/*
 * Copyright (C) 2016 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package android.support.transition;

import android.animation.Animator;
import android.animation.TimeInterpolator;
import android.os.Build;
import android.support.annotation.IdRes;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.view.SurfaceView;
import android.view.TextureView;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Spinner;

import java.util.List;

/**
 * A Transition holds information about animations that will be run on its
 * targets during a scene change. Subclasses of this abstract class may
 * choreograph several child transitions ({@link TransitionSet} or they may
 * perform custom animations themselves. Any Transition has two main jobs:
 * (1) capture property values, and (2) play animations based on changes to
 * captured property values. A custom transition knows what property values
 * on View objects are of interest to it, and also knows how to animate
 * changes to those values. For example, the {@link Fade} transition tracks
 * changes to visibility-related properties and is able to construct and run
 * animations that fade items in or out based on changes to those properties.
 *
 * <p>Note: Transitions may not work correctly with either {@link SurfaceView}
 * or {@link TextureView}, due to the way that these views are displayed
 * on the screen. For SurfaceView, the problem is that the view is updated from
 * a non-UI thread, so changes to the view due to transitions (such as moving
 * and resizing the view) may be out of sync with the display inside those bounds.
 * TextureView is more compatible with transitions in general, but some
 * specific transitions (such as {@link Fade}) may not be compatible
 * with TextureView because they rely on {@link ViewOverlay} functionality,
 * which does not currently work with TextureView.</p>
 *
 * <p>Unlike the platform version, this does not support declaration by XML resources.</p>
 */
public abstract class Transition implements TransitionInterface {

    /* package */ TransitionImpl mImpl;

    /**
     * Constructs a Transition object with no target objects. A transition with
     * no targets defaults to running on all target objects in the scene hierarchy
     * (if the transition is not contained in a TransitionSet), or all target
     * objects passed down from its parent (if it is in a TransitionSet).
     */
    public Transition() {
        this(false);
    }

    // Hidden constructor for built-in transitions
    protected Transition(boolean deferred) {
        if (!deferred) {
            mImpl = Build.VERSION.SDK_INT < 19 ? new TransitionIcs() : new TransitionKitKat();
            mImpl.init(this);
        }
    }

    /**
     * Adds a listener to the set of listeners that are sent events through the
     * life of an animation, such as start, repeat, and end.
     *
     * @param listener the listener to be added to the current set of listeners
     *                 for this animation.
     * @return This transition object.
     */
    @NonNull
    public Transition addListener(@NonNull TransitionListener listener) {
        mImpl.addListener(listener);
        return this;
    }

    /**
     * Sets the target view instances that this Transition is interested in
     * animating. By default, there are no targets, and a Transition will
     * listen for changes on every view in the hierarchy below the sceneRoot
     * of the Scene being transitioned into. Setting targets constrains
     * the Transition to only listen for, and act on, these views.
     * All other views will be ignored.
     *
     * <p>The target list is like the {@link #addTarget(int) targetId}
     * list except this list specifies the actual View instances, not the ids
     * of the views. This is an important distinction when scene changes involve
     * view hierarchies which have been inflated separately; different views may
     * share the same id but not actually be the same instance. If the transition
     * should treat those views as the same, then {@link #addTarget(int)} should be used
     * instead of {@link #addTarget(View)}. If, on the other hand, scene changes involve
     * changes all within the same view hierarchy, among views which do not
     * necessarily have ids set on them, then the target list of views may be more
     * convenient.</p>
     *
     * @param target A View on which the Transition will act, must be non-null.
     * @return The Transition to which the target is added.
     * Returning the same object makes it easier to chain calls during
     * construction, such as
     * <code>transitionSet.addTransitions(new Fade()).addTarget(someView);</code>
     * @see #addTarget(int)
     */
    @NonNull
    public Transition addTarget(@NonNull View target) {
        mImpl.addTarget(target);
        return this;
    }

