;; $Id$
;;
;; This file is part of the Modular DocBook Stylesheet distribution.
;; See ../README or http://www.berkshire.net/~norm/dsssl/
;;
;; Table support completely reimplemented by norm 15/16 Nov 1997.
;; Adapted from print support.
;;
;; ======================================================================
;;
;; This code is intended to implement the SGML Open Exchange Table Model
;; (http://www.sgmlopen.org/sgml/docs/techpubs.htm) as far as is possible
;; in HTML.  There are a few areas where this code probably fails to 
;; perfectly implement the model:
;;
;; - Mixed column width units (4*+2pi) are not supported.
;; - The behavior that results from mixing relative units with 
;;   absolute units has not been carefully considered.
;;
;; ======================================================================
;; 
;; My goal in reimplementing the table model was to provide correct
;; formatting in tables that use MOREROWS. The difficulty is that
;; correct formatting depends on calculating the column into which
;; an ENTRY will fall.
;;
;; This is a non-trivial problem because MOREROWS can hang down from
;; preceding rows and ENTRYs may specify starting columns (skipping
;; preceding ones).
;;
;; A simple, elegant recursive algorithm exists. Unfortunately it 
;; requires calculating the column number of every preceding cell 
;; in the entire table. Without memoization, performance is unacceptable
;; even in relatively small tables (5x5, for example).
;;
;; In order to avoid recursion, the algorithm used below is one that
;; works forward from the beginning of the table and "passes along"
;; the relevant information (column number of the preceding cell and
;; overhang from the MOREROWS in preceding rows).
;;
;; Unfortunately, this means that element construction rules
;; can't always be used to fire the appropriate rule.  Instead,
;; each TGROUP has to process each THEAD/BODY/FOOT explicitly.
;; And each of those must process each ROW explicitly, then each
;; ENTRY/ENTRYTBL explicitly.
;;
;; ----------------------------------------------------------------------
;;
;; I attempted to simplify this code by relying on inheritence from
;; table-column flow objects, but that wasn't entirely successful.
;; Horizontally spanning cells didn't seem to inherit from table-column
;; flow objects that didn't specify equal spanning.  There seemed to
;; be other problems as well, but they could have been caused by coding
;; errors on my part.
;; 
;; Anyway, by the time I understood how I could use table-column
;; flow objects for inheritence, I'd already implemented all the
;; machinery below to "work it out by hand".  
;;
;; ======================================================================
;; NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE NOTE 
;; ----------------------------------------------------------------------
;; A fairly large chunk of this code is in dbcommon.dsl!
;; ======================================================================

;; Default for COLSEP/ROWSEP if unspecified
(define %cals-rule-default% "0")

;; Default for VALIGN if unspecified
(define %cals-valign-default% "TOP")

;; ======================================================================
;; Convert colwidth units into table-unit measurements

(define (colwidth-length lenstr)
  (if (string? lenstr)
      (let ((number (length-string-number-part lenstr))
	    (units  (length-string-unit-part lenstr)))
	(if (or (string=? units "*") (string=? number ""))
	    ;; relative units or no number, give up
	    0pt
	    (if (string=? units "")
		;; no units, default to pixels
		(* (string->number number) 1px)
		(let* ((unum  (string->number number))
		       (uname (case-fold-down units)))
		  (case uname
		    (("mm") (* unum 1mm))
		    (("cm") (* unum 1cm))
		    (("in") (* unum 1in))
		    (("pi") (* unum 1pi))
		    (("pt") (* unum 1pt))
		    (("px") (* unum 1px))
		    ;; unrecognized units; use pixels
		    (else   (* unum 1px)))))))
      ;; lenstr is not a string...probably #f
      0pt))

(define (cals-relative-colwidth? colwidth)
  (if (string? colwidth)
      (let ((strlen (string-length colwidth)))
	(if (string=? colwidth "*")
	    #t
	    (string=? (substring colwidth (- strlen 1) strlen) "*")))
      #f))

