/*
 * Copyright (C) 2010 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.view;

import android.os.Build;
import android.util.Log;

Checks whether a sequence of input events is self-consistent.
Logs a description of each problem detected.

When a problem is detected, the event is tainted.  This mechanism prevents the same
error from being reported multiple times.

@hide
/**
 * Checks whether a sequence of input events is self-consistent.
 * Logs a description of each problem detected.
 * <p>
 * When a problem is detected, the event is tainted.  This mechanism prevents the same
 * error from being reported multiple times.
 * </p>
 *
 * @hide
 */
public final class InputEventConsistencyVerifier {
    private static final boolean IS_ENG_BUILD = Build.IS_ENG;

    private static final String EVENT_TYPE_KEY = "KeyEvent";
    private static final String EVENT_TYPE_TRACKBALL = "TrackballEvent";
    private static final String EVENT_TYPE_TOUCH = "TouchEvent";
    private static final String EVENT_TYPE_GENERIC_MOTION = "GenericMotionEvent";

    // The number of recent events to log when a problem is detected.
    // Can be set to 0 to disable logging recent events but the runtime overhead of
    // this feature is negligible on current hardware.
    private static final int RECENT_EVENTS_TO_LOG = 5;

    // The object to which the verifier is attached.
    private final Object mCaller;

    // Consistency verifier flags.
    private final int mFlags;

    // Tag for logging which a client can set to help distinguish the output
    // from different verifiers since several can be active at the same time.
    // If not provided defaults to the simple class name.
    private final String mLogTag;

    // The most recently checked event and the nesting level at which it was checked.
    // This is only set when the verifier is called from a nesting level greater than 0
    // so that the verifier can detect when it has been asked to verify the same event twice.
    // It does not make sense to examine the contents of the last event since it may have
    // been recycled.
    private int mLastEventSeq;
    private String mLastEventType;
    private int mLastNestingLevel;

    // Copy of the most recent events.
    private InputEvent[] mRecentEvents;
    private boolean[] mRecentEventsUnhandled;
    private int mMostRecentEventIndex;

    // Current event and its type.
    private InputEvent mCurrentEvent;
    private String mCurrentEventType;

    // Linked list of key state objects.
    private KeyState mKeyStateList;

    // Current state of the trackball.
    private boolean mTrackballDown;
    private boolean mTrackballUnhandled;

    // Bitfield of pointer ids that are currently down.
    // Assumes that the largest possible pointer id is 31, which is potentially subject to change.
    // (See MAX_POINTER_ID in frameworks/base/include/ui/Input.h)
    private int mTouchEventStreamPointers;

    // The device id and source of the current stream of touch events.
    private int mTouchEventStreamDeviceId = -1;
    private int mTouchEventStreamSource;

    // Set to true when we discover that the touch event stream is inconsistent.
    // Reset on down or cancel.
    private boolean mTouchEventStreamIsTainted;

    // Set to true if the touch event stream is partially unhandled.
    private boolean mTouchEventStreamUnhandled;

    // Set to true if we received hover enter.
    private boolean mHoverEntered;

    // The bitset of buttons which we've received ACTION_BUTTON_PRESS for.
    private int mButtonsPressed;

    // The current violation message.
    private StringBuilder mViolationMessage;

    
Indicates that the verifier is intended to act on raw device input event streams.
Disables certain checks for invariants that are established by the input dispatcher
itself as it delivers input events, such as key repeating behavior.
/**
     * Indicates that the verifier is intended to act on raw device input event streams.
     * Disables certain checks for invariants that are established by the input dispatcher
     * itself as it delivers input events, such as key repeating behavior.
     */
    public static final int FLAG_RAW_DEVICE_INPUT = 1 << 0;

    
Creates an input consistency verifier.
Params:
caller – The object to which the verifier is attached.
flags – Flags to the verifier, or 0 if none./**
     * Creates an input consistency verifier.
     * @param caller The object to which the verifier is attached.
     * @param flags Flags to the verifier, or 0 if none.
     */
    public InputEventConsistencyVerifier(Object caller, int flags) {
        this(caller, flags, null);
    }

