MD -> TXT:
	scripts/preprocmdheaders.pl -n $docdir
MD -> HTML:
	scripts/preprocmdheaders.pl -nl $docdir
	scripts/linkpages.pl $docdir
	markdown $docdir/index.txt > $docdir/index.html
	while read file; do \
			markdown $docdir/$file.txt > $docdir/$file.html
		done < $docdir/series
	scripts/postprochtmlheaders.pl -anL $docdir


scripts/preprocmdheaders.pl [-ntl] docdir
	options
		-n  prepend section numbers to headers
		-l  handle hyperlinks to sections in text and table of contents
	pseudocode
		chapter = 0
		for each file in $docdir/series:
			++chapter
			...
			for each header:
				if opt n:
					...
				...
scripts/linkpages.pl docdir
scripts/postprochtmlheaders.pl [-anL] docdir
	options
		-a  add "id" attributes to headers
		-n  remove section numbers from "id" attributes (use with -a)

scripts/preproc.pl
	options
		-f format
			"txt" or "html"
	pseudopseudocode
		scan each source file for sections
		build a ToC
			print('  ' x $seclev, "* [$secnum $sectitle][$secid]\n");
		if txt
			add section numbers to headers
			add $title . "\n" . '*' x strlen($title)
		if html
			add link defs "[$secid]: $chapter.html#$section_id"
scripts/postproc.pl
	options
		-f format
			"txt" or "html"
	pseudopseudocode
		if txt
			blame the schools and bail out
		add section numbers and "id" attributes to headers


$docdir/
 +- appendices
 |    A list of appendix documents in the book.
 +- chapters
 |    A list of chapter documents in the book.
 +- first-chapter.md
 |    The source file for a chapter.
 +- first-chapter.html
 |    The rendered HTML file for a chapter.
 +- first-chapter.txt
 |    The rendered text file for a chapter.
 +- reference-stuff.md
 |    The source file for an appendix.
 +- second-chapter.md
 |    The source file for a chapter.
 \- title.md
      The source file for the title page.


ToC substitution:
$[toc]

section link substitution:
$[sectlink][foo]
[§ 1.10.11][foo]

# create book and documents             - DONE
# book->parse()                         - DONE
#   foreach document:                   - DONE
#     doc->parse()                      - DONE
#       foreach heading:                - DONE
#         section = new Section         - DONE
#         push(self->sections, section) - DONE
#         book->add_section()           - DONE
#         prefix section title with num - DONE
# book->output()                        - DONE
#   book->subst_macros                  - DONE
#     build ToC string                  - DONE
#   foreach document:                   - DONE
#     doc(Txt)->output()                - DONE
#       book->subst_macros()            - DONE
#       write title                     - DONE
#       dump Markdown text              - DONE
#     doc(HTML)->output()               - DONE
#       book->subst_macros()            - DONE
#       append link defs string         - DONE
#       generate HTML (markdown)        - DONE
#       parse HTML                      - DONE
#       foreach heading:                - DONE
#         set id attribute              - DONE
#       write templated documents       - DONE
#
# Book
#   new
#   add_section
#     indexes section by id
#     appends to link defs string
#   parse
#   output
#   add_section
#   add_macro
#   subst_macros
#   _do_subst_macro
# Document
#   new
#   parse
# Document::Txt
#   output
# Document::HTML
#   output
# Section
#   new
#   number
#   id
#   title