#lang r7rs

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;;                                Score ADT                                  ;;
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;; Tracks the player's score. Contains NO graphics code.

(define-library (pacman-project adt score)
  (import (scheme base)
          (pacman-project constants))
  (export make-score)

  (begin

    ;; make-score :: -> score
    ;; Creates a new score object, starting at 0.
    (define (make-score)
      (let ((points 0))

        ;; increase! :: -> /
        ;; Increases the score by points-per-coin.
        (define (increase!)
          (set! points (+ points points-per-coin)))

        ;; dispatch-score :: symbol -> any
        (define (dispatch-score msg)
          (cond ((eq? msg 'points) points)
                ((eq? msg 'increase!) increase!)
                (else (error "Score ADT -- Unknown message:" msg))))

        dispatch-score))))