# subtext -*- awk -*-
# (C) C Duckworth <acdw@acdw.net>
## Subtext is an awk program that converts roff-like input to a shell script
## that can output markup.  Lines prefixed with . are wrapped in $(...)
## constructs within the `body' function, but lines prefixed with # are
## transported to the top of the file, where they're executed within the shell
## environment.

BEGIN {
	## Tuneables
	dryrun = dryrun ? dryrun : 0
	sopath = sopath ? sopath : "."
	sofile = sofile ? sofile : ""
	shxend = shxend ? shxend : "%%end"
	## Shellfix: escape ` and $ in input
	# Ask sed to do these b/c awk has no capture groups ;_;
	shellfix = "sed -E" \
		" -e 's/`/\\\\`/g'" \
		" -e 's/(^|[^\\$])\\$([^\\$]|$)/\\1\\\\$\\2/g'" \
		" -e 's/(^|[^\\$])\\$(\\$+)([^\\$]|$)/\\1\\2\\3/g'"
}

/\\$/ { # line continuation
	getline nl
	sub(/\\$/, "")
	$0 = $0 " " nl
}

### AWK layer

/^%so/ { # source a file
	pushpar()
	source($2)
	next
}

/^%/ { next } # comments

### Shell layer

/^#/ { # head lines
	sub(/^#+[ 	]*/,"")
	head = head (head?"\n":"") $0
	next
}

### Text layer

end[endn] && $0 == end[endn] {
	par = par "\n" end[endn--] "\n)"
	next
}

/^\.\./ { # block
	if (match($0, /[ 	]*<<[ 	]*/))
		end[++endn] = substr($0, RSTART+RLENGTH)
	else
		end[++endn] = ".."
	$0 = substr($0, 3, RSTART?RSTART-3:length)
	par = par (par?"\n":"") \
		"$$(" ($1 ? $1 " " shquote(2) : "") " << " end[endn]
	# par = par (par?"\n":"") \
	# 	"$$(unquote + << .." \
	# 	(length>2 ? " | " substr($1,3) " " shquote(2) : "") \
	# 	slurp("..") \
	# 	"..\n)"
	next
}

/^\.$/ { next } # continuation line

/^\./ { # line
	par = par (body?"\n":"") \
		"$$(" substr($1, 2) " " shquote(2) ")"
	next
}

/^\\/ { # special line escape
	$0 = substr($0, 2)
}

/^$/ { # blank line
	if (!pushpar()) next
}

{ # regular text
	par = par (par?"\n":"") $0
}

END {
	if (dead) exit dead

	print "#!/bin/sh"
	print "### generated with subtext"
	print "quote()(sed \"s/^/$1/\")"
	print "unquote()(sed \"s/^$1//\")"
	printf "shexpand()(eval \"$(echo 'cat<<%s';cat;echo '%s')\")\n", \
		shxend, shxend
	printf "shellfix()(%s)\n", shellfix
	print "echo()(printf '%s\\n' \"$@\")"
	print "handle_input()("\
		"test -n \"$1\" && printf '%s' \"$*\";"\
		"if read -r first_line;"\
		"then echo \"$first_line\";cat;return 0;"\
		"else echo;return 1;fi)"
	printf "ST_SOPATH=%s\n", sopath
	if (sofile) source(sofile)
	print "### head"
	print head
	print "### body"
	print "body(){ unquote : << \\_ | shexpand"
	pushpar()
	shfq = shellfix " -e 's/^/:/'"
	print body | shfq
	close(shfq)
	print "_"
	print "}"
	if (!dryrun) print "body"
}

function shquote(begin, end,	quoted, out) {
	if (!begin) begin = 1
	if (!end) end = NF
	for (i=begin; i<=NF; i++) {
		if ($i ~ /^\$/) {
			quoted = 1
			out = out (out?" ":"") "\"" $i
			continue
		}
		if (($i ~ /\)$/) && quoted) {
			quoted = 0
			out = out (out?" ":"") $i "\""
			continue
		}
		if (!quoted) {
			gsub(/"/, "\\\"", $i)
			out = out (out?" ":"") "\"" $i "\""
		} else out = out (out?" ":"") $i
	}
	return out
}

function slurp(to,	out, nl) {
	while (nl != to) {
		getline nl
		out = out "\n+" nl
	}
	sub("\\+"to"$", "", out)
	return out
}

function pushpar() {
	if (!par) return 0
	if (!match(par, /^[ \t\n]*[<$]/)) {
		par = "$$(p<<../p\n" par "\n../p\n)"
	}
	body = body (body?"\n":"") par
	par = ""
	return 1
}

function source(name,	found, sp) {
	split(sopath, asopath, ":")
	for (dir in asopath) {
		fn = asopath[dir] "/" name
		sp = asopath[dir] "\n\t" sp
		while ((getline ln < fn) > 0) {
			found = 1
			head = head (head?"\n":"") ln
		}
		close(fn)
		if (found) break
	}
	if (!found) {
		printf "Couldn't source %s; looked in:\n\t%s", name, sp
		dead = 127
		exit
	}
}