    /**
     * Adds the id of a target view that this Transition is interested in
     * animating. By default, there are no targetIds, and a Transition will
     * listen for changes on every view in the hierarchy below the sceneRoot
     * of the Scene being transitioned into. Setting targetIds constrains
     * the Transition to only listen for, and act on, views with these IDs.
     * Views with different IDs, or no IDs whatsoever, will be ignored.
     *
     * <p>Note that using ids to specify targets implies that ids should be unique
     * within the view hierarchy underneat the scene root.</p>
     *
     * @param targetId The id of a target view, must be a positive number.
     * @return The Transition to which the targetId is added.
     * Returning the same object makes it easier to chain calls during
     * construction, such as
     * <code>transitionSet.addTransitions(new Fade()).addTarget(someId);</code>
     * @see View#getId()
     */
    @NonNull
    public Transition addTarget(@IdRes int targetId) {
        mImpl.addTarget(targetId);
        return this;
    }

    /**
     * Captures the values in the end scene for the properties that this
     * transition monitors. These values are then passed as the endValues
     * structure in a later call to
     * {@link #createAnimator(ViewGroup, TransitionValues, TransitionValues)}.
     * The main concern for an implementation is what the
     * properties are that the transition cares about and what the values are
     * for all of those properties. The start and end values will be compared
     * later during the
     * {@link #createAnimator(ViewGroup, TransitionValues, TransitionValues)}
     * method to determine what, if any, animations, should be run.
     *
     * <p>Subclasses must implement this method. The method should only be called by the
     * transition system; it is not intended to be called from external classes.</p>
     *
     * @param transitionValues The holder for any values that the Transition
     *                         wishes to store. Values are stored in the <code>values</code> field
     *                         of this TransitionValues object and are keyed from
     *                         a String value. For example, to store a view's rotation value,
     *                         a transition might call
     *                         <code>transitionValues.values.put("appname:transitionname:rotation",
     *                         view.getRotation())</code>. The target view will already be stored
     *                         in
     *                         the transitionValues structure when this method is called.
     * @see #captureStartValues(TransitionValues)
     * @see #createAnimator(ViewGroup, TransitionValues, TransitionValues)
     */
    public abstract void captureEndValues(@NonNull TransitionValues transitionValues);

    /**
     * Captures the values in the start scene for the properties that this
     * transition monitors. These values are then passed as the startValues
     * structure in a later call to
     * {@link #createAnimator(ViewGroup, TransitionValues, TransitionValues)}.
     * The main concern for an implementation is what the
     * properties are that the transition cares about and what the values are
     * for all of those properties. The start and end values will be compared
     * later during the
     * {@link #createAnimator(ViewGroup, TransitionValues, TransitionValues)}
     * method to determine what, if any, animations, should be run.
     *
     * <p>Subclasses must implement this method. The method should only be called by the
     * transition system; it is not intended to be called from external classes.</p>
     *
     * @param transitionValues The holder for any values that the Transition
     *                         wishes to store. Values are stored in the <code>values</code> field
     *                         of this TransitionValues object and are keyed from
     *                         a String value. For example, to store a view's rotation value,
     *                         a transition might call
     *                         <code>transitionValues.values.put("appname:transitionname:rotation",
     *                         view.getRotation())</code>. The target view will already be stored
     *                         in
     *                         the transitionValues structure when this method is called.
     * @see #captureEndValues(TransitionValues)
     * @see #createAnimator(ViewGroup, TransitionValues, TransitionValues)
     */
    public abstract void captureStartValues(@NonNull TransitionValues transitionValues);

