class ActiveStorage::Service::GCSService

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

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

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

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

def download(key)
  instrument :download, key: key do
    io = file_for(key).download
    io.rewind
    if block_given?
      yield io.string
    else
      io.string
    end
  end
end

def download_chunk(key, range)
  instrument :download_chunk, key: key, range: range do
    file = file_for(key)
    uri  = URI(file.signed_url(expires: 30.seconds))
    Net::HTTP.start(uri.host, uri.port, use_ssl: uri.scheme == "https") do |client|
      client.get(uri, "Range" => "bytes=#{range.begin}-#{range.exclude_end? ? range.end - 1 : range.end}").body
    end
  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)
  bucket.file(key, skip_lookup: true)
end

def headers_for_direct_upload(key, checksum:, **)
  { "Content-MD5" => checksum }
end

def initialize(**config)
  @config = config
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
    begin
      # 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
end

def url(key, expires_in:, filename:, content_type:, disposition:)
  instrument :url, key: key do |payload|
    generated_url = file_for(key).signed_url expires: expires_in, query: {
      "response-content-disposition" => content_disposition_with(type: disposition, filename: filename),
      "response-content-type" => content_type
    }
    payload[:url] = generated_url
    generated_url
  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