class Aws::CredentialProviderChain

def env_credentials(options)
  key =    %w(AWS_ACCESS_KEY_ID     AMAZON_ACCESS_KEY_ID     AWS_ACCESS_KEY)
  secret = %w(AWS_SECRET_ACCESS_KEY AMAZON_SECRET_ACCESS_KEY AWS_SECRET_KEY)
  token =  %w(AWS_SESSION_TOKEN     AMAZON_SESSION_TOKEN)
  Credentials.new(envar(key), envar(secret), envar(token))
end

def envar(keys)
  keys.each do |key|
    if ENV.key?(key)
      return ENV[key]
    end
  end
  nil
end

def initialize(config)
  @config = config
end

def instance_profile_credentials(options)
  InstanceProfileCredentials.new(options)
end

def providers
  [
    [:static_credentials, {}],
    [:env_credentials, {}],
    [:shared_credentials, {}],
    [:instance_profile_credentials, {
      retries: 0,
      http_open_timeout: 1,
      http_read_timeout: 1,
    }],
  ]
end

def resolve
  providers.each do |method_name, options|
    provider = send(method_name, options.merge(config: @config))
    return provider if provider && provider.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