import type { Db } from "../db.js";
import { nowIso, tx } from "../db.js";
import { audit } from "./audit.js";

/**
 * Pula kodów EAN wydawanych wariantom. FIFO — kolejny wolny kod to
 * najniższe id ze statusem 'available'. Przydział zapisuje też audit.
 */

export interface EanPoolRow {
  id: number;
  ean: string;
  status: "available" | "assigned";
  assigned_variant_id: string | null;
  assigned_at: string | null;
}

/** Doładowanie puli. Duplikaty EAN są pomijane (UNIQUE + OR IGNORE). */
export function addEans(db: Db, eans: string[]): { added: number; skipped: number } {
  let added = 0;
  let skipped = 0;
  tx(db, () => {
    const ins = db.prepare("INSERT OR IGNORE INTO ean_pool (ean) VALUES (?)");
    for (const ean of eans) {
      const normalized = ean.trim();
      if (!normalized || !/^\d{13}$/.test(normalized)) {
        skipped++;
        continue;
      }
      if (ins.run(normalized).changes > 0) added++;
      else skipped++;
    }
  });
  return { added, skipped };
}

/**
 * Przydziela wariantowi kolejny wolny EAN (FIFO po id). Wywoływane
 * wewnątrz transakcji tworzącej wariant — przydział jest atomowy
 * z INSERT-em wariantu. Zwraca przydzielony kod albo null, gdy pula pusta.
 */
export function claimNextEan(db: Db, variantId: string, actor = "system"): string | null {
  return tx(db, () => {
    const row = db
      .prepare("SELECT * FROM ean_pool WHERE status = 'available' ORDER BY id LIMIT 1")
      .get() as unknown as EanPoolRow | undefined;
    if (!row) return null;
    db.prepare(
      "UPDATE ean_pool SET status = 'assigned', assigned_variant_id = ?, assigned_at = ? WHERE id = ?"
    ).run(variantId, nowIso(), row.id);
    audit(db, {
      actor,
      action: "ean.assigned",
      entity: "variants",
      entityId: variantId,
      detail: { ean: row.ean, poolId: row.id },
    });
    return row.ean;
  });
}

/** Zwraca EAN-y wskazanych wariantów do puli (np. przy usuwaniu wariantów). */
export function releaseEansForVariants(db: Db, variantIds: string[], actor = "system"): number {
  if (!variantIds.length) return 0;
  const released = Number(
    db
      .prepare(
        `UPDATE ean_pool SET status = 'available', assigned_variant_id = NULL, assigned_at = NULL
         WHERE assigned_variant_id IN (SELECT value FROM json_each(?))`
      )
      .run(JSON.stringify(variantIds)).changes
  );
  if (released > 0) {
    audit(db, {
      actor,
      action: "ean.released",
      entity: "variants",
      entityId: variantIds[0]!,
      detail: { variantIds, released },
    });
  }
  return released;
}

export function eanForVariant(db: Db, variantId: string): string | null {
  const row = db
    .prepare("SELECT ean FROM ean_pool WHERE assigned_variant_id = ?")
    .get(variantId) as unknown as { ean: string } | undefined;
  return row?.ean ?? null;
}

/**
 * Backfill: przydziela kolejne wolne EAN-y wariantom, które powstały
 * zanim pula została zasilona (albo gdy pula była pusta). Kolejność
 * wariantów = kolejność utworzenia; FIFO puli po id — jak przy tworzeniu.
 */
export function backfillVariantEans(db: Db, productId?: string, actor = "system"): number {
  const missing = db
    .prepare(
      `SELECT v.id FROM variants v
       LEFT JOIN ean_pool e ON e.assigned_variant_id = v.id
       WHERE e.id IS NULL ${productId ? "AND v.product_id = ?" : ""}
       ORDER BY v.created_at, v.id`
    )
    .all(...(productId ? [productId] : [])) as unknown as Array<{ id: string }>;
  let assigned = 0;
  for (const v of missing) {
    if (claimNextEan(db, v.id, actor)) assigned++;
    else break; // pula wyczerpana
  }
  return assigned;
}