// (currency, date) pairs once through fetchExchangeRate WITH the supabase
// client (so the shared `exchange_rates` cache absorbs repeat dates) and WITH
// the document date, then map synchronously against that index.

/**
 * Currencies Riksbanken publishes a series for (SERIES_IDS in
 * lib/currency/riksbanken.ts). A document in any other currency has no rate
 * source at all, so it is reported rather than written with a silent null.
 */
const CONVERTIBLE_CURRENCIES: readonly Currency[] = ['SEK', 'EUR', 'USD', 'GBP', 'NOK', 'DKK']

/** Riksbanken fan-out bound, mirroring ingest.ts: a wide historical backfill
 *  used to fire every pair at once and get the whole batch rate-limited. */
const FX_FETCH_CONCURRENCY = 4

function asConvertibleCurrency(code: string | undefined | null): Currency | null {
  if (!code) return null
  const upper = code.toUpperCase() as Currency
  return CONVERTIBLE_CURRENCIES.includes(upper) ? upper : null
}

/** Normalize a DTO date to a plain ISO day, or null when it isn't one. */
function isoDay(value: string | undefined | null): string | null {
  if (!value || !/^\d{4}-\d{2}-\d{2}/.test(value)) return null
  return value.slice(0, 10)
}

/** Pre-resolved rates, keyed by `${CURRENCY}|${YYYY-MM-DD}`. */
export type FxRateIndex = Map<string, ExchangeRate>

export function fxRateKey(currencyCode: string, isoDate: string): string {
  return `${currencyCode.toUpperCase()}|${isoDate}`
}

/** Why a foreign-currency document could not be converted to SEK. */
export type FxUnresolvedReason =
  /** Currency outside Riksbanken's published series: no rate source exists. */
  | 'unsupported_currency'
  /** Rate source exists but no observation could be obtained for that date. */
  | 'rate_unavailable'

export interface FxUnresolved {
  currency: string
  /** The document's own date, i.e. the date a rate was needed for. */
  date: string
  reason: FxUnresolvedReason
}

interface FxResolution {
  /** null for SEK documents (no rate applies) and for unconvertible ones. */
  rate: number | null
  /** Riksbanken observation date behind `rate`; null when there is no rate. */
  rateDate: string | null
  /** Factor to reach SEK: 1 for SEK documents, `rate` otherwise, null when
   *  the conversion could not be established at all. */
  sekFactor: number | null
  /** Set ONLY when a foreign document could not be converted. */
  unresolved: FxUnresolved | null
}

/**
 * Fetch the rate valid on each document's own date, once per unique
 * (currency, date) pair. SEK documents need no rate and are skipped.
 *
 * A pair that cannot be fetched is simply absent from the index; the mapper
 * then reports that document as unresolved rather than inventing a number.
 */
export async function buildFxRateIndex(
  supabase: SupabaseClient,
  documents: { currencyCode?: string; issueDate?: string }[],
): Promise<FxRateIndex> {
  const index: FxRateIndex = new Map()

  const pairs = new Map<string, { currency: Currency; date: string }>()
  for (const doc of documents) {
    const currency = asConvertibleCurrency(doc.currencyCode)
    if (!currency || currency === 'SEK') continue
    const date = isoDay(doc.issueDate)
    if (!date) continue
    const key = fxRateKey(currency, date)
    if (!pairs.has(key)) pairs.set(key, { currency, date })
  }
  if (pairs.size === 0) return index

  const entries = [...pairs.entries()]
  for (let i = 0; i < entries.length; i += FX_FETCH_CONCURRENCY) {
    const slice = entries.slice(i, i + FX_FETCH_CONCURRENCY)
    const settled = await Promise.allSettled(
      slice.map(([, { currency, date }]) => fetchExchangeRate(currency, new Date(date), supabase)),
    )
    for (let j = 0; j < slice.length; j++) {
      const outcome = settled[j]
      if (outcome.status === 'fulfilled' && outcome.value && outcome.value.rate > 0) {
        index.set(slice[j][0], outcome.value)
      }
      // A miss deliberately leaves the key unset: never a made-up rate.
    }
  }

