require 'docile'

module Cfer
  # Represents the base class of a Cfer DSL
  class Block < ActiveSupport::HashWithIndifferentAccess
    # Evaluates a DSL directly from a Ruby block, calling pre- and post- hooks.
    # @param args [Array<Object>] Extra arguments to be passed into the block.
    def build_from_block(*args, &block)
      pre_block
      Docile.dsl_eval(self, *args, &block) if block
      post_block
      self
    end

    # Evaluates a DSL from a Ruby script file
    # @param args [Array<Object>] (see: #build_from_block)
    # @param file [File] The Ruby script to evaluate
    def build_from_file(*args, file)
      build_from_block(*args) do
        instance_eval File.read(file), file
      end
      self
    end

    # Executed just before the DSL is evaluated
    def pre_block
    end

    # Executed just after the DSL is evaluated
    def post_block
    end
  end

  class BlockHash < Block
    NON_PROXIED_METHODS = [:parameters, :options, :lookup_output]

    def properties(keyvals = {})
      self.merge!(keyvals)
    end

    def get_property(key)
      self.fetch key
    end

    def respond_to?(method_sym)
      !non_proxied_methods.include?(method_sym)
    end

    def method_missing(method_sym, *arguments, &block)
      key = camelize_property(method_sym)
      properties key =>
        case arguments.size
        when 0
          if block
            BlockHash.new.build_from_block(&block)
          else
            raise "Expected a value or block when setting property #{key}"
          end
        when 1
          arguments.first
        else
          arguments
        end
    end

    private
    def non_proxied_methods
      NON_PROXIED_METHODS
    end

    def camelize_property(sym)
      sym.to_s.camelize.to_sym
    end
  end
end