rust: Add script to automatically generate packages

This is a very tiring and repetitive process which is now automated in
this script which will find the latest version and create a LFS file for
it.

Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>

diff --git a/tools/download-rust-crate b/tools/download-rust-crate
new file mode 100755 (executable)
index 0000000..bae6b60
--- /dev/null
+++ b/tools/download-rust-crate
@@ -0,0 +1,82 @@
+#!/bin/bash
+
+set -o pipefail
+
+RUST_TEMPLATE="lfs/rust-rand"
+
+fetch_latest_version() {
+       local name="${1}"
+
+       if ! curl --silent "https://crates.io/api/v1/crates/${name}" | \
+                       jq --raw-output .crate.max_stable_version; then
+               echo "${0}: Could not find the latest stable version of ${name}" >&2
+               return 1
+       fi
+}
+
+main() {
+       local name="${1}"
+       local version="${2}"
+
+       if [ -z "${name}" ]; then
+               echo "${0}: You need to pass a name of a crate" >&2
+               return 2
+       fi
+
+       if [ -z "${version}" ]; then
+               version="$(fetch_latest_version "${name}")"
+               if [ -z "${version}" ]; then
+                       # error message has already been printed
+                       return 1
+               fi
+       fi
+
+       # Compose download URL
+       local url="https://crates.io/api/v1/crates/${name}/${version}/download"
+       local download="$(mktemp)"
+
+       # Perform download
+       if ! curl -L "${url}" -o "${download}"; then
+               echo "${0}: Could not download ${name}-${version}" >&2
+               unlink "${download}"
+               return 1
+       fi
+
+       # Check if download is an orderly tar file
+       if ! tar tvf "${download}" &>/dev/null; then
+               echo "${0}: Download is not a tar file" >&2
+               unlink "${download}"
+               return 1
+       fi
+
+       # Hash the downloaded file
+       local md5sum="$(md5sum "${download}" | awk '{ print $1 }')"
+       if [ -z "${md5sum}" ]; then
+               echo "${0}: Could not hash download" >&2
+               unlink "${download}"
+               return 1
+       fi
+
+       local filename="cache/${name}-${version}.tar.gz"
+
+       # Move to final destination
+       if ! install -m 644 "${download}" "${filename}"; then
+               echo "${0}: Could not move downloaded file to ${filename}" >&2
+               unlink "${download}"
+               return 1
+       fi
+
+       # Remove download
+       unlink "${download}"
+
+       # Create a new LFS file
+       sed < "${RUST_TEMPLATE}" > "lfs/rust-${name}" \
+               -e "s/^VER.*/VER        = ${version}/" \
+               -e "s/^THISAPP.*/THISAPP    = ${name}-\$(VER)/" \
+               -e "s/^\$(DL_FILE)_MD5.*/\$(DL_FILE)_MD5 = ${md5sum}/"
+
+       echo "Done"
+       return 0
+}
+
+main "$@" || exit $?