  return index
}

/**
 * Resolve the SEK conversion for one document.
 *
 * `rates` is optional so existing callers keep compiling; when it is omitted a
 * foreign document resolves to `rate_unavailable` (reported), never to a
 * silent 1:1. Only an actually-fetched positive rate produces a conversion.
 */
function resolveFx(
  currencyCode: string | undefined,
  issueDate: string | undefined,
  rates?: FxRateIndex,
): FxResolution {
  const code = (currencyCode || 'SEK').toUpperCase()

  if (code === 'SEK') {
    // Domestic document: the ledger currency IS SEK, so there is no exchange
    // rate to record. A plain null, not a conversion we failed to make. The
    // SEK amount columns still get filled, via sekFactor 1.
    return { rate: null, rateDate: null, sekFactor: 1, unresolved: null }
  }

  const currency = asConvertibleCurrency(code)
  if (!currency) {
    return {
      rate: null, rateDate: null, sekFactor: null,
      unresolved: { currency: code, date: isoDay(issueDate) ?? '', reason: 'unsupported_currency' },
    }
  }

  const date = isoDay(issueDate)
  if (!date) {
    return {
      rate: null, rateDate: null, sekFactor: null,
      unresolved: { currency: code, date: issueDate ?? '', reason: 'rate_unavailable' },
    }
  }

  const hit = rates?.get(fxRateKey(currency, date))
  if (!hit || !(hit.rate > 0)) {
    return {
      rate: null, rateDate: null, sekFactor: null,
      unresolved: { currency: code, date, reason: 'rate_unavailable' },
    }
  }

  return { rate: hit.rate, rateDate: hit.date, sekFactor: hit.rate, unresolved: null }
}

/** Convert to SEK, or null when no conversion could be established. */
function toSek(amount: number, sekFactor: number | null): number | null {
  return sekFactor === null ? null : round2(amount * sekFactor)
}

/**
 * A mapped invoice plus the FX verdict for it. `fxUnresolved` is non-null only
 * for a FOREIGN document whose SEK value could not be established: the caller
 * must surface those as needing attention instead of letting them pass as
 * ordinary imports. They are still imported (dropping them would lose
 * räkenskapsinformation) but carry exchange_rate = null, so every booking path
 * refuses them loudly (SupplierInvoiceFxRateMissingError /
 * InvoiceBookingRateMissingError) rather than posting at a fabricated 1:1.
 */
export interface MappedInvoice {
  invoice: Record<string, unknown>
  items: Record<string, unknown>[]
  fxUnresolved: FxUnresolved | null
  /**
   * True when the provider payload established no VAT at all, so the invoice
   * carries its gross as its subtotal, 0 kr of VAT and a null rate. Counted
   * into the migration summary the same way `fxUnresolved` is, so a run that
   * could not establish VAT says so instead of looking clean.
   */
  vatUnresolved: boolean
  /**
   * True for an imported kreditfaktura that carries no pointer at the invoice
   * it credits.
   *
   * `invoices` models that relation only through `credited_invoice_id`, and no
   * provider DTO carries a reference to the credited invoice: SalesInvoiceDto
   * and SupplierInvoiceDto (lib/providers/dto.ts) state the type through
   * `invoiceTypeCode` 381 and nothing else. So every credit note the migration
   * imports lands unlinked, and guessing the original from a number in a note
   * or from the amount would put a wrong pair in the AR ledger. The row itself
   * is complete räkenskapsinformation (reversed amounts, terminal status);
   * only the pairing is missing. Meant to be counted into the migration
   * summary the way `vatUnresolved` is, so the user is told instead of finding
   * it out in the ledger; the orchestrator does not read it yet, and the copy
   * that reports it waits in `ext_arcim_credit_notes_unlinked_detail`.
   */
  creditNoteUnlinked: boolean
}

