movelang

#!/bin/bash

error() {
	echo "$1" && exit 1
}

while getopts "k:s:t:" FLAGS; do
	case $FLAGS in
		k) KEYS="${OPTARG}" ;;
		s) SOURCE_DIRECTORY="${OPTARG}" ;;
		t) TARGET_DIRECTORY="${OPTARG}" ;;
		*) exit 1 ;;
	esac
done

[ -n "${KEYS}" ] || error "Add a space-separated string of language keys with '-k'"
[ -n "${SOURCE_DIRECTORY}" ] || error "Add a source directory with '-s'"
[ -n "${TARGET_DIRECTORY}" ] || error "Add a target directory with '-t'"
[ -d "${SOURCE_DIRECTORY}" ] || error "Source directory does not exist: ${SOURCE_DIRECTORY}"
[ -d "${TARGET_DIRECTORY}" ] || error "Target directory does not exist: ${TARGET_DIRECTORY}"

KEYS_PATTERN="^${KEYS// /|}="

for SOURCE_FILE in "${SOURCE_DIRECTORY}"/Language*.properties ; do
	TARGET_FILE="${TARGET_DIRECTORY}/${SOURCE_FILE##*/}"

	# If the target file exists, append a new line
	if [ -s "${TARGET_FILE}" ]; then
		echo >> "${TARGET_FILE}"
	fi

	# Append all the matching lines to the target file
	grep -E "${KEYS_PATTERN}" "${SOURCE_FILE}" >> "${TARGET_FILE}"

	# Remove the matching lines from the source file
	sed -Ei "/${KEYS_PATTERN}/d" "${SOURCE_FILE}"
	
	# If on MacOS, install 'gnu-sed' with brew and call 'gsed' instead:
	# gsed -Ei "/${KEYS_PATTERN}/d" "${SOURCE_FILE}"
done

echo 👍

This script uses gsed, which is just GNU sed installed on MacOS. If you're on a Linux distro you can just replace it with sed.