class Aws::CredentialProviderChain

def env_credentials(options)
  env_keys = []
  if prefix = options[:prefix]
    env_keys << "#{prefix}_ACCESS_KEY_ID"
    env_keys << "#{prefix}_SECRET_ACCESS_KEY"
    env_keys << "#{prefix}_SESSION_TOKEN"
  else
    env_keys << options[:key]
    env_keys << options[:secret]
  end
  Credentials.new(*ENV.values_at(*env_keys))
end

def initialize(config)
  @config = config
end

def instance_profile_credentials(*args)
  InstanceProfileCredentials.new
end

def providers
  [
    [:static_credentials, {}],
    [:env_credentials, { prefix: 'AWS' }],
    [:env_credentials, { prefix: 'AMAZON' }],
    [:env_credentials, { key:'AWS_ACCESS_KEY', secret:'AWS_SECRET_KEY' }],
    [:shared_credentials, {}],
    [:instance_profile_credentials, {}],
  ]
end

def resolve
  providers.each do |method_name, options|
    credentials = send(method_name, options.merge(config: @config))
    return credentials if credentials && credentials.set?
  end
  nil
end

def shared_credentials(options = {})
  SharedCredentials.new(profile_name: options[:config].profile)
rescue Errors::NoSuchProfileError
  nil
end

def static_credentials(options)
  config = options[:config]
  Credentials.new(
    config.access_key_id,
    config.secret_access_key,
    config.session_token)
end