// ── Public mappers ──────────────────────────────────────────────────

export function mapCustomer(dto: CustomerDto, userId: string, companyId: string): Record<string, unknown> {
  const addr = formatAddress(dto.party.postalAddress)
  const customerType = inferCustomerType(dto)
  const number = getOrgNumber(dto.party)
  // The provider exposes a single identity-number field, but Accounted stores a
  // personnummer in `personal_number` (individuals) and an org number in
  // `org_number` (businesses). Route it to the column the type expects: else a
  // Privatperson's personnummer lands in org_number and is hidden by the
  // individual customer form, which renders personal_number for individuals.
  const isIndividual = customerType === 'individual'
  // personal_number is an encrypted column: customers_personal_number_check
  // (migration 20260726110000) accepts AES-256-GCM hex and nothing else, so
  // writing the identity number in plaintext here aborts the whole import with
  // 23514 the moment a Privatperson appears in the source data.
  return {
    user_id: userId,
    company_id: companyId,
    name: dto.party.name,
    customer_type: customerType,
    contact_person: dto.party.contact?.name || null,
    email: dto.party.contact?.email || null,
    phone: dto.party.contact?.telephone || null,
    invoice_email_cc_addresses: dto.invoiceEmailCcAddresses ?? null,
    invoice_email_bcc_addresses: dto.invoiceEmailBccAddresses ?? null,
    ...addr,
    org_number: isIndividual ? null : number,
    personal_number: isIndividual ? encryptCustomerPersonalNumber(number) : null,
    vat_number: dto.vatNumber || null,
    vat_number_validated: false,
    default_payment_terms: dto.defaultPaymentTermsDays || 30,
    notes: dto.note || null,
  }
}

export function mapSupplier(dto: SupplierDto, userId: string, companyId: string): Record<string, unknown> {
  const addr = formatAddress(dto.party.postalAddress)
  return {
    user_id: userId,
    company_id: companyId,
    name: dto.party.name,
    supplier_type: inferSupplierType(dto),
    email: dto.party.contact?.email || null,
    phone: dto.party.contact?.telephone || null,
    ...addr,
    org_number: getOrgNumber(dto.party),
    vat_number: dto.vatNumber || null,
    bankgiro: dto.bankGiro || null,
    plusgiro: dto.plusGiro || null,
    bank_account: dto.bankAccount || null,
    // SupplierDto carries bankAccount/bankGiro/plusGiro only: it has no IBAN,
    // BIC or default expense account, so these are honest nulls, not dropped
    // data. The user fills them in when a foreign payment first needs them.
    iban: null,
    bic: null,
    default_expense_account: null,
    default_payment_terms: dto.defaultPaymentTermsDays || 30,
    default_currency: 'SEK',
    notes: dto.note || null,
  }
}

/** Reversed sign for a kreditfaktura amount, without producing -0. */
function negate(n: number): number {
  return n === 0 ? 0 : -n
}

/**
 * The same document stated in magnitudes.
 *
 * Providers disagree on the sign a kreditfaktura carries: Visma reports a
 * credit invoice with a negative TotalAmount (lib/providers/visma/mapper.ts)
 * while the arcim gateway states the magnitude beside invoiceTypeCode 381.
 * Both have to land on the single convention Accounted stores, so the amounts
 * are resolved from the magnitudes and the credit sign is applied once, at the
 * end. It is also what lets resolveInvoiceVat classify the rate at all: it
 * divides VAT by subtotal, which only yields a statutory rate when both are
 * positive.
 */
function withAbsoluteAmounts(dto: SalesInvoiceDto): SalesInvoiceDto {
  const abs = (amount: AmountType): AmountType => ({ ...amount, value: Math.abs(amount.value) })
  return {
    ...dto,
    lines: dto.lines.map((line) => ({
      ...line,
      quantity: line.quantity != null ? Math.abs(line.quantity) : undefined,
      unitPrice: line.unitPrice ? abs(line.unitPrice) : undefined,
      lineExtensionAmount: abs(line.lineExtensionAmount),
      taxAmount: line.taxAmount ? abs(line.taxAmount) : undefined,
    })),
    taxTotal: dto.taxTotal ? { ...dto.taxTotal, taxAmount: abs(dto.taxTotal.taxAmount) } : undefined,
    legalMonetaryTotal: {
      ...dto.legalMonetaryTotal,
      lineExtensionAmount: dto.legalMonetaryTotal.lineExtensionAmount
        ? abs(dto.legalMonetaryTotal.lineExtensionAmount)
        : undefined,
      payableAmount: abs(dto.legalMonetaryTotal.payableAmount),
    },
  }
}

