#lang scheme/base

(require web-server/servlet
         web-server/managers/lru)

(require (planet "xhtml.ss" ("dherman" "xhtml.plt" 1 2))
         (planet "parameter.ss" ("untyped" "unlib.plt" 3)))

;; (string (listof xexpr) -> response)
(define (default-page title body)
  (make-response/xhtml
   `(html (head (title ,title)
                (link ((media "screen")
                       (rel "stylesheet")
                       (href "style/style.css")
                       (type "text/css"))))
          (body (div ((class "box"))
                     (div ((class "content"))
                          (h1 ,title)
                          
                          (div ((class "body"))
                               ,@body)))))))

(define (default-instance-expiration-handler exn)
  (default-page "Page Has Expired"
    '((p ((class "message"))
         "Sorry, this page has expired.  Please go back "
         (a ((href "/")) "home")))))

(define (default-servlet request)
  (default-page "Hello!"
    '((p "Hello! This is my new website.  Nothing to see yet, but check back soon!"))))

(define-parameter current-instance-expiration-handler
  default-instance-expiration-handler
  (make-guard procedure? "procedure?")
  with-instance-expiration-handler)

(define-parameter current-servlet-function
  default-servlet
  (make-guard procedure? "procedure?")
  with-servlet-function)

(define (instance-expiration-handler exn)
  ((current-instance-expiration-handler) exn))

(define interface-version 'v2)

(define manager
  (let ([memory-threshold (* 64 1024 1024)]) ; in bytes
    (create-LRU-manager
     ;; Called when an instance has expired.
     instance-expiration-handler
     ;; The condition below is checked every 5 seconds
     5
     ;; One 'life point' is deducted every 10 minutes
     (* 10 60)
     ;; If this condition is true a 'life point' is deducted
     ;; from the continuation
     (lambda ()
       (define memory-use (current-memory-use))
       (define collect?   (or (>= memory-use memory-threshold)
                              (< memory-use 0)))
       collect?)
     ;; The number of 'life points' an continuation starts with
     #:initial-count 24
     ;; Logging done whenever an continuation is collected
     #:inform-p (lambda args
                  (void)))))

(define (start request)
  ((current-servlet-function) request))

; Provide statements -----------------------------

(provide interface-version
         manager
         start
         
         with-servlet-function
         with-instance-expiration-handler)