    
Creates an input consistency verifier.
Params:
caller – The object to which the verifier is attached.
flags – Flags to the verifier, or 0 if none.
logTag – Tag for logging. If null defaults to the short class name./**
     * Creates an input consistency verifier.
     * @param caller The object to which the verifier is attached.
     * @param flags Flags to the verifier, or 0 if none.
     * @param logTag Tag for logging. If null defaults to the short class name.
     */
    public InputEventConsistencyVerifier(Object caller, int flags, String logTag) {
        this.mCaller = caller;
        this.mFlags = flags;
        this.mLogTag = (logTag != null) ? logTag : "InputEventConsistencyVerifier";
    }

    
Determines whether the instrumentation should be enabled.
Returns:
True if it should be enabled./**
     * Determines whether the instrumentation should be enabled.
     * @return True if it should be enabled.
     */
    public static boolean isInstrumentationEnabled() {
        return IS_ENG_BUILD;
    }

    
Resets the state of the input event consistency verifier.
/**
     * Resets the state of the input event consistency verifier.
     */
    public void reset() {
        mLastEventSeq = -1;
        mLastNestingLevel = 0;
        mTrackballDown = false;
        mTrackballUnhandled = false;
        mTouchEventStreamPointers = 0;
        mTouchEventStreamIsTainted = false;
        mTouchEventStreamUnhandled = false;
        mHoverEntered = false;
        mButtonsPressed = 0;

        while (mKeyStateList != null) {
            final KeyState state = mKeyStateList;
            mKeyStateList = state.next;
            state.recycle();
        }
    }

    
Checks an arbitrary input event.
Params:
event – The event.
nestingLevel – The nesting level: 0 if called from the base class,
or 1 from a subclass.  If the event was already checked by this consistency verifier
at a higher nesting level, it will not be checked again.  Used to handle the situation
where a subclass dispatching method delegates to its superclass's dispatching method
and both dispatching methods call into the consistency verifier./**
     * Checks an arbitrary input event.
     * @param event The event.
     * @param nestingLevel The nesting level: 0 if called from the base class,
     * or 1 from a subclass.  If the event was already checked by this consistency verifier
     * at a higher nesting level, it will not be checked again.  Used to handle the situation
     * where a subclass dispatching method delegates to its superclass's dispatching method
     * and both dispatching methods call into the consistency verifier.
     */
    public void onInputEvent(InputEvent event, int nestingLevel) {
        if (event instanceof KeyEvent) {
            final KeyEvent keyEvent = (KeyEvent)event;
            onKeyEvent(keyEvent, nestingLevel);
        } else {
            final MotionEvent motionEvent = (MotionEvent)event;
            if (motionEvent.isTouchEvent()) {
                onTouchEvent(motionEvent, nestingLevel);
            } else if ((motionEvent.getSource() & InputDevice.SOURCE_CLASS_TRACKBALL) != 0) {
                onTrackballEvent(motionEvent, nestingLevel);
            } else {
                onGenericMotionEvent(motionEvent, nestingLevel);
            }
        }
    }

    
Checks a key event.
Params:
event – The event.
nestingLevel – The nesting level: 0 if called from the base class,
or 1 from a subclass.  If the event was already checked by this consistency verifier
at a higher nesting level, it will not be checked again.  Used to handle the situation
where a subclass dispatching method delegates to its superclass's dispatching method
and both dispatching methods call into the consistency verifier./**
     * Checks a key event.
     * @param event The event.
     * @param nestingLevel The nesting level: 0 if called from the base class,
     * or 1 from a subclass.  If the event was already checked by this consistency verifier
     * at a higher nesting level, it will not be checked again.  Used to handle the situation
     * where a subclass dispatching method delegates to its superclass's dispatching method
     * and both dispatching methods call into the consistency verifier.
     */
    public void onKeyEvent(KeyEvent event, int nestingLevel) {
        if (!startEvent(event, nestingLevel, EVENT_TYPE_KEY)) {
            return;
        }

