import { ok, err } from "@tailor-platform/erp-kit/core";
import type { Transaction } from "../generated/kysely-tailordb";
import {
  NodeHasAssignmentsError,
  NodeHasChildrenError,
  NodeNotFoundError,
} from "../lib/errors.generated";

export interface DeleteTaxonomyNodeInput {
  id: string;
}

/**
 * Function: deleteTaxonomyNode
 *
 * Permanently removes a leaf taxonomy node with no item assignments.
 * The node's code becomes available for reuse.
 */
export async function run(db: Transaction, input: DeleteTaxonomyNodeInput) {
  const { id } = input;

  // 1. Check node exists (read-then-delete — lock)
  const node = await db
    .selectFrom("TaxonomyNode")
    .selectAll()
    .where("id", "=", id)
    .forUpdate()
    .executeTakeFirst();

  if (!node) {
    return err(new NodeNotFoundError(id));
  }

  // 2. Check no children (validation only — no lock)
  const children = await db
    .selectFrom("TaxonomyNode")
    .selectAll()
    .where("parentId", "=", id)
    .execute();

  if (children.length > 0) {
    return err(new NodeHasChildrenError(id));
  }

  // 3. Check no item assignments (validation only — no lock)
  const assignments = await db
    .selectFrom("ItemTaxonomyAssignment")
    .selectAll()
    .where("taxonomyNodeId", "=", id)
    .execute();

  if (assignments.length > 0) {
    return err(new NodeHasAssignmentsError(id));
  }

  // 4. Delete node
  await db.deleteFrom("TaxonomyNode").where("id", "=", id).execute();

  return ok({ success: true as const });
}