Gotchas!
=======

All items for a page *must* be part of a list!
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

   OK:     (list (function1 param1)(function2 param2))
   NOT OK: (begin (function1 param1)(function2 param2))


Various components

~~~~~~~~~~~~~~~~~~

The URL:

http://the.domain.com/pagename/p1/p2/p3?param1=value1

(s:get-page-params) => '("p1" "p2")



Create a link.
~~~~~~~~~~~~~~

(s:null "[" (s:a name 'href 
               (s:link-to (string-append "location/" (string-intersperse p "/") ""))) "] ")))



Call current page with new param
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

In view.scm:

 (s:center "[" (s:a 'href (s:link-to "polls"
                           'id
                            (begin
                              (poll:poll 'fill-polls)
                              (poll:poll 'get-next-poll)))
                          "Go to the next poll")  "]")

In control.scm:

(let ((poll-id (s:get-param 'id)))
 ;; do stuff based on poll-id


Call an action on a specific page
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

 (s:a 'href (s:link-to "polls" 'id (poll:poll 'get 'id) 
			       'action "poll.edit")
            "Suggest changes to this poll")

 NOT TRUE! This calls fuction poll.edit (should be in control.scm). Parameter set is 'id to a poll num.


A complex link example
~~~~~~~~~~~~~~~~~~~~~~

(s:a "Reply" 'href (s:link-to (s:current-page) 
	           'action "discussion.reply" ;; <page>.<action>
	           'reply_to (number->string (hash-table-ref row 'posts.id)) 
	           'id (s:get "discussion.parent_object_id")) "reply")

;; use (s:get-param to get the 'id, or 'reply_to values


Get and set a session var
~~~~~~~~~~~~~~~~~~~~~~~~~

(s:session-var-get "keyname")
(s:session-var-set! "keyname" "value")

5.1 Page local vars

(s:set! key val)
(s:get key)


make a selection drop down
~~~~~~~~~~~~~~~~~~~~~~~~~~

In view.scm: 

(s:select '(("World" 0)("Country" 1)("State" 2)("Town/City" 3)) 'name 'scope)

In control.scm:

(let ((scope (s:get-input 'scope)))
  ....


Simple error reporting
~~~~~~~~~~~~~~~~~~~~~~

In control.scm:
(s:set-err "You must provide an email address")

In view.scm:
(s:get-err s:err-font)

Or:
(s:get-err (lambda (x)(s:err-font x (s:br))))


Sharing data between pages
~~~~~~~~~~~~~~~~~~~~~~~~~~

NOTE: This data is *not* preserved between cgi calls.

;; In first page called
(s:shared-set! "somekey" somevalue)

;; In a page called later
(let ((dat (s:shared-get "somekey")))
  ( .... ))


Misc useful stuff
~~~~~~~~~~~~~~~~~

  i. Lazy/safe string->number 

(s:any->number val)

  ii. Random string

(session:make-rand-string len)

 iii. string to number for pgint
 
(s:any->pgint val)


Forms and input
~~~~~~~~~~~~~~~

(s:form 'action "login.login" 'method "post"
   (s:input-preserve 'type "text" 'name "email-address" 'size "16" 'maxlength "30")
   (s:input 'type "submit"   'name "form-name" 'value "login"))

(s:get-input 'email-address)

To preserve the input simply do a set of the value on the 'name field:
(s:set! "email-address" "matt@kiatoa.com")

  (session:del! s:session "*sessionvars*" key))

;; utility to get all vars as hash table
(define (s:session-get-sessionvars)
  (sdat-get-sessionvars s:session))

;; inputs
;;
(define (s:get-input key)
  (session:get-input s:session key))

(define (s:load-model model)
  (session:load-model s:session model))

(define (s:model-path model)
  (session:model-path s:session model))

;; share data between pages calls
;;
(define (s:shared-hash)
  (sdat-get-shared-hash s:session))

(define (s:shared-set! key val)
  (hash-table-set! (sdat-get-shared-hash s:session) key val))

(define (s:shared-get key)
  (hash-table-ref (sdat-get-shared-hash s:session) key))

;; http://foo.bar.com/pagename/p1/p2 => '("p1" "p2")
;;
(define (s:get-page-params)
  (sdat-get-page-params s:session))

(define (s:db)
  (sdat-get-conn s:session))

;;     [(_ s x y) (if (s:get s) x y)]))
;; ;; 
;; (define-syntax s:if-test
;;   (syntax-rules ()
;;     [(_ s x) (if   (string=? "yep" s)   x (list "s:if not"))]
;;     [(_ s x y) (if (string=? "yep" s) x y)]))

;; Some of these routines use:
;;
;;     http://www.cs.toronto.edu/~gfb/scheme/simple-macros.html
;;
;; Syntax for defining macros in a simple style similar to function definiton,
;;  when there is a single pattern for the argument list and there are no keywords.
;;
;; (define-simple-syntax (name arg ...) body ...)
;;

(define-syntax define-simple-syntax
  (syntax-rules ()
    ((_ (name arg ...) body ...)
     (define-syntax name (syntax-rules () ((name arg ...) (begin body ...)))))))

;;======================================================================
;; syntatic sugar items
;;======================================================================

;; We often seem to want to include stuff if a conditional is met
;; otherwise not include it. This routine makes that slightly cleaner
;; since using a pure if results in #<undefined> objects. (admittedly they 
;; should be ignored but this is slightly cleaner I think). 
;;
;; NOTE: This has to be a macro or the true clause will be evaluated 
;; whether "a" is true or false

;; If a is true return b, else return '()
(define-simple-syntax (s:if a b)
  (if a b '()))


;; Using the Simple-Syntax System
;; 
;; The syntax for defining macros in this system is similar to that for defining functions. In fact if the macro has a fixed number of arguments the syntax is identical. For example:
;; 
;;   ; Define a simple macro to add a value to a variable.
;;   ;
;;   (define-simple-syntax (+= variable value)
;;     (set! variable (+ variable value)))
;; 
;;   ; Use it.
;;   ;
;;   (define v 2)
;;   (+= v 7)
;;   v ; => 9
;; 
;; For a fixed number of arguments followed by an unknown number of arguments we use ... after a single argument to represent the unknown number (possibly zero) of arguments. For example, let's revise our definition of += to allow zero or more values to be added:
;; 
;;   ; Define a simple macro to add a zero or more values to a variable
;;   ;
;;   (define-simple-syntax (+= variable value ...)
;;     (set! variable (+ variable value ...)))
;; 
;;   ; Use it
;;   ;
;;   (define v 2)
;;   (+= v 7)
;;   v ; => 9
;;   (+= v 3 4)
;;   v ; => 16
;;   (+= v)
;;   v ; => 16
;; 


;; (define-macro (s:if-param varname . dat)
;;   (match dat
;; 	 (()    '())
;; 	 ((a)    `(if (s:get ,varname) ,a '()))
;; 	 ((a b)  `(if (s:get ,varname) ,a ,b))))
;; 
;; (define-macro (s:if-sessionvar varname . dat)
;;   (match dat
;; 	 (()    '())
;; 	 ((a)    `(if (s:session-var-get ,varname) ,a '()))
;; 	 ((a b)  `(if (s:session-var-get ,varname) ,a ,b))))
;;