export function mapSalesInvoice(
  dto: SalesInvoiceDto,
  userId: string,
  companyId: string,
  customerId: string,
  fxRates?: FxRateIndex
): MappedInvoice {
  const isCreditNote = dto.invoiceTypeCode === '381'

  const amounts = isCreditNote ? withAbsoluteAmounts(dto) : dto
  const sign = (n: number): number => (isCreditNote ? negate(n) : n)

  const total = sign(round2(amounts.legalMonetaryTotal.payableAmount.value))
  const vat = resolveInvoiceVat(amounts)
  const subtotal = sign(vat.subtotal)
  const vatAmount = sign(vat.vatAmount)

  // Map Arcim status to Accounted status
  const statusMap: Record<string, string> = {
    draft: 'draft',
    sent: 'sent',
    booked: 'sent', // Accounted has no 'booked' status: treat as sent
    paid: 'paid',
    overdue: 'overdue',
    cancelled: 'cancelled',
    credited: 'credited',
  }

  // A kreditfaktura is never an open or a paid receivable, so it gets a
  // terminal status regardless of the provider's lifecycle status:
  // invoiceTypeCode is the only signal that the document IS a credit note, and
  // the arcim gateway is not guaranteed to also send status='credited'. Same
  // reasoning as mapSupplierInvoice.
  const status = isCreditNote ? 'credited' : (statusMap[dto.status] || 'sent')

  // Nothing is ever collected on a kreditfaktura: it reduces what the customer
  // owes rather than settling anything. This also keeps the row clear of
  // invoices_credit_note_not_paid, which forbids paid/partially_paid the moment
  // the row points at the invoice it credits.
  const settlement = isCreditNote
    ? { paidAt: null as string | null, paidAmount: 0, remainingAmount: 0 }
    : {
        paidAt: dto.paymentStatus.paid
          ? dto.paymentStatus.lastPaymentDate || dto.issueDate
          : null,
        paidAmount: dto.paymentStatus.paid
          ? total
          : round2(total - dto.paymentStatus.balance.value),
        remainingAmount: dto.paymentStatus.paid
          ? 0
          : Math.max(0, round2(dto.paymentStatus.balance.value)),
      }

  // SEK value of a foreign invoice, at the rate valid on its own issue date.
  const fx = resolveFx(dto.currencyCode, dto.issueDate, fxRates)