(define (cals-relative-colwidth colwidth)
  (let ((number (length-string-number-part colwidth))
	(units  (length-string-unit-part colwidth)))
    (if (string=? units "*")
	(if (string=? number "")
	    1
	    (string->number number))
	0)))

(define (cell-relative-colwidth cell relative)
  (let* ((tgroup (find-tgroup cell)))
    (let loop ((colspecs (select-elements (children tgroup)
					  (normalize "colspec")))
	       (reltotal 0))
      (if (node-list-empty? colspecs)
	  (string-append (number->string (round (* (/ relative reltotal) 100))) "%")
	  (loop (node-list-rest colspecs) 
		(+ reltotal (cals-relative-colwidth 
			     (colspec-colwidth 
			      (node-list-first colspecs)))))))))

(define (cell-colwidth cell colnum)
  (let* ((entry     (ancestor-member cell (list (normalize "entry") 
						(normalize "entrytbl"))))
	 (colspec   (find-colspec-by-number colnum))
	 (colwidth  (colspec-colwidth colspec))
	 (width     (round (/ (colwidth-length colwidth) 1px))))
    (if (node-list-empty? colspec)
	""
	(if (and (equal? (hspan entry) 1) colwidth)
	    (if (cals-relative-colwidth? colwidth)
		(cell-relative-colwidth cell (cals-relative-colwidth colwidth))
		(number->string width))
	    ""))))

;; ======================================================================

(define (cell-align cell colnum)
  (let* ((entry     (ancestor-member cell (list (normalize "entry") 
						(normalize "entrytbl"))))
	 (tgroup    (find-tgroup entry))
	 (spanname  (attribute-string (normalize "spanname") entry))
	 (calsalign (if (attribute-string (normalize "align") entry)
			(attribute-string (normalize "align") entry)
			(if (and spanname 
				 (spanspec-align (find-spanspec spanname)))
			    (spanspec-align (find-spanspec spanname))
			    (if (colspec-align (find-colspec-by-number colnum))
				(colspec-align (find-colspec-by-number colnum))
				(if (tgroup-align tgroup)
				    (tgroup-align tgroup)
				    (normalize "left")))))))
    (cond
     ((equal? calsalign (normalize "left")) "LEFT")
     ((equal? calsalign (normalize "center")) "CENTER")
     ((equal? calsalign (normalize "right")) "RIGHT")
     (else "LEFT"))))
    
(define (cell-valign cell colnum)
  (let* ((entry      (ancestor-member cell (list (normalize "entry")
						 (normalize "entrytbl"))))
	 (row        (ancestor (normalize "row") entry))
	 (tbody      (ancestor-member cell (list (normalize "tbody") 
						 (normalize "thead") (normalize "tfoot"))))
	 (tgroup     (find-tgroup entry))
	 (calsvalign (if (attribute-string (normalize "valign") entry)
			 (attribute-string (normalize "valign") entry)
			 (if (attribute-string (normalize "valign") row)
			     (attribute-string (normalize "valign") row)
			     (if (attribute-string (normalize "valign") tbody)
				 (attribute-string (normalize "valign") tbody)
				 %cals-valign-default%)))))
    (cond
     ((equal? calsvalign (normalize "top")) "TOP")
     ((equal? calsvalign (normalize "middle")) "MIDDLE")
     ((equal? calsvalign (normalize "bottom")) "BOTTOM")
     (else "MIDDLE"))))

;; ======================================================================
;; Element rules

(element tgroup
  (let* ((wrapper   (parent (current-node)))
	 (frameattr (attribute-string (normalize "frame") wrapper))
	 (pgwide    (attribute-string (normalize "pgwide") wrapper))
	 (footnotes (select-elements (descendants (current-node)) 
				     (normalize "footnote")))
	 (border (if (equal? frameattr (normalize "none"))
		     '(("BORDER" "0"))
		     '(("BORDER" "1"))))
	 (width (if (equal? pgwide "1")
		    (list (list "WIDTH" ($table-width$)))
		    '()))
	 (head (select-elements (children (current-node)) (normalize "thead")))
	 (body (select-elements (children (current-node)) (normalize "tbody")))
	 (feet (select-elements (children (current-node)) (normalize "tfoot"))))
    (make element gi: "TABLE"
	  attributes: (append
		       border
		       width
		       (if %cals-table-class%
			   (list (list "CLASS" %cals-table-class%))
			   '()))
	  (process-node-list head)
	  (process-node-list body)
	  (process-node-list feet)
	  (make-table-endnotes))))

