# Pastebin QmJXAyuB
#lang rhombus

;; =========================================================
;; AST DEFINITIONS
;; =========================================================

struct invoice(id, date, client, items, tax)
struct item(desc, hours, rate)

;; =========================================================
;; DSL SYNTAX CLASSES
;; =========================================================

syntax_class invoice_item:
  pattern [item desc hours h rate r]:
    #'(item desc h r)

syntax_class invoice_clause:
  pattern ~or:
    [date d]
    [client c]
    invoice_item
    [tax t]

;; =========================================================
;; MAIN INVOICE DSL FORM
;; =========================================================

syntax_class invoice_block:
  pattern [invoice id clause ...]:
    #'(build-invoice id (list clause ...))

;; =========================================================
;; EXPANDER / EVALUATOR
;; =========================================================

(define (parse-tax t)
  ;; converts 8% -> 0.08
  (define s (symbol->string t))
  (define num (string->number (regexp-replace #px"%" s "")))
  (/ num 100.0))

(define (build-invoice id clauses)
  (define date #f)
  (define client #f)
  (define items '())
  (define tax 0.0)

  (for ([c clauses])
    (match c
      [(list 'date d)
       (set! date d)]

      [(list 'client c)
       (set! client c)]

      [(item desc h r)
       (set! items (cons (item desc h r) items))]

      [(list 'tax t)
       (set! tax (parse-tax t))]))

  (invoice id date client (reverse items) tax))

;; =========================================================
;; BUSINESS LOGIC
;; =========================================================

(define (subtotal inv)
  (for/sum ([i (invoice-items inv)])
    (* (item-hours i)
       (item-rate i))))

(define (total inv)
  (define sub (subtotal inv))
  (+ sub (* sub (invoice-tax inv))))

;; =========================================================
;; DSL EXAMPLE
;; =========================================================

invoice INV-001:
  date 2026-04-29
  client "Acme Corp"

  item "Website redesign" hours 10 rate 150
  item "Hosting setup" hours 2 rate 100

  tax 8%

;; =========================================================
;; OPTIONAL TEST EVALUATION
;; =========================================================

;; If your Rhombus environment supports evaluating last form:
;; you can bind and compute like this:

(define example-invoice
  (build-invoice 'INV-001
    (list
      '(date "2026-04-29")
      '(client "Acme Corp")
      (item "Website redesign" 10 150)
      (item "Hosting setup" 2 100)
      '(tax 8%))))

(define example-total (total example-invoice))

example-invoice
example-total