    /**
     * This method creates an animation that will be run for this transition
     * given the information in the startValues and endValues structures captured
     * earlier for the start and end scenes. Subclasses of Transition should override
     * this method. The method should only be called by the transition system; it is
     * not intended to be called from external classes.
     *
     * <p>This method is called by the transition's parent (all the way up to the
     * topmost Transition in the hierarchy) with the sceneRoot and start/end
     * values that the transition may need to set up initial target values
     * and construct an appropriate animation. For example, if an overall
     * Transition is a {@link TransitionSet} consisting of several
     * child transitions in sequence, then some of the child transitions may
     * want to set initial values on target views prior to the overall
     * Transition commencing, to put them in an appropriate state for the
     * delay between that start and the child Transition start time. For
     * example, a transition that fades an item in may wish to set the starting
     * alpha value to 0, to avoid it blinking in prior to the transition
     * actually starting the animation. This is necessary because the scene
     * change that triggers the Transition will automatically set the end-scene
     * on all target views, so a Transition that wants to animate from a
     * different value should set that value prior to returning from this method.</p>
     *
     * <p>Additionally, a Transition can perform logic to determine whether
     * the transition needs to run on the given target and start/end values.
     * For example, a transition that resizes objects on the screen may wish
     * to avoid running for views which are not present in either the start
     * or end scenes.</p>
     *
     * <p>If there is an animator created and returned from this method, the
     * transition mechanism will apply any applicable duration, startDelay,
     * and interpolator to that animation and start it. A return value of
     * <code>null</code> indicates that no animation should run. The default
     * implementation returns null.</p>
     *
     * <p>The method is called for every applicable target object, which is
     * stored in the {@link TransitionValues#view} field.</p>
     *
     * @param sceneRoot   The root of the transition hierarchy.
     * @param startValues The values for a specific target in the start scene.
     * @param endValues   The values for the target in the end scene.
     * @return A Animator to be started at the appropriate time in the
     * overall transition for this scene change. A null value means no animation
     * should be run.
     */
    @Nullable
    public abstract Animator createAnimator(@NonNull ViewGroup sceneRoot,
            @NonNull TransitionValues startValues, @NonNull TransitionValues endValues);

    /**
     * Whether to add the children of given target to the list of target children
     * to exclude from this transition. The <code>exclude</code> parameter specifies
     * whether the target should be added to or removed from the excluded list.
     *
     * <p>Excluding targets is a general mechanism for allowing transitions to run on
     * a view hierarchy while skipping target views that should not be part of
     * the transition. For example, you may want to avoid animating children
     * of a specific ListView or Spinner. Views can be excluded either by their
     * id, or by their instance reference, or by the Class of that view
     * (eg, {@link Spinner}).</p>
     *
     * @param target  The target to ignore when running this transition.
     * @param exclude Whether to add the target to or remove the target from the
     *                current list of excluded targets.
     * @return This transition object.
     * @see #excludeTarget(View, boolean)
     * @see #excludeChildren(int, boolean)
     * @see #excludeChildren(Class, boolean)
     */
    @NonNull
    public Transition excludeChildren(@NonNull View target, boolean exclude) {
        mImpl.excludeChildren(target, exclude);
        return this;
    }

    /**
     * Whether to add the children of the given id to the list of targets to exclude
     * from this transition. The <code>exclude</code> parameter specifies whether
     * the children of the target should be added to or removed from the excluded list.
     * Excluding children in this way provides a simple mechanism for excluding all
     * children of specific targets, rather than individually excluding each
     * child individually.
     *
     * <p>Excluding targets is a general mechanism for allowing transitions to run on
     * a view hierarchy while skipping target views that should not be part of
     * the transition. For example, you may want to avoid animating children
     * of a specific ListView or Spinner. Views can be excluded either by their
     * id, or by their instance reference, or by the Class of that view
     * (eg, {@link Spinner}).</p>
     *
     * @param targetId The id of a target whose children should be ignored when running
     *                 this transition.
     * @param exclude  Whether to add the target to or remove the target from the
     *                 current list of excluded-child targets.
     * @return This transition object.
     * @see #excludeTarget(int, boolean)
     * @see #excludeChildren(View, boolean)
     * @see #excludeChildren(Class, boolean)
     */
    @NonNull
    public Transition excludeChildren(@IdRes int targetId, boolean exclude) {
        mImpl.excludeChildren(targetId, exclude);
        return this;
    }

    /**
     * Whether to add the given type to the list of types whose children should
     * be excluded from this transition. The <code>exclude</code> parameter
     * specifies whether the target type should be added to or removed from
     * the excluded list.
     *
     * <p>Excluding targets is a general mechanism for allowing transitions to run on
     * a view hierarchy while skipping target views that should not be part of
     * the transition. For example, you may want to avoid animating children
     * of a specific ListView or Spinner. Views can be excluded either by their
     * id, or by their instance reference, or by the Class of that view
     * (eg, {@link Spinner}).</p>
     *
     * @param type    The type to ignore when running this transition.
     * @param exclude Whether to add the target type to or remove it from the
     *                current list of excluded target types.
     * @return This transition object.
     * @see #excludeTarget(Class, boolean)
     * @see #excludeChildren(int, boolean)
     * @see #excludeChildren(View, boolean)
     */
    @NonNull
    public Transition excludeChildren(@NonNull Class type, boolean exclude) {
        mImpl.excludeChildren(type, exclude);
        return this;
    }

