;; Copyright 2010, 2011 Mikhail Kryshen <mikhail@kryshen.net>
;; This file is part of Indyvon.
;; Indyvon is free software: you can redistribute it and/or modify it
;; under the terms of the GNU Lesser General Public License version 3
;; only, as published by the Free Software Foundation.
;; Indyvon is distributed in the hope that it will be useful, but
;; WITHOUT ANY WARRANTY; without even the implied warranty of
;; Lesser General Public License for more details.
;; You should have received a copy of the GNU Lesser General Public
;; License along with Indyvon.  If not, see
;; <http://www.gnu.org/licenses/>.

(ns net.kryshen.indyvon.core
   (java.awt Graphics2D RenderingHints Component Color Font Shape)
   (java.awt.geom AffineTransform Point2D$Double Rectangle2D$Double Area)
   (java.awt.event MouseListener MouseMotionListener)
   (java.awt.font FontRenderContext)

;; Layer context

(def ^Graphics2D *graphics*)

(def ^FontRenderContext *font-context*)

(def ^{:tag Component
       :doc "Target AWT component, may be nil if drawing off-screen."}

(def ^{:doc "Width of the rendering area."}

(def ^{:doc "Height of the rendering area."}

(def ^Shape *clip*)

(def ^{:doc "The root (background) layer of the scene."}

(def ^{:doc "Time in nanoseconds when the rendering of the current
             frame starts."}

(def *event-dispatcher*)

(def ^{:tag AffineTransform
       :doc "Initial transform associated with the graphics context."}

(def ^{:tag AffineTransform
       :doc "Inversion of the initial transform associated with
            the graphics context."}

(defrecord Theme [fore-color back-color alt-back-color border-color font])

;; REMIND: use system colors, see java.awt.SystemColor.
(defn default-theme []
  (Theme. Color/BLACK Color/WHITE Color/LIGHT_GRAY
          Color/BLUE (Font. "Sans" Font/PLAIN 12)))

(def *theme* (default-theme))

(defrecord Location [x y])
(defrecord Size [width height])
(defrecord Bounds [x y width height])

;; Core protocols and types

(defprotocol Layer
  "Basic UI element."
  (render! [this])
  (layer-size [this]))

;; TODO: modifiers
(defrecord MouseEvent [id when x y x-on-screen y-on-screen button])

;; TODO: KeyEvent

(defprotocol EventDispatcher
  (listen! [this ^Component component]
     "Listen for events on the specified AWT Component.")
  (create-dispatcher [this handle handlers]
     "Returns new event dispatcher associated with the specified event
      handlers (an event-id -> handler-fn map). Handle is used to
      match the contexts between commits.")
  (commit [this]
     "Apply the registered handlers for event processing.")
  (handle-picked? [this handle]
     "Returns true if the specified handle received the :mouse-pressed
      event and have not yet received :moused-released.")
  (handle-hovered? [this handle]
     "Returns true if the specified handle received the :mouse-entered
      event and have not yet received :mouse-exited."))

(defprotocol Anchored
  "Provide anchor point for Layers. Used by viewport."
  (anchor [this h-align v-align]
     "Anchor point: [x y], h-align could be :left, :center or :right,
      v-align is :top, :center or :bottom"))

(defn default-anchor [layer h-align v-align]
  (if (and (= h-align :left)
           (= v-align :top))
    (Location. 0 0)
    (let [size (layer-size layer)]
       (case h-align
             :top 0
             :center (/ (:width size) 2)
             :right (:width size))
       (case v-align
             :left 0
             :center (/ (:height size) 2)
             :bottom (:height size))))))

;; Default implementation of Anchored for any Layer.
(extend-protocol Anchored
  (anchor [this h-align v-align]
    (default-anchor this h-align v-align)))

(defn- assoc-cons [m key val]
  (->> (get m key) (cons val) (assoc m key)))

;; Observers
;; The mechanism used by layers to request repaints

(def ^ConcurrentMap observers
     (-> (MapMaker.) (.weakKeys) (.makeMap)))

(defn- cm-replace!
  "Wrap ConcurrentMap replace method to treat nil value as absent
   mapping. Use with maps that does not support nil values."
  [^ConcurrentMap cmap key old new]
  (if (nil? old)
    (nil? (.putIfAbsent cmap key new))
    (.replace cmap key old new)))

