/**
 * Supplier-invoice lifecycle helpers for the 'overdue' label.
 *
 * 'overdue' is derived state (an unpaid payable past its due date) that we
 * store as a lifecycle status: the daily pg_cron job
 * update_overdue_supplier_invoices() flips 'registered'/'approved' rows there.
 * Because it is stored rather than computed, every path that can change
 * due_date, or that gates on the status, has to use the same predicate as the
 * cron. When they diverge the label sticks: before #1206 nothing ever flipped
 * back, so an unbooked invoice that aged past its due date became read-only
 * and could not even have its due date extended.
 *
 * Keep this file in sync with update_overdue_supplier_invoices()
 * (supabase/migrations/20260727160000_supplier_invoice_overdue_symmetric.sql).
 */

/**
 * "Nothing left to pay" threshold, mirroring the cron and the payment/match
 * paths: öre-level rounding must not leave a payable looking unsettled.
 */
const FULLY_PAID_EPSILON = 0.005

/**
 * Statuses the overdue flip/un-flip owns. They are also exactly the statuses
 * in which an invoice is still unsettled, so metadata editing is allowed:
 * 'paid'/'partially_paid'/'credited'/'reversed'/'disputed' are settled or
 * disputed states that other flows own.
 */
export const UNSETTLED_SUPPLIER_INVOICE_STATUSES = [
  'registered',
  'approved',
  'overdue',
] as const

export type UnsettledSupplierInvoiceStatus =
  (typeof UNSETTLED_SUPPLIER_INVOICE_STATUSES)[number]

export function isUnsettledSupplierInvoiceStatus(
  status: string,
): status is UnsettledSupplierInvoiceStatus {
  return (UNSETTLED_SUPPLIER_INVOICE_STATUSES as readonly string[]).includes(status)
}

/** The facts the overdue predicate reads. `today` is an ISO yyyy-MM-dd date. */
export type SupplierInvoiceLifecycleFacts = {
  due_date: string
  remaining_amount: number
  is_credit_note?: boolean | null
  /** Set when the invoice has been attested; null/undefined when it has not. */
  approved_at?: string | null
}

/**
 * True when the invoice is a payable that has fallen due: the exact predicate
 * update_overdue_supplier_invoices() flips on. Credit notes are not payables,
 * and a fully settled row has nothing to fall due.
 */
export function isOverduePayable(
  facts: Pick<SupplierInvoiceLifecycleFacts, 'due_date' | 'remaining_amount' | 'is_credit_note'>,
  today: string,
): boolean {
  if (facts.is_credit_note) return false
  if (facts.remaining_amount <= FULLY_PAID_EPSILON) return false
  return facts.due_date < today
}

/**
 * The status an unsettled invoice should rest at right now.
 *
 * The flip collapses 'registered' and 'approved' into 'overdue', so the way
 * back needs approved_at: without it an un-flip would silently strip an
 * attested invoice of its approval (and with it the "Markera som betald"
 * path). Rows that were already 'overdue' when approved_at was introduced
 * carry no timestamp and therefore return to 'registered', where they can be
 * re-approved.
 */
export function resolveUnsettledStatus(
  facts: SupplierInvoiceLifecycleFacts,
  today: string,
): UnsettledSupplierInvoiceStatus {
  if (isOverduePayable(facts, today)) return 'overdue'
  return facts.approved_at ? 'approved' : 'registered'
}

/**
 * True when the invoice can still be attested. 'overdue' is included because
 * the cron puts unbooked invoices there just by aging; approved_at (not the
 * status) is what makes approval idempotent.
 */
export function canApproveSupplierInvoice(invoice: {
  status: string
  approved_at?: string | null
}): boolean {
  if (invoice.approved_at) return false
  return invoice.status === 'registered' || invoice.status === 'overdue'
}