        try {
            ensureMetaStateIsNormalized(event.getMetaState());

            final int action = event.getAction();
            final int deviceId = event.getDeviceId();
            final int source = event.getSource();
            final int keyCode = event.getKeyCode();
            switch (action) {
                case KeyEvent.ACTION_DOWN: {
                    KeyState state = findKeyState(deviceId, source, keyCode, /*remove*/ false);
                    if (state != null) {
                        // If the key is already down, ensure it is a repeat.
                        // We don't perform this check when processing raw device input
                        // because the input dispatcher itself is responsible for setting
                        // the key repeat count before it delivers input events.
                        if (state.unhandled) {
                            state.unhandled = false;
                        } else if ((mFlags & FLAG_RAW_DEVICE_INPUT) == 0
                                && event.getRepeatCount() == 0) {
                            problem("ACTION_DOWN but key is already down and this event "
                                    + "is not a key repeat.");
                        }
                    } else {
                        addKeyState(deviceId, source, keyCode);
                    }
                    break;
                }
                case KeyEvent.ACTION_UP: {
                    KeyState state = findKeyState(deviceId, source, keyCode, /*remove*/ true);
                    if (state == null) {
                        problem("ACTION_UP but key was not down.");
                    } else {
                        state.recycle();
                    }
                    break;
                }
                case KeyEvent.ACTION_MULTIPLE:
                    break;
                default:
                    problem("Invalid action " + KeyEvent.actionToString(action)
                            + " for key event.");
                    break;
            }
        } finally {
            finishEvent();
        }
    }

    
Checks a trackball event.
Params:
event – The event.
nestingLevel – The nesting level: 0 if called from the base class,
or 1 from a subclass.  If the event was already checked by this consistency verifier
at a higher nesting level, it will not be checked again.  Used to handle the situation
where a subclass dispatching method delegates to its superclass's dispatching method
and both dispatching methods call into the consistency verifier./**
     * Checks a trackball event.
     * @param event The event.
     * @param nestingLevel The nesting level: 0 if called from the base class,
     * or 1 from a subclass.  If the event was already checked by this consistency verifier
     * at a higher nesting level, it will not be checked again.  Used to handle the situation
     * where a subclass dispatching method delegates to its superclass's dispatching method
     * and both dispatching methods call into the consistency verifier.
     */
    public void onTrackballEvent(MotionEvent event, int nestingLevel) {
        if (!startEvent(event, nestingLevel, EVENT_TYPE_TRACKBALL)) {
            return;
        }

        try {
            ensureMetaStateIsNormalized(event.getMetaState());

            final int action = event.getAction();
            final int source = event.getSource();
            if ((source & InputDevice.SOURCE_CLASS_TRACKBALL) != 0) {
                switch (action) {
                    case MotionEvent.ACTION_DOWN:
                        if (mTrackballDown && !mTrackballUnhandled) {
                            problem("ACTION_DOWN but trackball is already down.");
                        } else {
                            mTrackballDown = true;
                            mTrackballUnhandled = false;
                        }
                        ensureHistorySizeIsZeroForThisAction(event);
                        ensurePointerCountIsOneForThisAction(event);
                        break;
                    case MotionEvent.ACTION_UP:
                        if (!mTrackballDown) {
                            problem("ACTION_UP but trackball is not down.");
                        } else {
                            mTrackballDown = false;
                            mTrackballUnhandled = false;
                        }
                        ensureHistorySizeIsZeroForThisAction(event);
                        ensurePointerCountIsOneForThisAction(event);
                        break;
                    case MotionEvent.ACTION_MOVE:
                        ensurePointerCountIsOneForThisAction(event);
                        break;
                    default:
                        problem("Invalid action " + MotionEvent.actionToString(action)
                                + " for trackball event.");
                        break;
                }

                if (mTrackballDown && event.getPressure() <= 0) {
                    problem("Trackball is down but pressure is not greater than 0.");
                } else if (!mTrackballDown && event.getPressure() != 0) {
                    problem("Trackball is up but pressure is not equal to 0.");
                }
            } else {
                problem("Source was not SOURCE_CLASS_TRACKBALL.");
            }
        } finally {
            finishEvent();
        }
    }

