require 'facter'
require 'facter/util/fact'
require 'facter/util/loader'

# Manage which facts exist and how we access them.  Largely just a wrapper
# around a hash of facts.
#
# @api private
class Facter::Util::Collection

  def initialize(internal_loader, external_loader)
    @facts = Hash.new
    @internal_loader = internal_loader
    @external_loader = external_loader
  end

  # Return a fact object by name.
  def [](name)
    value(name)
  end

  # Define a new fact or extend an existing fact.
  #
  # @param name [Symbol] The name of the fact to define
  # @param options [Hash] A hash of options to set on the fact
  #
  # @return [Facter::Util::Fact] The fact that was defined
  def define_fact(name, options = {}, &block)
    fact = create_or_return_fact(name, options)

    if block_given?
      fact.instance_eval(&block)
    end

    fact
  rescue => e
    Facter.log_exception(e, "Unable to add fact #{name}: #{e}")
  end

  # Add a resolution mechanism for a named fact.  This does not distinguish
  # between adding a new fact and adding a new way to resolve a fact.
  #
  # @param name [Symbol] The name of the fact to define
  # @param options [Hash] A hash of options to set on the fact and resolution
  #
  # @return [Facter::Util::Fact] The fact that was defined
  def add(name, options = {}, &block)
    fact = create_or_return_fact(name, options)

    fact.add(options, &block)

    return fact
  end

  include Enumerable

  # Iterate across all of the facts.
  def each
    load_all
    @facts.each do |name, fact|
      value = fact.value
      unless value.nil?
        yield name.to_s, value
      end
    end
  end

  # Return a fact by name.
  def fact(name)
    name = canonicalize(name)

    # Try to load the fact if necessary
    load(name) unless @facts[name]

    # Try HARDER
    internal_loader.load_all unless @facts[name]

    if @facts.empty?
      Facter.warnonce("No facts loaded from #{internal_loader.search_path.join(File::PATH_SEPARATOR)}")
    end

    @facts[name]
  end

  # Flush all cached values.
  def flush
    @facts.each { |name, fact| fact.flush }
    @external_facts_loaded = nil
  end

  # Return a list of all of the facts.
  def list
    load_all
    return @facts.keys
  end

  def load(name)
    internal_loader.load(name)
    load_external_facts
  end

  # Load all known facts.
  def load_all
    internal_loader.load_all
    load_external_facts
  end

  def internal_loader
    @internal_loader
  end

  def external_loader
    @external_loader
  end

  # Return a hash of all of our facts.
  def to_hash
    @facts.inject({}) do |h, ary|
      value = ary[1].value
      if ! value.nil?
        # For backwards compatibility, convert the fact name to a string.
        h[ary[0].to_s] = value
      end
      h
    end
  end

  def value(name)
    if fact = fact(name)
      fact.value
    end
  end

  private

  def create_or_return_fact(name, options)
    name = canonicalize(name)

    fact = @facts[name]

    if fact.nil?
      fact = Facter::Util::Fact.new(name, options)
      @facts[name] = fact
    else
      fact.extract_ldapname_option!(options)
    end

    fact
  end

  def canonicalize(name)
    name.to_s.downcase.to_sym
  end

  def load_external_facts
    if ! @external_facts_loaded
      @external_facts_loaded = true
      external_loader.load(self)
    end
  end
end