# Copyright (c) 2004-2008 David Heinemeier Hansson
#
# Permission is hereby granted, free of charge, to any person obtaining
# a copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish,
# distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so, subject to
# the following conditions:
#
# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
# LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
# WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
# Allows attributes to be shared within an inheritance hierarchy, but where
# each descendant gets a copy of their parents' attributes, instead of just a
# pointer to the same. This means that the child can add elements to, for
# example, an array without those additions being shared with either their
# parent, siblings, or children, which is unlike the regular class-level
# attributes that are shared across the entire hierarchy.
module CouchRest
  module ClassExtension
    def self.included(base)
      if CouchRest::ClassExtension::InstanceMethods.instance_methods.all? {|m| base.respond_to?(m)}
        # do nothing
      elsif CouchRest::ClassExtension::InstanceMethods.instance_methods.any? {|m| base.respond_to?(m)}
        raise RuntimeError, "Conflicting extentions to Class, work it out"
      else
        base.send(:include, CouchRest::ClassExtension::InstanceMethods)
      end
    end
    
    module InstanceMethods
      # Defines class-level and instance-level attribute reader.
      #
      # @param *syms<Array> Array of attributes to define reader for.
      # @return <Array[#to_s]> List of attributes that were made into cattr_readers
      #
      # @api public
      #
      # @todo Is this inconsistent in that it does not allow you to prevent
      # an instance_reader via :instance_reader => false
      def cattr_reader(*syms)
        syms.flatten.each do |sym|
          next if sym.is_a?(Hash)
          class_eval(<<-RUBY, __FILE__, __LINE__ + 1)
    unless defined? @@#{sym}
    @@#{sym} = nil
    end
 
    def self.#{sym}
    @@#{sym}
    end
 
    def #{sym}
    @@#{sym}
    end
    RUBY
        end
      end
 
      # Defines class-level (and optionally instance-level) attribute writer.
      #
      # @param <Array[*#to_s, Hash{:instance_writer => Boolean}]> Array of attributes to define writer for.
      # @option syms :instance_writer<Boolean> if true, instance-level attribute writer is defined.
      # @return <Array[#to_s]> List of attributes that were made into cattr_writers
      #
      # @api public
      def cattr_writer(*syms)
        options = syms.last.is_a?(Hash) ? syms.pop : {}
        syms.flatten.each do |sym|
          class_eval(<<-RUBY, __FILE__, __LINE__ + 1)
    unless defined? @@#{sym}
    @@#{sym} = nil
    end
 
    def self.#{sym}=(obj)
    @@#{sym} = obj
    end
    RUBY
 
          unless options[:instance_writer] == false
            class_eval(<<-RUBY, __FILE__, __LINE__ + 1)
    def #{sym}=(obj)
    @@#{sym} = obj
    end
    RUBY
          end
        end
      end
 
      # Defines class-level (and optionally instance-level) attribute accessor.
      #
      # @param *syms<Array[*#to_s, Hash{:instance_writer => Boolean}]> Array of attributes to define accessor for.
      # @option syms :instance_writer<Boolean> if true, instance-level attribute writer is defined.
      # @return <Array[#to_s]> List of attributes that were made into accessors
      #
      # @api public
      def cattr_accessor(*syms)
        cattr_reader(*syms)
        cattr_writer(*syms)
      end
 
      # Defines class-level inheritable attribute reader. Attributes are available to subclasses,
      # each subclass has a copy of parent's attribute.
      #
      # @param *syms<Array[#to_s]> Array of attributes to define inheritable reader for.
      # @return <Array[#to_s]> Array of attributes converted into inheritable_readers.
      #
      # @api public
      #
      # @todo Do we want to block instance_reader via :instance_reader => false
      # @todo It would be preferable that we do something with a Hash passed in
      # (error out or do the same as other methods above) instead of silently
      # moving on). In particular, this makes the return value of this function
      # less useful.
      def class_inheritable_reader(*ivars)
        instance_reader = ivars.pop[:reader] if ivars.last.is_a?(Hash)
 
        ivars.each do |ivar|
          self.class_eval <<-RUBY, __FILE__, __LINE__ + 1
    def self.#{ivar}
    return @#{ivar} if self.object_id == #{self.object_id} || defined?(@#{ivar})
    ivar = superclass.#{ivar}
    return nil if ivar.nil? && !#{self}.instance_variable_defined?("@#{ivar}")
    @#{ivar} = ivar && !ivar.is_a?(Module) && !ivar.is_a?(Numeric) && !ivar.is_a?(TrueClass) && !ivar.is_a?(FalseClass) && !ivar.is_a?(Symbol) ? ivar.dup : ivar
    end
    RUBY
          unless instance_reader == false
            self.class_eval <<-RUBY, __FILE__, __LINE__ + 1
    def #{ivar}
    self.class.#{ivar}
    end
    RUBY
          end
        end
      end
 
      # Defines class-level inheritable attribute writer. Attributes are available to subclasses,
      # each subclass has a copy of parent's attribute.
      #
      # @param *syms<Array[*#to_s, Hash{:instance_writer => Boolean}]> Array of attributes to
      # define inheritable writer for.
      # @option syms :instance_writer<Boolean> if true, instance-level inheritable attribute writer is defined.
      # @return <Array[#to_s]> An Array of the attributes that were made into inheritable writers.
      #
      # @api public
      #
      # @todo We need a style for class_eval <<-HEREDOC. I'd like to make it
      # class_eval(<<-RUBY, __FILE__, __LINE__), but we should codify it somewhere.
      def class_inheritable_writer(*ivars)
        instance_writer = ivars.pop[:instance_writer] if ivars.last.is_a?(Hash)
        ivars.each do |ivar|
          self.class_eval <<-RUBY, __FILE__, __LINE__ + 1
    def self.#{ivar}=(obj)
    @#{ivar} = obj
    end
    RUBY
          unless instance_writer == false
            self.class_eval <<-RUBY, __FILE__, __LINE__ + 1
    def #{ivar}=(obj) self.class.#{ivar} = obj end
    RUBY
          end
        end
      end
 
      # Defines class-level inheritable attribute accessor. Attributes are available to subclasses,
      # each subclass has a copy of parent's attribute.
      #
      # @param *syms<Array[*#to_s, Hash{:instance_writer => Boolean}]> Array of attributes to
      # define inheritable accessor for.
      # @option syms :instance_writer<Boolean> if true, instance-level inheritable attribute writer is defined.
      # @return <Array[#to_s]> An Array of attributes turned into inheritable accessors.
      #
      # @api public
      def class_inheritable_accessor(*syms)
        class_inheritable_reader(*syms)
        class_inheritable_writer(*syms)
      end
    end
  end
end

Class.send(:include, CouchRest::ClassExtension)