    
Checks a touch event.
Params:
event – The event.
nestingLevel – The nesting level: 0 if called from the base class,
or 1 from a subclass.  If the event was already checked by this consistency verifier
at a higher nesting level, it will not be checked again.  Used to handle the situation
where a subclass dispatching method delegates to its superclass's dispatching method
and both dispatching methods call into the consistency verifier./**
     * Checks a touch event.
     * @param event The event.
     * @param nestingLevel The nesting level: 0 if called from the base class,
     * or 1 from a subclass.  If the event was already checked by this consistency verifier
     * at a higher nesting level, it will not be checked again.  Used to handle the situation
     * where a subclass dispatching method delegates to its superclass's dispatching method
     * and both dispatching methods call into the consistency verifier.
     */
    public void onTouchEvent(MotionEvent event, int nestingLevel) {
        if (!startEvent(event, nestingLevel, EVENT_TYPE_TOUCH)) {
            return;
        }

        final int action = event.getAction();
        final boolean newStream = action == MotionEvent.ACTION_DOWN
                || action == MotionEvent.ACTION_CANCEL || action == MotionEvent.ACTION_OUTSIDE;
        if (newStream && (mTouchEventStreamIsTainted || mTouchEventStreamUnhandled)) {
            mTouchEventStreamIsTainted = false;
            mTouchEventStreamUnhandled = false;
            mTouchEventStreamPointers = 0;
        }
        if (mTouchEventStreamIsTainted) {
            event.setTainted(true);
        }

        try {
            ensureMetaStateIsNormalized(event.getMetaState());

            final int deviceId = event.getDeviceId();
            final int source = event.getSource();

            if (!newStream && mTouchEventStreamDeviceId != -1
                    && (mTouchEventStreamDeviceId != deviceId
                            || mTouchEventStreamSource != source)) {
                problem("Touch event stream contains events from multiple sources: "
                        + "previous device id " + mTouchEventStreamDeviceId
                        + ", previous source " + Integer.toHexString(mTouchEventStreamSource)
                        + ", new device id " + deviceId
                        + ", new source " + Integer.toHexString(source));
            }
            mTouchEventStreamDeviceId = deviceId;
            mTouchEventStreamSource = source;

