(use srfi-27)
(use srfi-1)

(define-syntax while
  (syntax-rules ()
    ((while condition
       things
       ...)
     (do ()
         ((not condition))
       things
       ...))))

;; (define x 0)
;; (while (< x 10) (set! x (+ x 1)) (display x))

(define (uniform min max)
  (+ min (* (- max min) (random-real))))

(define obra
  (graph
   ;; nodes and distributions
   `((T1 . ,(lambda () (uniform 32 48)))
     (T2 . ,(lambda () (uniform 40 60)))
     (T3 . ,(lambda () (uniform 15 25)))
     (T4 . ,(lambda () (uniform 10 15)))
     (T5 . ,(lambda () (uniform 10 15)))
     (T6 . ,(lambda () (uniform 6 10)))
     (T7 . ,(lambda () (uniform 18 24)))
     (T8 . ,(lambda () (uniform 4 8))))
   ;; dependencies
   '((T2 . (T1))
     (T3 . (T1 T2))
     (T4 . (T2))
     (T5 . (T2 T3))
     (T6 . (T2))
     (T7 . (T2 T4 T5))
     (T8 . (T4 T5 T6 T7)))))

(define (graph list-of-distributions list-of-dependencies)
  ;; start -> initializes alist of (TX . -1)
  (define (start lst) (map (lambda (node) (cons (car node) -1)) lst))
  (define global-association-list (start list-of-distributions))
  ;; nodes-left? -> is there any node with -1?
  (define (nodes-left?) (any (lambda (x) (= -1 (cdr x))) global-association-list))
  ;; dependencies -> dependencies of a certain element
  (define (dependencies token) (cdr (assq token list-of-dependencies)))
  ;; dep-solved? -> all dependencies already have their value != 1
  (define (dep-solved? token)
    (not (any (lambda (dep)
                (= -1 (cdr (assq dep global-association-list))))
              (dependencies token))))
  ;; need-and-ready -> items which have both all deps and need a time
  (define (need-and-ready)
    (filter (lambda (node)
              (and (= -1 (cdr node))
                   (dep-solved? (car node))))
            global-association-list))
  ;; compute-ready-nodes! -> compute nodes which have no precedence problem
  (define (compute-ready-nodes!)
    (for-each (lambda (node)
                (set-cdr! node
                          (+ ((cdr (assq (car node) list-of-distributions)))
                             something-here)))
              (need-and-ready)))
  (while (nodes-left?)
    (compute-ready-nodes!))
  global-association-list)