import type { SupabaseClient } from '@supabase/supabase-js'
import { fetchAllRows } from '@/lib/supabase/fetch-all'
import { roundOre } from '@/lib/money'

/**
 * Payment history for reconstructing a reskontra as of an arbitrary date.
 *
 * `paidThrough` sums the payment rows dated on or before the as-of date, per
 * invoice. `hasRows` marks invoices that have ANY payment rows (any date):
 * callers need it to tell "paid, but after the as-of date" (reconstructable,
 * paid-through 0) apart from "no payment rows recorded at all" (legacy data,
 * fall back to the invoice's own paid_at / stored amounts).
 */
export interface PaymentsAsOf {
  paidThrough: Map<string, number>
  hasRows: Set<string>
}

interface PaymentRow {
  amount: number | string | null
  payment_date: string
}

/**
 * Fetch the company's payment rows for one of the two invoice ledgers and
 * aggregate them per invoice as of `asOfDate` (inclusive). Amounts are in the
 * invoice's own currency, matching how the ledger generators convert to SEK
 * with the invoice-date exchange_rate.
 */
export async function fetchPaymentsAsOf(
  supabase: SupabaseClient,
  table: 'invoice_payments' | 'supplier_invoice_payments',
  invoiceIdColumn: 'invoice_id' | 'supplier_invoice_id',
  companyId: string,
  asOfDate: string
): Promise<PaymentsAsOf> {
  const rows = await fetchAllRows<PaymentRow & Record<string, unknown>>(({ from, to }) =>
    supabase
      .from(table)
      .select(`${invoiceIdColumn}, amount, payment_date`)
      .eq('company_id', companyId)
      // Stable total order for correct paging (see fetch-all.ts).
      .order('id', { ascending: true })
      .range(from, to)
  )

  const paidThrough = new Map<string, number>()
  const hasRows = new Set<string>()

  for (const row of rows) {
    const invoiceId = row[invoiceIdColumn] as string | null
    if (!invoiceId) continue
    hasRows.add(invoiceId)
    if (row.payment_date && row.payment_date <= asOfDate) {
      const prev = paidThrough.get(invoiceId) ?? 0
      paidThrough.set(invoiceId, roundOre(prev + (Number(row.amount) || 0)))
    }
  }

  return { paidThrough, hasRows }
}

/**
 * An invoice's outstanding amount (in invoice currency) as of the
 * reconstruction date.
 *
 * Priority order:
 * 1. Payment rows exist: they are authoritative. Outstanding is the invoice
 *    total minus the rows dated on or before the as-of date, including the
 *    "all payments came later" case, which reopens the full total.
 * 2. No rows but the invoice is fully paid (`paid_at` set): paid before or on
 *    the as-of date means the live (settled) outstanding stands; paid after
 *    it means the full total was still open.
 * 3. No rows and no `paid_at` (legacy partial payments recorded before the
 *    payment tables carried every settlement): the history cannot be dated,
 *    so the live outstanding is assumed to have stood at the as-of date.
 *    This matches what the live ledger reports for the same rows.
 */
export function outstandingAsOf(
  invoice: { id: string; paid_at?: string | null },
  total: number,
  liveOutstanding: number,
  payments: PaymentsAsOf,
  asOfDate: string
): number {
  if (payments.hasRows.has(invoice.id)) {
    const paid = payments.paidThrough.get(invoice.id) ?? 0
    return roundOre(total - paid)
  }
  if (invoice.paid_at) {
    return String(invoice.paid_at).slice(0, 10) <= asOfDate ? liveOutstanding : total
  }
  return liveOutstanding
}

/** Local calendar date (YYYY-MM-DD) used to decide whether an as-of date needs
 * historical reconstruction at all. */
export function todayIsoDate(): string {
  const now = new Date()
  const y = now.getFullYear()
  const m = String(now.getMonth() + 1).padStart(2, '0')
  const d = String(now.getDate()).padStart(2, '0')
  return `${y}-${m}-${d}`
}