#!/bin/sh

set -e

# if this is running on an interactive terminal (as opposed to in a script),
# and if tput is installed and knows some color codes...
if [ -t 1 ] && [ "$(tput colors 2>/dev/null || echo 0)" -ge 8 ]; then 
    _clr="$(tput sgr0)"
    _red="$(tput setaf 1)"
fi
err() { echo "$_red[ERR]$_clr $@" >&2; exit 1; }

VERCMPROOT="$(dirname "$(readlink -f "$0")")"

[ "$1" ] || cat <<EOF
usage:
    $(basename $0) [-f <format>] <comparison string>
    $(basename $0) formats

comparison string:
    "<version 1> <op> <version 2>"

op:
    == equal
    != not equal
    >= greater than or equal
    <= less than or equal
    >  greater than
    <  less than

format:
    the name of the format to use for parsing and comparing the versions.
	see '$(basename $0) formats' for a list of formats.
	(format scripts are kept in $VERCMPROOT/format)
EOF

[ -d "$VERCMPROOT/format" ] \
|| err "no format directory! install one. see makefile or README for details."

if [ "$1" = "formats" ]; then
    ls $VERCMPROOT/format/*.sh | sed -e 's/.*\/\(.*\).sh/\1/'
    exit 0
fi

[ "$1" = "-f" ] && { fmt="$2"; shift; shift; } || fmt="default"

# make $fmt available to version format scripts
export fmt

v1="$(echo "$1" | awk '{ print $1 }')"
op="$(echo "$1" | awk '{ print $2 }')"
v2="$(echo "$1" | awk '{ print $3 }')"

[ "$v2" ] || err "could not determine second version to use in comparison!"

[ -e "$VERCMPROOT/format/$fmt.sh" ] || err "unrecognized version format: $fmt"

. "$VERCMPROOT/format/$fmt.sh"

# 'comparever' returns =, <, or >
relation="$(comparever $v1 $v2)"

no() { echo "no" && exit 0; }
case $op in
    '!=') [ "$relation" != "=" ] || no ;;
    '=='|'='|'>'|'<'|'>='|'<=') [ "${op#*$relation}" != "${op}" ] || no ;;
       *) err "unrecognized operator: $op" ;;
esac
echo "yes"