; Model 3 - Continuous Simulation Model
(require (planet "simulation-with-graphics.ss"
                 ("williams" "simulation.plt")))
(require (planet "random-distributions.ss"
                 ("williams" "science.plt")))

;; Simulation Parameters
(define end-time 720.0)
(define n-pits 7)
(define initial-furnace-temp 1000.0)

; Data collection variables
(define total-ingots 0)
(define wait-time #f)
(define heat-time #f)
(define leave-temp #f)

;;; Model Definition
(define random-sources (make-random-source-vector 4))

(define furnace-set #f)
(define furnace-temp #f)
(define pit #f)

(define (scheduler)
  (let loop ((i 0))
    (schedule now (ingot i))
    (wait (random-exponential (vector-ref random-sources 0) 1.5))
    (loop (+ i 1))))

(define-process (furnace)
  (set! furnace-temp (make-continuous-variable initial-furnace-temp))
     furnace-temp (* (- 2500.0 (variable-value furnace-temp)) 0.05))))

(define-process (ingot i)
  (let* ((initial-temp (random-flat (vector-ref random-sources 1) 100.0 200.0))
         (heat-coeff (+ (random-gaussian
                         (vector-ref random-sources 2) 0.05 0.01) 0.07))
         (final-temp (random-flat (vector-ref random-sources 3) 800.0 1000.0))
         (current-temp (make-continuous-variable initial-temp))
         (arrive-time (current-simulation-time))
         (start-time #f))
;    (if (= (modulo i 100) 0)
;        (accumulate (variable-history current-temp)))
    (with-resource (pit)
      (set-variable-value! wait-time (- (current-simulation-time) arrive-time))
      (set-insert! furnace-set self)
      (set! start-time (current-simulation-time))
        until (>= (variable-value current-temp) final-temp)
         (* (- (variable-value furnace-temp) (variable-value current-temp))
      (set-variable-value! heat-time (- (current-simulation-time) start-time))
      (set-variable-value! leave-temp (variable-value current-temp))
      (set-remove! furnace-set self))
    (if (variable-history current-temp)
        (printf "~a~n"
                (history-plot (variable-history current-temp)
                              (format "Ingot ~a Temperature History" i))))
    (set! total-ingots (+ total-ingots 1))))

(define (stop-sim)
  (printf "Report after ~a Simulated Hours - ~a Ingots Processed~n"
          (current-simulation-time) total-ingots)
  (printf "~n-- Ingot Waiting Time Statistics --~n")
  (printf "Mean Wait Time        = ~a~n" (variable-mean wait-time))
  (printf "Variance              = ~a~n" (variable-variance wait-time))
  (printf "Maximum Wait Time     = ~a~n" (variable-maximum wait-time))
  (printf "~n-- Ingot Heating Time Statistics --~n")
  (printf "Mean Heat Time        = ~a~n" (variable-mean heat-time))
  (printf "Variance              = ~a~n" (variable-variance heat-time))
  (printf "Maximum Heat Time     = ~a~n" (variable-maximum heat-time))
  (printf "Minimum Heat Time     = ~a~n" (variable-minimum heat-time))
  (printf "~n-- Final Temperature Statistics --~n")
  (printf "Mean Leave Temp       = ~a~n" (variable-mean leave-temp))
  (printf "Variance              = ~a~n" (variable-variance leave-temp))
  (printf "Maximum Leave Temp    = ~a~n" (variable-maximum leave-temp))
  (printf "Minimum Leave Temp    = ~a~n" (variable-minimum leave-temp))
  (printf "~a~n"
          (history-plot (variable-history leave-temp)
                        "Final Temperature Histogram"))
  (printf "~n-- Furnace Utilization Statistics --~n")
  (printf "Mean No. of Ingots    = ~a~n"
          (variable-mean (set-variable-n furnace-set)))
  (printf "Variance              = ~a~n"
          (variable-variance (set-variable-n furnace-set)))
  (printf "Maximum No. of Ingots = ~a~n"
          (variable-maximum (set-variable-n furnace-set)))
  (printf "Minimum No. of Ingots = ~a~n"
          (variable-minimum (set-variable-n furnace-set)))
  (printf "~a~n"
          (history-plot (variable-history (set-variable-n furnace-set))
                        "Furnace Utilization History"))

(define (initialize)
  (current-simulation-max-step-size (/ 1.0 60.0))
  (set! total-ingots 0)
  (set! wait-time (make-variable))
  (set! heat-time (make-variable))
  (set! leave-temp (make-variable))
  (set! pit (make-resource n-pits))
  (set! furnace-set (make-set))
  (accumulate (variable-history (set-variable-n furnace-set)))
  (tally (variable-statistics wait-time))
  (tally (variable-statistics heat-time))
  (tally (variable-statistics leave-temp))
  (tally (variable-history leave-temp))
  (schedule (at end-time) (stop-sim))
  (schedule (at 0.0) (scheduler))
  (schedule now (furnace)))

(define (run-simulation)