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

usage() {
  sed -n '2,22p' "$0"
}

# Build and publish a Docker image with buildx.
#
# Usage:
#   publish.sh --registry HOST --repository PATH --tag TAG --platform PLATFORMS [options]
#
# Options:
#   --registry HOST       Registry host, without a URL scheme
#   --repository PATH     Repository path, such as team/service
#   --tag TAG             Image tag
#   --platform LIST       Comma-separated platforms
#   --file PATH           Dockerfile path (default: Dockerfile)
#   --context PATH        Build context (default: .)
#   --builder NAME        Existing buildx builder
#   --load                Load a single-platform image instead of pushing
#   --dry-run             Print the resolved build without executing it
#   --help                Show this help

registry=
repository=
tag=
platform=
dockerfile=Dockerfile
build_context=.
builder=
mode=push
dry_run=false

while (($#)); do
  case "$1" in
    --registry) registry=${2-}; shift 2 ;;
    --repository) repository=${2-}; shift 2 ;;
    --tag) tag=${2-}; shift 2 ;;
    --platform) platform=${2-}; shift 2 ;;
    --file) dockerfile=${2-}; shift 2 ;;
    --context) build_context=${2-}; shift 2 ;;
    --builder) builder=${2-}; shift 2 ;;
    --load) mode=load; shift ;;
    --dry-run) dry_run=true; shift ;;
    --help|-h) usage; exit 0 ;;
    *) printf 'Unknown argument: %s\n' "$1" >&2; usage >&2; exit 2 ;;
  esac
done

for required_name in registry repository tag platform; do
  if [[ -z ${!required_name} ]]; then
    printf 'Missing required option: --%s\n' "$required_name" >&2
    exit 2
  fi
done

if [[ $registry == *://* || $registry == */* ]]; then
  printf '%s\n' 'Registry must be a host without a URL scheme or path.' >&2
  exit 2
fi
if [[ $repository == /* || $repository == */ || $repository != */* ]]; then
  printf '%s\n' 'Repository must look like namespace/image.' >&2
  exit 2
fi
if [[ $tag == *:* || $tag == */* ]]; then
  printf '%s\n' 'Tag must not contain ":" or "/".' >&2
  exit 2
fi
if [[ $mode == load && $platform == *,* ]]; then
  printf '%s\n' '--load supports only one platform.' >&2
  exit 2
fi
if [[ ! -f $dockerfile ]]; then
  printf 'Dockerfile not found: %s\n' "$dockerfile" >&2
  exit 2
fi
if [[ ! -d $build_context ]]; then
  printf 'Build context not found: %s\n' "$build_context" >&2
  exit 2
fi
if [[ $dry_run == false ]] && ! command -v docker >/dev/null 2>&1; then
  printf '%s\n' 'docker is not installed or not available in PATH.' >&2
  exit 127
fi

image_ref="${registry}/${repository}:${tag}"
build_cmd=(docker buildx build --file "$dockerfile" --platform "$platform" --tag "$image_ref")
if [[ -n $builder ]]; then
  build_cmd+=(--builder "$builder")
fi
if [[ $mode == push ]]; then
  build_cmd+=(--push)
else
  build_cmd+=(--load)
fi
build_cmd+=("$build_context")

printf 'Image: %s\n' "$image_ref"
printf 'Platform: %s\n' "$platform"
printf 'Dockerfile: %s\n' "$dockerfile"
printf 'Context: %s\n' "$build_context"
printf 'Mode: %s\n' "$mode"

if [[ $dry_run == true ]]; then
  printf 'Command:'
  printf ' %q' "${build_cmd[@]}"
  printf '\n'
  exit 0
fi

"${build_cmd[@]}"

if [[ $mode == push ]]; then
  docker buildx imagetools inspect "$image_ref"
fi