    /**
     * Whether to add the given target to the list of targets to exclude from this
     * transition. The <code>exclude</code> parameter specifies whether the target
     * should be added to or removed from the excluded list.
     *
     * <p>Excluding targets is a general mechanism for allowing transitions to run on
     * a view hierarchy while skipping target views that should not be part of
     * the transition. For example, you may want to avoid animating children
     * of a specific ListView or Spinner. Views can be excluded either by their
     * id, or by their instance reference, or by the Class of that view
     * (eg, {@link Spinner}).</p>
     *
     * @param target  The target to ignore when running this transition.
     * @param exclude Whether to add the target to or remove the target from the
     *                current list of excluded targets.
     * @return This transition object.
     * @see #excludeChildren(View, boolean)
     * @see #excludeTarget(int, boolean)
     * @see #excludeTarget(Class, boolean)
     */
    @NonNull
    public Transition excludeTarget(@NonNull View target, boolean exclude) {
        mImpl.excludeTarget(target, exclude);
        return this;
    }

    /**
     * Whether to add the given id to the list of target ids to exclude from this
     * transition. The <code>exclude</code> parameter specifies whether the target
     * should be added to or removed from the excluded list.
     *
     * <p>Excluding targets is a general mechanism for allowing transitions to run on
     * a view hierarchy while skipping target views that should not be part of
     * the transition. For example, you may want to avoid animating children
     * of a specific ListView or Spinner. Views can be excluded either by their
     * id, or by their instance reference, or by the Class of that view
     * (eg, {@link Spinner}).</p>
     *
     * @param targetId The id of a target to ignore when running this transition.
     * @param exclude  Whether to add the target to or remove the target from the
     *                 current list of excluded targets.
     * @return This transition object.
     * @see #excludeChildren(int, boolean)
     * @see #excludeTarget(View, boolean)
     * @see #excludeTarget(Class, boolean)
     */
    @NonNull
    public Transition excludeTarget(@IdRes int targetId, boolean exclude) {
        mImpl.excludeTarget(targetId, exclude);
        return this;
    }

    /**
     * Whether to add the given type to the list of types to exclude from this
     * transition. The <code>exclude</code> parameter specifies whether the target
     * type should be added to or removed from the excluded list.
     *
     * <p>Excluding targets is a general mechanism for allowing transitions to run on
     * a view hierarchy while skipping target views that should not be part of
     * the transition. For example, you may want to avoid animating children
     * of a specific ListView or Spinner. Views can be excluded either by their
     * id, or by their instance reference, or by the Class of that view
     * (eg, {@link Spinner}).</p>
     *
     * @param type    The type to ignore when running this transition.
     * @param exclude Whether to add the target type to or remove it from the
     *                current list of excluded target types.
     * @return This transition object.
     * @see #excludeChildren(Class, boolean)
     * @see #excludeTarget(int, boolean)
     * @see #excludeTarget(View, boolean)
     */
    @NonNull
    public Transition excludeTarget(@NonNull Class type, boolean exclude) {
        mImpl.excludeTarget(type, exclude);
        return this;
    }

    /**
     * Returns the duration set on this transition. If no duration has been set,
     * the returned value will be negative, indicating that resulting animators will
     * retain their own durations.
     *
     * @return The duration set on this transition, in milliseconds, if one has been
     * set, otherwise returns a negative number.
     */
    public long getDuration() {
        return mImpl.getDuration();
    }

