(define make-room
    (lambda (name)
        (local                    ; local state of room object
            ((define thing #f)    ; by default, nothing in room
             (define east #f)     ; by default, no adjoining rooms
             (define west #f)     ;   ...
             (define north #f)    ;   ...
             (define south #f))   ;   ...
            (lambda (msg)         ; start of object returned
               (cond
                  ((null? msg) 'badmessage)

                  ; initialize things and adjoining rooms
                  ((eq? (car msg) 'set-thing!) (set! thing (car (cdr msg))))
                  ((eq? (car msg) 'set-east!) (set! east (car (cdr msg))))
                  ((eq? (car msg) 'set-west!) (set! west (car (cdr msg))))
                  ((eq? (car msg) 'set-north!) (set! north (car (cdr msg))))
                  ((eq? (car msg) 'set-south!) (set! south (car (cdr msg))))

		  ((eq? (car msg) 'name) name)
		  
                  ; look at surroundings
                  ((eq? (car msg) 'observe-thing) thing)
                  ((eq? (car msg) 'observe-east) east)
                  ((eq? (car msg) 'observe-west) west)
                  ((eq? (car msg) 'observe-north) north)
                  ((eq? (car msg) 'observe-south) south)

                  ((eq? (car msg) 'take-thing)
                   (local ((define x thing)) (set! thing #f) x))

                  (else 'badmessage))))))

(define make-person
    (lambda (initial-room)
       (local
           ((define thing #f)           ; initially, nothing carried
            (define room initial-room))
           (lambda (msg)                ; start of object returned
              (cond
                 ((null? msg) 'badmessage)

                 ; initialize thing and room
                 ((eq? (car msg) 'set-thing!) (set! thing (car (cdr msg))))
                 ((eq? (car msg) 'set-room!) (set! room (car (cdr msg))))

                 ; look around
                 ((eq? (car msg) 'look-room)
                  (if room
		      (local
			  ((define eastroom (room (list 'observe-east)))
			   (define westroom (room (list 'observe-west)))
			   (define northroom (room (list 'observe-north)))
			   (define southroom (room (list 'observe-south))))
			  (list (room (list 'observe-thing))
				(if eastroom (eastroom (list 'name)) #f)
				(if westroom (westroom (list 'name)) #f)
				(if northroom (northroom (list 'name)) #f)
				(if southroom (southroom (list 'name)) #f)))
                      'badmessage))
                 ((eq? (car msg) 'look-self)
                  thing)

                 ; move, if possible
                 ((eq? (car msg) 'go-east)
                  (if (and room (room (list 'observe-east)))
                      (set! room (room (list 'observe-east)))
                      'badmessage))
                 ((eq? (car msg) 'go-west)
                  (if (and room (room (list 'observe-west)))
                      (set! room (room (list 'observe-west)))
                      'badmessage))
                 ((eq? (car msg) 'go-north)
                  (if (and room (room (list 'observe-north)))
                      (set! room (room (list 'observe-north)))
                      'badmessage))
                 ((eq? (car msg) 'go-south)
                  (if (and room (room (list 'observe-south)))
                      (set! room (room (list 'observe-south)))
                      'badmessage))

                 ; get the room's thing if any, dropping our current thing
                 ((eq? (car msg) 'get-thing)
                  (if (and room (room (list 'observe-thing)))
                      (local
                          ((define temp-thing (room (list 'observe-thing))))
                          (room (list 'set-thing! thing))
                          (set! thing temp-thing))
                      'badmessage)

                 (else 'badmessage)))))))

(define room1 (make-room 'joes-office))
(define room2 (make-room 'johns-office))
(define room3 (make-room 'PL210))
(define room4 (make-room 'CS-office))

(room1 (list 'set-thing! 'ball))
(room2 (list 'set-thing! 'key))
(room4 (list 'set-thing! 'stapler))

(room1 (list 'set-east! room3))
(room1 (list 'set-north! room2))
(room2 (list 'set-south! room1))
(room2 (list 'set-west! room4))
(room3 (list 'set-south! room1))
(room3 (list 'set-north! room2))
(room4 (list 'set-east! room2))
(room4 (list 'set-west! room1))
(room4 (list 'set-north! room1))

(define joe (make-person room1))
(define john (make-person room2))