module Lipsiadmin
  module Attachment
    # Handles thumbnailing images that are uploaded.
    class Thumbnail < Processor

      attr_accessor :current_geometry, :target_geometry, :format, :whiny, :convert_options

      # Creates a Thumbnail object set to work on the +file+ given. It
      # will attempt to transform the image into one defined by +target_geometry+
      # which is a "WxH"-style string. +format+ will be inferred from the +file+
      # unless specified. Thumbnail creation will raise no errors unless
      # +whiny+ is true (which it is, by default. If +convert_options+ is
      # set, the options will be appended to the convert command upon image conversion
      def initialize(file, options = {})
        super
        geometry          = options[:geometry]
        @file             = file
        @crop             = geometry[-1,1] == '#'
        @target_geometry  = Geometry.parse geometry
        @current_geometry = Geometry.from_file @file
        @convert_options  = options[:convert_options]
        @whiny            = options[:whiny].nil? ? true : options[:whiny]
        @format           = options[:format]

        @current_format   = File.extname(@file.path)
        @basename         = File.basename(@file.path, @current_format)
      end

      # Returns true if the +target_geometry+ is meant to crop.
      def crop?
        @crop
      end

      # Returns true if the image is meant to make use of additional convert options.
      def convert_options?
        not @convert_options.blank?
      end

      # Performs the conversion of the +file+ into a thumbnail. Returns the Tempfile
      # that contains the new image.
      def make
        src = @file
        dst = Tempfile.new([@basename, @format].compact.join("."))
        dst.binmode

        command = <<-end_command
          "#{ File.expand_path(src.path) }[0]"
          #{ transformation_command }
          "#{ File.expand_path(dst.path) }"
        end_command

        begin
          success = Attachment.run("convert", command.gsub(/\s+/, " "))
        rescue AttachmentCommandLineError
          raise AttachmentError, "There was an error processing the thumbnail for #{@basename}" if @whiny
        end

        dst
      end

      # Returns the command ImageMagick's +convert+ needs to transform the image
      # into the thumbnail.
      def transformation_command
        scale, crop = @current_geometry.transformation_to(@target_geometry, crop?)
        trans = "-resize \"#{scale}\""
        trans << " -crop \"#{crop}\" +repage" if crop
        trans << " #{convert_options}" if convert_options?
        trans
      end
    end
  end
end
