package com.android.systemui.statusbar

import android.animation.Animator
import android.animation.AnimatorListenerAdapter
import android.animation.ObjectAnimator
import android.animation.ValueAnimator
import android.content.Context
import android.content.res.Configuration
import android.os.SystemClock
import android.util.IndentingPrintWriter
import android.util.MathUtils
import android.view.MotionEvent
import android.view.View
import android.view.ViewConfiguration
import androidx.annotation.VisibleForTesting
import com.android.systemui.Dumpable
import com.android.systemui.ExpandHelper
import com.android.systemui.Gefingerpoken
import com.android.systemui.R
import com.android.systemui.animation.Interpolators
import com.android.systemui.biometrics.UdfpsKeyguardViewController
import com.android.systemui.classifier.Classifier
import com.android.systemui.classifier.FalsingCollector
import com.android.systemui.dagger.SysUISingleton
import com.android.systemui.dump.DumpManager
import com.android.systemui.keyguard.WakefulnessLifecycle
import com.android.systemui.media.MediaHierarchyManager
import com.android.systemui.plugins.ActivityStarter.OnDismissAction
import com.android.systemui.plugins.FalsingManager
import com.android.systemui.plugins.qs.QS
import com.android.systemui.plugins.statusbar.StatusBarStateController
import com.android.systemui.statusbar.notification.collection.NotificationEntry
import com.android.systemui.statusbar.notification.row.ExpandableNotificationRow
import com.android.systemui.statusbar.notification.row.ExpandableView
import com.android.systemui.statusbar.notification.stack.AmbientState
import com.android.systemui.statusbar.notification.stack.NotificationStackScrollLayoutController
import com.android.systemui.statusbar.phone.KeyguardBypassController
import com.android.systemui.statusbar.phone.LSShadeTransitionLogger
import com.android.systemui.statusbar.phone.NotificationPanelViewController
import com.android.systemui.statusbar.phone.ScrimController
import com.android.systemui.statusbar.phone.StatusBar
import com.android.systemui.statusbar.policy.ConfigurationController
import com.android.systemui.util.Utils
import java.io.FileDescriptor
import java.io.PrintWriter
import javax.inject.Inject

private const val SPRING_BACK_ANIMATION_LENGTH_MS = 375L
private const val RUBBERBAND_FACTOR_STATIC = 0.15f
private const val RUBBERBAND_FACTOR_EXPANDABLE = 0.5f

/**
 * A class that controls the lockscreen to shade transition
 */
@SysUISingleton
class LockscreenShadeTransitionController @Inject constructor(
    private val statusBarStateController: SysuiStatusBarStateController,
    private val logger: LSShadeTransitionLogger,
    private val keyguardBypassController: KeyguardBypassController,
    private val lockScreenUserManager: NotificationLockscreenUserManager,
    private val falsingCollector: FalsingCollector,
    private val ambientState: AmbientState,
    private val mediaHierarchyManager: MediaHierarchyManager,
    private val scrimController: ScrimController,
    private val depthController: NotificationShadeDepthController,
    private val context: Context,
    wakefulnessLifecycle: WakefulnessLifecycle,
    configurationController: ConfigurationController,
    falsingManager: FalsingManager,
    dumpManager: DumpManager,
) : Dumpable {
    private var pulseHeight: Float = 0f
    private var useSplitShade: Boolean = false
    private lateinit var nsslController: NotificationStackScrollLayoutController
    lateinit var notificationPanelController: NotificationPanelViewController
    lateinit var statusbar: StatusBar
    lateinit var qS: QS

    /**
     * A handler that handles the next keyguard dismiss animation.
     */
    private var animationHandlerOnKeyguardDismiss: ((Long) -> Unit)? = null

    /**
     * The entry that was just dragged down on.
     */
    private var draggedDownEntry: NotificationEntry? = null

    /**
     * The current animator if any
     */
    @VisibleForTesting
    internal var dragDownAnimator: ValueAnimator? = null

    /**
     * The current pulse height animator if any
     */
    @VisibleForTesting
    internal var pulseHeightAnimator: ValueAnimator? = null

    /**
     * Distance that the full shade transition takes in order for scrim to fully transition to
     * the shade (in alpha)
     */
    private var scrimTransitionDistance = 0

    /**
     * Distance that the full transition takes in order for us to fully transition to the shade
     */
    private var fullTransitionDistance = 0