  const invoice: Record<string, unknown> = {
    user_id: userId,
    company_id: companyId,
    customer_id: customerId,
    // Empty string must become NULL: the UNIQUE (company_id, invoice_number)
    // index is partial on NOT NULL, so '' from a provider payload missing the
    // field would collide on the second invoice and reject the insert.
    invoice_number: dto.invoiceNumber || null,
    invoice_date: dto.issueDate,
    due_date: dto.dueDate || dto.issueDate,
    status,
    currency: dto.currencyCode || 'SEK',
    // null for a SEK invoice (no rate applies) and for a foreign invoice whose
    // rate could not be established: that case is reported via fxUnresolved.
    exchange_rate: fx.rate,
    exchange_rate_date: fx.rateDate,
    subtotal,
    subtotal_sek: toSek(subtotal, fx.sekFactor),
    vat_amount: vatAmount,
    vat_amount_sek: toSek(vatAmount, fx.sekFactor),
    total,
    total_sek: toSek(total, fx.sekFactor),
    vat_treatment: vat.treatment,
    // null, not 25, when the payload established no rate. The column is
    // nullable and defaults to 25; writing the default explicitly is what made
    // 8 700+ migrated invoices assert "25 % moms" beside 0 kr of it.
    vat_rate: vat.rate,
    your_reference: null,
    our_reference: null,
    notes: isCreditNote ? creditNoteUnlinkedNote(dto.note) : (dto.note || null),
    // Always 'invoice'. invoices_document_type_check allows only
    // ('invoice', 'proforma', 'delivery_note'), and Accounted models a
    // kreditfaktura as an invoice row with reversed amounts plus
    // credited_invoice_id, not as a document type of its own (see
    // app/api/invoices/route.ts and .../invoices/[id]/credit/route.ts).
    // Writing 'credit_note' here made Postgres reject every migrated
    // kreditfaktura with a 23514, and the run counted each one as skipped.
    document_type: 'invoice',
    paid_at: settlement.paidAt,
    paid_amount: settlement.paidAmount,
    // remaining_amount is NOT NULL DEFAULT 0, so omitting it makes every
    // migrated open invoice look fully settled in AR aging.
    remaining_amount: settlement.remainingAmount,
  }

  const items = amounts.lines.map((line, idx) => mapSalesInvoiceLine(line, idx, vat.rate, isCreditNote))

  return {
    invoice,
    items,
    fxUnresolved: fx.unresolved,
    vatUnresolved: vat.unresolved,
    creditNoteUnlinked: isCreditNote,
  }
}

/**
 * Durable note for a migrated kreditfaktura that carries no pointer at the
 * invoice it credits.
 *
 * ML 17 kap 22-23 § requires a kreditfaktura to reference the original
 * invoice, and BFL 5 kap 6-7 § requires a verifikation to reference its
 * underlag. No provider DTO carries that reference (lib/providers/dto.ts), so
 * the pairing cannot be resolved at import time and guessing it would corrupt
 * the AR ledger. The wizard reports the count, but a wizard result screen is
 * not rakenskapsinformation: the gap has to be legible on the record itself,
 * years later, to whoever opens the invoice. So it is written into `notes`,
 * preserving whatever note the provider sent.
 */
function creditNoteUnlinkedNote(providerNote: string | null | undefined): string {
  const disclosure =
    'Kreditfaktura importerad vid systembyte. Referens till ursprungsfakturan '
    + 'saknas: kallsystemet skickade ingen sadan referens vid migreringen.'
  const existing = (providerNote || '').trim()
  return existing ? `${existing}\n\n${disclosure}` : disclosure
}

/**
 * One invoice_items row.
 *
 * `invoiceRate` is the rate resolved for the invoice as a whole, used only
 * when the line itself states none. The booking engine sums `vat_amount`
 * across items to post 2611, so a line that carried a rate but no amount used
 * to contribute nothing: 3 451 of 4 030 migrated items at 25 % hold 0 kr.
 * Deriving the amount from whichever rate is known fixes that at the source.
 *
 * invoice_items.vat_rate is stored as a PERCENT (25), unlike
 * supplier_invoice_items.vat_rate which is a fraction (0.25).
 */
function mapSalesInvoiceLine(
  line: SalesInvoiceLineDto,
  index: number,
  invoiceRate: number | null,
  isCreditNote: boolean,
): Record<string, unknown> {
  const lineTotal = round2(line.lineExtensionAmount.value)
  const rate = line.taxPercent != null ? snapToSwedishRate(line.taxPercent) : invoiceRate
  const vatAmount = line.taxAmount?.value ?? lineVatFromPercent(lineTotal, rate ?? undefined)
  // A kreditfaktura reverses quantity, line total and VAT and keeps the unit
  // price and the rate positive: exactly what buildCreditNoteItem writes for a
  // credit note issued in-app (lib/invoices/build-credit-note-item.ts).
  const sign = (n: number): number => (isCreditNote ? negate(n) : n)