    /**
     * Sets the duration of this transition. By default, there is no duration
     * (indicated by a negative number), which means that the Animator created by
     * the transition will have its own specified duration. If the duration of a
     * Transition is set, that duration will override the Animator duration.
     *
     * @param duration The length of the animation, in milliseconds.
     * @return This transition object.
     * @attr ref android.R.styleable#Transition_duration
     */
    @NonNull
    public Transition setDuration(long duration) {
        mImpl.setDuration(duration);
        return this;
    }

    /**
     * Returns the interpolator set on this transition. If no interpolator has been set,
     * the returned value will be null, indicating that resulting animators will
     * retain their own interpolators.
     *
     * @return The interpolator set on this transition, if one has been set, otherwise
     * returns null.
     */
    @Nullable
    public TimeInterpolator getInterpolator() {
        return mImpl.getInterpolator();
    }

    /**
     * Sets the interpolator of this transition. By default, the interpolator
     * is null, which means that the Animator created by the transition
     * will have its own specified interpolator. If the interpolator of a
     * Transition is set, that interpolator will override the Animator interpolator.
     *
     * @param interpolator The time interpolator used by the transition
     * @return This transition object.
     * @attr ref android.R.styleable#Transition_interpolator
     */
    @NonNull
    public Transition setInterpolator(@Nullable TimeInterpolator interpolator) {
        mImpl.setInterpolator(interpolator);
        return this;
    }

    /**
     * Returns the name of this Transition. This name is used internally to distinguish
     * between different transitions to determine when interrupting transitions overlap.
     * For example, a ChangeBounds running on the same target view as another ChangeBounds
     * should determine whether the old transition is animating to different end values
     * and should be canceled in favor of the new transition.
     *
     * <p>By default, a Transition's name is simply the value of {@link Class#getName()},
     * but subclasses are free to override and return something different.</p>
     *
     * @return The name of this transition.
     */
    @NonNull
    public String getName() {
        return mImpl.getName();
    }

    /**
     * Returns the startDelay set on this transition. If no startDelay has been set,
     * the returned value will be negative, indicating that resulting animators will
     * retain their own startDelays.
     *
     * @return The startDelay set on this transition, in milliseconds, if one has
     * been set, otherwise returns a negative number.
     */
    public long getStartDelay() {
        return mImpl.getStartDelay();
    }

    /**
     * Sets the startDelay of this transition. By default, there is no delay
     * (indicated by a negative number), which means that the Animator created by
     * the transition will have its own specified startDelay. If the delay of a
     * Transition is set, that delay will override the Animator delay.
     *
     * @param startDelay The length of the delay, in milliseconds.
     * @return This transition object.
     * @attr ref android.R.styleable#Transition_startDelay
     */
    @NonNull
    public Transition setStartDelay(long startDelay) {
        mImpl.setStartDelay(startDelay);
        return this;
    }

    /**
     * Returns the array of target IDs that this transition limits itself to
     * tracking and animating. If the array is null for both this method and
     * {@link #getTargets()}, then this transition is
     * not limited to specific views, and will handle changes to any views
     * in the hierarchy of a scene change.
     *
     * @return the list of target IDs
     */
    @NonNull
    public List<Integer> getTargetIds() {
        return mImpl.getTargetIds();
    }

    /**
     * Returns the array of target views that this transition limits itself to
     * tracking and animating. If the array is null for both this method and
     * {@link #getTargetIds()}, then this transition is
     * not limited to specific views, and will handle changes to any views
     * in the hierarchy of a scene change.
     *
     * @return the list of target views
     */
    @NonNull
    public List<View> getTargets() {
        return mImpl.getTargets();
    }

    /**
     * Returns the set of property names used stored in the {@link TransitionValues}
     * object passed into {@link #captureStartValues(TransitionValues)} that
     * this transition cares about for the purposes of canceling overlapping animations.
     * When any transition is started on a given scene root, all transitions
     * currently running on that same scene root are checked to see whether the
     * properties on which they based their animations agree with the end values of
     * the same properties in the new transition. If the end values are not equal,
     * then the old animation is canceled since the new transition will start a new
     * animation to these new values. If the values are equal, the old animation is
     * allowed to continue and no new animation is started for that transition.
     *
     * <p>A transition does not need to override this method. However, not doing so
     * will mean that the cancellation logic outlined in the previous paragraph
     * will be skipped for that transition, possibly leading to artifacts as
     * old transitions and new transitions on the same targets run in parallel,
     * animating views toward potentially different end values.</p>
     *
     * @return An array of property names as described in the class documentation for
     * {@link TransitionValues}. The default implementation returns <code>null</code>.
     */
    @Nullable
    public String[] getTransitionProperties() {
        return mImpl.getTransitionProperties();
    }

