#!/bin/sh
set -eu

usage() {
	cat <<-'EOF'
		Usage:
		  pre [-c COLOR] PREFIX
		  pre -h
	EOF
}

help() {
	cat <<-'EOF'

		Options:
		  -c COLOR      ANSI color to be used on the prefix text
		  -h, --help    show this message
	EOF
}

for flag in "$@"; do
	case "$flag" in
		--)
			break
			;;
		--help)
			usage
			help
			exit
			;;
		*)
			;;
	esac
done

COLOR=''
while getopts 'c:h' flag; do
	case "$flag" in
		c)
			COLOR="$OPTARG"
			;;
		h)
			usage
			help
			exit
			;;
		*)
			usage >&2
			exit 2
			;;
	esac
done
shift $((OPTIND - 1))

assert_arg() {
	if [ -z "$1" ]; then
		printf 'Missing %s\n\n' "$2" >&2
		usage >&2
		exit 2
	fi
}

PREFIX="${1:-}"
assert_arg "$PREFIX" 'PREFIX'

while read -r line; do
	if [ -z "$COLOR" ]; then
		printf '%s: %s\n' "$PREFIX" "$line"
	else
		printf '%s: %s\n' "$(color -c "$COLOR" "$PREFIX")" "$line"
	fi
done