/**
 * The aisle the customer app actually displays, and how a category becomes one.
 *
 * ── What the app does ───────────────────────────────────────────────────────
 *
 * Its browse screen calls
 *
 *   GET /mob/products/getproductsbysubcategory?categoryid=2&tenantid=…&locationid=…
 *
 * and that endpoint does two things (`services/productService.go:237`):
 *
 *   1. `GetProducts` filters on `a.categoryid = ?` — UNCONDITIONALLY, with the
 *      2 from the query string.
 *   2. It then buckets the result by `products.subcategoryid`, against the rows
 *      of `productsubcategories` for category 2. Anything with subcategoryid 0
 *      falls into a bucket literally named "Uncategorized".
 *
 * So the heading a shopper reads is the SUBCATEGORY, not the category — and
 * `categoryid` is not a label at all, it is the filter that decides whether the
 * product comes back. Measured on live tenant 1135/1166: every product returns
 * `categoryid: 2, subcategoryid: 0`, so the app renders a single heading,
 * "Uncategorized", holding the whole shop. That is exactly the report from the
 * app side, and it is why nothing displays category-wise.
 *
 * TWO CONSEQUENCES, both the opposite of what looks obvious:
 *
 *   - `categoryid` must stay 2. Writing a per-product categoryid — 91 for
 *     Dairy, 92 for Spices — does not label the product, it removes it: the app
 *     asks for 2 and the row no longer matches.
 *   - `subcategoryid` is what has to be written, and it can only be one of the
 *     ten rows `productsubcategories` holds for category 2. Those are platform
 *     rows shared by every tenant, not something a shop creates.
 *
 * ── Why the ids are looked up rather than hardcoded ─────────────────────────
 *
 * `productsubcategories` (subcatid 14-23) and the app's own utils list
 * (`/mob/utils/getsubcategories`, ids 9-18) carry the SAME TEN NAMES under
 * different ids. The grouping reads the first, so those are the ids to write —
 * but two tables one offset apart is precisely the shape that gets confused, so
 * the ids are read back by name from the same API the grouping uses, and
 * `FALLBACK_AISLE_IDS` is used only when that call cannot be made.
 */

import type { ProductSubCategory } from '@/api/types';

/** The ten aisles, in the order the app lists them. */
export const APP_AISLES = [
  'Vegetables & Fruits',
  'Dairy, Deli & Egg',
  'Meat, Chicken & Fish',
  'Bakes & Nuts',
  'Foodgrains & Pulses',
  'Oil & Ghee',
  'Rice & Cereals',
  'Snacks & Drinks',
  'Beauty & Personal Care',
  'Hygiene Essentials',
] as const;

export type AppAisle = (typeof APP_AISLES)[number];

/**
 * The ids as `productsubcategories` holds them today, read from live on
 * 2026-09-08. Used only when the lookup cannot be made — see the header.
 */
export const FALLBACK_AISLE_IDS: Record<AppAisle, number> = {
  'Vegetables & Fruits': 14,
  'Dairy, Deli & Egg': 15,
  'Meat, Chicken & Fish': 16,
  'Bakes & Nuts': 17,
  'Foodgrains & Pulses': 18,
  'Oil & Ghee': 19,
  'Rice & Cereals': 20,
  'Snacks & Drinks': 21,
  'Beauty & Personal Care': 22,
  'Hygiene Essentials': 23,
};

/**
 * The catalogue team's 31 categories, folded into the app's ten aisles.
 *
 * The 31 are a finer classification than the shop floor has room for, so this
 * is a real narrowing and some of it is judgement rather than fact: "Spices &
 * Masalas" has no aisle of its own and goes to Foodgrains & Pulses, the nearest
 * the app offers. Where a category could sit in two it goes to the one a
 * shopper would look in first — instant noodles to Snacks & Drinks rather than
 * Rice & Cereals, because that is where a shop stocks them.
 *
 * Anything not listed — including "General", the ladder's explicit "we do not
 * know" — has no aisle, and `aisleForCategory` returns null rather than
 * guessing. Those products land in the app's own "Uncategorized" bucket, which
 * is honest: it says the classification failed, instead of shelving bleach with
 * the butter.
 */
const AISLE_FOR_CATEGORY: Record<string, AppAisle> = {
  /* Bakes & Nuts */
  'biscuits & cookies': 'Bakes & Nuts',
  rusk: 'Bakes & Nuts',
  crackers: 'Bakes & Nuts',
  'cakes & muffins': 'Bakes & Nuts',
  'bakery & breads': 'Bakes & Nuts',