    /**
     * This method can be called by transitions to get the TransitionValues for
     * any particular view during the transition-playing process. This might be
     * necessary, for example, to query the before/after state of related views
     * for a given transition.
     */
    @NonNull
    public TransitionValues getTransitionValues(@NonNull View view, boolean start) {
        return mImpl.getTransitionValues(view, start);
    }

    /**
     * Removes a listener from the set listening to this animation.
     *
     * @param listener the listener to be removed from the current set of
     *                 listeners for this transition.
     * @return This transition object.
     */
    @NonNull
    public Transition removeListener(@NonNull TransitionListener listener) {
        mImpl.removeListener(listener);
        return this;
    }

    /**
     * Removes the given target from the list of targets that this Transition
     * is interested in animating.
     *
     * @param target The target view, must be non-null.
     * @return Transition The Transition from which the target is removed.
     * Returning the same object makes it easier to chain calls during
     * construction, such as
     * <code>transitionSet.addTransitions(new Fade()).removeTarget(someView);</code>
     */
    @NonNull
    public Transition removeTarget(@NonNull View target) {
        mImpl.removeTarget(target);
        return this;
    }

    /**
     * Removes the given targetId from the list of ids that this Transition
     * is interested in animating.
     *
     * @param targetId The id of a target view, must be a positive number.
     * @return The Transition from which the targetId is removed.
     * Returning the same object makes it easier to chain calls during
     * construction, such as
     * <code>transitionSet.addTransitions(new Fade()).removeTargetId(someId);</code>
     */
    @NonNull
    public Transition removeTarget(@IdRes int targetId) {
        mImpl.removeTarget(targetId);
        return this;
    }

    @Override
    public String toString() {
        return mImpl.toString();
    }

    /**
     * A transition listener receives notifications from a transition.
     * Notifications indicate transition lifecycle events.
     */
    public interface TransitionListener extends TransitionInterfaceListener<Transition> {

        /**
         * Notification about the start of the transition.
         *
         * @param transition The started transition.
         */
        void onTransitionStart(@NonNull Transition transition);

        /**
         * Notification about the end of the transition. Canceled transitions
         * will always notify listeners of both the cancellation and end
         * events. That is, {@link #onTransitionEnd(Transition)} is always called,
         * regardless of whether the transition was canceled or played
         * through to completion.
         *
         * @param transition The transition which reached its end.
         */
        void onTransitionEnd(@NonNull Transition transition);

        /**
         * Notification about the cancellation of the transition.
         * Note that cancel may be called by a parent {@link TransitionSet} on
         * a child transition which has not yet started. This allows the child
         * transition to restore state on target objects which was set at
         * {@link #createAnimator(android.view.ViewGroup, TransitionValues, TransitionValues)
         * createAnimator()} time.
         *
         * @param transition The transition which was canceled.
         */
        void onTransitionCancel(@NonNull Transition transition);

        /**
         * Notification when a transition is paused.
         * Note that createAnimator() may be called by a parent {@link TransitionSet} on
         * a child transition which has not yet started. This allows the child
         * transition to restore state on target objects which was set at
         * {@link #createAnimator(android.view.ViewGroup, TransitionValues, TransitionValues)
         * createAnimator()} time.
         *
         * @param transition The transition which was paused.
         */
        void onTransitionPause(@NonNull Transition transition);

        /**
         * Notification when a transition is resumed.
         * Note that resume() may be called by a parent {@link TransitionSet} on
         * a child transition which has not yet started. This allows the child
         * transition to restore state which may have changed in an earlier call
         * to {@link #onTransitionPause(Transition)}.
         *
         * @param transition The transition which was resumed.
         */
        void onTransitionResume(@NonNull Transition transition);
    }

}