            final int pointerCount = event.getPointerCount();
            if ((source & InputDevice.SOURCE_CLASS_POINTER) != 0) {
                switch (action) {
                    case MotionEvent.ACTION_DOWN:
                        if (mTouchEventStreamPointers != 0) {
                            problem("ACTION_DOWN but pointers are already down.  "
                                    + "Probably missing ACTION_UP from previous gesture.");
                        }
                        ensureHistorySizeIsZeroForThisAction(event);
                        ensurePointerCountIsOneForThisAction(event);
                        mTouchEventStreamPointers = 1 << event.getPointerId(0);
                        break;
                    case MotionEvent.ACTION_UP:
                        ensureHistorySizeIsZeroForThisAction(event);
                        ensurePointerCountIsOneForThisAction(event);
                        mTouchEventStreamPointers = 0;
                        mTouchEventStreamIsTainted = false;
                        break;
                    case MotionEvent.ACTION_MOVE: {
                        final int expectedPointerCount =
                                Integer.bitCount(mTouchEventStreamPointers);
                        if (pointerCount != expectedPointerCount) {
                            problem("ACTION_MOVE contained " + pointerCount
                                    + " pointers but there are currently "
                                    + expectedPointerCount + " pointers down.");
                            mTouchEventStreamIsTainted = true;
                        }
                        break;
                    }
                    case MotionEvent.ACTION_CANCEL:
                        mTouchEventStreamPointers = 0;
                        mTouchEventStreamIsTainted = false;
                        break;
                    case MotionEvent.ACTION_OUTSIDE:
                        if (mTouchEventStreamPointers != 0) {
                            problem("ACTION_OUTSIDE but pointers are still down.");
                        }
                        ensureHistorySizeIsZeroForThisAction(event);
                        ensurePointerCountIsOneForThisAction(event);
                        mTouchEventStreamIsTainted = false;
                        break;
                    default: {
                        final int actionMasked = event.getActionMasked();
                        final int actionIndex = event.getActionIndex();
                        if (actionMasked == MotionEvent.ACTION_POINTER_DOWN) {
                            if (mTouchEventStreamPointers == 0) {
                                problem("ACTION_POINTER_DOWN but no other pointers were down.");
                                mTouchEventStreamIsTainted = true;
                            }
                            if (actionIndex < 0 || actionIndex >= pointerCount) {
                                problem("ACTION_POINTER_DOWN index is " + actionIndex
                                        + " but the pointer count is " + pointerCount + ".");
                                mTouchEventStreamIsTainted = true;
                            } else {
                                final int id = event.getPointerId(actionIndex);
                                final int idBit = 1 << id;
                                if ((mTouchEventStreamPointers & idBit) != 0) {
                                    problem("ACTION_POINTER_DOWN specified pointer id " + id
                                            + " which is already down.");
                                    mTouchEventStreamIsTainted = true;
                                } else {
                                    mTouchEventStreamPointers |= idBit;
                                }
                            }
                            ensureHistorySizeIsZeroForThisAction(event);
                        } else if (actionMasked == MotionEvent.ACTION_POINTER_UP) {
                            if (actionIndex < 0 || actionIndex >= pointerCount) {
                                problem("ACTION_POINTER_UP index is " + actionIndex
                                        + " but the pointer count is " + pointerCount + ".");
                                mTouchEventStreamIsTainted = true;
                            } else {
                                final int id = event.getPointerId(actionIndex);
                                final int idBit = 1 << id;
                                if ((mTouchEventStreamPointers & idBit) == 0) {
                                    problem("ACTION_POINTER_UP specified pointer id " + id
                                            + " which is not currently down.");
                                    mTouchEventStreamIsTainted = true;
                                } else {
                                    mTouchEventStreamPointers &= ~idBit;
                                }
                            }
                            ensureHistorySizeIsZeroForThisAction(event);
                        } else {
                            problem("Invalid action " + MotionEvent.actionToString(action)
                                    + " for touch event.");
                        }
                        break;
                    }
                }
            } else {
                problem("Source was not SOURCE_CLASS_POINTER.");
            }
        } finally {
            finishEvent();
        }
    }

    
Checks a generic motion event.
Params:
event – The event.
nestingLevel – The nesting level: 0 if called from the base class,
or 1 from a subclass.  If the event was already checked by this consistency verifier
at a higher nesting level, it will not be checked again.  Used to handle the situation
where a subclass dispatching method delegates to its superclass's dispatching method
and both dispatching methods call into the consistency verifier./**
     * Checks a generic motion event.
     * @param event The event.
     * @param nestingLevel The nesting level: 0 if called from the base class,
     * or 1 from a subclass.  If the event was already checked by this consistency verifier
     * at a higher nesting level, it will not be checked again.  Used to handle the situation
     * where a subclass dispatching method delegates to its superclass's dispatching method
     * and both dispatching methods call into the consistency verifier.
     */
    public void onGenericMotionEvent(MotionEvent event, int nestingLevel) {
        if (!startEvent(event, nestingLevel, EVENT_TYPE_GENERIC_MOTION)) {
            return;
        }

        try {
            ensureMetaStateIsNormalized(event.getMetaState());

