;;; Provides a read-only Racket connection to public Liitin objects and a set of functions to utilize them locally.
(module liitin-lib racket
  
  ;;; Note that while an external connection to Liitin objects provides access to the persistent storage system along with dynamic updates,
  ;;; it cannot quarantee compatibility between diverse operating systems and application versions under constant changes. 
  ;;; For full benefits, a native Liitin account is needed.
  ;;; Finndesign Liitin home page: http://liitin.finndesign.fi
  
  
  ;; A set of requires to approximate the Liitin environment.
  ;; You may additionally want to set the DrRacket language level to 'Pretty Big', uncheck case sensivity,
  ;; and uncheck 'Disallow redefinition of initial bindings' to further improve compatibility.
  (require (lib "process.ss")
           mzlib/string
           racket/port
           racket/file
           racket/gui
           framework
           racket/date)
  
  (provide 
   (rename-out [my-top #%top])
   (except-out (all-from-out racket) #%top)
   (all-defined-out)
   (all-from-out mzlib/string)
   (all-from-out racket/file)
   (except-out (all-from-out racket/gui) #%top)
   (all-from-out framework)
   (all-from-out racket/port))
  
  
  ;XXX  READ-ONLY LIITIN CLIENT XXX
  
  (define server-name "liitin.finndesign.fi")
  (define server-port 9877)
  
  (define (eval-in-server server-name server-port expr)
    (let-values (((server->me me->server)
                  (tcp-connect server-name server-port)))
      (write expr me->server)-
      (close-output-port me->server)
      (let ((response (read server->me)))
        (close-input-port server->me)
        response)))
  
  (define (quotify var) (eval-string (string-append "''" (symbol->string var))))
  
  (define-syntax-rule (my-top . id) 
    (lookup 'id))
  
  (define (lookup id)
    (define (symbolize id-candidate)
      (eval-string (string-append "'" (symbol->string id-candidate))))
    (if (l-exists? (symbolize id))
        (eval-string (l-get (symbolize id)))
        (error (string-append "reference to undefined identifier: " (symbol->string id)))))
  
  
  ;XXX  UTILS  XXX
  
  ;; For the future use: requests Liitin server identification
  (define (l-id server-name server-port)
    (eval-in-server server-name server-port '(identify-yourself)))
  
  ;; Liitin-object-exists?. 
  ;; E.g. (l-exists? 'gaia:fibonacci) or (l-exists? 'gaia:fibonacci:2011-06-30T12:00:00) >> #t/#f
  ;; Leaving the timestamp out returns #t if any version exists
  ;; The timestamp can point to the future but pointing too early in history returns #f
  (define (l-exists? liitin-object)
    (eval-in-server server-name server-port (list 'public-object-exists? (quotify liitin-object))))
  
  ;; Fetches the specified Liitin object
  ;; E.g. (l-get 'gaia:fibonacci) or (l-get 'gaia:fibonacci:2011-06-30T12:00:00) >> string
  ;; Leaving the timestamp out returns the latest version
  ;; Inexact timestamp returns the latest version at the specified time
  (define (l-get liitin-object)
    (eval-in-server server-name server-port (list 'fetch-public-object-contents (quotify liitin-object))))
  
  ;; Lists all existing versions of the specified Liitin object
  ;; E.g. (l-versions 'gaia:fibonacci) >> list 
  (define (l-versions liitin-object)
    (eval-in-server server-name server-port (list 'public-object-versions (quotify liitin-object))))
  
  ;; To allow using the same top-level definition format as in Liitin
  ;; i.e. (named-lambda (name args) ...) = (define (name args) ...)
  (define-syntax named-lambda
    (syntax-rules ()
      ((rec (name . variables) . body)
       (letrec ((name (lambda variables . body))) name))
      ((rec name expression)
       (letrec ((name expression)) name))))
  
  
;;XXX  EXAMPLES  XXX
;
;;; Use of the provided primitives (see liitin-lib.rkt for more information)
;(l-id server-name server-port)
;(l-exists? 'gaia:fibonacci:2011-01-01T12:00:00)
;(l-get 'gaia:fibonacci:2011-01-01T12:00:00)
;(l-versions 'gaia:fibonacci)
;
;;; Calling Liitin objects
;(gaia:fibonacci 10)
;(mirko:eliza "i can't play piano")
;(map gaia:fibonacci '(1 2 3 4 5 6 7 8 9 10)); combine freely with local primitives (map in this case)
;(jtu100:calculator~); GUI example (functionality not implemented)
  
  )