# Pastebin IY0Z8pcR
#lang racket

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

(struct invoice (id date client items tax) #:transparent)
(struct item (desc hours rate) #:transparent)

;; =========================================================
;; SIMPLE INDENTATION PARSER
;; Converts DSL text → nested S-expressions
;; =========================================================

(define (indent-level line)
  (length (regexp-match* #px"^ *" line)))

(define (tokenize line)
  (map string->symbol
       (regexp-split #px"\\s+" (string-trim line))))

(define (parse-dsl text)
  (define lines
    (filter (λ (l) (not (regexp-match? #px"^\\s*$" l)))
            (string-split text "\n")))

  (define stack '())   ;; (indent . node)
  (define root '())

  (for ([line lines])
    (define ind (indent-level line))
    (define node (tokenize line))

    ;; pop until correct parent
    (set! stack
          (let loop ([st stack])
            (cond
              [(empty? st) st]
              [(<= ind (caar st)) (loop (cdr st))]
              [else st])))

    (cond
      [(empty? stack)
       (set! root (cons node root))]

      [else
       (define parent (cdar stack))
       (set-cdr! (car stack)
                 (append parent (list node)))])

    (set! stack (cons (cons ind node) stack)))

  (reverse root))

;; =========================================================
;; DSL → AST
;; =========================================================

(define (parse-invoice expr)
  (match expr
    [(list '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 cl)
          (set! client cl)]

         [(list 'item desc 'hours h 'rate r)
          (set! items
                (cons (item desc
                             (string->number (symbol->string h))
                             (string->number (symbol->string r)))
                      items))]

         [(list 'tax t)
          (define s (symbol->string t))
          (define num (string->number (regexp-replace #px"%" s "")))
          (set! tax (/ num 100.0))]))

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

;; =========================================================
;; EVALUATION
;; =========================================================

(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))))

;; =========================================================
;; RUNNER
;; =========================================================

(define (run text)
  (define parsed (parse-dsl text))
  (define inv (parse-invoice (car parsed)))
  (values inv (total inv)))

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

(define input
"invoice INV-001
  date 2026-04-29
  client AcmeCorp
  item WebsiteRedesign hours 10 rate 150
  item HostingSetup hours 2 rate 100
  tax 8%")

;; =========================================================
;; EXECUTION
;; =========================================================

(define-values (inv total-cost)
  (run input))

(displayln inv)
(displayln total-cost)