require('md5')

class FileCache
  cattr_accessor :config

  @@config = { 
    :default_dir => RAILS_ROOT + "/public/images/cache/",
    :default_extension => ""
  }
  
  def self.get(options = {}, &block)
    get_or_create(options, &block)
  end
  
  def self.get_filename(options = {}, &block)
    get_or_create(options.merge(:get => :filename), &block)
  end
  
  def self.file_exists?(options = {})
    File.exist?(filename(options.dup))
  end
  
  def self.put(options = {}, &block)
    get_or_create(options.merge(:recreate => true), &block)
  end
  
  protected
  def self.filename(opts)
    options = opts.sort {|a,b| a[0].to_s<=>b[0].to_s}
    # dump(options)
    prefix = options.delete(:prefix) || ""
    dir = options.delete(:dir) || @@config[:default_dir]
    extension = options.delete(:extension) || @@config[:default_extension]
    filename = options.delete(:filename) || (MD5.new(options.to_s).to_s + extension)
    filename = "#{prefix}#{filename}" if prefix
    filename  = "#{dir}/#{filename}"
  end
  
  def self.get_or_create(opts = {}, &block)
    options = opts.dup
    get = options.delete(:get)
    recreate = options.delete(:recreate)
    filename = filename(options)
    obj = nil
    if recreate || !File.exist?(filename) 
      FileUtils.mkdir_p(filename.slice(%r{.+/}))
      obj = block.call(options)
      File.open(filename, "wb") {|f| obj.is_a?(String) ? f.write(obj) : Marshal.dump(obj, f)}
    end
    return filename if (get == :filename)
    return obj unless obj.nil?
    File.open(filename, "rb") do |f|
      if (f.getc == Marshal::MAJOR_VERSION && f.getc == Marshal::MINOR_VERSION)
        f.rewind
        obj = Marshal.load(f)
      else
        f.rewind
        obj = f.read
      end
    end
    obj
  end
  
end