  return {
    sort_order: index + 1,
    description: line.description || line.itemName || '',
    quantity: sign(line.quantity || 1),
    unit: line.unitCode || 'st',
    unit_price: round2(line.unitPrice?.value ?? line.lineExtensionAmount.value),
    line_total: sign(lineTotal),
    // 0 rather than the old hardcoded 25 when nothing established a rate: a
    // 0 % line beside 0 kr of VAT is at least internally consistent.
    vat_rate: rate ?? 0,
    vat_amount: sign(round2(vatAmount ?? 0)),
  }
}

export function mapSupplierInvoice(
  dto: SupplierInvoiceDto,
  userId: string,
  companyId: string,
  supplierId: string,
  fxRates?: FxRateIndex
): MappedInvoice {
  const total = round2(dto.legalMonetaryTotal.payableAmount.value)
  const vat = resolveInvoiceVat(dto)
  const subtotal = vat.subtotal
  const vatAmount = vat.vatAmount
  const vatTreatment = vat.treatment

  const statusMap: Record<string, string> = {
    draft: 'registered',
    sent: 'registered',
    booked: 'registered',
    paid: 'paid',
    overdue: 'overdue',
    cancelled: 'credited',
    credited: 'credited',
  }

  const isCreditNote = dto.invoiceTypeCode === '381'

  // Payment-derived amounts. Treat Balance numerically (never strict === 0) so
  // floating drift or a residual öre resolves cleanly to paid/unpaid.
  const balance = round2(dto.paymentStatus.balance.value)
  const paidAmount = dto.paymentStatus.paid ? total : round2(total - balance)

  // Status MUST stay consistent with the payment amounts. The provider's
  // lifecycle status (dto.status) and its payment status are computed
  // independently upstream and can contradict each other (e.g. a Fortnox
  // invoice that is "booked" but fully paid). Payment state wins:
  //   fully paid           -> 'paid'
  //   0 < paid < total     -> 'partially_paid'
  //   otherwise            -> the mapped lifecycle status
  const mappedStatus = statusMap[dto.status] || 'registered'
  let resolvedStatus: string
  if (isCreditNote) {
    // A kreditfaktura is never an open or "paid" payable. Force a credit-note
    // terminal status regardless of the provider's lifecycle status: the
    // arcim gateway is the only source of invoiceTypeCode and is NOT guaranteed
    // to also send status='credited', so trusting dto.status here could persist
    // a credit note as 'registered'/'paid' (contradicting its amounts).
    resolvedStatus = mappedStatus === 'reversed' ? 'reversed' : 'credited'
  } else if (mappedStatus === 'credited' || mappedStatus === 'reversed') {
    // Terminal states from the provider: never flipped by payment.
    resolvedStatus = mappedStatus
  } else if (dto.paymentStatus.paid || balance <= 0) {
    resolvedStatus = 'paid'
  } else if (paidAmount > 0 && paidAmount < total) {
    resolvedStatus = 'partially_paid'
  } else {
    resolvedStatus = mappedStatus
  }

  // SEK value of a foreign invoice, at the rate valid on its own issue date.
  const fx = resolveFx(dto.currencyCode, dto.issueDate, fxRates)