    /**
     * Flag to make sure that the dragDownAmount is applied to the listeners even when in the
     * locked down shade.
     */
    private var forceApplyAmount = false

    /**
     * A flag to suppress the default animation when unlocking in the locked down shade.
     */
    private var nextHideKeyguardNeedsNoAnimation = false

    /**
     * Are we currently waking up to the shade locked
     */
    var isWakingToShadeLocked: Boolean = false
        private set

    /**
     * The distance until we're showing the notifications when pulsing
     */
    val distanceUntilShowingPulsingNotifications
        get() = scrimTransitionDistance

    /**
     * The udfpsKeyguardViewController if it exists.
     */
    var udfpsKeyguardViewController: UdfpsKeyguardViewController? = null

    /**
     * The touch helper responsible for the drag down animation.
     */
    val touchHelper = DragDownHelper(falsingManager, falsingCollector, this, context)

    init {
        updateResources()
        configurationController.addCallback(object : ConfigurationController.ConfigurationListener {
            override fun onConfigChanged(newConfig: Configuration?) {
                updateResources()
                touchHelper.updateResources(context)
            }
        })
        dumpManager.registerDumpable(this)
        statusBarStateController.addCallback(object : StatusBarStateController.StateListener {
            override fun onExpandedChanged(isExpanded: Boolean) {
                // safeguard: When the panel is fully collapsed, let's make sure to reset.
                // See b/198098523
                if (!isExpanded) {
                    if (dragDownAmount != 0f && dragDownAnimator?.isRunning != true) {
                        logger.logDragDownAmountResetWhenFullyCollapsed()
                        dragDownAmount = 0f
                    }
                    if (pulseHeight != 0f && pulseHeightAnimator?.isRunning != true) {
                        logger.logPulseHeightNotResetWhenFullyCollapsed()
                        setPulseHeight(0f, animate = false)
                    }
                }
            }
        })
        wakefulnessLifecycle.addObserver(object : WakefulnessLifecycle.Observer {
            override fun onPostFinishedWakingUp() {
                // when finishing waking up, the UnlockedScreenOffAnimation has another attempt
                // to reset keyguard. Let's do it in post
                isWakingToShadeLocked = false
            }
        })
    }

    private fun updateResources() {
        scrimTransitionDistance = context.resources.getDimensionPixelSize(
                R.dimen.lockscreen_shade_scrim_transition_distance)
        fullTransitionDistance = context.resources.getDimensionPixelSize(
                R.dimen.lockscreen_shade_qs_transition_distance)
        useSplitShade = Utils.shouldUseSplitNotificationShade(context.resources)
    }

    fun setStackScroller(nsslController: NotificationStackScrollLayoutController) {
        this.nsslController = nsslController
        touchHelper.host = nsslController.view
        touchHelper.expandCallback = nsslController.expandHelperCallback
    }

    /**
     * Initialize the shelf controller such that clicks on it will expand the shade
     */
    fun bindController(notificationShelfController: NotificationShelfController) {
        // Bind the click listener of the shelf to go to the full shade
        notificationShelfController.setOnClickListener {
            if (statusBarStateController.state == StatusBarState.KEYGUARD) {
                statusbar.wakeUpIfDozing(SystemClock.uptimeMillis(), it, "SHADE_CLICK")
                goToLockedShade(it)
            }
        }
    }

    /**
     * @return true if the interaction is accepted, false if it should be cancelled
     */
    internal fun canDragDown(): Boolean {
        return (statusBarStateController.state == StatusBarState.KEYGUARD ||
                nsslController.isInLockedDownShade()) &&
                (qS.isFullyCollapsed || useSplitShade)
    }

    /**
     * Called by the touch helper when when a gesture has completed all the way and released.
     */
    internal fun onDraggedDown(startingChild: View?, dragLengthY: Int) {
        if (canDragDown()) {
            val cancelRunnable = Runnable {
                logger.logGoingToLockedShadeAborted()
                setDragDownAmountAnimated(0f)
            }
            if (nsslController.isInLockedDownShade()) {
                logger.logDraggedDownLockDownShade(startingChild)
                statusBarStateController.setLeaveOpenOnKeyguardHide(true)
                statusbar.dismissKeyguardThenExecute(OnDismissAction {
                    nextHideKeyguardNeedsNoAnimation = true
                    false
                }, cancelRunnable, false /* afterKeyguardGone */)
            } else {
                logger.logDraggedDown(startingChild, dragLengthY)
                if (!ambientState.isDozing() || startingChild != null) {
                    // go to locked shade while animating the drag down amount from its current
                    // value
                    val animationHandler = { delay: Long ->
                        if (startingChild is ExpandableNotificationRow) {
                            startingChild.onExpandedByGesture(
                                    true /* drag down is always an open */)
                        }
                        notificationPanelController.animateToFullShade(delay)
                        notificationPanelController.setTransitionToFullShadeAmount(0f,
                                true /* animated */, delay)