            final int action = event.getAction();
            final int source = event.getSource();
            final int buttonState = event.getButtonState();
            final int actionButton = event.getActionButton();
            if ((source & InputDevice.SOURCE_CLASS_POINTER) != 0) {
                switch (action) {
                    case MotionEvent.ACTION_HOVER_ENTER:
                        ensurePointerCountIsOneForThisAction(event);
                        mHoverEntered = true;
                        break;
                    case MotionEvent.ACTION_HOVER_MOVE:
                        ensurePointerCountIsOneForThisAction(event);
                        break;
                    case MotionEvent.ACTION_HOVER_EXIT:
                        ensurePointerCountIsOneForThisAction(event);
                        if (!mHoverEntered) {
                            problem("ACTION_HOVER_EXIT without prior ACTION_HOVER_ENTER");
                        }
                        mHoverEntered = false;
                        break;
                    case MotionEvent.ACTION_SCROLL:
                        ensureHistorySizeIsZeroForThisAction(event);
                        ensurePointerCountIsOneForThisAction(event);
                        break;
                    case MotionEvent.ACTION_BUTTON_PRESS:
                        ensureActionButtonIsNonZeroForThisAction(event);
                        if ((mButtonsPressed & actionButton) != 0) {
                            problem("Action button for ACTION_BUTTON_PRESS event is " +
                                    actionButton + ", but it has already been pressed and " +
                                    "has yet to be released.");
                        }

                        mButtonsPressed |= actionButton;
                        // The system will automatically mirror the stylus buttons onto the button
                        // state as the old set of generic buttons for apps targeting pre-M. If
                        // it looks this has happened, go ahead and set the generic buttons as
                        // pressed to prevent spurious errors.
                        if (actionButton == MotionEvent.BUTTON_STYLUS_PRIMARY &&
                                (buttonState & MotionEvent.BUTTON_SECONDARY) != 0) {
                            mButtonsPressed |= MotionEvent.BUTTON_SECONDARY;
                        } else if (actionButton == MotionEvent.BUTTON_STYLUS_SECONDARY &&
                                (buttonState & MotionEvent.BUTTON_TERTIARY) != 0) {
                            mButtonsPressed |= MotionEvent.BUTTON_TERTIARY;
                        }

                        if (mButtonsPressed != buttonState) {
                            problem(String.format("Reported button state differs from " +
                                    "expected button state based on press and release events. " +
                                    "Is 0x%08x but expected 0x%08x.",
                                    buttonState, mButtonsPressed));
                        }
                        break;
                    case MotionEvent.ACTION_BUTTON_RELEASE:
                        ensureActionButtonIsNonZeroForThisAction(event);
                        if ((mButtonsPressed & actionButton) != actionButton) {
                            problem("Action button for ACTION_BUTTON_RELEASE event is " +
                                    actionButton + ", but it was either never pressed or has " +
                                    "already been released.");
                        }

                        mButtonsPressed &= ~actionButton;
                        // The system will automatically mirror the stylus buttons onto the button
                        // state as the old set of generic buttons for apps targeting pre-M. If
                        // it looks this has happened, go ahead and set the generic buttons as
                        // released to prevent spurious errors.
                        if (actionButton == MotionEvent.BUTTON_STYLUS_PRIMARY &&
                                (buttonState & MotionEvent.BUTTON_SECONDARY) == 0) {
                            mButtonsPressed &= ~MotionEvent.BUTTON_SECONDARY;
                        } else if (actionButton == MotionEvent.BUTTON_STYLUS_SECONDARY &&
                                (buttonState & MotionEvent.BUTTON_TERTIARY) == 0) {
                            mButtonsPressed &= ~MotionEvent.BUTTON_TERTIARY;
                        }

                        if (mButtonsPressed != buttonState) {
                            problem(String.format("Reported button state differs from " +
                                    "expected button state based on press and release events. " +
                                    "Is 0x%08x but expected 0x%08x.",
                                    buttonState, mButtonsPressed));
                        }
                        break;
                    default:
                        problem("Invalid action for generic pointer event.");
                        break;
                }
            } else if ((source & InputDevice.SOURCE_CLASS_JOYSTICK) != 0) {
                switch (action) {
                    case MotionEvent.ACTION_MOVE:
                        ensurePointerCountIsOneForThisAction(event);
                        break;
                    default:
                        problem("Invalid action for generic joystick event.");
                        break;
                }
            }
        } finally {
            finishEvent();
        }
    }

