require 'facter'
require 'pathname'
require 'facter/util/directory_loader'

# Load facts on demand.
class Facter::Util::Loader

  def initialize(environment_vars = ENV)
    @loaded = []
    @environment_vars = environment_vars
  end

  # Load all resolutions for a single fact.
  #
  # @api public
  # @param name [Symbol]
  def load(fact)
    # Now load from the search path
    shortname = fact.to_s.downcase
    load_env(shortname)

    filename = shortname + ".rb"

    paths = search_path
    unless paths.nil?
      paths.each do |dir|
        # Load individual files
        file = File.join(dir, filename)

        load_file(file) if File.file?(file)
      end
    end
  end

  # Load all facts from all directories.
  #
  # @api public
  def load_all
    return if defined?(@loaded_all)

    load_env

    paths = search_path
    unless paths.nil?
      paths.each do |dir|
        # dir is already an absolute path
        Dir.glob(File.join(dir, '*.rb')).each do |path|
          # exclude dirs that end with .rb
          load_file(path) if File.file?(path)
        end
      end
    end

    @loaded_all = true
  end

  # List directories to search for fact files.
  #
  # Search paths are gathered from the following sources:
  #
  # 1. $LOAD_PATH entries are expanded to absolute paths
  # 2. ENV['FACTERLIB'] is split and used verbatim
  # 3. Entries from Facter.search_path are used verbatim
  #
  # A warning will be generated for paths in Facter.search_path that are not
  # absolute directories.
  #
  # @api public
  # @return [Array<String>]
  def search_path
    search_paths = []
    search_paths += $LOAD_PATH.map { |path| File.expand_path('facter', path) }

    if @environment_vars.include?("FACTERLIB")
      search_paths += @environment_vars["FACTERLIB"].split(File::PATH_SEPARATOR)
    end

    search_paths.delete_if { |path| ! valid_search_path?(path) }

    Facter.search_path.each do |path|
      if valid_search_path?(path)
        search_paths << path
      else
        Facter.warn "Excluding #{path} from search path. Fact file paths must be an absolute directory"
      end
    end

    search_paths.delete_if { |path| ! File.directory?(path) }

    search_paths.uniq
  end

  private

  # Validate that the given path is valid, ie it is an absolute path.
  #
  # @api private
  # @param path [String]
  # @return [Boolean]
  def valid_search_path?(path)
    Pathname.new(path).absolute?
  end

  # Load a file and record is paths to prevent duplicate loads.
  #
  # @api private
  # @params file [String] The *absolute path* to the file to load
  def load_file(file)
    return if @loaded.include? file

    # We have to specify Kernel.load, because we have a load method.
    begin
      # Store the file path so we don't try to reload it
      @loaded << file
      Kernel.load(file)
    rescue ScriptError => detail
      # Don't store the path if the file can't be loaded
      # in case it's loadable later on.
      @loaded.delete(file)
      Facter.log_exception(detail, "Error loading fact #{file}: #{detail.message}")
    end
  end

  # Load facts from the environment.  If no name is provided,
  # all will be loaded.
  def load_env(fact = nil)
    # Load from the environment, if possible
    @environment_vars.each do |name, value|
      # Skip anything that doesn't match our regex.
      next unless name =~ /^facter_?(\w+)$/i
      env_name = $1

      # If a fact name was specified, skip anything that doesn't
      # match it.
      next if fact and env_name != fact

      Facter.add($1) do
        has_weight 1_000_000
        setcode { value }
      end

      # Short-cut, if we are only looking for one value.
      break if fact
    end
  end
end