require 'pathname'

# A module that provides utility methods for handling XDG Base Directory
# specification compliance.
#
# This module offers functionality to determine the appropriate configuration
# directory based on the XDG Base Directory specification, construct paths for
# configuration files, and retrieve configuration data from those files. It
# helps ensure consistent and standardized handling of user configuration files
# across different operating systems.
#
# @example Determining the XDG configuration directory
#   config_dir = GemHadar::Utils.xdg_config_home
#
# @example Retrieving configuration file contents
#   config_content = GemHadar::Utils.xdg_config('myapp', 'default_value')
module GemHadar::Utils
  # The xdg_config_home method determines the path to the XDG configuration
  # directory.
  #
  # It first checks if the XDG_CONFIG_HOME environment variable is set and not
  # empty. If it is set, the method returns the value as a Pathname object. If
  # XDG_CONFIG_HOME is not set, it defaults to using the HOME environment
  # variable to construct the path within the standard .config directory.
  #
  # @return [ Pathname ] the Pathname object representing the XDG configuration directory
  def xdg_config_home
    ENV['XDG_CONFIG_HOME'].full? { Pathname.new(_1) } ||
      Pathname.new(ENV.fetch('HOME')) + '.config'
  end

  # The xdg_config_filename method constructs the full path to a configuration
  # file based on the XDG Base Directory specification.
  #
  # It first checks if the XDG_CONFIG_HOME environment variable is set and not
  # empty. If it is set, the method joins this directory with the provided
  # filename to form the complete path. If XDG_CONFIG_HOME is not set, it
  # defaults to using the HOME environment variable to construct the path
  # within the standard .config directory.
  #
  # @param name [ String ] the name of the configuration file
  #
  # @return [ String ] the full path to the configuration file
  def xdg_config_filename(name)
    xdg_config_home + name
  end

  memoize method:
  # The xdg_config method retrieves configuration data from a file following
  # the XDG Base Directory specification.
  #
  # It checks for the existence of a configuration file using the
  # xdg_config_filename method and returns its contents if found. If the file
  # does not exist, it returns the provided default value instead.
  #
  # @param name [ String ] the name of the configuration file to retrieve
  # @param default [ Object ] the default value to return if the configuration file is not found
  #
  # @return [ String ] the content of the configuration file or the default value
  def xdg_config(name, default)
    if File.exist?(xdg_config_filename(name))
      File.read(xdg_config_filename(name))
    else
      default
    end
  end
end