# 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 : ".:" ENVIRON["HOME"] "/.subtext"
	shxend = shxend ? shxend : "%%end"
	## Kernel
	# 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'"
	shxquote = " -e 's/^/:/'"
}

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

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

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

/^\.\./ { # block
	body = body (body?"\n":"") \
		"$$(unquote + << .." \
		(length>2 ? " | " substr($1,3) " " shquote(2) : "") \
		slurp("..") \
		"..\n)"
	next
}

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

/^$/ { # line break
	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
	printf "ST_SOPATH=%s\n", sopath
	print "### head"
	print head
	print "### body"
	print "body(){ unquote : << \\_ | shexpand"
	pushpar()
	print body | (shellfix shxquote)
	close(shellfix shxquote)
	print "_"
	print "}"
	if (!dryrun) print "body"
}

function shquote(begin, end,	out) {
	if (!begin) begin = 1
	if (!end) end = NF
	for (i=begin; i<=NF; i++) {
		gsub(/"/, "\\\"", $i)
		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, /^[ 	]*</))
		par = "<p>" par "</p>"
	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
		}
		if (found) break
	}
	if (!found) {
		printf "Couldn't source %s; looked in:\n\t%s", name, sp
		dead = 127
		exit
	}
}