enhance(scripts/generate-bootstraps.sh): add caching support

scripts/generate-bootstraps.sh

@@ -13,6 +13,11 @@ trap 'rm -rf $BOOTSTRAP_TMPDIR' EXIT
 # and <10.
 BOOTSTRAP_ANDROID10_COMPATIBLE=false
 
+# Optional caching of downloaded packages in output directory
+# Apt only for now
+TERMUX_PACKAGE_DOWNLOAD_CACHE=false
+TERMUX_PACKAGE_DOWNLOAD_CACHE_DIR="$PWD/output"
+
 # By default, bootstrap archives will be built for all architectures
 # supported by Termux application.
 # Override with option '--architectures'.
@@ -119,8 +124,9 @@ pull_package() {
 	mkdir -p "$package_tmpdir"
 
 	if [ ${TERMUX_PACKAGE_MANAGER} = "apt" ]; then
-		local package_url
+		local package_url package_file
 		package_url="$REPO_BASE_URL/$(echo "${PACKAGE_METADATA[${package_name}]}" | grep -i "^Filename:" | awk '{ print $2 }')"
+		package_file="$(echo "$package_url" | sed -e 's|\(.*\)\/\(.*\).deb$|\2.deb|')"
 		if [ "${package_url}" = "$REPO_BASE_URL" ] || [ "${package_url}" = "${REPO_BASE_URL}/" ]; then
 			echo "[!] Failed to determine URL for package '$package_name'."
 			exit 1
@@ -144,10 +150,28 @@ pull_package() {
 			unset dep
 		fi
 
+		if [ "$TERMUX_PACKAGE_DOWNLOAD_CACHE" = true ]; then
+			# since each generate-bootstraps.sh run will have different package_tmpdir
+			# we dont have to check existence of both files and even so prioritise the cached copy
+			# also use symbolic link to save space and I/O
+			echo "[*] Checking '$TERMUX_PACKAGE_DOWNLOAD_CACHE_DIR' for cached copy of '$package_name' package file..."
+			if [ -e "$TERMUX_PACKAGE_DOWNLOAD_CACHE_DIR/$package_file" ]; then
+				echo "[*] Symlinking cached '$package_file' to '$package_tmpdir'..."
+				ln -fsT "$TERMUX_PACKAGE_DOWNLOAD_CACHE_DIR/$package_file" "$package_tmpdir/package.deb"
+			else
+				echo "[*] Cached copy of '$package_file' not found. Skipping..."
+			fi
+		fi
+
 		if [ ! -e "$package_tmpdir/package.deb" ]; then
 			echo "[*] Downloading '$package_name'..."
 			curl --fail --location --output "$package_tmpdir/package.deb" "$package_url"
 
+			if [ "$TERMUX_PACKAGE_DOWNLOAD_CACHE" = true ]; then
+				echo "[*] Caching '$package_name' package.deb to '$TERMUX_PACKAGE_DOWNLOAD_CACHE_DIR/$package_file'..."
+				cp -f "$package_tmpdir/package.deb" "$TERMUX_PACKAGE_DOWNLOAD_CACHE_DIR/$package_file"
+			fi
+
 			echo "[*] Extracting '$package_name'..."
 			(cd "$package_tmpdir"
 				ar x package.deb
@@ -295,6 +319,11 @@ show_usage() {
 	echo "                             Multiple packages should be passed as"
 	echo "                             comma-separated list."
 	echo
+	echo " -c, --cache [DIR]           Enable caching. Downloaded package files will be"
+	echo "                             stored at output directory unless specified another"
+	echo "                             path. The files can be reused at later runs."
+	echo "                             This option is disabled by default and for apt only."
+	echo
 	echo " --pm MANAGER                Set up a package manager in bootstrap."
 	echo "                             It can only be pacman or apt (the default is apt)."
 	echo
@@ -311,7 +340,7 @@ show_usage() {
 	echo "Architectures: ${TERMUX_ARCHITECTURES[*]}"
 	echo "Repository Base Url: ${REPO_BASE_URL}"
 	echo "Prefix: ${TERMUX_PREFIX}"
-        echo "Package manager: ${TERMUX_PACKAGE_MANAGER}"
+	echo "Package manager: ${TERMUX_PACKAGE_MANAGER}"
 	echo
 }
 
@@ -372,6 +401,13 @@ while (($# > 0)); do
 				exit 1
 			fi
 			;;
+		-c|--cache)
+			if [ $# -gt 1 ] && [ -n "$2" ] && [[ $2 != -* ]]; then
+				TERMUX_PACKAGE_DOWNLOAD_CACHE_DIR="$2"
+				shift 1
+			fi
+			TERMUX_PACKAGE_DOWNLOAD_CACHE=true
+			;;
 		*)
 			echo "[!] Got unknown option '$1'"
 			show_usage
@@ -392,6 +428,15 @@ if [ -z "$REPO_BASE_URL" ]; then
 	exit 1
 fi
 
+if [ "$TERMUX_PACKAGE_DOWNLOAD_CACHE" = true ]; then
+	if [ "$TERMUX_PACKAGE_MANAGER" != apt ]; then
+		echo "[!] Option '--cache' does not support '$TERMUX_PACKAGE_MANAGER' yet." 1>&2
+		exit 1
+	fi
+	echo "[*] Caching enabled. Cached packages will be stored at '$TERMUX_PACKAGE_DOWNLOAD_CACHE_DIR'."
+	mkdir -p "$TERMUX_PACKAGE_DOWNLOAD_CACHE_DIR"
+fi
+
 for package_arch in "${TERMUX_ARCHITECTURES[@]}"; do
 	BOOTSTRAP_ROOTFS="$BOOTSTRAP_TMPDIR/rootfs-${package_arch}"
 	BOOTSTRAP_PKGDIR="$BOOTSTRAP_TMPDIR/packages-${package_arch}"