(element entrytbl ;; sortof like a tgroup...
  (let* ((wrapper   (parent (parent (parent (parent (current-node))))))
	 ;;	     table   tgroup  tbody   row  
	 (frameattr (attribute-string (normalize "frame") wrapper))
	 (tgrstyle  (attribute-string (normalize "tgroupstyle")))
	 (border    (if (and (or (equal? frameattr (normalize "none"))
				 (equal? tgrstyle (normalize "noborder")))
			     (not (equal? tgrstyle (normalize "border"))))
			'(("BORDER" "0"))
			'(("BORDER" "1"))))
	 (head (select-elements (children (current-node)) (normalize "thead")))
	 (body (select-elements (children (current-node)) (normalize "tbody"))))
    (make element gi: "TABLE"
	  attributes: (append
		       border
		       (if %cals-table-class%
			   (list (list "CLASS" %cals-table-class%))
			   '()))
	  (process-node-list head)
	  (process-node-list body))))

(element colspec
  (empty-sosofo))

(element spanspec
  (empty-sosofo))

(element thead
  (if %html40%
      (make element gi: "THEAD"
	    ($process-table-body$ (current-node)))
      ($process-table-body$ (current-node))))

(element tfoot
  (if %html40%
      (make element gi: "TFOOT"
	    ($process-table-body$ (current-node)))
      ($process-table-body$ (current-node))))

(element tbody
  (if %html40%
      (make element gi: "TBODY"
	    ($process-table-body$ (current-node)))
      ($process-table-body$ (current-node))))

(element row
  (empty-sosofo)) ;; this should never happen, they're processed explicitly

(element entry
  (empty-sosofo)) ;; this should never happen, they're processed explicitly

;; ======================================================================
;; Functions that handle processing of table bodies, rows, and cells

(define ($process-table-body$ body)
  (let* ((tgroup (find-tgroup body))
	 (cols   (string->number (attribute-string (normalize "cols") 
						   tgroup))))
    (let loop ((rows (select-elements (children body) (normalize "row")))
	       (overhang (constant-list 0 cols)))
      (if (node-list-empty? rows)
	  (empty-sosofo)
	  (make sequence
	    ($process-row$ (node-list-first rows) overhang)
	    (loop (node-list-rest rows)
		  (update-overhang (node-list-first rows) overhang)))))))

(define ($process-row$ row overhang)
  (let* ((tgroup (find-tgroup row))
	 (rowcells (node-list-filter-out-pis (children row)))
	 (maxcol (string->number (attribute-string (normalize "cols") tgroup)))
	 (lastentry (node-list-last rowcells))
	 (table  (ancestor-member tgroup (list (normalize "table")
					       (normalize "informaltable"))))
	 (rowsep (if (attribute-string (normalize "rowsep") row)
		     (attribute-string (normalize "rowsep") row)
		     (if (attribute-string (normalize "rowsep") tgroup)
			 (attribute-string (normalize "rowsep") tgroup)
			 (if (attribute-string (normalize "rowsep") table)
			     (attribute-string (normalize "rowsep") table)
			     %cals-rule-default%))))
	 (after-row-border (if rowsep
			       (> (string->number rowsep) 0)
			       #f)))
    (make element gi: "TR"
	  (let loop ((cells rowcells)
		     (prevcell (empty-node-list)))
	    (if (node-list-empty? cells)
		(empty-sosofo)
		(make sequence
		  ($process-cell$ (node-list-first cells) 
				  prevcell overhang)
		  (loop (node-list-rest cells) 
			(node-list-first cells)))))
	  
