#
# The Scope class allows you to easily stack more than one scope on top
# of a ActiveRecord::Base class.
class Scope

  def initialize(klass, scope=nil)
    @klass = klass
    @scopes = []
    @joins = []
    add(scope) if scope
  end

  def joins(s);       add(:joins => s); end
  def conditions(s);  add(:conditions => s); end
  def include(s);     add(:include => s); end

  def find(*opts)
    exec(0) { @klass.find *prepare_find_options(*opts) }
  end

  def count(*opts)
    exec(0) { @klass.count *prepare_find_options(*opts) }
  end

  private

  def add(scope)
    scope = scope.dup
    if joins = scope[:joins]
      @joins << scope.delete(:joins)
    end
    @scopes << { :find => scope }

    self
  end

  def exec(i)
    if i == @scopes.length
      yield
    else
      @klass.with_scope(@scopes[i]) do
        exec(i+1) { yield }
      end
    end
  end

  def prepare_find_options(*opts)
    hash = opts.last.is_a?(Hash) ? opts.pop.dup : {}

    joins = ([ hash.delete(:joins) ] + @joins).compact

    hash.update(:joins => joins.join(" ")) unless joins.empty?

    opts.push hash
    opts
  end
end