ioquatix/build-environment

# Copyright, 2012, by Samuel G. D. Williams. <http://www.codeotaku.com>
# 
# 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.

module Build
    class Environment
        class Evaluator
            def initialize(environment)
                @environment = environment
                @cache = {}
            end
            
            def initialize_dup(other)
                @environment = other.instance_variable_get(:@environment)
                @cache = other.instance_variable_get(:@cache).dup
                
                super
            end
            
            def respond_to?(name, include_private = false)
                @environment.include?(name) || super
            end
            
            def method_missing(name)
                @cache[name] ||= object_value(@environment[name])
            end
            
            # Compute the literal object value for a given key:
            def object_value(value)
                case value
                when Array
                    value.collect{|item| object_value(item)}.flatten
                when Symbol
                    object_value(@environment[value])
                when Proc
                    object_value(instance_exec(&value))
                when Default
                    object_value(value.value)
                when Replace
                    object_value(value.value)
                else
                    value
                end
            end
        end
    end
end