import { ok, err } from "@tailor-platform/erp-kit/core";
import { departmentLifecycle } from "../db/department.lifecycle.generated";
import type { Transaction } from "../generated/kysely-tailordb";
import {
  DepartmentNotFoundError,
  InvalidStateError,
  HasActiveChildrenError,
} from "../lib/errors.generated";

export interface DeactivateDepartmentInput {
  departmentId: string;
}

/**
 * Function: deactivateDepartment
 *
 * Deactivates a department, preventing it from being used in new assignments.
 * Fails if the department has active sub-departments.
 */
export async function run(db: Transaction, input: DeactivateDepartmentInput) {
  const { departmentId } = input;

  // 1. Find department
  const existing = await db
    .selectFrom("Department")
    .selectAll()
    .where("id", "=", departmentId)
    .forUpdate()
    .executeTakeFirst();

  if (!existing) {
    return err(new DepartmentNotFoundError(departmentId));
  }

  // 2. Check status is ACTIVE
  const nextStatus = departmentLifecycle.tryTransition(existing.status, "deactivate");
  if (!nextStatus) {
    return err(new InvalidStateError(departmentId));
  }

  // 3. Check for active sub-departments
  const activeChild = await db
    .selectFrom("Department")
    .selectAll()
    .where("parentDepartmentId", "=", departmentId)
    .where("status", "=", "ACTIVE")
    .executeTakeFirst();

  if (activeChild) {
    return err(new HasActiveChildrenError(departmentId));
  }

  // 4. Set status INACTIVE
  const department = await db
    .updateTable("Department")
    .set({
      status: nextStatus,
    })
    .where("id", "=", departmentId)
    .returningAll()
    .executeTakeFirstOrThrow();

  return ok({ department });
}