From 3336085d81231d520e6fd2004f69deeeea2fa405 Mon Sep 17 00:00:00 2001
From: Jakob Kaivo <jkk@ung.org>
Date: Tue, 3 Nov 2020 17:10:43 -0500
Subject: add input type detection

---
 m4n.sh | 47 ++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 44 insertions(+), 3 deletions(-)

diff --git a/m4n.sh b/m4n.sh
index 8e70b9e..69a3648 100644
--- a/m4n.sh
+++ b/m4n.sh
@@ -4,9 +4,42 @@ die() {
 	exit 1
 }
 
-main() {
-	om4=text_m4
+get_file_type() {
+	if (head -n1 $1 | grep -q m4npage); then
+		echo m4n
+		return
+	fi
 
+	if grep -q 'int main' $1; then
+		echo utility
+		return
+	fi
+
+	# TODO: detect other types
+	echo function
+}
+
+m4n_m4n() {
+	cat
+}
+
+utility_m4n() {
+	cat <<-EOF
+	m4npage($1, utility)
+	brief(something)
+	describe(is a program.)
+	EOF
+}
+
+function_m4n() {
+	cat <<-EOF
+	m4npage($1, function)
+	brief(something else)
+	describe(is a function.)
+	EOF
+}
+
+main() {
 	while getopts O: opt; do
 		case $opt in
 
@@ -24,12 +57,20 @@ main() {
 
 	shift $((OPTIND - 1))
 
+
 	if [ $# -lt 1 ]; then
 		die 'missing operand\n'
 	elif [ $# -gt 1 ]; then
 		die 'too many operands\n'
+	fi
+
+	type=$(get_file_type $1)
+
+	if [ $type != "m4n" ]; then
+		# TODO: handle -O output (default to M4N)
+		${type}_m4n $1
 	else
-		$om4 $1 | m4
+		${om4:-text_m4} $1 | m4
 	fi
 }
 
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