import type { TenantDb } from "@/server/db";

export type NumberKey = "customer" | "work_order" | "emergency" | "report";

const DEFAULT_PREFIX: Record<NumberKey, string> = {
  customer: "K-",
  work_order: "A-",
  emergency: "N-",
  report: "B-",
};

/**
 * Allocate the next number of a tenant sequence, e.g. "A-00042".
 * The increment is a single UPDATE … RETURNING (atomic); the very first call per key
 * creates the row and retries once if a concurrent call created it first.
 */
export async function nextNumber(db: TenantDb, tenantId: string, key: NumberKey): Promise<string> {
  for (let attempt = 0; attempt < 3; attempt++) {
    const existing = await db.numberSequence.findFirst({ where: { tenantId, key }, select: { id: true } });
    if (existing) {
      const seq = await db.numberSequence.update({
        where: { id: existing.id },
        data: { nextValue: { increment: 1 } },
      });
      return format(seq.prefix, seq.nextValue - 1, seq.padding);
    }
    try {
      const seq = await db.numberSequence.create({
        data: { tenantId, key, prefix: DEFAULT_PREFIX[key], nextValue: 2 },
      });
      return format(seq.prefix, 1, seq.padding);
    } catch (err) {
      if ((err as { code?: string }).code !== "P2002") throw err; // unique race → retry via update path
    }
  }
  throw new Error(`could not allocate number for ${key}`);
}

function format(prefix: string, value: number, padding: number): string {
  return `${prefix}${String(value).padStart(padding, "0")}`;
}