    
Notifies the verifier that a given event was unhandled and the rest of the trace for the event should be ignored. This method should only be called if the event was previously checked by the consistency verifier using onInputEvent and other methods. 
Params:
event – The event.
nestingLevel – The nesting level: 0 if called from the base class,
or 1 from a subclass.  If the event was already checked by this consistency verifier
at a higher nesting level, it will not be checked again.  Used to handle the situation
where a subclass dispatching method delegates to its superclass's dispatching method
and both dispatching methods call into the consistency verifier./**
     * Notifies the verifier that a given event was unhandled and the rest of the
     * trace for the event should be ignored.
     * This method should only be called if the event was previously checked by
     * the consistency verifier using {@link #onInputEvent} and other methods.
     * @param event The event.
     * @param nestingLevel The nesting level: 0 if called from the base class,
     * or 1 from a subclass.  If the event was already checked by this consistency verifier
     * at a higher nesting level, it will not be checked again.  Used to handle the situation
     * where a subclass dispatching method delegates to its superclass's dispatching method
     * and both dispatching methods call into the consistency verifier.
     */
    public void onUnhandledEvent(InputEvent event, int nestingLevel) {
        if (nestingLevel != mLastNestingLevel) {
            return;
        }

        if (mRecentEventsUnhandled != null) {
            mRecentEventsUnhandled[mMostRecentEventIndex] = true;
        }

        if (event instanceof KeyEvent) {
            final KeyEvent keyEvent = (KeyEvent)event;
            final int deviceId = keyEvent.getDeviceId();
            final int source = keyEvent.getSource();
            final int keyCode = keyEvent.getKeyCode();
            final KeyState state = findKeyState(deviceId, source, keyCode, /*remove*/ false);
            if (state != null) {
                state.unhandled = true;
            }
        } else {
            final MotionEvent motionEvent = (MotionEvent)event;
            if (motionEvent.isTouchEvent()) {
                mTouchEventStreamUnhandled = true;
            } else if ((motionEvent.getSource() & InputDevice.SOURCE_CLASS_TRACKBALL) != 0) {
                if (mTrackballDown) {
                    mTrackballUnhandled = true;
                }
            }
        }
    }

    private void ensureMetaStateIsNormalized(int metaState) {
        final int normalizedMetaState = KeyEvent.normalizeMetaState(metaState);
        if (normalizedMetaState != metaState) {
            problem(String.format("Metastate not normalized.  Was 0x%08x but expected 0x%08x.",
                    metaState, normalizedMetaState));
        }
    }

    private void ensurePointerCountIsOneForThisAction(MotionEvent event) {
        final int pointerCount = event.getPointerCount();
        if (pointerCount != 1) {
            problem("Pointer count is " + pointerCount + " but it should always be 1 for "
                    + MotionEvent.actionToString(event.getAction()));
        }
    }

    private void ensureActionButtonIsNonZeroForThisAction(MotionEvent event) {
        final int actionButton = event.getActionButton();
        if (actionButton == 0) {
            problem("No action button set. Action button should always be non-zero for " +
                    MotionEvent.actionToString(event.getAction()));

        }
    }

    private void ensureHistorySizeIsZeroForThisAction(MotionEvent event) {
        final int historySize = event.getHistorySize();
        if (historySize != 0) {
            problem("History size is " + historySize + " but it should always be 0 for "
                    + MotionEvent.actionToString(event.getAction()));
        }
    }

    private boolean startEvent(InputEvent event, int nestingLevel, String eventType) {
        // Ignore the event if we already checked it at a higher nesting level.
        final int seq = event.getSequenceNumber();
        if (seq == mLastEventSeq && nestingLevel < mLastNestingLevel
                && eventType == mLastEventType) {
            return false;
        }

        if (nestingLevel > 0) {
            mLastEventSeq = seq;
            mLastEventType = eventType;
            mLastNestingLevel = nestingLevel;
        } else {
            mLastEventSeq = -1;
            mLastEventType = null;
            mLastNestingLevel = 0;
        }

        mCurrentEvent = event;
        mCurrentEventType = eventType;
        return true;
    }

