require 'glimmer/error'
require 'glimmer/swt/swt_proxy'
require 'glimmer/swt/display_proxy'

module Glimmer
  module SWT
    # Proxy for org.eclipse.swt.graphics.Font
    #
    # This class is meant to be used with WidgetProxy to manipulate
    # an SWT widget font.
    #
    # It is not meant to create new SWT fonts form scratch without
    # a widget proxy.
    #
    # Invoking `#swt_font` returns the SWT Font object wrapped by this proxy
    #
    # Follows the Proxy Design Pattern
    class FontProxy
      ERROR_INVALID_FONT_STYLE = " is an invalid font style! Valid values are :normal, :bold, and :italic"
      FONT_STYLES = [:normal, :bold, :italic]

      include_package 'org.eclipse.swt.graphics'

      attr_reader :widget_proxy, :swt_font

      # Builds a new font proxy from passed in widget_proxy and font_properties hash,
      #
      # It begins with existing SWT widget font and amends it with font properties.
      #
      # Font properties consist of: :name, :height, and :style (one needed minimum)
      #
      # Style (:style value) can only be one of FontProxy::FONT_STYLES values:
      # that is :normal, :bold, or :italic
      def initialize(widget_proxy, font_properties)
        @widget_proxy = widget_proxy
        detect_invalid_font_property(font_properties)
        font_properties[:style] = SWTProxy[*font_properties[:style]]
        font_data_args = [:name, :height, :style].map do |font_property_name|
          font_properties[font_property_name] || send(font_property_name)
        end
        font_datum = FontData.new(*font_data_args)
        @swt_font = Font.new(DisplayProxy.instance.swt_display, font_datum)
      end

      def name
        font_datum.getName
      end

      def height
        font_datum.getHeight
      end

      def style
        font_datum.getStyle
      end

      private

      def font_datum
        @font_datum ||= @widget_proxy.swt_widget.getFont.getFontData[0]
      end

      def detect_invalid_font_property(font_properties)
        [font_properties[:style]].flatten.select do |style|
          style.is_a?(Symbol) || style.is_a?(String)
        end.each do |style|
          raise Error, style.to_s + ERROR_INVALID_FONT_STYLE if !FONT_STYLES.include?(style.to_sym)
        end
      end
    end
  end
end