#!/usr/bin/env bash

# This script deletes all the files under the buildkit cache blob directory that
# are not referred to in the cache manifest file.

set -eu

export DOCKER_BUILDKIT_CACHE=${DOCKER_BUILDKIT_CACHE:-}

manifest_sha=$(jq -r .manifests[0].digest < "${DOCKER_BUILDKIT_CACHE}/index.json")
manifest=${manifest_sha#"sha256:"}
files=("$manifest")
while IFS= read -r line; do files+=("$line"); done <<< "$(jq -r '.manifests[].digest | sub("^sha256:"; "")' < "${DOCKER_BUILDKIT_CACHE}/blobs/sha256/$manifest")"
for file in "${DOCKER_BUILDKIT_CACHE}"/blobs/sha256/*; do
  name=$(basename "$file")
  # shellcheck disable=SC2199
  if [[ ! "${files[@]}" =~ ${name} ]]; then
    printf 'pruned from cache: %s\n' "$file"
		rm -f "$file"
  fi
done