                        // Let's reset ourselves, ready for the next animation

                        // changing to shade locked will make isInLockDownShade true, so let's
                        // override that
                        forceApplyAmount = true
                        // Reset the behavior. At this point the animation is already started
                        dragDownAmount = 0f
                        forceApplyAmount = false
                    }
                    goToLockedShadeInternal(startingChild, animationHandler, cancelRunnable)
                }
            }
        } else {
            logger.logUnSuccessfulDragDown(startingChild)
            setDragDownAmountAnimated(0f)
        }
    }

    /**
     * Called by the touch helper when the drag down was aborted and should be reset.
     */
    internal fun onDragDownReset() {
        logger.logDragDownAborted()
        nsslController.setDimmed(true /* dimmed */, true /* animated */)
        nsslController.resetScrollPosition()
        nsslController.resetCheckSnoozeLeavebehind()
        setDragDownAmountAnimated(0f)
    }

    /**
     * The user has dragged either above or below the threshold which changes the dimmed state.
     * @param above whether they dragged above it
     */
    internal fun onCrossedThreshold(above: Boolean) {
        nsslController.setDimmed(!above /* dimmed */, true /* animate */)
    }

    /**
     * Called by the touch helper when the drag down was started
     */
    internal fun onDragDownStarted(startingChild: ExpandableView?) {
        logger.logDragDownStarted(startingChild)
        nsslController.cancelLongPress()
        nsslController.checkSnoozeLeavebehind()
        dragDownAnimator?.apply {
            if (isRunning) {
                logger.logAnimationCancelled(isPulse = false)
                cancel()
            }
        }
    }

    /**
     * Do we need a falsing check currently?
     */
    internal val isFalsingCheckNeeded: Boolean
        get() = statusBarStateController.state == StatusBarState.KEYGUARD

    /**
     * Is dragging down enabled on a given view
     * @param view The view to check or `null` to check if it's enabled at all
     */
    internal fun isDragDownEnabledForView(view: ExpandableView?): Boolean {
        if (isDragDownAnywhereEnabled) {
            return true
        }
        if (nsslController.isInLockedDownShade()) {
            if (view == null) {
                // Dragging down is allowed in general
                return true
            }
            if (view is ExpandableNotificationRow) {
                // Only drag down on sensitive views, otherwise the ExpandHelper will take this
                return view.entry.isSensitive
            }
        }
        return false
    }

    /**
     * @return if drag down is enabled anywhere, not just on selected views.
     */
    internal val isDragDownAnywhereEnabled: Boolean
        get() = (statusBarStateController.getState() == StatusBarState.KEYGUARD &&
                !keyguardBypassController.bypassEnabled &&
                (qS.isFullyCollapsed || useSplitShade))

    /**
     * The amount in pixels that the user has dragged down.
     */
    internal var dragDownAmount = 0f
        set(value) {
            if (field != value || forceApplyAmount) {
                field = value
                if (!nsslController.isInLockedDownShade() || field == 0f || forceApplyAmount) {
                    nsslController.setTransitionToFullShadeAmount(field)
                    notificationPanelController.setTransitionToFullShadeAmount(field,
                            false /* animate */, 0 /* delay */)
                    val progress = MathUtils.saturate(dragDownAmount / scrimTransitionDistance)
                    qS.setTransitionToFullShadeAmount(field, progress)
                    // TODO: appear media also in split shade
                    val mediaAmount = if (useSplitShade) 0f else field
                    mediaHierarchyManager.setTransitionToFullShadeAmount(mediaAmount)
                    transitionToShadeAmountCommon(field)
                }
            }
        }

