/*
 * Copyright (C) 2023 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 com.android.systemui.keyguard.ui.viewmodel

import androidx.annotation.VisibleForTesting
import com.android.app.tracing.FlowTracing.traceEmissionCount
import com.android.app.tracing.coroutines.flow.flowName
import com.android.systemui.Flags
import com.android.systemui.common.shared.model.Icon
import com.android.systemui.dagger.qualifiers.Application
import com.android.systemui.keyguard.domain.interactor.KeyguardInteractor
import com.android.systemui.keyguard.domain.interactor.KeyguardQuickAffordanceInteractor
import com.android.systemui.keyguard.domain.interactor.KeyguardTransitionInteractor
import com.android.systemui.keyguard.domain.model.KeyguardQuickAffordanceModel
import com.android.systemui.keyguard.shared.model.KeyguardState
import com.android.systemui.keyguard.shared.quickaffordance.ActivationState
import com.android.systemui.keyguard.shared.quickaffordance.KeyguardQuickAffordancePosition
import com.android.systemui.shade.domain.interactor.ShadeInteractor
import com.android.systemui.shared.Flags as SharedFlags
import com.android.systemui.shared.keyguard.shared.model.KeyguardQuickAffordanceSlots
import com.android.systemui.utils.coroutines.flow.flatMapLatestConflated
import javax.inject.Inject
import kotlinx.coroutines.CoroutineScope
import kotlinx.coroutines.flow.Flow
import kotlinx.coroutines.flow.MutableStateFlow
import kotlinx.coroutines.flow.SharingStarted
import kotlinx.coroutines.flow.combine
import kotlinx.coroutines.flow.distinctUntilChanged
import kotlinx.coroutines.flow.flatMapLatest
import kotlinx.coroutines.flow.map
import kotlinx.coroutines.flow.merge
import kotlinx.coroutines.flow.stateIn

class KeyguardQuickAffordancesCombinedViewModel
@Inject
constructor(
    @Application private val applicationScope: CoroutineScope,
    private val quickAffordanceInteractor: KeyguardQuickAffordanceInteractor,
    private val keyguardInteractor: KeyguardInteractor,
    shadeInteractor: ShadeInteractor,
    aodToLockscreenTransitionViewModel: AodToLockscreenTransitionViewModel,
    dozingToLockscreenTransitionViewModel: DozingToLockscreenTransitionViewModel,
    dreamingToLockscreenTransitionViewModel: DreamingToLockscreenTransitionViewModel,
    goneToLockscreenTransitionViewModel: GoneToLockscreenTransitionViewModel,
    occludedToLockscreenTransitionViewModel: OccludedToLockscreenTransitionViewModel,
    offToLockscreenTransitionViewModel: OffToLockscreenTransitionViewModel,
    primaryBouncerToLockscreenTransitionViewModel: PrimaryBouncerToLockscreenTransitionViewModel,
    glanceableHubToLockscreenTransitionViewModel: GlanceableHubToLockscreenTransitionViewModel,
    lockscreenToAodTransitionViewModel: LockscreenToAodTransitionViewModel,
    lockscreenToDozingTransitionViewModel: LockscreenToDozingTransitionViewModel,
    lockscreenToDreamingTransitionViewModel: LockscreenToDreamingTransitionViewModel,
    lockscreenToGoneTransitionViewModel: LockscreenToGoneTransitionViewModel,
    lockscreenToOccludedTransitionViewModel: LockscreenToOccludedTransitionViewModel,
    lockscreenToPrimaryBouncerTransitionViewModel: LockscreenToPrimaryBouncerTransitionViewModel,
    lockscreenToGlanceableHubTransitionViewModel: LockscreenToGlanceableHubTransitionViewModel,
    transitionInteractor: KeyguardTransitionInteractor,
) {

    data class PreviewMode(
        val isInPreviewMode: Boolean = false,
        val shouldHighlightSelectedAffordance: Boolean = false,
    )

    /**
     * Whether this view-model instance is powering the preview experience that renders exclusively
     * in the wallpaper picker application. This should _always_ be `false` for the real lock screen
     * experience.
     */
    private val previewMode = MutableStateFlow(PreviewMode())

    private val showingLockscreen: Flow<Boolean> =
        transitionInteractor.isFinishedIn(KeyguardState.LOCKSCREEN)

    /** The only time the expansion is important is while lockscreen is actively displayed */
    private val shadeExpansionAlpha =
        combine(showingLockscreen, shadeInteractor.anyExpansion) { showingLockscreen, expansion ->
            if (showingLockscreen) {
                1 - expansion
            } else {
                0f
            }
        }

    /**
     * ID of the slot that's currently selected in the preview that renders exclusively in the
     * wallpaper picker application. This is ignored for the actual, real lock screen experience.
     */
    private val selectedPreviewSlotId =
        MutableStateFlow(KeyguardQuickAffordanceSlots.SLOT_ID_BOTTOM_START)

