redefined-designs/backend/src/itemSelect.ts

// Shared item SELECT shapes for the public and admin routes, and the row types
// they return.
//
// The types live here rather than in types.ts because they describe a
// projection, not a table. ADMIN_ITEM_SELECT takes `i.*` and PUBLIC_ITEM_SELECT
// names its columns so the storefront never sees paypal_order_id or
// reserved_until — typing both as "an items row" would quietly re-admit exactly
// the columns that select was written to exclude.
//
// KEPT IN STEP BY HAND. `pool.query<T>` asserts a shape; it does not check the
// SQL, which TypeScript never reads. Dropping a column from a select below
// without dropping it from its type compiles cleanly and every read of it goes
// on type-checking while being undefined at runtime. The integration suite is
// the only thing that catches that, because it runs these queries against a
// real schema. Change a select and its type together.
//
// Images and tags are pulled as scalar subqueries rather than LEFT JOIN +
// GROUP BY. Joining two one-to-many relations in the same query multiplies
// their rows together — an item with 2 images and 3 tags would aggregate 6
// rows, silently repeating every image three times. Subqueries keep each
// aggregate independent and drop the GROUP BY entirely.

import { ItemStatus, ItemImage, ItemTag } from './types';

const IMAGES_SUBQUERY = `
  COALESCE((
    SELECT json_agg(json_build_object('id', img.id, 'image_path', img.image_path, 'sort_order', img.sort_order)
                    ORDER BY img.sort_order)
    FROM item_images img
    WHERE img.item_id = i.id
  ), '[]') AS images`;

const TAGS_SUBQUERY = `
  COALESCE((
    SELECT json_agg(json_build_object('id', t.id, 'name', t.name, 'color', t.color) ORDER BY t.name)
    FROM item_tags it
    JOIN tags t ON t.id = it.tag_id
    WHERE it.item_id = i.id
  ), '[]') AS tags`;

const FROM_CLAUSE = `
  FROM items i
  LEFT JOIN categories c ON c.id = i.category_id`;

// The storefront gets an explicit column list — it has no business seeing
// paypal_order_id or reserved_until.
export const PUBLIC_ITEM_SELECT = `
  SELECT i.id, i.name, i.description, i.price_cents, i.status, i.created_at, i.category_id,
    c.name AS category_name,
    ${IMAGES_SUBQUERY},
    ${TAGS_SUBQUERY}
  ${FROM_CLAUSE}`;

export const ADMIN_ITEM_SELECT = `
  SELECT i.*,
    c.name AS category_name,
    ${IMAGES_SUBQUERY},
    ${TAGS_SUBQUERY}
  ${FROM_CLAUSE}`;

/** The columns every item select returns, whichever of the two it is. */
interface ItemRowBase {
  id: number;
  name: string;
  description: string | null;
  price_cents: number;
  status: ItemStatus;
  created_at: Date;
  category_id: number | null;
  category_name: string | null;
  // json_agg with a COALESCE fallback, so these are always arrays and never null.
  images: ItemImage[];
  tags: ItemTag[];
}

/** What PUBLIC_ITEM_SELECT returns. Deliberately no payment or reservation columns. */
export type PublicItemRow = ItemRowBase;

/**
 * What ADMIN_ITEM_SELECT returns: `i.*`, so every column on the table.
 *
 * The extra fields are the ones the storefront is not allowed to see, which is
 * the whole reason the two selects differ.
 */
export interface AdminItemRow extends ItemRowBase {
  reserved_until: Date | null;
  sold_at: Date | null;
  paypal_order_id: string | null;
}

/**
 * A bare `items` row, as `RETURNING *` gives it back.
 *
 * Distinct from the two select rows above and not interchangeable with them:
 * this is the table, so it has no category_name, no images and no tags. Those
 * come from the joins and subqueries the selects add, and typing a RETURNING *
 * as AdminItemRow would promise three fields that are not in the result.
 */
export interface ItemRecord {
  id: number;
  name: string;
  description: string | null;
  price_cents: number;
  status: ItemStatus;
  reserved_until: Date | null;
  sold_at: Date | null;
  paypal_order_id: string | null;
  created_at: Date;
  category_id: number | null;
}