    private fun transitionToShadeAmountCommon(dragDownAmount: Float) {
        val scrimProgress = MathUtils.saturate(dragDownAmount / scrimTransitionDistance)
        scrimController.setTransitionToFullShadeProgress(scrimProgress)
        // Fade out all content only visible on the lockscreen
        notificationPanelController.setKeyguardOnlyContentAlpha(1.0f - scrimProgress)
        depthController.transitionToFullShadeProgress = scrimProgress
        udfpsKeyguardViewController?.setTransitionToFullShadeProgress(scrimProgress)
    }

    private fun setDragDownAmountAnimated(
        target: Float,
        delay: Long = 0,
        endlistener: (() -> Unit)? = null
    ) {
        logger.logDragDownAnimation(target)
        val dragDownAnimator = ValueAnimator.ofFloat(dragDownAmount, target)
        dragDownAnimator.interpolator = Interpolators.FAST_OUT_SLOW_IN
        dragDownAnimator.duration = SPRING_BACK_ANIMATION_LENGTH_MS
        dragDownAnimator.addUpdateListener { animation: ValueAnimator ->
            dragDownAmount = animation.animatedValue as Float
        }
        if (delay > 0) {
            dragDownAnimator.startDelay = delay
        }
        if (endlistener != null) {
            dragDownAnimator.addListener(object : AnimatorListenerAdapter() {
                override fun onAnimationEnd(animation: Animator?) {
                    endlistener.invoke()
                }
            })
        }
        dragDownAnimator.start()
        this.dragDownAnimator = dragDownAnimator
    }

    /**
     * Animate appear the drag down amount.
     */
    private fun animateAppear(delay: Long = 0) {
        // changing to shade locked will make isInLockDownShade true, so let's override
        // that
        forceApplyAmount = true

        // we set the value initially to 1 pixel, since that will make sure we're
        // transitioning to the full shade. this is important to avoid flickering,
        // as the below animation only starts once the shade is unlocked, which can
        // be a couple of frames later. if we're setting it to 0, it will use the
        // default inset and therefore flicker
        dragDownAmount = 1f
        setDragDownAmountAnimated(fullTransitionDistance.toFloat(), delay = delay) {
            // End listener:
            // Reset
            dragDownAmount = 0f
            forceApplyAmount = false
        }
    }

    /**
     * Ask this controller to go to the locked shade, changing the state change and doing
     * an animation, where the qs appears from 0 from the top
     *
     * If secure with redaction: Show bouncer, go to unlocked shade.
     * If secure without redaction or no security: Go to [StatusBarState.SHADE_LOCKED].
     *
     * @param expandView The view to expand after going to the shade
     * @param needsQSAnimation if this needs the quick settings to slide in from the top or if
     *                         that's already handled separately
     */
    @JvmOverloads
    fun goToLockedShade(expandedView: View?, needsQSAnimation: Boolean = true) {
        val isKeyguard = statusBarStateController.state == StatusBarState.KEYGUARD
        logger.logTryGoToLockedShade(isKeyguard)
        if (isKeyguard) {
            val animationHandler: ((Long) -> Unit)?
            if (needsQSAnimation) {
                // Let's use the default animation
                animationHandler = null
            } else {
                // Let's only animate notifications
                animationHandler = { delay: Long ->
                    notificationPanelController.animateToFullShade(delay)
                }
            }
            goToLockedShadeInternal(expandedView, animationHandler,
                    cancelAction = null)
        }
    }

