require 'plist4r/backend'
module Plist4r
  class PlistCache
    def initialize plist, *args, &blk
      @plist = plist
      @backend = Backend.new plist, *args, &blk
    end
  
    def checksum
      @plist.to_hash.hash
    end
  
    def last_checksum
      @checksum
    end

    def update_checksum
      @checksum = @plist.to_hash.hash
    end

    def needs_update
      checksum != last_checksum
    end

    def from_string
      @backend.call :from_string
      update_checksum
      @plist.detect_plist_type
      @plist
    end

    def to_xml
      if needs_update || @xml.nil?
        puts "needs update"
        update_checksum
        @xml = @backend.call :to_xml
      else
        @xml
      end
    end
  
    def to_binary
      if needs_update || @binary.nil?
        update_checksum
        @binary = @backend.call :to_binary
      else
        @binary
      end
    end

    def to_next_step
      if needs_update || @next_step.nil?
        update_checksum
        @next_step = @backend.call :to_next_step
      else
        @next_step
      end
    end
  
    def open
      @backend.call :open
      update_checksum
      @plist.detect_plist_type
      @plist
    end
  
    def save
      if needs_update
        update_checksum
        @backend.call :save
      else
        true
      end
    end
  end
end