    /** alpha while fading the quick affordances out */
    private val fadeInAlpha: Flow<Float> =
        merge(
            aodToLockscreenTransitionViewModel.shortcutsAlpha,
            dozingToLockscreenTransitionViewModel.shortcutsAlpha,
            dreamingToLockscreenTransitionViewModel.shortcutsAlpha,
            goneToLockscreenTransitionViewModel.shortcutsAlpha,
            occludedToLockscreenTransitionViewModel.shortcutsAlpha,
            offToLockscreenTransitionViewModel.shortcutsAlpha,
            primaryBouncerToLockscreenTransitionViewModel.shortcutsAlpha,
            glanceableHubToLockscreenTransitionViewModel.shortcutsAlpha,
        )

    /** alpha while fading the quick affordances in */
    private val fadeOutAlpha: Flow<Float> =
        merge(
            lockscreenToAodTransitionViewModel.shortcutsAlpha,
            lockscreenToDozingTransitionViewModel.shortcutsAlpha,
            lockscreenToDreamingTransitionViewModel.shortcutsAlpha,
            lockscreenToGoneTransitionViewModel.shortcutsAlpha,
            lockscreenToOccludedTransitionViewModel.shortcutsAlpha,
            lockscreenToPrimaryBouncerTransitionViewModel.shortcutsAlpha,
            lockscreenToGlanceableHubTransitionViewModel.shortcutsAlpha,
            shadeExpansionAlpha,
        )

    /** The source of truth of alpha for all of the quick affordances on lockscreen */
    val transitionAlpha: Flow<Float> =
        merge(fadeInAlpha, fadeOutAlpha)
            .flowName("transitionAlpha")
            .stateIn(
                scope = applicationScope,
                started = SharingStarted.WhileSubscribed(),
                initialValue = 0f,
            )

    /**
     * Whether quick affordances are "opaque enough" to be considered visible to and interactive by
     * the user. If they are not interactive, user input should not be allowed on them.
     *
     * Note that there is a margin of error, where we allow very, very slightly transparent views to
     * be considered "fully opaque" for the purpose of being interactive. This is to accommodate the
     * error margin of floating point arithmetic.
     *
     * A view that is visible but with an alpha of less than our threshold either means it's not
     * fully done fading in or is fading/faded out. Either way, it should not be
     * interactive/clickable unless "fully opaque" to avoid issues like in b/241830987.
     */
    private val areQuickAffordancesFullyOpaque: Flow<Boolean> =
        transitionAlpha
            .map { alpha -> alpha >= AFFORDANCE_FULLY_OPAQUE_ALPHA_THRESHOLD }
            .distinctUntilChanged()

    private val previewAffordances =
        MutableStateFlow<Map<KeyguardQuickAffordancePosition, String>>(emptyMap())

    /** An observable for the view-model of the "start button" quick affordance. */
    val startButton: Flow<KeyguardQuickAffordanceViewModel> =
        if (SharedFlags.newCustomizationPickerUi()) {
            previewAffordances.flatMapLatestConflated {
                button(
                    position = KeyguardQuickAffordancePosition.BOTTOM_START,
                    overrideQuickAffordanceId = it[KeyguardQuickAffordancePosition.BOTTOM_START],
                )
            }
        } else {
            button(KeyguardQuickAffordancePosition.BOTTOM_START)
        }

    /** An observable for the view-model of the "end button" quick affordance. */
    val endButton: Flow<KeyguardQuickAffordanceViewModel> =
        if (SharedFlags.newCustomizationPickerUi()) {
            previewAffordances.flatMapLatestConflated {
                button(
                    position = KeyguardQuickAffordancePosition.BOTTOM_END,
                    overrideQuickAffordanceId = it[KeyguardQuickAffordancePosition.BOTTOM_END],
                )
            }
        } else {
            button(KeyguardQuickAffordancePosition.BOTTOM_END)
        }

    /**
     * Notifies that a slot with the given ID has been selected in the preview experience that is
     * rendering in the wallpaper picker. This is ignored for the real lock screen experience.
     *
     * @see [enablePreviewMode]
     */
    fun onPreviewSlotSelected(slotId: String) {
        selectedPreviewSlotId.value = slotId
    }

    /**
     * Notifies to preview an affordance at a given slot ID. This is ignored for the real lock
     * screen experience.
     */
    fun onPreviewQuickAffordanceSelected(slotId: String, affordanceId: String) {
        val position =
            KeyguardQuickAffordancePosition.parseKeyguardQuickAffordancePosition(slotId) ?: return
        previewAffordances.value =
            previewAffordances.value.toMutableMap().let {
                it[position] = affordanceId
                HashMap(it)
            }
    }

    /**
     * Notifies to clear up the preview affordances map. This is ignored for the real lock screen
     * experience.
     */
    fun onClearPreviewQuickAffordances() {
        previewAffordances.value = emptyMap()
    }

