class Aws::SharedConfig

def assume_role_from_profile(cfg, profile, opts, chain_config)
  if cfg && prof_cfg = cfg[profile]
    opts[:source_profile] ||= prof_cfg["source_profile"]
    credential_source = opts.delete(:credential_source)
    credential_source ||= prof_cfg["credential_source"]
    if opts[:source_profile] && credential_source
      raise Errors::CredentialSourceConflictError.new(
        "Profile #{profile} has a source_profile, and "\
          "a credential_source. For assume role credentials, must "\
          "provide only source_profile or credential_source, not both."
      )
    elsif opts[:source_profile]
      opts[:credentials] = credentials(profile: opts[:source_profile])
      if opts[:credentials]
        opts[:role_session_name] ||= prof_cfg["role_session_name"]
        opts[:role_session_name] ||= "default_session"
        opts[:role_arn] ||= prof_cfg["role_arn"]
        opts[:external_id] ||= prof_cfg["external_id"]
        opts[:serial_number] ||= prof_cfg["mfa_serial"]
        opts[:profile] = opts.delete(:source_profile)
        AssumeRoleCredentials.new(opts)
      else
        raise Errors::NoSourceProfileError.new(
          "Profile #{profile} has a role_arn, and source_profile, but the"\
            " source_profile does not have credentials."
        )
      end
    elsif credential_source
      opts[:credentials] = credentials_from_source(
        credential_source,
        chain_config
      )
      if opts[:credentials]
        opts[:role_session_name] ||= prof_cfg["role_session_name"]
        opts[:role_session_name] ||= "default_session"
        opts[:role_arn] ||= prof_cfg["role_arn"]
        opts[:external_id] ||= prof_cfg["external_id"]
        opts[:serial_number] ||= prof_cfg["mfa_serial"]
        opts.delete(:source_profile) # Cleanup
        AssumeRoleCredentials.new(opts)
      else
        raise Errors::NoSourceCredentials.new(
          "Profile #{profile} could not get source credentials from"\
            " provider #{credential_source}"
        )
      end
    elsif prof_cfg["role_arn"]
      raise Errors::NoSourceProfileError.new(
        "Profile #{profile} has a role_arn, but no source_profile."
      )
    else
      nil
    end
  else
    nil
  end
end