#lang racket/base

(require racket/runtime-path)

(provide mk-tray
         tray-close
         tray-set-icon!
         tray-set-menu!)

;; The platform implementation is loaded dynamically so that requiring
;; racket-tray remains possible on platforms that do not yet have a backend.
(define-runtime-module-path windows-module "private/windows.rkt")

(define platform-mk-tray #f)
(define platform-tray-close #f)
(define platform-tray-set-icon! #f)
(define platform-tray-set-menu! #f)

(when (eq? (system-type 'os*) 'windows)
  (set! platform-mk-tray
        (dynamic-require windows-module 'mk-tray))
  (set! platform-tray-close
        (dynamic-require windows-module 'tray-close))
  (set! platform-tray-set-icon!
        (dynamic-require windows-module 'tray-set-icon!))
  (set! platform-tray-set-menu!
        (dynamic-require windows-module 'tray-set-menu!)))

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Supporting functions
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; goal   : Report that the current operating system has no tray backend.
; pre    : who is the name of the public procedure being called.
; post   : No state is changed.
; result : Does not return; raises an exception naming the unsupported OS.
; internals:
;          The public module remains loadable on every platform; only an
;          attempted tray operation fails when no backend was loaded.
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(define (unsupported who)
  (error who "not supported on this operating system: ~a" (system-type 'os*)))

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; Provided functions
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; goal   : Create a tray icon using the backend for the current platform.
; pre    : frame, icon-file, on-click-cb and hide-on-minimize? satisfy the
;          requirements documented for mk-tray.
; post   : On a supported platform a tray icon is created; otherwise an
;          unsupported-platform exception is raised.
; result : The platform tray value accepted by the other public procedures.
; internals:
;          This module is a small platform-neutral dispatcher. Windows code is
;          loaded dynamically only on Windows so requiring racket-tray remains
;          possible on other operating systems.
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(define (mk-tray frame
                 icon-file
                 on-click-cb
                 #:hide-on-minimize? [hide-on-minimize? #f])
  (if platform-mk-tray
      (platform-mk-tray frame
                        icon-file
                        on-click-cb
                        #:hide-on-minimize? hide-on-minimize?)
      (unsupported 'mk-tray)))

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; goal   : Close a tray icon through the active platform backend.
; pre    : tray is a value previously returned by mk-tray.
; post   : Platform tray resources are released on supported systems.
; result : void on success; raises when the platform is unsupported.
; internals:
;          All resource ownership and idempotence rules are implemented by the
;          platform backend.
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(define (tray-close tray)
  (if platform-tray-close
      (platform-tray-close tray)
      (unsupported 'tray-close)))

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; goal   : Replace the image of an existing tray icon.
; pre    : tray is open and icon-file names a format supported by the backend.
; post   : The active tray image is replaced when the backend succeeds.
; result : The backend result; the Windows implementation returns void.
; internals:
;          The public facade performs no image conversion itself.
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(define (tray-set-icon! tray icon-file)
  (if platform-tray-set-icon!
      (platform-tray-set-icon! tray icon-file)
      (unsupported 'tray-set-icon!)))

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; goal   : Set or remove the context menu of an existing tray icon.
; pre    : tray is open and menu is accepted by the active backend.
; post   : The tray uses the supplied menu specification on success.
; result : void on Windows; raises when the platform is unsupported.
; internals:
;          Menu normalization belongs to the platform implementation because
;          native event integration is platform-specific.
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(define (tray-set-menu! tray menu)
  (if platform-tray-set-menu!
      (platform-tray-set-menu! tray menu)
      (unsupported 'tray-set-menu!)))