(import srfi-69 matchable)

;;;
;;; Actor creation
;;;

(define actor-table (make-hash-table))

(define (make-actor-with-address address behaviour)
  (hash-table-set! actor-table address behaviour)
  address)

(define next-actor-address 1)

(define (make-actor behaviour)
  (make-actor-with-id next-actor-address behaviour)
  (let ((address next-actor-address))
    (set! next-actor-address (+ next-actor-address 1))
    address))

;;;
;;; Message dispatch
;;;

(define (dispatch-message address message)
  (let ((behaviour (hash-table-ref actor-table address)))
    (unless (null? behaviour)
      ((hash-table-ref actor-table address)))) message)

;;;
;;; FIFO queue implementation
;;;

(define (make-fifo)
  (define (cell val prev next)
    (list val prev next))
  (define cell-val car)
  (define cell-prev cadr)
  (define cell-next caddr)
  (define (set-cell-prev! cell prev-cell)
    (set-car! (cdr cell) prev-cell))
  (define (set-cell-next! cell next-cell)
    (set-car! (cddr cell) next-cell))

  (let ((head '())
        (tail '()))
    (lambda (cmd . args)
      (case cmd
        ((empty?) (null? head))
        ((push) (if (not (= (length args) 1))
                    (error "Wrong number of arguments to push.")
                    (if (not (null? head))
                        (let ((old-head head))
                          (set! head (cell (car args) '() old-head))
                          (set-cell-prev! old-head head))
                        (begin
                          ;; Initialize list
                          (set! head (cell (car args) '() '()))
                          (set! tail head)))))
        ((pop) (if (not (= (length args) 0))
                   (error "Wrong number of arguments to pop.")
                   (if (null? head)
                       (error "FIFO empty.")
                       (let ((old-tail tail))
                         (set! tail (cell-prev old-tail))
                         (if (null? tail)
                             (set! head '())
                             (set-cell-next! tail '()))
                         (cell-val old-tail)))))))))

(define (fifo-push fifo x)
  (fifo 'push x))

(define (fifo-pop fifo)
  (fifo 'pop))

(define (fifo-empty? fifo)
  (fifo 'empty?))


;;;
;;; Message queue
;;;

(define message-queue (make-fifo))

(define (next-addressed-msg)
  (if (fifo-empty? message-queue)
      '()
      (fifo-pop message-queue)))

(define (send-message actor message)
  (fifo-push message-queue (cons actor message)))

(define (run)
  (let ((addressed-msg (next-addressed-msg)))
    (if (null? msg)
        'done
        (begin
          (apply dispatch-message addressed-msg)
          (run)))))

;;;
;;; Send
;;;