#!/bin/sh
set -eu

usage() {
	cat <<-'EOF'
		Usage:
		  mail -s SUBJECT ADDRESS... < BODY
		  mail -h
	EOF
}

help() {
	cat <<-'EOF'

		Options:
		  -s SUBJECT    the email subject
		  -h, --help    show this message

		ADDRESS         the email addresses to send the email to
		BODY            the text to be sent as the body
	EOF
}

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

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

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

assert_arg "${SUBJECT:-}" '-s SUBJECT'
assert_arg "${1:-}"       'ADDRESS'

printf 'Subject: %s\n\n%s' \
	"$(echo "$SUBJECT" | tr -d '\n')" \
	"$(cat)" |
		msmtpq -a euandreh "$@"