/*
 * Copyright (C) 2014 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.transition;

import android.graphics.Rect;
import android.view.View;
import android.view.ViewGroup;

A propagation that varies with the distance to the epicenter of the Transition or center of the scene if no epicenter exists. When a View is visible in the start of the transition, Views farther from the epicenter will transition sooner than Views closer to the epicenter. When a View is not in the start of the transition or is not visible at the start of the transition, it will transition sooner when closer to the epicenter and later when farther from the epicenter. This is the default TransitionPropagation used with Explode. /**
 * A propagation that varies with the distance to the epicenter of the Transition
 * or center of the scene if no epicenter exists. When a View is visible in the
 * start of the transition, Views farther from the epicenter will transition
 * sooner than Views closer to the epicenter. When a View is not in the start
 * of the transition or is not visible at the start of the transition, it will
 * transition sooner when closer to the epicenter and later when farther from
 * the epicenter. This is the default TransitionPropagation used with
 * {@link android.transition.Explode}.
 */
public class CircularPropagation extends VisibilityPropagation {
    private static final String TAG = "CircularPropagation";

    private float mPropagationSpeed = 3.0f;

    
Sets the speed at which transition propagation happens, relative to the duration of the
Transition. A propagationSpeed of 1 means that a View centered farthest from
the epicenter and View centered at the epicenter will have a difference
in start delay of approximately the duration of the Transition. A speed of 2 means the
start delay difference will be approximately half of the duration of the transition. A
value of 0 is illegal, but negative values will invert the propagation.
Params:
propagationSpeed – The speed at which propagation occurs, relative to the duration
                        of the transition. A speed of 4 means it works 4 times as fast
                        as the duration of the transition. May not be 0./**
     * Sets the speed at which transition propagation happens, relative to the duration of the
     * Transition. A <code>propagationSpeed</code> of 1 means that a View centered farthest from
     * the epicenter and View centered at the epicenter will have a difference
     * in start delay of approximately the duration of the Transition. A speed of 2 means the
     * start delay difference will be approximately half of the duration of the transition. A
     * value of 0 is illegal, but negative values will invert the propagation.
     *
     * @param propagationSpeed The speed at which propagation occurs, relative to the duration
     *                         of the transition. A speed of 4 means it works 4 times as fast
     *                         as the duration of the transition. May not be 0.
     */
    public void setPropagationSpeed(float propagationSpeed) {
        if (propagationSpeed == 0) {
            throw new IllegalArgumentException("propagationSpeed may not be 0");
        }
        mPropagationSpeed = propagationSpeed;
    }

    @Override
    public long getStartDelay(ViewGroup sceneRoot, Transition transition,
            TransitionValues startValues, TransitionValues endValues) {
        if (startValues == null && endValues == null) {
            return 0;
        }
        int directionMultiplier = 1;
        TransitionValues positionValues;
        if (endValues == null || getViewVisibility(startValues) == View.VISIBLE) {
            positionValues = startValues;
            directionMultiplier = -1;
        } else {
            positionValues = endValues;
        }

        int viewCenterX = getViewX(positionValues);
        int viewCenterY = getViewY(positionValues);

        Rect epicenter = transition.getEpicenter();
        int epicenterX;
        int epicenterY;
        if (epicenter != null) {
            epicenterX = epicenter.centerX();
            epicenterY = epicenter.centerY();
        } else {
            int[] loc = new int[2];
            sceneRoot.getLocationOnScreen(loc);
            epicenterX = Math.round(loc[0] + (sceneRoot.getWidth() / 2)
                    + sceneRoot.getTranslationX());
            epicenterY = Math.round(loc[1] + (sceneRoot.getHeight() / 2)
                    + sceneRoot.getTranslationY());
        }
        double distance = distance(viewCenterX, viewCenterY, epicenterX, epicenterY);
        double maxDistance = distance(0, 0, sceneRoot.getWidth(), sceneRoot.getHeight());
        double distanceFraction = distance/maxDistance;

        long duration = transition.getDuration();
        if (duration < 0) {
            duration = 300;
        }

        return Math.round(duration * directionMultiplier / mPropagationSpeed * distanceFraction);
    }

    private static double distance(float x1, float y1, float x2, float y2) {
        double x = x2 - x1;
        double y = y2 - y1;
        return Math.hypot(x, y);
    }
}