class AwsIamAccessKeys < Inspec.resource(1)
  name 'aws_iam_access_keys'
  desc 'Verifies settings for AWS IAM Access Keys in bulk'
  example '
    describe aws_iam_access_keys do
      it { should_not exist }
    end
  '

  VALUED_CRITERIA = [
    :username,
    :id,
    :access_key_id,
    :created_date,
  ].freeze

  # Constructor.  Args are reserved for row fetch filtering.
  def initialize(filter_criteria = {})
    filter_criteria = validate_filter_criteria(filter_criteria)
    @table = AccessKeyProvider.create.fetch(filter_criteria)
  end

  def validate_filter_criteria(criteria)
    # Allow passing a scalar string, the Access Key ID.
    criteria = { access_key_id: criteria } if criteria.is_a? String
    unless criteria.is_a? Hash
      raise 'Unrecognized criteria for fetching Access Keys. ' \
            "Use 'criteria: value' format."
    end

    # id and access_key_id are aliases; standardize on access_key_id
    criteria[:access_key_id] = criteria.delete(:id) if criteria.key?(:id)
    if criteria[:access_key_id] and
       criteria[:access_key_id] !~ /^AKIA[0-9A-Z]{16}$/
      raise 'Incorrect format for Access Key ID - expected AKIA followed ' \
            'by 16 letters or numbers'
    end

    criteria.each_key do |criterion|
      unless VALUED_CRITERIA.include?(criterion) # rubocop:disable Style/Next
        raise 'Unrecognized filter criterion for aws_iam_access_keys, ' \
          "'#{criterion}'.  Valid choices are " \
          "#{VALUED_CRITERIA.join(', ')}."
      end
    end

    criteria
  end

  # Underlying FilterTable implementation.
  filter = FilterTable.create
  filter.add_accessor(:where)
        .add_accessor(:entries)
        .add(:exists?) { |x| !x.entries.empty? }
        .add(:access_key_ids, field: :access_key_id)
        .add(:created_date, field: :created_date)
        .add(:created_days_ago, field: :created_days_ago)
        .add(:created_hours_ago, field: :created_hours_ago)
        .add(:usernames, field: :username)
        .add(:active, field: :active)
        .add(:inactive, field: :inactive)
        .add(:last_used_date, field: :last_used_date)
        .add(:last_used_hours_ago, field: :last_used_hours_ago)
        .add(:last_used_days_ago,  field: :last_used_days_ago)
        .add(:ever_used,           field: :ever_used)
        .add(:never_used,          field: :never_used)
  filter.connect(self, :access_key_data)

  def access_key_data
    @table
  end

  def to_s
    'IAM Access Keys'
  end

  # Internal support class.  This is used to fetch
  # the users and access keys.  We have an abstract
  # class with a concrete AWS implementation provided here;
  # a few mock implementations are also provided in the unit tests.
  class AccessKeyProvider
    # Implementation of AccessKeyProvider which operates by looping over
    # all users, then fetching their access keys.
    # TODO: An alternate, more scalable implementation could be made
    # using the Credential Report.
    class AwsUserIterator < AccessKeyProvider
      def fetch(criteria)
        iam_client = AWSConnection.new.iam_client
        usernames = []
        if criteria.key?(:username)
          usernames.push criteria[:username]
        else
          # TODO: pagination check and resume
          usernames = iam_client.list_users.users.map(&:user_name)
        end

        access_key_data = []
        usernames.each do |username|
          begin
            user_keys = iam_client.list_access_keys(user_name: username)
                                  .access_key_metadata
            user_keys = user_keys.map do |metadata|
              {
                access_key_id: metadata.access_key_id,
                username: username,
                status: metadata.status,
                create_date: metadata.create_date, # DateTime.parse(metadata.create_date),
              }
            end

            # Synthetics
            user_keys.each do |key_info|
              add_synthetic_fields(key_info)
            end
            access_key_data.concat(user_keys)
          rescue Aws::IAM::Errors::NoSuchEntity # rubocop:disable Lint/HandleExceptions
            # Swallow - a miss on search results should return an empty table
          end
        end
        access_key_data
      end

      def add_synthetic_fields(key_info) # rubocop:disable Metrics/AbcSize
        key_info[:id] = key_info[:access_key_id]
        key_info[:active] = key_info[:status] == 'Active'
        key_info[:inactive] = key_info[:status] != 'Active'
        key_info[:created_hours_ago] = ((Time.now - key_info[:create_date]) / (60*60)).to_i
        key_info[:created_days_ago] = (key_info[:created_hours_ago] / 24).to_i

        # Last used is a separate API call
        iam_client = AWSConnection.new.iam_client
        last_used =
          iam_client.get_access_key_last_used(access_key_id: key_info[:access_key_id])
                    .access_key_last_used.last_used_date
        key_info[:ever_used] = !last_used.nil?
        key_info[:never_used] = last_used.nil?
        key_info[:last_used_time] = last_used
        return unless last_used
        key_info[:last_used_hours_ago] = ((Time.now - last_used) / (60*60)).to_i
        key_info[:last_used_days_ago] = (key_info[:last_used_hours_ago]/24).to_i
      end
    end

    DEFAULT_PROVIDER = AwsIamAccessKeys::AccessKeyProvider::AwsUserIterator
    @selected_implementation = DEFAULT_PROVIDER

    # Use this to change what class is created by create().
    def self.select(klass)
      @selected_implementation = klass
    end

    def self.reset
      @selected_implementation = DEFAULT_PROVIDER
    end

    def self.create
      @selected_implementation.new
    end

    def fetch(_filter_criteria)
      raise 'Unimplemented abstract method - internal error.'
    end
  end
end