#!/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 b2sum="$(b2sum "${download}" | awk '{ print $1 }')"
	if [ -z "${b2sum}" ]; 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)_BLAKE2.*/\$(DL_FILE)_BLAKE2 = ${b2sum}/"

	echo "Done"
	return 0
}

main "$@" || exit $?