import { AppError, badRequest } from "@conusai-kit/core"
import { LEDGER_ERRORS, type RecordTerms } from "../contract/index.js"
import type { LedgerReads, LedgerService } from "./ports.js"

/** Optional preview only. Never run mutable account reads ahead of service replay. */
export async function validateBalanced(service: LedgerReads, terms: RecordTerms): Promise<void> {
  const accounts = new Map(
    await Promise.all(
      [...new Set(terms.entries.map((entry) => entry.accountId))].map(
        async (id) => [id, await service.account(id)] as const,
      ),
    ),
  )
  const totals = new Map<string, bigint>()
  for (const entry of terms.entries) {
    const account = accounts.get(entry.accountId)
    if (account?.status !== "active") throw badRequest("Choose active ledger accounts.")
    totals.set(
      account.currency,
      (totals.get(account.currency) ?? 0n) + BigInt(entry.amountMinor) * (entry.direction === "debit" ? 1n : -1n),
    )
  }
  if ([...totals.values()].some((amount) => amount !== 0n))
    throw badRequest("Balance debits and credits separately in every currency.")
}
export async function recordBalanced(service: LedgerService, terms: RecordTerms, requestId: string) {
  await assertProjection(service)
  // Service replay precedes account status, locking, funds, currency and overflow checks.
  return service.record(terms, operationKey("record", requestId))
}
export async function assertProjection(service: LedgerReads): Promise<void> {
  const health = await service.verify()
  if (health.drift.length)
    throw new AppError({
      type: `/problems/${LEDGER_ERRORS.drift}`,
      code: LEDGER_ERRORS.drift,
      status: 409,
      title: "Ledger posting fenced",
      detail: "Ledger projections require operator recovery before posting.",
    })
}
export async function transition(
  service: LedgerService,
  action: "post" | "void" | "reverse",
  id: string,
  revision: string,
  requestId: string,
) {
  if (action !== "void") await assertProjection(service)
  return service.transition(action, id, revision, operationKey(action, requestId))
}
export const operationKey = (action: string, requestId: string): string => `app-ledger:${action}:${requestId}`