    /**
     * If secure with redaction: Show bouncer, go to unlocked shade.
     *
     * If secure without redaction or no security: Go to [StatusBarState.SHADE_LOCKED].
     *
     * @param expandView The view to expand after going to the shade.
     * @param animationHandler The handler which performs the go to full shade animation. If null,
     *                         the default handler will do the animation, otherwise the caller is
     *                         responsible for the animation. The input value is a Long for the
     *                         delay for the animation.
     * @param cancelAction The runnable to invoke when the transition is aborted. This happens if
     *                     the user goes to the bouncer and goes back.
     */
    private fun goToLockedShadeInternal(
        expandView: View?,
        animationHandler: ((Long) -> Unit)? = null,
        cancelAction: Runnable? = null
    ) {
        if (statusbar.isShadeDisabled) {
            cancelAction?.run()
            logger.logShadeDisabledOnGoToLockedShade()
            return
        }
        var userId: Int = lockScreenUserManager.getCurrentUserId()
        var entry: NotificationEntry? = null
        if (expandView is ExpandableNotificationRow) {
            entry = expandView.entry
            entry.setUserExpanded(true /* userExpanded */, true /* allowChildExpansion */)
            // Indicate that the group expansion is changing at this time -- this way the group
            // and children backgrounds / divider animations will look correct.
            entry.setGroupExpansionChanging(true)
            userId = entry.sbn.userId
        }
        var fullShadeNeedsBouncer = (!lockScreenUserManager.userAllowsPrivateNotificationsInPublic(
                lockScreenUserManager.getCurrentUserId()) ||
                !lockScreenUserManager.shouldShowLockscreenNotifications() ||
                falsingCollector.shouldEnforceBouncer())
        if (keyguardBypassController.bypassEnabled) {
            fullShadeNeedsBouncer = false
        }
        if (lockScreenUserManager.isLockscreenPublicMode(userId) && fullShadeNeedsBouncer) {
            statusBarStateController.setLeaveOpenOnKeyguardHide(true)
            var onDismissAction: OnDismissAction? = null
            if (animationHandler != null) {
                onDismissAction = OnDismissAction {
                    // We're waiting on keyguard to hide before triggering the action,
                    // as that will make the animation work properly
                    animationHandlerOnKeyguardDismiss = animationHandler
                    false
                }
            }
            val cancelHandler = Runnable {
                draggedDownEntry?.apply {
                    setUserLocked(false)
                    notifyHeightChanged(false /* needsAnimation */)
                    draggedDownEntry = null
                }
                cancelAction?.run()
            }
            logger.logShowBouncerOnGoToLockedShade()
            statusbar.showBouncerWithDimissAndCancelIfKeyguard(onDismissAction, cancelHandler)
            draggedDownEntry = entry
        } else {
            logger.logGoingToLockedShade(animationHandler != null)
            if (statusBarStateController.isDozing) {
                // Make sure we don't go back to keyguard immediately again after waking up
                isWakingToShadeLocked = true
            }
            statusBarStateController.setState(StatusBarState.SHADE_LOCKED)
            // This call needs to be after updating the shade state since otherwise
            // the scrimstate resets too early
            if (animationHandler != null) {
                animationHandler.invoke(0 /* delay */)
            } else {
                performDefaultGoToFullShadeAnimation(0)
            }
        }
    }

    /**
     * Notify this handler that the keyguard was just dismissed and that a animation to
     * the full shade should happen.
     *
     * @param delay the delay to do the animation with
     * @param previousState which state were we in when we hid the keyguard?
     */
    fun onHideKeyguard(delay: Long, previousState: Int) {
        logger.logOnHideKeyguard()
        if (animationHandlerOnKeyguardDismiss != null) {
            animationHandlerOnKeyguardDismiss!!.invoke(delay)
            animationHandlerOnKeyguardDismiss = null
        } else {
            if (nextHideKeyguardNeedsNoAnimation) {
                nextHideKeyguardNeedsNoAnimation = false
            } else if (previousState != StatusBarState.SHADE_LOCKED) {
                // No animation necessary if we already were in the shade locked!
                performDefaultGoToFullShadeAnimation(delay)
            }
        }
        draggedDownEntry?.apply {
            setUserLocked(false)
            draggedDownEntry = null
        }
    }

    /**
     * Perform the default appear animation when going to the full shade. This is called when
     * not triggered by gestures, e.g. when clicking on the shelf or expand button.
     */
    private fun performDefaultGoToFullShadeAnimation(delay: Long) {
        logger.logDefaultGoToFullShadeAnimation(delay)
        notificationPanelController.animateToFullShade(delay)
        animateAppear(delay)
    }

    //
    // PULSE EXPANSION
    //

    /**
     * Set the height how tall notifications are pulsing. This is only set whenever we are expanding
     * from a pulse and determines how much the notifications are expanded.
     */
    fun setPulseHeight(height: Float, animate: Boolean = false) {
        if (animate) {
            val pulseHeightAnimator = ValueAnimator.ofFloat(pulseHeight, height)
            pulseHeightAnimator.interpolator = Interpolators.FAST_OUT_SLOW_IN
            pulseHeightAnimator.duration = SPRING_BACK_ANIMATION_LENGTH_MS
            pulseHeightAnimator.addUpdateListener { animation: ValueAnimator ->
                setPulseHeight(animation.animatedValue as Float)
            }
            pulseHeightAnimator.start()
            this.pulseHeightAnimator = pulseHeightAnimator
        } else {
            pulseHeight = height
            val overflow = nsslController.setPulseHeight(height)
            notificationPanelController.setOverStrechAmount(overflow)
            val transitionHeight = if (keyguardBypassController.bypassEnabled) height else 0.0f
            transitionToShadeAmountCommon(transitionHeight)
        }
    }