(defn- cm-swap!
  "Atomically swaps the value associated with key in ConcurrentMap
   to be (apply f current-value args). Returns the new value."
  [^ConcurrentMap cmap key f & args]
  (loop []
    (let [old (.get cmap key)
          new (apply f old args)]
      (if (cm-replace! cmap key old new)

(defn add-observer
  "Add observer fn for the target. Watcher identifies the group of
  observers and could be used to remove the group. Watcher is weakly
  referenced, all associated observers will be removed when the
  wathcer is removed by gc. The observer fn will be called with
  watcher and target arguments and any additional arguments specified
  in update call."
  [watcher target f]
  (cm-swap! observers watcher assoc-cons target f)

(defn remove-observers
  "Remove group of observers associated with the specified watcher."
  (.remove observers watcher)

(defn- replace-observers-watcher
  [old-watcher new-watcher]
  (if-let [old (.remove observers old-watcher)]
    (.put observers new-watcher old))

(defn update
  "Notify observers."
  [target & args]
  (doseq [entry observers
          f (get (val entry) target)]
    (apply f (key entry) target args)))

(defn add-context-observer
  "Observer registered with this function will be automatically
  removed after the next frame rendering is complete."
  [target f]
  (let [root *root*]
    (add-observer root target f)))

(defn repaint-on-update
  "Trigger repaint of the current scene when the target updates."
  (let [root *root*]
    (if (not= root target)
      (add-observer root target (fn [w _] (update w))))))

(defn repaint
  "Repaint the current scene."
  (update *root*))

;; Rendering

(defn relative-transform
  "Returns AffineTransform: layer context -> AWT component."
  (let [tr (.getTransform *graphics*)]
    (.preConcatenate tr *inverse-initial-transform*)

(defn inverse-relative-transform
  "Returns AffineTransform: AWT component -> layer context."
  (let [tr (.getTransform *graphics*)]
    (.invert tr)                          ; absolute -> layer
    (.concatenate tr *initial-transform*) ; component -> absolute

(defn transform-point [^AffineTransform tr x y]
  (let [p (Point2D$Double. x y)]
    (.transform tr p p)
    [(.x p) (.y p)]))

;; (defn- clip
;;   "Intersect clipping area with the specified shape or bounds.
;;    Returns new clip (Shape or nil if empty)."
;;   ([x y w h]
;;      (clip (Rectangle2D$Double. x y w h)))
;;   ([shape]
;;      (let [a1 (Area. shape)
;;            a2 (if (instance? Area *clip*) *clip* (Area. *clip*))]
;;        (.transform a1 (relative-transform))
;;        (.intersect a1 a2)
;;        (if (.isEmpty a1)
;;          nil
;;          a1))))

;; Use faster clipping calculation provided by Graphics2D.
(defn- clip
  "Intersect clipping area with the specified bounds in current
   transform coordinates. Returns new clip in the AWT component
   coordinates (Shape or nil if empty)."
  [x y w h]
  (let [^Graphics2D clip-g (.create *graphics*)]
    (doto clip-g
      (.setClip x y w h)
      (.setTransform *initial-transform*)
      (.clip *clip*))
      (if (.isEmpty (.getClipBounds clip-g))
        (.getClip clip-g))
       (.dispose clip-g)))))

(defn- ^Graphics2D apply-theme
  "Set graphics' color and font to match theme.
   Modifies and returns the first argument."
     (apply-theme *graphics* *theme*))
  ([^Graphics2D graphics theme]
  (doto graphics
    (.setColor (:fore-color theme))
    (.setFont (:font theme)))))

(defn- ^Graphics2D create-graphics
     (create-graphics 0 0 *width* *height*))
  ([x y w h]
     (apply-theme (.create *graphics* x y w h) *theme*)))

(defn with-bounds*
  [x y w h f & args]
  (when-let [clip (clip x y w h)]
    (let [graphics (create-graphics x y w h)]
        (binding [*width* w
                  *height* h
                  *clip* clip
                  *graphics* graphics]
          (apply f args))
         (.dispose graphics))))))

(defmacro with-bounds
  [x y w h & body]
  `(with-bounds* ~x ~y ~w ~h (fn [] ~@body)))

(defmacro with-theme
  [theme & body]
  `(binding [*theme* (merge *theme* ~theme)]

(defmacro with-color
  [color-or-keyword & body]
  (let [color-form (if (keyword? color-or-keyword)
                     `(~color-or-keyword *theme*)
    `(let [color# ~color-form
           old-color# (.getColor *graphics*)]
         (.setColor *graphics* color#)
          (.setColor *graphics* old-color#))))))

