require 'puppet/indirector'
require 'puppet/indirector/errors'
require 'puppet/indirector/indirection'
require 'puppet/util/instance_loader'

# A simple class that can function as the base class for indirected types.
class Puppet::Indirector::Terminus
  require 'puppet/util/docs'
  extend Puppet::Util::Docs

  class << self
    include Puppet::Util::InstanceLoader

    attr_accessor :name, :terminus_type
    attr_reader :abstract_terminus, :indirection

    # Are we an abstract terminus type, rather than an instance with an
    # associated indirection?
    def abstract_terminus?
      abstract_terminus
    end

    # Convert a constant to a short name.
    def const2name(const)
      const.sub(/^[A-Z]/) { |i| i.downcase }.gsub(/[A-Z]/) { |i| "_#{i.downcase}" }.intern
    end

    # Look up the indirection if we were only provided a name.
    def indirection=(name)
      if name.is_a?(Puppet::Indirector::Indirection)
        @indirection = name
      elsif ind = Puppet::Indirector::Indirection.instance(name)
        @indirection = ind
      else
        raise ArgumentError, "Could not find indirection instance #{name} for #{self.name}"
      end
    end

    def indirection_name
      @indirection.name
    end

    # Register our subclass with the appropriate indirection.
    # This follows the convention that our terminus is named after the
    # indirection.
    def inherited(subclass)
      longname = subclass.to_s
      if longname =~ /#<Class/
        raise Puppet::DevError, "Terminus subclasses must have associated constants"
      end
      names = longname.split("::")

      # Convert everything to a lower-case symbol, converting camelcase to underscore word separation.
      name = names.pop.sub(/^[A-Z]/) { |i| i.downcase }.gsub(/[A-Z]/) { |i| "_#{i.downcase}" }.intern

      subclass.name = name

      # Short-circuit the abstract types, which are those that directly subclass
      # the Terminus class.
      if self == Puppet::Indirector::Terminus
        subclass.mark_as_abstract_terminus
        return
      end

      # Set the terminus type to be the name of the abstract terminus type.
      # Yay, class/instance confusion.
      subclass.terminus_type = self.name

      # Our subclass is specifically associated with an indirection.
      raise("Invalid name #{longname}") unless names.length > 0
      indirection_name = names.pop.sub(/^[A-Z]/) { |i| i.downcase }.gsub(/[A-Z]/) { |i| "_#{i.downcase}" }.intern

      if indirection_name == "" or indirection_name.nil?
        raise Puppet::DevError, "Could not discern indirection model from class constant"
      end

      # This will throw an exception if the indirection instance cannot be found.
      # Do this last, because it also registers the terminus type with the indirection,
      # which needs the above information.
      subclass.indirection = indirection_name

      # And add this instance to the instance hash.
      Puppet::Indirector::Terminus.register_terminus_class(subclass)
    end

    # Mark that this instance is abstract.
    def mark_as_abstract_terminus
      @abstract_terminus = true
    end

    def model
      indirection.model
    end

    # Convert a short name to a constant.
    def name2const(name)
      name.to_s.capitalize.sub(/_(.)/) { |i| $1.upcase }
    end

    # Register a class, probably autoloaded.
    def register_terminus_class(klass)
      setup_instance_loading klass.indirection_name
      instance_hash(klass.indirection_name)[klass.name] = klass
    end

    # Return a terminus by name, using the autoloader.
    def terminus_class(indirection_name, terminus_type)
      setup_instance_loading indirection_name
      loaded_instance(indirection_name, terminus_type)
    end

    # Return all terminus classes for a given indirection.
    def terminus_classes(indirection_name)
      setup_instance_loading indirection_name
      instance_loader(indirection_name).files_to_load.map do |file|
        File.basename(file).chomp(".rb").intern
      end
    end

    private

    def setup_instance_loading(type)
      instance_load type, "puppet/indirector/#{type}" unless instance_loading?(type)
    end
  end

  def indirection
    self.class.indirection
  end

  def initialize
    raise Puppet::DevError, "Cannot create instances of abstract terminus types" if self.class.abstract_terminus?
  end

  def model
    self.class.model
  end

  def name
    self.class.name
  end

  def terminus_type
    self.class.terminus_type
  end

  def validate(request)
    if request.instance
      validate_model(request)
      validate_key(request)
    end
  end

  def validate_key(request)
    unless request.key == request.instance.name
      raise Puppet::Indirector::ValidationError, "Instance name #{request.instance.name.inspect} does not match requested key #{request.key.inspect}"
    end
  end

  def validate_model(request)
    unless model === request.instance
      raise Puppet::Indirector::ValidationError, "Invalid instance type #{request.instance.class.inspect}, expected #{model.inspect}"
    end
  end
end