  /* Snacks & Drinks */
  snacks: 'Snacks & Drinks',
  chocolates: 'Snacks & Drinks',
  'candy & confectionery': 'Snacks & Drinks',
  beverages: 'Snacks & Drinks',
  'noodles & instant food': 'Snacks & Drinks',

  /* Foodgrains & Pulses */
  'pulses, grains & spices': 'Foodgrains & Pulses',
  'spices & masalas': 'Foodgrains & Pulses',
  'salt & staples': 'Foodgrains & Pulses',
  'sugar & jaggery': 'Foodgrains & Pulses',

  /* Rice & Cereals */
  'atta & staples': 'Rice & Cereals',

  /* Oil & Ghee */
  'cooking oils': 'Oil & Ghee',

  /* Dairy, Deli & Egg */
  dairy: 'Dairy, Deli & Egg',
  eggs: 'Dairy, Deli & Egg',

  /* Meat, Chicken & Fish */
  'fish & seafood': 'Meat, Chicken & Fish',

  /* Vegetables & Fruits */
  'fruits & vegetables': 'Vegetables & Fruits',
  'fresh herbs & greens': 'Vegetables & Fruits',
  flowers: 'Vegetables & Fruits',

  /* Beauty & Personal Care */
  'oral care': 'Beauty & Personal Care',
  'hair care': 'Beauty & Personal Care',
  'bath soap': 'Beauty & Personal Care',
  'skin & bath care': 'Beauty & Personal Care',
  'fragrance & deodorants': 'Beauty & Personal Care',

  /* Hygiene Essentials */
  'household cleaning': 'Hygiene Essentials',
  'health care - antiseptic': 'Hygiene Essentials',
  'household - agarbatti': 'Hygiene Essentials',
  'household - lamp oil': 'Hygiene Essentials',
};

/**
 * Every dash normalised to a plain hyphen before lookup.
 *
 * The registry writes "Household – Agarbatti" with an en-dash and a sheet typed
 * by hand will not. Two strings that read identically must not reach different
 * aisles because of which key somebody pressed.
 */
function keyOf(category: string | null | undefined): string {
  return (category ?? '')
    .trim()
    .toLowerCase()
    .replace(/[‐-―]/g, '-')
    .replace(/\s*-\s*/g, ' - ')
    .replace(/\s+/g, ' ');
}

/** The aisle a classified category belongs in, or null when there is none. */
export function aisleForCategory(category: string | null | undefined): AppAisle | null {
  return AISLE_FOR_CATEGORY[keyOf(category)] ?? null;
}

/**
 * Aisle name to the id the app groups on, from the platform's own list.
 *
 * Matched on the NAME, because the id is exactly what differs between the two
 * tables carrying these ten rows. A name the API does not return has no id, and
 * the caller writes 0 rather than a number out of the wrong table.
 */
export function aisleIdsFrom(
  subcategories: readonly ProductSubCategory[] | undefined,
): Map<string, number> {
  const out = new Map<string, number>();
  for (const row of subcategories ?? []) {
    const name = (row.subcatname ?? '').trim();
    if (name && row.subcatid > 0) out.set(name.toLowerCase(), row.subcatid);
  }
  if (out.size === 0) {
    for (const [name, id] of Object.entries(FALLBACK_AISLE_IDS)) out.set(name.toLowerCase(), id);
  }
  return out;
}

/** The subcategory id for a classified category — 0 when it has no aisle. */
export function aisleIdForCategory(
  category: string | null | undefined,
  aisleIds: ReadonlyMap<string, number>,
): number {
  const aisle = aisleForCategory(category);
  if (!aisle) return 0;
  return aisleIds.get(aisle.toLowerCase()) ?? FALLBACK_AISLE_IDS[aisle];
}