#!/usr/bin/env sh
set -e

# See https://www.gnu.org/prep/standards/html_node/Directory-Variables.html
prefix=/usr/local
exec_prefix='$(PREFIX)'
exec_suffix=
bindir='$(EXEC_PREFIX)/bin'


main() {
    parseArgs "$@"
    mangleMakefile
}


printHelp() {
    echo ''
    echo "Example usage:   $0 --prefix /usr/local"
    echo ''
    echo 'Options:'
    echo '    --prefix <path>      Default "/usr/local"'
    echo '    --exec-prefix <path> Default "$(PREFIX)"'
    echo '    --exec-suffix <path> Default <empty>'
    echo '    --bindir <path>      Default "$(EXEC_PREFIX)/bin"'
    echo ''
}


parseArgs() {
    # See: https://stackoverflow.com/a/14203146/4415884
    while test $# -gt 0 ; do
        case $1 in
            --help)        printHelp; exit 1; ;;
            --prefix)      prefix="$2"      shift; shift; ;;
            --exec-prefix) exec_prefix="$2" shift; shift; ;;
            --exec-suffix) exec_suffix="$2" shift; shift; ;;
            --bindir)      bindir="$2"      shift; shift; ;;
            *) echo "[ERROR] Unexpected argument: $1"; exit 1 ;;
        esac
    done
}


mangleMakefile() {
    sed -i 's;^PREFIX=.*$;PREFIX='"$prefix"';' Makefile
    sed -i 's;^EXEC_PREFIX=.*$;EXEC_PREFIX='"$exec_prefix"';' Makefile
    sed -i 's;^EXEC_SUFFIX=.*$;EXEC_SUFFIX='"$exec_suffix"';' Makefile
    sed -i 's;^BINDIR=.*$;BINDIR='"$bindir"';' Makefile
}


main "$@"