;; lib/commerce/tests/nettax.sx — discount-aware (net) tax policy.
;; Uses (commerce-test name got expected) provided by conformance.sh.

(define
  pcat
  (make-catalog
    (list
      (list "widget" 1000 :standard)
      (list "tea" 1000 :reduced))
    (list)
    (list)))

(define
  rules
  (list
    (list :uk :standard :guest 2000)
    (list :uk :reduced :guest 500)))

(define gctx (make-pricing-context pcat rules :uk :guest))

;; widget x3 = 3000 (standard), tea x6 = 6000 (reduced); subtotal 9000
(define
  cart
  (list (list "widget" :none 3) (list "tea" :none 6)))

(define ruleset (list (list :percent "TEN" :standard 1000)))

;; --- allocation: proportional, sums exactly to the discount ---

(commerce-test
  "allocate-even"
  (allocate-discount pcat cart 300)
  (list 100 200))
(commerce-test
  "allocate-sums-to-discount"
  (ct-sum (allocate-discount pcat cart 300))
  300)

;; remainder distribution: 100 over (3000,6000)/9000 = (33,66) rem 1 -> (34,66)
(commerce-test
  "allocate-remainder"
  (allocate-discount pcat cart 100)
  (list 34 66))
(commerce-test
  "allocate-remainder-sums"
  (ct-sum (allocate-discount pcat cart 100))
  100)

(commerce-test
  "allocate-zero"
  (allocate-discount pcat cart 0)
  (list 0 0))
(commerce-test
  "allocate-empty"
  (allocate-discount pcat empty-cart 0)
  (list))

;; --- net tax vs gross tax ---
;; discount = TEN 10% of standard 3000 = 300, allocated (100 200).
;; net: widget 2900@20%=580, tea 5800@5%=290 -> net tax 870 (gross was 900).

(commerce-test
  "net-quote"
  (cart-quote-net gctx cart ruleset (list))
  {:codes (list "TEN") :subtotal 9000 :discount 300 :total 9570 :tax 870})

;; same cart through the gross policy taxes 900 (the documented default)
(commerce-test
  "gross-quote-for-contrast"
  (quote-tax (cart-quote gctx cart ruleset (list)))
  900)

(commerce-test
  "net-tax-lower"
  (quote-tax (cart-quote-net gctx cart ruleset (list)))
  870)

;; --- no discount: net policy == gross policy ---

(commerce-test
  "no-discount-net-equals-gross"
  (=
    (cart-quote-net gctx cart (list) (list))
    (cart-quote gctx cart (list) (list)))
  true)

;; --- empty cart ---

(commerce-test
  "net-empty"
  (cart-quote-net gctx empty-cart ruleset (list))
  {:codes (list) :subtotal 0 :discount 0 :total 0 :tax 0})