# Copyright 2015, Google Inc.
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#
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# modification, are permitted provided that the following conditions are
# met:
#
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# notice, this list of conditions and the following disclaimer.
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# in the documentation and/or other materials provided with the
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# this software without specific prior written permission.
#
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require "multi_json"
require "stringio"

require "googleauth/credentials_loader"
require "googleauth/service_account"
require "googleauth/user_refresh"

module Google
  # Module Auth provides classes that provide Google-specific authorization
  # used to access Google APIs.
  module Auth
    # DefaultCredentials is used to preload the credentials file, to determine
    # which type of credentials should be loaded.
    class DefaultCredentials
      extend CredentialsLoader

      # override CredentialsLoader#make_creds to use the class determined by
      # loading the json.
      def self.make_creds options = {}
        json_key_io = options[:json_key_io]
        if json_key_io
          json_key, clz = determine_creds_class json_key_io
          warn_if_cloud_sdk_credentials json_key["client_id"]
          io = StringIO.new MultiJson.dump(json_key)
          clz.make_creds options.merge(json_key_io: io)
        else
          warn_if_cloud_sdk_credentials ENV[CredentialsLoader::CLIENT_ID_VAR]
          clz = read_creds
          clz.make_creds options
        end
      end

      def self.read_creds
        env_var = CredentialsLoader::ACCOUNT_TYPE_VAR
        type = ENV[env_var]
        raise "#{env_var} is undefined in env" unless type
        case type
        when "service_account"
          ServiceAccountCredentials
        when "authorized_user"
          UserRefreshCredentials
        else
          raise "credentials type '#{type}' is not supported"
        end
      end

      # Reads the input json and determines which creds class to use.
      def self.determine_creds_class json_key_io
        json_key = MultiJson.load json_key_io.read
        key = "type"
        raise "the json is missing the '#{key}' field" unless json_key.key? key
        type = json_key[key]
        case type
        when "service_account"
          [json_key, ServiceAccountCredentials]
        when "authorized_user"
          [json_key, UserRefreshCredentials]
        else
          raise "credentials type '#{type}' is not supported"
        end
      end
    end
  end
end