module Google::Auth::CredentialsLoader

def from_env(scope)
  return nil unless ENV.key?(ENV_VAR)
  path = ENV[ENV_VAR]
  fail 'file #{path} does not exist' unless File.exist?(path)
  File.open(path) do |f|
    return make_creds(scope, f)
  end
rescue StandardError => e
  raise "#{NOT_FOUND_ERROR}: #{e}"
end

def from_well_known_path(scope)
  home_var, base = windows? ? 'APPDATA' : 'HOME', WELL_KNOWN_PATH
  root = ENV[home_var].nil? ? '' : ENV[home_var]
  base = File.join('.config', base) unless windows?
  path = File.join(root, base)
  return nil unless File.exist?(path)
  File.open(path) do |f|
    return make_creds(scope, f)
  end
rescue StandardError => e
  raise "#{WELL_KNOWN_ERROR}: #{e}"
end

def make_creds(*args)
  new(*args)
end

def windows?
  RbConfig::CONFIG['host_os'] =~ /Windows|mswin/
end