#!/usr/bin/env zsh
#
# Copyright © 2010-2012 Nick Bowler
#
# License WTFPL2: Do What The Fuck You Want To Public License, version 2.
# This is free software: you are free to do what the fuck you want to.
# There is NO WARRANTY, to the extent permitted by law.
#
# A convenient script to download an OpenGL extension specification from the
# Khronos registry into the current working directory.

IFS=_ extension=(${=1})

case $extension[1] in
GL|GLX|WGL)
	;;
*)
	extension=(GL $extension)
	;;
esac

api=$extension[1]
vendor=$extension[2]
name=${(j:_:)extension[3,-1]}
fullname=${(j:_:)extension}

if [[ -z $api || -z $vendor || -z $name ]]; then
	printf 'usage: %s extension\n' $0 1>&2
	exit 1
fi

urls=(
	http://www.opengl.org/registry/specs/$vendor/$name.txt
	http://www.opengl.org/registry/specs/$vendor/${api:l}_$name.txt
)

for url in $urls; do
	if wget -O $fullname $url; then
		gzip -f $fullname || exit 1
		exit 0
	fi

	rm -f $fullname
done

exit 1