; ORACLE: Simple magic 8-ball program
; Requires Aubrey Jaffer's SLIB
(require 'random)

; Basic decision roller for the Oracle
(define (oracle-roll)
  (exact->inexact (/ (random 100) 10)))

; Advanced contemplator for the Oracle
(define (oracle-think i j w)
  (begin
    (cond
      ((< j 1) (oracle-process w))
      (else (let ((op (random 4)))
              (cond
                ((= op 0) (oracle-think i (- j 1) (/ w (oracle-roll))))
                ((= op 1) (oracle-think i (- j 1) (* w (oracle-roll))))
                ((= op 2) (oracle-think i (- j 1) (- w (oracle-roll))))
                ((= op 3) (oracle-think i (- j 1) (+ w (oracle-roll))))))))))

; Decimal shifter for processing the end result of a contemplation cycle
(define (oracle-process n)
  (begin
    (cond
      ((< n 0) (oracle-process (abs n)))
      ((< n 10) n)
      (else (oracle-process (exact->inexact (/ n 10)))))))

; Decision processor for the Oracle
(define (oracle-decide r)
  (begin
    (cond
      ((< r 1)   (display "NOT A CHANCE"))
      ((< r 2)   (display "NOT AT ALL LIKELY"))
      ((< r 3)   (display "NO"))
      ((< r 4.5) (display "OUTLOOK NOT GOOD"))
      ((< r 5.5) (display "CANNOT REACH A DECISION"))
      ((< r 7)   (display "OUTLOOK GOOD"))
      ((< r 8)   (display "YES"))
      ((< r 9)   (display "ABSOLUTELY"))
      ((< r 10)  (display "YOU MAY RELY ON IT")))
    (newline)
    r))

; Receive a random answer from the Oracle
(define (oracle)
  (oracle-decide (oracle-roll)))

; Ask the Oracle a single question
(define (ask-oracle question)
  (begin
    (display "Q: ") (display question) (newline)
    (display "A: ") (oracle)))

; Ask the Oracle to contemplate a question
(define (oracle-contemplate question)
    (let ((i (random 15)))
      (begin
        (display "Q: ") (display question) (newline)
        (display "PROCESSING...") (newline)
        (display "A: ") (oracle-decide (oracle-think i i (oracle-roll))))))

; Initiate a dialog with the Oracle
(define (oracle-dialog)
  (begin
    (display "Pose a question to the Oracle... ")
    (let ((q (read-line)))
      (cond
        ; ::::: Dialog exit checks :::::
        ((or
           (string-ci=? q "bye")
           (string-ci=? q "goodbye")
           (string-ci=? q "exit")
           (string-ci=? q "quit")) (display "A: GOODBYE"))
        ; ::::: Question processing :::::
        (else (begin
                (cond
                  ; ::::: For getting quick answers :::::
                  ((or
                     (string-ci=? q "q")
                     (string-ci=? q "quick")
                     (string-ci=? q "quickly")
                     (string-ci=? q "fast")) (begin
                                               (display "A: ")
                                               (let ((answer (oracle)))
                                                 (display "<")
                                                 (display answer)
                                                 (display ">")
                                                 (newline))))
                  ; ::::: Standard dialog processing, contemplates more deeply :::::
                  (else (begin
                          (let ((answer (oracle-contemplate q)))
                            (display "<")
                            (display answer)
                            (display ">")
                            (newline)))))
                (oracle-dialog)))))))