class ActiveStorage::Service::GCSService

def bucket
  @bucket ||= client.bucket(config.fetch(:bucket), skip_lookup: true)
end

def client
  @client ||= Google::Cloud::Storage.new(**config.except(:bucket))
end

def delete(key)
  instrument :delete, key: key do
    file_for(key).delete
  rescue Google::Cloud::NotFoundError
    # Ignore files already deleted
  end
end

def delete_prefixed(prefix)
  instrument :delete_prefixed, prefix: prefix do
    bucket.files(prefix: prefix).all do |file|
      file.delete
    rescue Google::Cloud::NotFoundError
      # Ignore concurrently-deleted files
    end
  end
end

def download(key, &block)
  if block_given?
    instrument :streaming_download, key: key do
      stream(key, &block)
    end
  else
    instrument :download, key: key do
      file_for(key).download.string
    rescue Google::Cloud::NotFoundError
      raise ActiveStorage::FileNotFoundError
    end
  end
end

def download_chunk(key, range)
  instrument :download_chunk, key: key, range: range do
    file_for(key).download(range: range).string
  rescue Google::Cloud::NotFoundError
    raise ActiveStorage::FileNotFoundError
  end
end

def exist?(key)
  instrument :exist, key: key do |payload|
    answer = file_for(key).exists?
    payload[:exist] = answer
    answer
  end
end

def file_for(key, skip_lookup: true)
  bucket.file(key, skip_lookup: skip_lookup)
end

def headers_for_direct_upload(key, checksum:, filename: nil, disposition: nil, **)
  content_disposition = content_disposition_with(type: disposition, filename: filename) if filename
  { "Content-MD5" => checksum, "Content-Disposition" => content_disposition }
end

def initialize(public: false, **config)
  @config = config
  @public = public
end

def private_url(key, expires_in:, filename:, content_type:, disposition:, **)
  file_for(key).signed_url expires: expires_in, query: {
    "response-content-disposition" => content_disposition_with(type: disposition, filename: filename),
    "response-content-type" => content_type
  }
end

def public_url(key, **)
  file_for(key).public_url
end

def stream(key)
  file = file_for(key, skip_lookup: false)
  chunk_size = 5.megabytes
  offset = 0
  raise ActiveStorage::FileNotFoundError unless file.present?
  while offset < file.size
    yield file.download(range: offset..(offset + chunk_size - 1)).string
    offset += chunk_size
  end
end

def update_metadata(key, content_type:, disposition: nil, filename: nil)
  instrument :update_metadata, key: key, content_type: content_type, disposition: disposition do
    file_for(key).update do |file|
      file.content_type = content_type
      file.content_disposition = content_disposition_with(type: disposition, filename: filename) if disposition && filename
    end
  end
end

def upload(key, io, checksum: nil, content_type: nil, disposition: nil, filename: nil)
  instrument :upload, key: key, checksum: checksum do
    # GCS's signed URLs don't include params such as response-content-type response-content_disposition
    # in the signature, which means an attacker can modify them and bypass our effort to force these to
    # binary and attachment when the file's content type requires it. The only way to force them is to
    # store them as object's metadata.
    content_disposition = content_disposition_with(type: disposition, filename: filename) if disposition && filename
    bucket.create_file(io, key, md5: checksum, content_type: content_type, content_disposition: content_disposition)
  rescue Google::Cloud::InvalidArgumentError
    raise ActiveStorage::IntegrityError
  end
end

def url_for_direct_upload(key, expires_in:, checksum:, **)
  instrument :url, key: key do |payload|
    generated_url = bucket.signed_url key, method: "PUT", expires: expires_in, content_md5: checksum
    payload[:url] = generated_url
    generated_url
  end
end