;; TODO: constructor for AffineTransform.
;; (transform :scale 0.3 0.5
;;            :translate 5 10
;;            :rotate (/ Math/PI 2))

(defmacro with-transform [transform & body]
  `(let [old-t# (.getTransform *graphics*)]
       (.transform *graphics* ~transform)
        (.setTransform *graphics* old-t#)))))

(defmacro with-rotate [theta ax ay & body]
  `(let [transform# (AffineTransform/getRotateInstance ~theta ~ax ~ay)]
     (with-transform transform# ~@body)))

(defn draw!
  "Draws layer."
     (let [graphics (create-graphics)]
         (binding [*graphics* graphics]
           (render! layer))
          (.dispose graphics)))))
  ([layer x y]
     (let [size (layer-size layer)]
       (draw! layer x y (:width size) (:height size))))
  ([layer x y width height]
     (with-bounds* x y width height render! layer)))

(defn draw-anchored!
  "Draws layer. Location is relative to the layer's anchor point for
   the specified alignment."
  ([layer h-align v-align x y]
     (let [anchor (anchor layer h-align v-align)]
       (draw! layer (- x (:x anchor)) (- y (:y anchor)))))
  ([layer h-align v-align x y w h]
     (let [anchor (anchor layer h-align v-align)]
       (draw! layer (- x (:x anchor)) (- y (:y anchor)) w h))))

(defn draw-root!
  "Draws the root layer."
  ([layer graphics width height event-dispatcher]
     (draw-root! layer graphics width height event-dispatcher nil))
  ([layer ^Graphics2D graphics width height event-dispatcher target]
     (binding [*root* layer
               *target* target
               *graphics* graphics
               *font-context* (.getFontRenderContext graphics)
               *initial-transform* (.getTransform graphics)
                 (-> graphics .getTransform .createInverse)
               *event-dispatcher* event-dispatcher
               *width* width
               *height* height
               *clip* (Rectangle2D$Double. 0 0 width height)
               *time* (System/nanoTime)]
       ;; (.setRenderingHint graphics
       ;;                    RenderingHints/KEY_INTERPOLATION
       ;;                    RenderingHints/VALUE_INTERPOLATION_BILINEAR)
       ;; (.setRenderingHint graphics
       ;;                    RenderingHints/KEY_ALPHA_INTERPOLATION
       ;;                    RenderingHints/VALUE_ALPHA_INTERPOLATION_QUALITY)
       ;; (.setRenderingHint graphics
       ;;                    RenderingHints/KEY_ANTIALIASING
       ;;                    RenderingHints/VALUE_ANTIALIAS_ON)
       (let [tmp-watcher (Object.)]
         ;; Keep current context observers until the rendering is
         ;; complete. Some observers may be invoked twice if they
         ;; appear in both groups until tmp-watcher is removed.
         (replace-observers-watcher layer tmp-watcher)
           (render! layer)
            (remove-observers tmp-watcher)
            (commit event-dispatcher)))))))

(defn root-size
  ([layer font-context]
     (root-size layer font-context nil))
  ([layer font-context target]
     (binding [*root* layer
               *target* target
               *font-context* font-context]
       (layer-size layer))))

;; Event handling.

(defn with-handlers*
  [handle handlers f & args]
  (binding [*event-dispatcher* (create-dispatcher
                                *event-dispatcher* handle handlers)]
    (apply f args)))

(defmacro with-handlers
  "specs => (:event-id name & handler-body)*

  Execute form with the specified event handlers."
  [handle form & specs]
  `(with-handlers* ~handle
     ~(reduce (fn [m spec]
                (assoc m (first spec)
                       `(fn [~(second spec)]
                          ~@(nnext spec)))) {}
     (fn [] ~form)))

(defn picked? [handle]
  (handle-picked? *event-dispatcher* handle))

(defn hovered? [handle]
  (handle-hovered? *event-dispatcher* handle))

;; EventDispatcher implementation

(def awt-events
     {java.awt.event.MouseEvent/MOUSE_CLICKED  :mouse-clicked
      java.awt.event.MouseEvent/MOUSE_DRAGGED  :mouse-dragged
      java.awt.event.MouseEvent/MOUSE_ENTERED  :mouse-entered
      java.awt.event.MouseEvent/MOUSE_EXITED   :mouse-exited
      java.awt.event.MouseEvent/MOUSE_MOVED    :mouse-moved
      java.awt.event.MouseEvent/MOUSE_PRESSED  :mouse-pressed
      java.awt.event.MouseEvent/MOUSE_RELEASED :mouse-released})