  const invoice: Record<string, unknown> = {
    user_id: userId,
    company_id: companyId,
    supplier_id: supplierId,
    // Empty string must become NULL: with '' every number-less invoice from
    // the same supplier collides on the UNIQUE
    // (company_id, supplier_id, supplier_invoice_number) index, while NULLs
    // are treated as distinct.
    supplier_invoice_number: dto.invoiceNumber || null,
    invoice_date: dto.issueDate,
    due_date: dto.dueDate || dto.issueDate,
    received_date: dto.issueDate,
    delivery_date: dto.deliveryDate || null,
    status: resolvedStatus,
    currency: dto.currencyCode || 'SEK',
    // null for a SEK invoice (no rate applies) and for a foreign invoice whose
    // rate could not be established: that case is reported via fxUnresolved.
    exchange_rate: fx.rate,
    exchange_rate_date: fx.rateDate,
    subtotal,
    subtotal_sek: toSek(subtotal, fx.sekFactor),
    vat_amount: vatAmount,
    vat_amount_sek: toSek(vatAmount, fx.sekFactor),
    total,
    total_sek: toSek(total, fx.sekFactor),
    vat_treatment: vatTreatment,
    reverse_charge: vatTreatment === 'reverse_charge',
    payment_reference: dto.ocrNumber || null,
    paid_at: resolvedStatus === 'paid' || resolvedStatus === 'partially_paid'
      ? dto.paymentStatus.lastPaymentDate || dto.issueDate
      : null,
    paid_amount: resolvedStatus === 'paid' ? total : Math.max(0, paidAmount),
    remaining_amount: resolvedStatus === 'paid' ? 0 : Math.max(0, balance),
    is_credit_note: isCreditNote,
    notes: isCreditNote ? creditNoteUnlinkedNote(dto.note) : (dto.note || null),
  }

  const items = dto.lines.map((line, idx) => mapSupplierInvoiceLine(line, idx, vat.rate))

  return {
    invoice,
    items,
    fxUnresolved: fx.unresolved,
    vatUnresolved: vat.unresolved,
    // supplier_invoices carries is_credit_note, so the row still reads as a
    // kreditfaktura on its own; what is missing is the same pointer at the
    // original that the sales side lacks.
    creditNoteUnlinked: isCreditNote,
  }
}

/**
 * One supplier_invoice_items row.
 *
 * `invoiceRate` (percent) is the rate resolved for the invoice as a whole and
 * is used only when the line states none: the previous `?? 25` asserted a
 * standard rate on every line of every provider that omits per-line VAT, and
 * paired it with a 0 kr amount.
 */
function mapSupplierInvoiceLine(
  line: SupplierInvoiceLineDto,
  index: number,
  invoiceRate: number | null,
): Record<string, unknown> {
  const lineTotal = round2(line.lineExtensionAmount.value)
  // Foreign rates (19 % DE) must survive rather than be snapped to a Swedish
  // one, so the line's own percent is used as stated; only the fallback comes
  // from the invoice-level resolution.
  const percent = line.taxPercent ?? invoiceRate ?? 0
  const vatAmount = line.taxAmount?.value ?? lineVatFromPercent(lineTotal, percent)

  return {
    sort_order: index + 1,
    description: line.description || line.itemName || '',
    quantity: line.quantity || 1,
    unit: line.unitCode || 'st',
    unit_price: round2(line.unitPrice?.value ?? line.lineExtensionAmount.value),
    line_total: lineTotal,
    account_number: line.accountNumber || '4000', // Default to purchases
    // supplier_invoice_items stores decimal fractions (0.25 = 25 %), unlike
    // customer invoice_items which store percent.
    vat_rate: normalizeVatRateToFraction(percent),
    vat_amount: round2(vatAmount ?? 0),
  }
}

export function mapCompanyInfo(dto: CompanyInformationDto): {
  company_name: string | null
  org_number: string | null
  vat_number: string | null
  fiscal_year_start_month: number
  address_line1: string | null
  postal_code: string | null
  city: string | null
  phone: string | null
  email: string | null
} {
  const addr = formatAddress(dto.address)
  // Parse fiscal year start month from "MM-DD" format
  let fiscalYearStartMonth = 1
  if (dto.fiscalYearStart) {
    const month = parseInt(dto.fiscalYearStart.split('-')[0], 10)
    if (month >= 1 && month <= 12) fiscalYearStartMonth = month
  }

  return {
    company_name: dto.companyName || null,
    org_number: dto.organizationNumber || null,
    vat_number: dto.vatNumber || null,
    fiscal_year_start_month: fiscalYearStartMonth,
    address_line1: addr.address_line1,
    postal_code: addr.postal_code,
    city: addr.city,
    phone: dto.contact?.telephone || null,
    email: dto.contact?.email || null,
  }
}