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package com.almeros.android.multitouch;

import android.content.Context;
import android.view.MotionEvent;

/**
 * @author Almer Thie (code.almeros.com)
 * Copyright (c) 2013, Almer Thie (code.almeros.com)
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
 *
 *  Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
 *  Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer
 *  in the documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
 * OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
 * OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
 * OF SUCH DAMAGE.
 */
public abstract class BaseGestureDetector {
  /**
   * This value is the threshold ratio between the previous combined pressure
   * and the current combined pressure. When pressure decreases rapidly
   * between events the position values can often be imprecise, as it usually
   * indicates that the user is in the process of lifting a pointer off of the
   * device. This value was tuned experimentally.
   */
  protected static final float PRESSURE_THRESHOLD = 0.67f;
  protected final Context mContext;
  protected boolean mGestureInProgress;
  protected MotionEvent mPrevEvent;
  protected MotionEvent mCurrEvent;
  protected float mCurrPressure;
  protected float mPrevPressure;
  protected long mTimeDelta;


  public BaseGestureDetector(Context context) {
    mContext = context;
  }

  /**
   * All gesture detectors need to be called through this method to be able to
   * detect gestures. This method delegates work to handler methods
   * (handleStartProgressEvent, handleInProgressEvent) implemented in
   * extending classes.
   *
   * @param event
   * @return
   */
  public boolean onTouchEvent(MotionEvent event) {
    final int actionCode = event.getAction() & MotionEvent.ACTION_MASK;
    if (!mGestureInProgress) {
      handleStartProgressEvent(actionCode, event);
    } else {
      handleInProgressEvent(actionCode, event);
    }
    return true;
  }

  /**
   * Called when the current event occurred when NO gesture is in progress
   * yet. The handling in this implementation may set the gesture in progress
   * (via mGestureInProgress) or out of progress
   * @param actionCode
   * @param event
   */
  protected abstract void handleStartProgressEvent(int actionCode, MotionEvent event);

  /**
   * Called when the current event occurred when a gesture IS in progress. The
   * handling in this implementation may set the gesture out of progress (via
   * mGestureInProgress).
   * @param actionCode
   * @param event
   */
  protected abstract void handleInProgressEvent(int actionCode, MotionEvent event);


  protected void updateStateByEvent(MotionEvent curr) {
    final MotionEvent prev = mPrevEvent;

    // Reset mCurrEvent
    if (mCurrEvent != null) {
      mCurrEvent.recycle();
      mCurrEvent = null;
    }
    mCurrEvent = MotionEvent.obtain(curr);


    // Delta time
    mTimeDelta = curr.getEventTime() - prev.getEventTime();

    // Pressure
    mCurrPressure = curr.getPressure(curr.getActionIndex());
    mPrevPressure = prev.getPressure(prev.getActionIndex());
  }

  protected void resetState() {
    if (mPrevEvent != null) {
      mPrevEvent.recycle();
      mPrevEvent = null;
    }
    if (mCurrEvent != null) {
      mCurrEvent.recycle();
      mCurrEvent = null;
    }
    mGestureInProgress = false;
  }


  /**
   * Returns {@code true} if a gesture is currently in progress.
   * @return {@code true} if a gesture is currently in progress, {@code false} otherwise.
   */
  public boolean isInProgress() {
    return mGestureInProgress;
  }

  /**
   * Return the time difference in milliseconds between the previous accepted
   * GestureDetector event and the current GestureDetector event.
   *
   * @return Time difference since the last move event in milliseconds.
   */
  public long getTimeDelta() {
    return mTimeDelta;
  }

  /**
   * Return the event time of the current GestureDetector event being
   * processed.
   *
   * @return Current GestureDetector event time in milliseconds.
   */
  public long getEventTime() {
    return mCurrEvent.getEventTime();
  }

}