	  ;; add any necessary empty cells to the end of the row
	  (let loop ((colnum (overhang-skip overhang
					    (+ (cell-column-number 
						lastentry overhang)
					       (hspan lastentry)))))
	    (if (> colnum maxcol)
		(empty-sosofo)
		(make sequence
		  (make element gi: "TD"
			(make entity-ref name: "nbsp"))
		  (loop (overhang-skip overhang (+ colnum 1)))))))))

(define (empty-cell? entry) 
  ;; Return #t if and only if entry is empty (or contains only PIs)
  (let loop ((nl (children entry)))
    (if (node-list-empty? nl)
	#t
	(let* ((node       (node-list-first nl))
	       (nodeclass  (node-property 'class-name node))
	       (nodechar   (if (equal? nodeclass 'data-char)
			       (node-property 'char node)
			       #f))
	       (whitespace? (and (equal? nodeclass 'data-char)
				(or (equal? nodechar #\space)
				    (equal? (data node) "	")
				    (equal? (data node) "
")
				    (equal? (data node) "
")))))
	  (if (not (or (equal? (node-property 'class-name node) 'pi)
		       whitespace?))
	      #f
	      (loop (node-list-rest nl)))))))

(define ($process-cell$ entry preventry overhang)
  (let* ((colnum (cell-column-number entry overhang))
	 (lastcellcolumn (if (node-list-empty? preventry)
			     0
			     (- (+ (cell-column-number preventry overhang)
				   (hspan preventry))
				1)))
	 (lastcolnum (if (> lastcellcolumn 0)
			 (overhang-skip overhang lastcellcolumn)
			 0))
	 (htmlgi (if (have-ancestor? (normalize "tbody") entry)
		     "TD"
		     "TH")))
    (make sequence
      (if (node-list-empty? (preced entry))
	  (if (attribute-string (normalize "id") (parent entry))
	      (make element gi: "A"
		    attributes: (list
				 (list
				  "NAME"
				  (attribute-string (normalize "id")
						    (parent entry))))
		    (empty-sosofo))
	      (empty-sosofo))
	  (empty-sosofo))

      (if (attribute-string (normalize "id") entry)
	  (make element gi: "A"
		attributes: (list
			     (list
			      "NAME"
			      (attribute-string (normalize "id") entry)))
		(empty-sosofo))
	  (empty-sosofo))

      ;; This is a little bit complicated.  We want to output empty cells
      ;; to skip over missing data.  We start count at the column number
      ;; arrived at by adding 1 to the column number of the previous entry
      ;; and skipping over any MOREROWS overhanging entrys.  Then for each
      ;; iteration, we add 1 and skip over any overhanging entrys.
      (let loop ((count (overhang-skip overhang (+ lastcolnum 1))))
	(if (>= count colnum)
	    (empty-sosofo)
	    (make sequence
	      (make element gi: htmlgi
		    (make entity-ref name: "nbsp")
;;		  (literal (number->string lastcellcolumn) ", ")
;;		  (literal (number->string lastcolnum) ", ")
;;		  (literal (number->string (hspan preventry)) ", ")
;;		  (literal (number->string colnum ", "))
;;		  ($debug-pr-overhang$ overhang)
		    )
	      (loop (overhang-skip overhang (+ count 1))))))

;      (if (equal? (gi entry) (normalize "entrytbl"))
;	  (make element gi: htmlgi
;		(literal "ENTRYTBL not supported."))
	  (make element gi: htmlgi
		attributes: (append
			     (if (> (hspan entry) 1)
				 (list (list "COLSPAN" (number->string (hspan entry))))
				 '())
			     (if (> (vspan entry) 1)
				 (list (list "ROWSPAN" (number->string (vspan entry))))
				 '())
			     (if (equal? (cell-colwidth entry colnum) "")
				 '()
				 (list (list "WIDTH" (cell-colwidth entry colnum))))
			     (list (list "ALIGN" (cell-align entry colnum)))
			     (list (list "VALIGN" (cell-valign entry colnum))))
		(if (empty-cell? entry) 
		    (make entity-ref name: "nbsp")
		    (if (equal? (gi entry) (normalize "entrytbl"))
			(process-node-list entry)
			(process-node-list (children entry))))))))

;; EOF dbtable.dsl