require 'set'
require 'mime/types'
require 'wand'

module Joint
  autoload :Version, 'joint/version'

  module ClassMethods
    def attachment(name)
      self.class.class_inheritable_accessor :attachment_names unless self.class.respond_to?(:attachment_names)
      self.class.attachment_names ||= []
      self.class.attachment_names << name

      after_save     :save_attachments
      after_save     :destroy_nil_attachments
      before_destroy :destroy_all_attachments

      key "#{name}_id".to_sym,   ObjectId
      key "#{name}_name".to_sym, String
      key "#{name}_size".to_sym, Integer
      key "#{name}_type".to_sym, String

      class_eval <<-EOC
        def #{name}
          @#{name} ||= AttachmentProxy.new(self, :#{name})
        end

        def #{name}?
          self.send(:#{name}_id?)
        end

        def #{name}=(file)
          if file.nil?
            nil_attachments << :#{name}
          else
            self["#{name}_id"]               = Mongo::ObjectID.new
            self["#{name}_size"]             = File.size(file)
            self["#{name}_type"]             = Wand.wave(file.path)
            self["#{name}_name"]             = Joint.file_name(file)
            assigned_attachments[:#{name}] = file
          end
        end
      EOC
    end
  end

  module InstanceMethods
    def grid
      @grid ||= Mongo::Grid.new(database)
    end

    private
      def assigned_attachments
        @assigned_attachments ||= {}
      end

      def nil_attachments
        @nil_attachments ||= Set.new
      end

      def save_attachments
        assigned_attachments.each do |attachment|
          name, file = attachment
          if file.respond_to?(:read)
            file.rewind if file.respond_to?(:rewind)
            grid.put(file.read, self["#{name}_name"], {
              :_id          => self["#{name}_id"],
              :content_type => self["#{name}_type"],
            })
          end
        end.tap(&:clear)
      end

      def destroy_nil_attachments
        nil_attachments.each { |name| grid.delete(self["#{name}_id"]) }.tap(&:clear)
      end

      def destroy_all_attachments
        self.class.attachment_names.each { |name| grid.delete(self["#{name}_id"]) }
      end
  end

  class AttachmentProxy
    def initialize(instance, name)
      @instance, @name = instance, name
    end

    def id
      @instance.send("#{@name}_id")
    end

    def name
      @instance.send("#{@name}_name")
    end

    def size
      @instance.send("#{@name}_size")
    end

    def type
      @instance.send("#{@name}_type")
    end

    def grid_io
      @grid_io ||= @instance.grid.get(id)
    end

    def method_missing(method, *args, &block)
      grid_io.send(method, *args, &block)
    end
  end

  def self.file_name(file)
    file.respond_to?(:original_filename) ? file.original_filename : File.basename(file.path)
  end
end