#!/bin/sh

BLOCK=
BUFFER=

process() {
	while read -r LINE
	do
		if test "$BLOCK" = verbatim
		then
			printf '%s\n' "$LINE"
			continue
		fi

		set -- $LINE

		case "$LINE" in
			('```')
				if test "$BLOCK" = verbatim
				then BLOCK=
				else BLOCK=verbatim
				fi
				;;
			('')
				if test "$BLOCK" = verbatim
				then bufpush $'\n'
				else bufclose
				fi
				;;
			('=>'*) link "$@" ;;
			('#'*) header "$@" ;;
			('*'*) shift; blknew list "$*" ;;
			('>'*) shift; blknew quote "$*" ;;
			(*) shift; blknew paragraph "$*" ;;
		esac
	done
	bufclose
}

blknew() {
	test "$BLOCK" = "$1" || bufclose
	bufpush "$(printf "$(eval echo "\$format_$BLOCK")" "$@")"
	BLOCK="$1"
}

bufclose() {
	if test -z "$BLOCK"
	then "$COLLAPSE_BLANKS" && return
	else newline; return
	fi

	# blockp "$BLOCK" || return
	# fillp $BLOCK && buffill "$(fillp $BLOCK)"

	# TODO: escape shit

	printf '%s%s%s\n' \
	       "$(echo eval "\$opener_$BLOCK")" \
	       "$BUFFER" \
	       "$(echo eval "\$closer_$BLOCK")"

	BLOCK=
}

buffill() { # buffill WIDTH
	if test $1 -lt 0
	then BUFFER="$(printf '%s\n' "$BUFFER" | tr '\n' ' ')"
	else
		out=
		nline=0
		printf '%s\n' "$BUFFER" | sed 's/[ \t]\+/\n/g' |
			while read -r word
			do
				if test $((nline + ${#word})) -ge "$1"
				then
					out="${out}"${out:+$'\n'}"${word}"
					nline=${#word}
				else
					out="${out}${out:+ }${word}"
					nline=$((nline + ${#word} + 1))
				fi
			done
		BUFFER="$out"
	fi
}

bufpush() { BUFFER="${BUFFER}$@"; }

fillp() {
	:
}

header() {
	bufclose
	lvl=${#1}; shift
	bufpush "$(printf "$(eval echo "\$format_h$lvl")" "$*")"
	BLOCK=header
}

link() {
	url="$2"; shift 2
	if test "$BLOCK" = paragraph #&& ! blockp link
	then bufpush "$(printf "$format_link" "$url" "$*")"
	else blknew linklist "$url" "$*"
	fi
}

newline() { printf '\n'; }

html() {
	format_link='<a href="%s">%s</a>\n'
	format_h1='<h1>%s</h1>\n'
	format_h2='<h2>%s</h2>\n'
	format_h3='<h3>%s</h3>\n'
	opener_verbatim='<pre><code>'
	closer_verbatim='</code></pre>\n'
	format_verbatim='%s\n'
	opener_paragraph='<p>'
	closer_paragraph='</p>\n'
	format_paragraph='%s\n'
	opener_quote='<blockquote>'
	closer_quote='</blockquote>\n'
	format_quote='%s\n'
	opener_list='<ul>\n'
	closer_list='</ul>\n'
	format_list='<li>%s</li>'
	opener_linklist='<ul class="linklist">'
	closer_linklist='</ul>'
	format_linklist="$(printf "$format_list" "$format_link")"
}

main() {
	html
	process "$@"
}

main "$@"