#!/usr/bin/env bash
set -euo pipefail

image_ref="${1:-}"

if [[ -z "$image_ref" ]]; then
  echo "usage: $0 <registry/repository:tag>" >&2
  exit 2
fi

failures=()

try_tool() {
  local name="$1"
  shift

  if ! command -v "$name" >/dev/null 2>&1; then
    return 1
  fi

  local output
  if output="$("$@" 2>&1 >/dev/null)"; then
    echo "ok: found image manifest with $name: $image_ref"
    exit 0
  fi

  failures+=("$name: $output")
  return 1
}

try_registry_api() {
  if ! command -v curl >/dev/null 2>&1; then
    return 1
  fi

  local ref_no_digest="${image_ref%@*}"
  local ref_without_tag tag registry repo url output

  if [[ "$ref_no_digest" != *:* ]]; then
    failures+=("registry-api: image ref must include an explicit tag")
    return 1
  fi

  tag="${ref_no_digest##*:}"
  ref_without_tag="${ref_no_digest%:*}"
  registry="${ref_without_tag%%/*}"
  repo="${ref_without_tag#*/}"

  if [[ -z "$registry" || -z "$repo" || "$registry" == "$repo" ]]; then
    failures+=("registry-api: image ref must include registry and repository")
    return 1
  fi

  url="https://${registry}/v2/${repo}/manifests/${tag}"
  if output="$(curl -fsSL \
      -H "Accept: application/vnd.oci.image.index.v1+json" \
      -H "Accept: application/vnd.oci.image.manifest.v1+json" \
      -H "Accept: application/vnd.docker.distribution.manifest.list.v2+json" \
      -H "Accept: application/vnd.docker.distribution.manifest.v2+json" \
      -o /dev/null "$url" 2>&1)"; then
    echo "ok: found image manifest with registry API: $image_ref"
    exit 0
  fi

  failures+=("registry-api: $output")
  return 1
}

try_tool skopeo skopeo inspect --raw "docker://${image_ref}" || true
try_tool crane crane manifest "$image_ref" || true
try_tool docker docker manifest inspect "$image_ref" || true
try_registry_api || true

echo "ERROR: image manifest not found or not accessible: $image_ref" >&2
if ((${#failures[@]} > 0)); then
  printf '%s\n' "${failures[@]}" >&2
else
  echo "No supported manifest inspection tool was available." >&2
fi
exit 1