    /**
     * Finish the pulse animation when the touch interaction finishes
     * @param cancelled was the interaction cancelled and this is a reset?
     */
    fun finishPulseAnimation(cancelled: Boolean) {
        logger.logPulseExpansionFinished(cancelled)
        if (cancelled) {
            setPulseHeight(0f, animate = true)
        } else {
            notificationPanelController.onPulseExpansionFinished()
            setPulseHeight(0f, animate = false)
        }
    }

    /**
     * Notify this class that a pulse expansion is starting
     */
    fun onPulseExpansionStarted() {
        logger.logPulseExpansionStarted()
        pulseHeightAnimator?.apply {
            if (isRunning) {
                logger.logAnimationCancelled(isPulse = true)
                cancel()
            }
        }
    }

    override fun dump(fd: FileDescriptor, pw: PrintWriter, args: Array<out String>) {
        IndentingPrintWriter(pw, "  ").let {
            it.println("LSShadeTransitionController:")
            it.increaseIndent()
            it.println("pulseHeight: $pulseHeight")
            it.println("useSplitShade: $useSplitShade")
            it.println("dragDownAmount: $dragDownAmount")
            it.println("isDragDownAnywhereEnabled: $isDragDownAnywhereEnabled")
            it.println("isFalsingCheckNeeded: $isFalsingCheckNeeded")
            it.println("isWakingToShadeLocked: $isWakingToShadeLocked")
            it.println("hasPendingHandlerOnKeyguardDismiss: " +
                "${animationHandlerOnKeyguardDismiss != null}")
        }
    }
}

/**
 * A utility class to enable the downward swipe on the lockscreen to go to the full shade and expand
 * the notification where the drag started.
 */
class DragDownHelper(
    private val falsingManager: FalsingManager,
    private val falsingCollector: FalsingCollector,
    private val dragDownCallback: LockscreenShadeTransitionController,
    context: Context
) : Gefingerpoken {

    private var dragDownAmountOnStart = 0.0f
    lateinit var expandCallback: ExpandHelper.Callback
    lateinit var host: View

    private var minDragDistance = 0
    private var initialTouchX = 0f
    private var initialTouchY = 0f
    private var touchSlop = 0f
    private var slopMultiplier = 0f
    private val temp2 = IntArray(2)
    private var draggedFarEnough = false
    private var startingChild: ExpandableView? = null
    private var lastHeight = 0f
    var isDraggingDown = false
        private set

    private val isFalseTouch: Boolean
        get() {
            return if (!dragDownCallback.isFalsingCheckNeeded) {
                false
            } else {
                falsingManager.isFalseTouch(Classifier.NOTIFICATION_DRAG_DOWN) || !draggedFarEnough
            }
        }

    val isDragDownEnabled: Boolean
        get() = dragDownCallback.isDragDownEnabledForView(null)

    init {
        updateResources(context)
    }

    fun updateResources(context: Context) {
        minDragDistance = context.resources.getDimensionPixelSize(
                R.dimen.keyguard_drag_down_min_distance)
        val configuration = ViewConfiguration.get(context)
        touchSlop = configuration.scaledTouchSlop.toFloat()
        slopMultiplier = configuration.scaledAmbiguousGestureMultiplier
    }

    override fun onInterceptTouchEvent(event: MotionEvent): Boolean {
        val x = event.x
        val y = event.y
        when (event.actionMasked) {
            MotionEvent.ACTION_DOWN -> {
                draggedFarEnough = false
                isDraggingDown = false
                startingChild = null
                initialTouchY = y
                initialTouchX = x
            }
            MotionEvent.ACTION_MOVE -> {
                val h = y - initialTouchY
                // Adjust the touch slop if another gesture may be being performed.
                val touchSlop = if (event.classification
                        == MotionEvent.CLASSIFICATION_AMBIGUOUS_GESTURE)
                    touchSlop * slopMultiplier
                else
                    touchSlop
                if (h > touchSlop && h > Math.abs(x - initialTouchX)) {
                    falsingCollector.onNotificationStartDraggingDown()
                    isDraggingDown = true
                    captureStartingChild(initialTouchX, initialTouchY)
                    initialTouchY = y
                    initialTouchX = x
                    dragDownCallback.onDragDownStarted(startingChild)
                    dragDownAmountOnStart = dragDownCallback.dragDownAmount
                    return startingChild != null || dragDownCallback.isDragDownAnywhereEnabled
                }
            }
        }
        return false
    }

