#!/usr/bin/sh -e
# Fortune implementation in POSIX sh/awk

usage() {
		echo 'Usage: fortune [OPTIONS]
a simple POSIX sh/awk implementation of fortune

	-h, --help                    show this help message
	-l, --list                    list installed cookie files
	-c FILE, --cookie FILE        specify cookie file
	-n LENGTH, --min LENGTH       specify min fortune length
	-N LENGTH, --max LENGTH       specify max fortune length

	fortune looks for fortunes in $FORTUNEDIR, which defaults to
	/usr/share/fortune.

Exit codes:
	0    success
	1    generic error
	2    argument parsing error'
}

parse_err() {
		echo "$1"
		$2
		exit 2
}

DIR=${FORTUNEDIR:-"/usr/share/fortune/"}
FILE="$(find $DIR -type f -not -name '*.dat')"
MAXLENGTH=1000000000000
MINLENGTH=0

while [ "$1" != "" ]; do
		case $1 in
				-h | --help)
						usage
						exit
						;;
				-c | --cookie)
						FILE=$DIR/$2
						;;
				-n | --min)
						MINLENGTH=$2
						;;
				-N | --max)
						MAXLENGTH=$2
						;;
				-l | --list)
						ls -1 $DIR
						exit
						;;
				*)
						parse_err "ERROR: unknown option \"$1\"" usage
						;;
		esac
		shift 2
done

[ "$MAXLENGTH" -lt "$MINLENGTH" ] && {
		parse_err "ERROR: maximum length is less than minimum length"
}

[ -d "$FILE" ] && {
		parse_err "ERROR: directory given, please provide a file or glob of files"
}

[ "$(find $FILE -maxdepth 1 -print -quit 2> /dev/null)" ] || {
		parse_err "ERROR: no such file or directory"
}

awk -v maxlen=$MAXLENGTH -v minlen=$MINLENGTH \
		'BEGIN {
	f++
}

$1 == "%" {
	len = length(fortunes[f])
	if ( len>maxlen || len<minlen ) {
		fortunes[f] = ""
	} else {
		f++
	}
}

{
	sub("%", "")
	fortunes[f] = fortunes[f] (length(fortunes[f])?"\n":"") $0
}

END {
	"od -A n -t d -N 3 /dev/urandom" | getline seed
	srand(seed)
	print fortunes[int(rand() * (f - 2)) + 1]
}' $FILE