    /**
     * Puts this view-model in "preview mode", which means it's being used for UI that is rendering
     * the lock screen preview in wallpaper picker / settings and not the real experience on the
     * lock screen.
     *
     * @param initiallySelectedSlotId The ID of the initial slot to render as the selected one.
     * @param shouldHighlightSelectedAffordance Whether the selected quick affordance should be
     *   highlighted (while all others are dimmed to make the selected one stand out).
     */
    fun enablePreviewMode(
        initiallySelectedSlotId: String?,
        shouldHighlightSelectedAffordance: Boolean,
    ) {
        val newPreviewMode =
            PreviewMode(
                isInPreviewMode = true,
                shouldHighlightSelectedAffordance = shouldHighlightSelectedAffordance,
            )
        onPreviewSlotSelected(
            initiallySelectedSlotId ?: KeyguardQuickAffordanceSlots.SLOT_ID_BOTTOM_START
        )
        previewMode.value = newPreviewMode
    }

    private fun button(
        position: KeyguardQuickAffordancePosition,
        overrideQuickAffordanceId: String? = null,
    ): Flow<KeyguardQuickAffordanceViewModel> {
        return previewMode
            .flatMapLatest { previewMode ->
                combine(
                        if (previewMode.isInPreviewMode) {
                            quickAffordanceInteractor.quickAffordanceAlwaysVisible(
                                position = position,
                                overrideQuickAffordanceId = overrideQuickAffordanceId,
                            )
                        } else {
                            quickAffordanceInteractor.quickAffordance(position = position)
                        },
                        keyguardInteractor.animateDozingTransitions.distinctUntilChanged(),
                        areQuickAffordancesFullyOpaque,
                        selectedPreviewSlotId,
                        quickAffordanceInteractor.useLongPress(),
                    ) { model, animateReveal, isFullyOpaque, selectedPreviewSlotId, useLongPress ->
                        val slotId = position.toSlotId()
                        val isSelected = selectedPreviewSlotId == slotId
                        model.toViewModel(
                            animateReveal = !previewMode.isInPreviewMode && animateReveal,
                            isClickable = isFullyOpaque && !previewMode.isInPreviewMode,
                            isSelected =
                                previewMode.isInPreviewMode &&
                                    previewMode.shouldHighlightSelectedAffordance &&
                                    isSelected,
                            isDimmed =
                                previewMode.isInPreviewMode &&
                                    previewMode.shouldHighlightSelectedAffordance &&
                                    !isSelected,
                            forceInactive = previewMode.isInPreviewMode,
                            slotId = slotId,
                            useLongPress = useLongPress,
                        )
                    }
                    .distinctUntilChanged()
            }
            .traceEmissionCount({ "QuickAfforcances#button${position.toSlotId()}" })
    }

    private fun KeyguardQuickAffordanceModel.toViewModel(
        animateReveal: Boolean,
        isClickable: Boolean,
        isSelected: Boolean,
        isDimmed: Boolean,
        forceInactive: Boolean,
        slotId: String,
        useLongPress: Boolean,
    ): KeyguardQuickAffordanceViewModel {
        return when (this) {
            is KeyguardQuickAffordanceModel.Visible ->
                KeyguardQuickAffordanceViewModel(
                    configKey = configKey,
                    isVisible = true,
                    animateReveal = animateReveal,
                    icon = nonTintedIcon(icon),
                    onClicked = { parameters ->
                        quickAffordanceInteractor.onQuickAffordanceTriggered(
                            configKey = parameters.configKey,
                            expandable = parameters.expandable,
                            slotId = parameters.slotId,
                        )
                    },
                    isClickable = isClickable,
                    isActivated = !forceInactive && activationState is ActivationState.Active,
                    isSelected = isSelected,
                    useLongPress = useLongPress,
                    isDimmed = isDimmed,
                    slotId = slotId,
                )
            is KeyguardQuickAffordanceModel.Hidden ->
                KeyguardQuickAffordanceViewModel(slotId = slotId)
        }
    }

    @VisibleForTesting
    fun nonTintedIcon(icon: Icon): Icon =
        if (Flags.clearShortcutIconTint() && icon is Icon.Loaded) {
            icon.apply { drawable.setTintList(null) }
        } else {
            icon
        }

    companion object {
        // We select a value that's less than 1.0 because we want floating point math precision to
        // not be a factor in determining whether the affordance UI is fully opaque. The number we
        // choose needs to be close enough 1.0 such that the user can't easily tell the difference
        // between the UI with an alpha at the threshold and when the alpha is 1.0. At the same
        // time, we don't want the number to be too close to 1.0 such that there is a chance that we
        // never treat the affordance UI as "fully opaque" as that would risk making it forever not
        // clickable.
        @VisibleForTesting const val AFFORDANCE_FULLY_OPAQUE_ALPHA_THRESHOLD = 0.95f
    }
}