    override fun onTouchEvent(event: MotionEvent): Boolean {
        if (!isDraggingDown) {
            return false
        }
        val x = event.x
        val y = event.y
        when (event.actionMasked) {
            MotionEvent.ACTION_MOVE -> {
                lastHeight = y - initialTouchY
                captureStartingChild(initialTouchX, initialTouchY)
                dragDownCallback.dragDownAmount = lastHeight + dragDownAmountOnStart
                if (startingChild != null) {
                    handleExpansion(lastHeight, startingChild!!)
                }
                if (lastHeight > minDragDistance) {
                    if (!draggedFarEnough) {
                        draggedFarEnough = true
                        dragDownCallback.onCrossedThreshold(true)
                    }
                } else {
                    if (draggedFarEnough) {
                        draggedFarEnough = false
                        dragDownCallback.onCrossedThreshold(false)
                    }
                }
                return true
            }
            MotionEvent.ACTION_UP -> if (!falsingManager.isUnlockingDisabled && !isFalseTouch &&
                    dragDownCallback.canDragDown()) {
                dragDownCallback.onDraggedDown(startingChild, (y - initialTouchY).toInt())
                if (startingChild != null) {
                    expandCallback.setUserLockedChild(startingChild, false)
                    startingChild = null
                }
                isDraggingDown = false
            } else {
                stopDragging()
                return false
            }
            MotionEvent.ACTION_CANCEL -> {
                stopDragging()
                return false
            }
        }
        return false
    }

    private fun captureStartingChild(x: Float, y: Float) {
        if (startingChild == null) {
            startingChild = findView(x, y)
            if (startingChild != null) {
                if (dragDownCallback.isDragDownEnabledForView(startingChild)) {
                    expandCallback.setUserLockedChild(startingChild, true)
                } else {
                    startingChild = null
                }
            }
        }
    }

    private fun handleExpansion(heightDelta: Float, child: ExpandableView) {
        var hDelta = heightDelta
        if (hDelta < 0) {
            hDelta = 0f
        }
        val expandable = child.isContentExpandable
        val rubberbandFactor = if (expandable) {
            RUBBERBAND_FACTOR_EXPANDABLE
        } else {
            RUBBERBAND_FACTOR_STATIC
        }
        var rubberband = hDelta * rubberbandFactor
        if (expandable && rubberband + child.collapsedHeight > child.maxContentHeight) {
            var overshoot = rubberband + child.collapsedHeight - child.maxContentHeight
            overshoot *= 1 - RUBBERBAND_FACTOR_STATIC
            rubberband -= overshoot
        }
        child.actualHeight = (child.collapsedHeight + rubberband).toInt()
    }

    private fun cancelChildExpansion(child: ExpandableView) {
        if (child.actualHeight == child.collapsedHeight) {
            expandCallback.setUserLockedChild(child, false)
            return
        }
        val anim = ObjectAnimator.ofInt(child, "actualHeight",
                child.actualHeight, child.collapsedHeight)
        anim.interpolator = Interpolators.FAST_OUT_SLOW_IN
        anim.duration = SPRING_BACK_ANIMATION_LENGTH_MS
        anim.addListener(object : AnimatorListenerAdapter() {
            override fun onAnimationEnd(animation: Animator) {
                expandCallback.setUserLockedChild(child, false)
            }
        })
        anim.start()
    }

    private fun stopDragging() {
        falsingCollector.onNotificationStopDraggingDown()
        if (startingChild != null) {
            cancelChildExpansion(startingChild!!)
            startingChild = null
        }
        isDraggingDown = false
        dragDownCallback.onDragDownReset()
    }

    private fun findView(x: Float, y: Float): ExpandableView? {
        host.getLocationOnScreen(temp2)
        return expandCallback.getChildAtRawPosition(x + temp2[0], y + temp2[1])
    }
}