;;
;; Copyright (C) 2010 Mikhail Kryshen <mikhail@kryshen.net>
;;
;; This file is part of Indyvon.
;;

(ns indyvon.event
  (:use indyvon.core)
  (:import (java.awt.event MouseEvent MouseListener MouseMotionListener)
           java.lang.ref.WeakReference))

(defprotocol EventDispatcher
  (listen! [this component])
  (register-mouse-handler [this context handler])
  (commit [this])
  (hovered? [this layer])
  (picked? [this layer]))

(defn mouse-handler [context handler & args]
  "The supplied handler function will be invoked with context, event
   and additional args when mouse event occurs on the context."
  (let [handler (if args #(apply handler %1 %2 args) handler)]
    (register-mouse-handler (:dispatcher context) context handler)))

(defn- registered-parent
  "Returns first context parent registered for event processing."
  [context-tree context]
  (let [parent (:parent context)]
    (cond
     (nil? parent) nil
     (contains? context-tree parent) parent
     :default (recur context-tree parent))))

(defn- add-context
  [context-tree context]
  (let [parent (registered-parent context-tree context)]
    (assoc context-tree parent (cons context (context-tree parent))
           context nil)))

(defn- inside?
  ([x y context]
     (inside? x y (:x context) (:y context)
              (:width context) (:height context)))
  ([px py x y w h]
     (and (>= px x)
          (>= py y)
          (< px (+ x w))
          (< py (+ y h)))))

(defn- under-cursor
  "Returns a sequence of contexts under cursor."
  ([context-tree x y]
     (under-cursor context-tree x y nil))
  ([context-tree x y context]
     (some #(if (inside? x y %)
              (conj (under-cursor context-tree x y %) %))
           (context-tree context))))

(defn- remove-all [coll1 coll2 pred]
  (filter #(not (some (partial pred %) coll2)) coll1))

(defn- translate-mouse-event
  [event x y id]
  (proxy [MouseEvent] [(.getComponent event)
                       id
                       (.getWhen event)
                       (.getModifiers event)
                       (- (.getX event) x)
                       (- (.getY event) y)
                       (.getClickCount event)
                       (.isPopupTrigger event)]
    (getXOnScreen [] (.getXOnScreen event))
    (getYOnScreen [] (.getYOnScreen event))))

(defn- dispatch-event [handlers context event]
  ((handlers context) context event))

(defn- translate-and-dispatch
  ([contexts handlers event]
     (translate-and-dispatch contexts handlers event (.getID event)))
  ([contexts handlers event id]
  (doseq [context contexts]
    (dispatch-event
     handlers
     context
     (translate-mouse-event event (:x context) (:y context) id)))))

(defn- dispatch-mouse-motion*
  "Dispatches mouse motion events. Returns a new set of contexts which
  currently are under cursor."
  [hovered context-tree handlers event]
  (let [x (.getX event)
        y (.getY event)
        hovered2 (under-cursor context-tree x y)
        pred #(= (:layer %1) (:layer %2))
        exited (remove-all hovered hovered2 pred)
        entered (remove-all hovered2 hovered pred)
        moved (remove-all hovered2 entered pred)]
    (translate-and-dispatch
     exited handlers event MouseEvent/MOUSE_EXITED)
    (translate-and-dispatch
     entered handlers event MouseEvent/MOUSE_ENTERED)
    (translate-and-dispatch
     moved handlers event MouseEvent/MOUSE_MOVED)
    hovered2))

(defn- dispatch-mouse-motion
  [hovered-ref context-tree handlers event]
  (dosync
   (alter hovered-ref dispatch-mouse-motion* context-tree handlers event)))

(defn- dispatch-mouse-button*
  "Dispatches mouse button events. Returns a new set of contexts which
  currently are picked with a pressed button."
  [picked hovered handlers event]
  (translate-and-dispatch hovered handlers event)
  (if (= (.getID event) MouseEvent/MOUSE_PRESSED)
    hovered
    nil))

(defn- dispatch-mouse-button
  [picked-ref hovered-ref handlers event]
  (dosync
   (alter picked-ref dispatch-mouse-button*
          @hovered-ref handlers event)))

(defn make-event-dispatcher []
  (let [context-tree-r (ref {}) ; register
        handlers-r (ref {})     ;
        context-tree (ref {})   ; dispatch
        handlers (ref {})       ;
        hovered (ref '())
        picked (ref '())]
    (reify
     EventDispatcher
     (listen! [this component]
        (doto component
          (.addMouseListener this)
          (.addMouseMotionListener this)))
     (register-mouse-handler [this context handler]
        (dosync (alter context-tree-r add-context context)
                (alter handlers-r assoc context handler)))
     (commit [this]
        (dosync (ref-set context-tree @context-tree-r)
                (ref-set context-tree-r {})
                (ref-set handlers @handlers-r)
                (ref-set handlers-r {})))
     (picked? [this layer] false)
     (hovered? [this layer] false)
     MouseListener
     (mouseEntered [this event]
        (dispatch-mouse-motion hovered context-tree handlers event))
     (mouseExited [this event]
        (dispatch-mouse-motion hovered context-tree handlers event))
     (mouseClicked [this event]
        (dispatch-mouse-button picked hovered handlers event))
     (mousePressed [this event]
        (dispatch-mouse-button picked hovered handlers  event))
     (mouseReleased [this event]
        (dispatch-mouse-button picked hovered handlers event))
     MouseMotionListener
     (mouseDragged [this event]
        (translate-and-dispatch @picked handlers event))
     (mouseMoved [this event]
        (dispatch-mouse-motion hovered context-tree handlers event)))))