(def dummy-event-dispatcher
      (listen! [this component])
      (create-dispatcher [this handle handlers] this)
      (commit [this])
      (handle-picked? [this handle])
      (handle-hovered? [this handle])))

(defrecord DispatcherNode [handle handlers parent
                           ^Shape clip ^AffineTransform transform
  (listen! [this component]
    (listen! parent component))
  (create-dispatcher [this handle handlers]
    (create-dispatcher parent handle handlers))
  (commit [this]
    (commit parent))
  (handle-picked? [this handle]
    (handle-picked? parent handle))
  (handle-hovered? [this handle]
    (handle-hovered? parent handle)))

(defn- make-node [handle handlers]
  (DispatcherNode. handle handlers *event-dispatcher* *clip*

(defn- add-node [tree node]
  (assoc-cons tree (:parent node) node))

(defn- under-cursor
  "Returns a vector of child nodes under cursor."
  [x y tree node]
  (some #(if (.contains ^Shape (:clip %) x y)
           (conj (vec (under-cursor x y tree %)) %))
        (get tree node)))

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

(defn- translate-mouse-event [^java.awt.event.MouseEvent event
                              ^AffineTransform tr id]
  (let [[x y] (transform-point tr (.getX event) (.getY event))]
    (MouseEvent. id (.getWhen event) x y
                 (.getXOnScreen event) (.getYOnScreen event)
                 (.getButton event))))

(defn- translate-and-dispatch
  ([nodes first-only ^java.awt.event.MouseEvent event]
     (translate-and-dispatch nodes first-only
       event (awt-events (.getID event))))
  ([nodes first-only event id]
     (if-let [node (first nodes)]
       (if-let [handler (get (:handlers node) id)]
           (with-bindings* (:bindings node)
             (translate-mouse-event event (:transform node) id))
           (if-not first-only
             (recur (rest nodes) false event id)))
         (recur (rest nodes) first-only event id)))))

(defn- dispatch-mouse-motion
  "Dispatches mouse motion events."
  [hovered-ref tree root ^java.awt.event.MouseEvent event]
  (let [x (.getX event)
        y (.getY event)
        [hovered hovered2] (dosync
                             (ref-set hovered-ref
                                      (under-cursor x y tree root))])
        pred #(= (:handle %1) (:handle %2))
        exited (remove-all hovered hovered2 pred)
        entered (remove-all hovered2 hovered pred)
        moved (remove-all hovered2 entered pred)]
    (translate-and-dispatch exited false event :mouse-exited)
    (translate-and-dispatch entered false event :mouse-entered)
    (translate-and-dispatch moved true event :mouse-moved)))

(defn- dispatch-mouse-button
  [picked-ref hovered-ref ^java.awt.event.MouseEvent event]
  (let [id (awt-events (.getID event))
        nodes (case id
                (ref-set picked-ref @hovered-ref))
                (let [picked @picked-ref]
                  (ref-set picked-ref nil)
    (translate-and-dispatch nodes true event id)))

(defn root-event-dispatcher []
  (let [tree-r (ref {})   ; register
        tree (ref {})     ; dispatch
        hovered (ref '())
        picked (ref '())]
     (listen! [this component]
       (doto component
         (.addMouseListener this)
         (.addMouseMotionListener this)))
     (create-dispatcher [this handle handlers]
       (let [node (make-node handle handlers)]
         (dosync (alter tree-r add-node node))
     (commit [this]
       (dosync (ref-set tree @tree-r)
               (ref-set tree-r {})))
     (handle-picked? [this handle]
       (some #(= handle (:handle %)) @picked))
     (handle-hovered? [this handle]
       (some #(= handle (:handle %)) @hovered))
     (mouseEntered [this event]
       (dispatch-mouse-motion hovered @tree this event))
     (mouseExited [this event]
       (dispatch-mouse-motion hovered @tree this event))
     (mouseClicked [this event]
       (dispatch-mouse-button picked hovered event))
     (mousePressed [this event]
       (dispatch-mouse-button picked hovered event))
     (mouseReleased [this event]
       (dispatch-mouse-button picked hovered event))
     (mouseDragged [this event]
       (translate-and-dispatch @picked true event))
     (mouseMoved [this event]
       (dispatch-mouse-motion hovered @tree this event)))))