    private void finishEvent() {
        if (mViolationMessage != null && mViolationMessage.length() != 0) {
            if (!mCurrentEvent.isTainted()) {
                // Write a log message only if the event was not already tainted.
                mViolationMessage.append("\n  in ").append(mCaller);
                mViolationMessage.append("\n  ");
                appendEvent(mViolationMessage, 0, mCurrentEvent, false);

                if (RECENT_EVENTS_TO_LOG != 0 && mRecentEvents != null) {
                    mViolationMessage.append("\n  -- recent events --");
                    for (int i = 0; i < RECENT_EVENTS_TO_LOG; i++) {
                        final int index = (mMostRecentEventIndex + RECENT_EVENTS_TO_LOG - i)
                                % RECENT_EVENTS_TO_LOG;
                        final InputEvent event = mRecentEvents[index];
                        if (event == null) {
                            break;
                        }
                        mViolationMessage.append("\n  ");
                        appendEvent(mViolationMessage, i + 1, event, mRecentEventsUnhandled[index]);
                    }
                }

                Log.d(mLogTag, mViolationMessage.toString());

                // Taint the event so that we do not generate additional violations from it
                // further downstream.
                mCurrentEvent.setTainted(true);
            }
            mViolationMessage.setLength(0);
        }

        if (RECENT_EVENTS_TO_LOG != 0) {
            if (mRecentEvents == null) {
                mRecentEvents = new InputEvent[RECENT_EVENTS_TO_LOG];
                mRecentEventsUnhandled = new boolean[RECENT_EVENTS_TO_LOG];
            }
            final int index = (mMostRecentEventIndex + 1) % RECENT_EVENTS_TO_LOG;
            mMostRecentEventIndex = index;
            if (mRecentEvents[index] != null) {
                mRecentEvents[index].recycle();
            }
            mRecentEvents[index] = mCurrentEvent.copy();
            mRecentEventsUnhandled[index] = false;
        }

        mCurrentEvent = null;
        mCurrentEventType = null;
    }

    private static void appendEvent(StringBuilder message, int index,
            InputEvent event, boolean unhandled) {
        message.append(index).append(": sent at ").append(event.getEventTimeNano());
        message.append(", ");
        if (unhandled) {
            message.append("(unhandled) ");
        }
        message.append(event);
    }

    private void problem(String message) {
        if (mViolationMessage == null) {
            mViolationMessage = new StringBuilder();
        }
        if (mViolationMessage.length() == 0) {
            mViolationMessage.append(mCurrentEventType).append(": ");
        } else {
            mViolationMessage.append("\n  ");
        }
        mViolationMessage.append(message);
    }

    private KeyState findKeyState(int deviceId, int source, int keyCode, boolean remove) {
        KeyState last = null;
        KeyState state = mKeyStateList;
        while (state != null) {
            if (state.deviceId == deviceId && state.source == source
                    && state.keyCode == keyCode) {
                if (remove) {
                    if (last != null) {
                        last.next = state.next;
                    } else {
                        mKeyStateList = state.next;
                    }
                    state.next = null;
                }
                return state;
            }
            last = state;
            state = state.next;
        }
        return null;
    }

    private void addKeyState(int deviceId, int source, int keyCode) {
        KeyState state = KeyState.obtain(deviceId, source, keyCode);
        state.next = mKeyStateList;
        mKeyStateList = state;
    }

    private static final class KeyState {
        private static Object mRecycledListLock = new Object();
        private static KeyState mRecycledList;

        public KeyState next;
        public int deviceId;
        public int source;
        public int keyCode;
        public boolean unhandled;

        private KeyState() {
        }

        public static KeyState obtain(int deviceId, int source, int keyCode) {
            KeyState state;
            synchronized (mRecycledListLock) {
                state = mRecycledList;
                if (state != null) {
                    mRecycledList = state.next;
                } else {
                    state = new KeyState();
                }
            }
            state.deviceId = deviceId;
            state.source = source;
            state.keyCode = keyCode;
            state.unhandled = false;
            return state;
        }

        public void recycle() {
            synchronized (mRecycledListLock) {
                next = mRecycledList;
                mRecycledList = next;
            }
        }
    }
}