import { formatDocNo } from '@sims/domain'
import type { DB } from './db'

export const TYPE_PREFIX: Record<string, string> = {
  QUOTATION: 'QT', PROFORMA: 'PI', INVOICE: 'INV', RECEIPT: 'RCT', CREDIT_NOTE: 'CN',
}

export async function nextDocNo(db: DB, docType: string, fy: string): Promise<string> {
  const prefix = `${TYPE_PREFIX[docType]}/${fy.slice(2)}`
  await db.run(
    // Portability quirk: ON CONFLICT upsert is SQLite/Postgres dialect (standard SQL has MERGE).
    `INSERT INTO doc_series (doc_type, fy, prefix, next_seq) VALUES (?, ?, ?, 1)
     ON CONFLICT (doc_type, fy) DO NOTHING`,
    docType, fy, prefix,
  )
  // D24 (red-team): allocate the number in ONE atomic UPDATE ... RETURNING. This takes a
  // row lock, so concurrent issuers serialize on the row and can never read the same seq
  // twice (the old read-then-bump raced → duplicate numbers / burned sequence on Postgres).
  // Both engines support UPDATE ... RETURNING (SQLite ≥3.35, node pg). Runs inside the
  // caller's issueDocument transaction.
  const row = (await db.get<{ prefix: string; seq: number }>(
    `UPDATE doc_series SET next_seq = next_seq + 1 WHERE doc_type=? AND fy=?
     RETURNING prefix, next_seq - 1 AS seq`,
    docType, fy,
  ))!
  return formatDocNo(row.prefix, row.seq, 4)
}

/** Mid-FY cutover (spec §4): continue after the last APEX-issued number. */
export async function seedSeries(db: DB, docType: string, fy: string, lastUsedSeq: number): Promise<void> {
  const prefix = `${TYPE_PREFIX[docType]}/${fy.slice(2)}`
  await db.run(
    // Portability quirk: ON CONFLICT upsert is SQLite/Postgres dialect (standard SQL has MERGE).
    `INSERT INTO doc_series (doc_type, fy, prefix, next_seq) VALUES (?, ?, ?, ?)
     ON CONFLICT (doc_type, fy) DO UPDATE SET next_seq = excluded.next_seq`,
    docType, fy, prefix, lastUsedSeq + 1,
  )
}