backend_fiesta/services/productVisibility.go

package services

import "nearle/models"

// InStockOnly drops the products an outlet cannot actually sell.
//
// Being on a shelf is not the same as being in stock. Suriya Store's Peelamedu
// branch listed three products in the customer app of which exactly one had any
// stock, so a shopper could add a chocolate bar to their basket and order
// something the shop did not have. The rule the business wants is the simple
// one: if we have the stock, it can be ordered — otherwise it is not on offer.
//
// ── Why here and not in the SQL ──────────────────────────────────────────────
//
// The obvious implementation is another correlated subquery in GetProducts'
// WHERE clause. This is better for a reason that outlives the convenience:
// `Productstock` is the number the app DISPLAYS, computed by that query as the
// live SUM(in)-SUM(out) balance. Filtering on the same value that is shown makes
// it impossible for the two to disagree. A second copy of the balance
// expression in a WHERE clause is a copy that can drift from the one in the
// SELECT, and the failure it produces — a product listed as "3 in stock" that
// the filter considers empty, or worse the reverse — is very hard to see.
//
// It also filters on the ledger rather than productlocations.status. That flag
// is derived and admits drift: SyncProductLocationStatus repairs it on the next
// ledger entry, so between an order and that entry it can still read
// "available" for an empty shelf. The ledger cannot drift from itself.
//
// ── The locationID guard ─────────────────────────────────────────────────────
//
// Not defensive padding. GetProducts computes the stock balance scoped to
// params.LocationID, and with no outlet the subquery matches nothing, so EVERY
// product comes back with Productstock 0. Filtering that would turn an unscoped
// browse into an empty catalogue rather than an unfiltered one.
//
// The console is deliberately unaffected: its inventory screens read
// GetLocationProducts, a different query, and they must keep showing the empty
// lines — restocking them is the entire point of that screen.
func InStockOnly(products []models.Products, locationID int) []models.Products {
	if locationID <= 0 {
		return products
	}

	// Rebuilt rather than filtered in place: the caller's slice is the
	// repository's own result and nothing here should be writing through it.
	inStock := make([]models.Products, 0, len(products))
	for _, p := range products {
		if p.Productstock > 0 {
			inStock = append(inStock, p)
		}
	}
	return inStock
}

// InStockOnlyGrouped is InStockOnly for the grouped shape `getallproducts`
// returns: a tenant with its products, rather than a flat list.
//
// ── Why this one does NOT skip when locationID is 0 ──────────────────────────
//
// InStockOnly above returns early without an outlet, because the query behind
// it computes stock scoped to that outlet and answers 0 for everything when
// there is none — filtering that would empty the catalogue rather than filter
// it. FetchFilteredProducts is built differently: its stock subquery reads
// `(? = 0 OR locationid = ?)`, so with no outlet it aggregates the ledger across
// the tenant's outlets and still returns a real number. Measured 2026-09-02 on
// R mart: 24 products unscoped, 20 with a live balance and 4 at zero.
//
// So the number is trustworthy either way, and the rule can be applied either
// way: a shop that holds none of something anywhere is not offering it.
//
// A tenant left with no sellable products keeps its group, with an empty list.
// Dropping the group would tell the app the shop does not exist, which is a
// different and wrong statement — the shop is open, it has nothing on the shelf.
func InStockOnlyGrouped(groups []models.Tenantproducts) []models.Tenantproducts {
	out := make([]models.Tenantproducts, 0, len(groups))
	for _, group := range groups {
		kept := make([]models.Products, 0, len(group.Products))
		for _, product := range group.Products {
			if product.Productstock > 0 {
				kept = append(kept, product)
			}
		}
		group.Products = kept
		out = append(out, group)
	}
	return out
}

// WithoutVariantChildren drops the products that are a size of another one.
//
// The companion to InStockOnlyGrouped, and applied only for the customer app.
// A shop stocking Aachi Baby Fryums in 100g, 500g and 1kg has three rows; the
// shopper should meet one product with three sizes, not three near-identical
// listings they have to read the suffix of to tell apart.
//
// The group's visible row is the PARENT, and it carries the whole set in
// `variantoptions` — including its own size — so nothing is unreachable: every
// size is one tap away from the one row that remains.
//
// The console is deliberately unaffected. A merchant prices, restocks and
// publishes each size separately, so all three must stay visible there.
func WithoutVariantChildren(groups []models.Tenantproducts, isChild map[int]bool) []models.Tenantproducts {
	if len(isChild) == 0 {
		return groups
	}
	out := make([]models.Tenantproducts, 0, len(groups))
	for _, group := range groups {
		kept := make([]models.Products, 0, len(group.Products))
		for _, product := range group.Products {
			if isChild[product.Productid] {
				continue
			}
			kept = append(kept, product)
		}
		group.Products = kept
		out = append(out, group)
	}
	return out
}

// PricedOnly drops the products a shopper cannot be charged for.
//
// The companion to InStockOnlyGrouped, and the same argument: being in a shop's
// catalogue is not the same as being on sale. A product with no price is not
// free, it is unfinished — but ₹0 on a phone reads as free, and a shopper who
// taps it either expects to pay nothing or decides the shop is broken.
//
// ── Where the ₹0 products come from ─────────────────────────────────────────
//
// Import used to write no price at all, and 159 of the 1,572 catalogue rows
// still carry no price for it to copy — loose produce has none by design, and
// some scraped rows never had one. So an import lands at ₹0, the merchant adds
// stock, and the product goes on sale at nothing. Measured 2026-09-03: Kmart's
// entire customer-facing catalogue was five products, every one at ₹0.
//
// The merchant is not left guessing: the console lists these as "unpriced" with
// a Set price button, and pricing one puts it on sale immediately.
//
// Deliberately NOT applied to the console, for the same reason as the stock
// filter — an unpriced product is precisely what a merchant needs to see in
// order to fix it.
func PricedOnly(groups []models.Tenantproducts) []models.Tenantproducts {
	out := make([]models.Tenantproducts, 0, len(groups))
	for _, group := range groups {
		kept := make([]models.Products, 0, len(group.Products))
		for _, product := range group.Products {
			// `Price` is the effective figure the same query computed — the
			// outlet's own price, falling back to the master. Filtering on the
			// number that is DISPLAYED means the list and the label cannot
			// disagree.
			if product.Price > 0 {
				kept = append(kept, product)
			}
		}
		group.Products = kept
		out = append(out, group)
	}
	return out
}