class EcoRake
  module Shell
    module Gpg
      include EcoRake::Shell::Command
      include EcoRake::Shell::Files

      GPG_VERSION_REGEX = /^gpg.*?gnupg.*?(?<maj>\d+)\.(?<min>\d+)\./i.freeze

      # @note
      #   1. The ENV var `GPG_KEY` specifies the `passphrase` to be able to use the
      #     private gpg key (suppsedly installed in the user's local `gpg keyring`).
      #   2. Depending on the `gpg` version, the option to prevent the interactive passphrase to prompt
      #     is different. This is the reason why we check what is the option for a `loopback`
      # @param gpg_file [String] the file meant to be decrypted.
      # @return [String] the command to decrypt `gpg_file`
      def decrypt_command(gpg_file, gpg_key: ENV["GPG_KEY"], ignore_mdc_error: false)
        csv_file = gpg_to_csv_filename(gpg_file)
        no_error = ignore_mdc_error ? '--ignore-mdc-error' : nil
        loopback = gpg_version_gte?(major: 2, minor: 1)? "--pinentry-mode=loopback" : "--batch --yes"
        args     = [
          no_error, loopback,
          '--passphrase', double_quote(gpg_key),
          '-o', double_quote(csv_file),
          '-d', double_quote(gpg_file)
        ]
        string_cmd('gpg', *args)
      end

      private

      # TODO: use a common end point from `Command`
      def shell_gpg_version
        `gpg --version`
      end

      # Checks if the host `gpg` version is **greater than or equal** (`gte`) to `major` and `minor`
      # @note the versioning format is `MAJOR.MINOR.PATCH`
      # @example if the host has this gpg version: `gpg (GnuPG) 2.1.10`. The following is to be expected:
      #   1. `gpg_version_gte?(major: 1, minor: 10)` return `true`
      #   2. `gpg_version_gte?(major: 3, minor: 0)` return `false`
      #   3. `gpg_version_gte?(major: 2, minor: 0)` return `true`
      #   4. `gpg_version_gte?(major: 2, minor: 1)` return `true`
      #   5. `gpg_version_gte?(major: 2, minor: 3)` return `false`
      # @return [Boolean]
      def gpg_version_gte?(major:, minor:)
        result = shell_gpg_version
        return false unless match = result.match(GPG_VERSION_REGEX)
        maj = match[:maj].to_i
        min = match[:min].to_i
        (maj >= major) && (min >= minor)
      end
    end
  end
end