module Uh
  module WM
    class Manager
      INPUT_MASK  = Events::SUBSTRUCTURE_REDIRECT_MASK
      ROOT_MASK   = Events::PROPERTY_CHANGE_MASK |
                    Events::SUBSTRUCTURE_REDIRECT_MASK |
                    Events::SUBSTRUCTURE_NOTIFY_MASK |
                    Events::STRUCTURE_NOTIFY_MASK

      attr_reader :modifier, :display, :clients

      def initialize events, modifier, display = Display.new
        @events   = events
        @modifier = modifier
        @display  = display
        @clients  = []
      end

      def to_io
        IO.new(@display.fileno)
      end

      def connect
        @events.emit :connecting, args: @display
        @display.open
        check_other_wm!
        Display.on_error { |*args| handle_error *args }
        @display.sync false
        @events.emit :connected, args: @display
        @display.root.mask = ROOT_MASK
      end

      def disconnect
        @display.close
        @events.emit :disconnected
      end

      def flush
        @display.flush
      end

      def grab_key keysym, mod = nil
        mod_mask = KEY_MODIFIERS[@modifier]
        mod_mask |= KEY_MODIFIERS[mod] if mod
        @display.grab_key keysym.to_s, mod_mask
      end

      def manage window
        return if window.override_redirect? || client_for(window)
        @clients << client = Client.new(window)
        @events.emit :manage, args: client
      end

      def handle_next_event
        handle @display.next_event
      end

      def handle_pending_events
        handle_next_event while @display.pending?
      end

      def handle event
        @events.emit :xevent, args: event
        return unless respond_to? handler = "handle_#{event.type}".to_sym, true
        send handler, event
      end


      private

      def handle_error *args
        @events.emit :xerror, args: args
      end

      def handle_key_press event
        key_selector = event.modifier_mask & KEY_MODIFIERS[:shift] == 1 ?
          [event.key.to_sym, :shift] :
          event.key.to_sym
        @events.emit :key, *key_selector
      end

      def handle_map_request event
        manage event.window
      end

      def client_for window
        @clients.find { |e| e.window == window }
      end

      def check_other_wm!
        Display.on_error { fail OtherWMRunningError }
        @display.listen_events INPUT_MASK
        @display.sync false
      end
    end
  end
end