;; cite
;; quote
;;




;; ian-xhtml->xhtml: xexpr -> xexpr
;; 
(define (ian-xhtml->xhtml src)
  (let {[work-mostly-done (fold transforms apply-to-each-sub-expr src))]

;; transforms: (list-of (list tag xexpr-morpher)),
;; where tag is a symbol (a ian-xhtml tag), and xexpr-morpher
;; is a funciton which takes in a ian-xhtml element of that tag,
;; and returns xhtml.  Other tags left intact.
;; (Since this only transforms tags specific to ian-xhtml,
;; and the output is xhtml, then there won't be any dependence
;; on the order of applications, if transforms are independent of the element-data.
;; That is, as long as the transform is only changing tag names and attributes,
;; and leaving the body unchanged, then there's not even potential for ambiguity... i think.)
;; 
(define transforms
  `{[keywords ,transform-keywords]
     [description ,transform-description]
     [footnote ,transform-footnote]
     [link          ,transform-link]
    })
  


;; Recur into the xexpr "src", and if we find an element in "transforms",
;; then replace it with the transformed element.
;; Notes: evaluation should be left-to-right.
;; (Both for the <eval> tag, and so if there are somehow two, say, "title" tags,
;; the second one overrides the first.)
;; Do we want to also guarantee pre-order traversal?
;; (that is, do the insides of an element, before doing the top-level element?)
;; Perhaps not -- for 'comment tags, we'd rather post-order it.
;; This question becomes:
;; consider the innards of a ian-xhtml tag; are they ian-xhtml or pure xhtml?
;; 
(define (traverse-n-morph src)
  (cond [(empty? src) empty]
           [(atom?   (first src)) (cons (first src) (traverse-n-morph (rest src)))]
           [else (let* {[tag (first (first src))]
                             [lookup (assoc tag transforms)]
                             [morpher (if (empty? lookup) identity (rest lookup))]}
                             ; Pre-order: recur *before* applying morpher:
                             [new-element (morpher (traverse-n-morph (rest (first src))))]
                             ; Left-to-right: we processed (first src), before doing (rest src):
                             [the-rest (traverse-n-morph (rest src))]
                 (cons new-element the-rest)))


;; transformers:
;; xhtml-ian
;;
;; link -> a
;; footnote
;; eval (first?, repeating?)
;; comments -- no need
;; footer
;; keywords, description
;; title

(define (convert-title-tag titl)
  (set! the-window-name

(define (transform-link link-xpr)
  link-xpr)

(define (transform-keywords kwd-xpr)
  `(meta {[name "keywords"] [contents ,kwd-xpr]} ))
(define (transform-description descr-xpr)
  `(meta {[name "description"] [contents ,descr-xpr]} ))
  
;; Global state:
;; title
;; footer
;; footnotes