compress-apks

#!/bin/bash

set -o errexit -o nounset -o pipefail

if [[ $# -eq 1 ]]; then
    fd=$1
else
    touch lock
    exec {fd}< lock
fi

if ! flock -n $fd; then
    echo already locked >&2
    exit 1
fi

maybe_brotli() {
    COMP="$1.br"
    if [[ -f $COMP ]]; then
        return
    fi

    TMP="$COMP.tmp"
    rm -f $TMP

    echo "brotli $1"
    brotli --suffix=".br.tmp" "$1"

    sync $TMP
    mv $TMP $COMP
    # fully preserve file times, brotli reduces precision of mtime to a second
    touch -r "$1" $COMP
}

export -f maybe_brotli

maybe_zopfli() {
    COMP="$1.gz"
    if [[ -f $COMP ]]; then
        return
    fi

    TMP="$COMP.tmp"
    rm -f $TMP

    echo "zopfli $1"
    zopfli -c "$1" > $TMP

    sync $TMP
    mv $TMP $COMP
    # preserve file times
    touch -r "$1" $COMP
}

export -f maybe_zopfli

find "apps/packages" -regex '.+\.apk' |
    parallel -q ::: maybe_brotli maybe_zopfli :::: -