18F/identity-idp

# frozen_string_literal: true

require 'digest'

class BackupCodeGenerator
  attr_reader :num_words

  NUMBER_OF_CODES = 10

  def initialize(user, num_words: BackupCodeConfiguration::NUM_WORDS)
    @num_words = num_words
    @user = user
  end

  def delete_and_regenerate(salt: SecureRandom.hex(32))
    codes = generate_new_codes

    BackupCodeConfiguration.transaction do
      @user.backup_code_configurations.destroy_all
      codes.each { |code| save_code(code: code, salt: salt) }
    end

    codes
  end

  # @return [BackupCodeConfiguration, nil]
  def if_valid_consume_code_return_config_created_at(plaintext_code)
    return unless plaintext_code.present?
    backup_code = RandomPhrase.normalize(plaintext_code)
    return nil unless backup_code

    salted_fingerprints =
      BackupCodeConfiguration.salted_fingerprints(code: backup_code, user_id: @user.id)

    query_result = BackupCodeConfiguration.transaction do
      sql = <<~SQL
        UPDATE backup_code_configurations
        SET
          used_at = NOW()
        WHERE user_id = ? AND salted_code_fingerprint IN (?) AND used_at IS NULL
        RETURNING created_at;
      SQL
      query = BackupCodeConfiguration.sanitize_sql_array(
        [sql, @user.id, salted_fingerprints],
      )
      BackupCodeConfiguration.connection.execute(query).first
    end

    query_result['created_at'] if query_result
  end

  private

  def generate_new_codes
    while result.length < NUMBER_OF_CODES
      code = backup_code
      result << code unless result.include?(code)
    end
    result
  end

  def code_usable?(code)
    code && code.used_at.nil?
  end

  def save_code(code:, salt:)
    @user.backup_code_configurations.create!(
      code_salt: salt,
      code_cost: cost,
      code: code,
    )
  end

  def backup_code
    RandomPhrase.new(num_words: num_words, separator: nil).to_s
  end

  def result
    @result ||= []
  end

  def cost
    IdentityConfig.store.backup_code_cost
  end
end