/*
 * 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.customization.picker.clock.ui.viewmodel

import android.content.res.Resources
import android.graphics.Color
import androidx.lifecycle.ViewModel
import androidx.lifecycle.ViewModelProvider
import androidx.lifecycle.viewModelScope
import com.android.customization.module.logging.ThemesUserEventLogger
import com.android.customization.picker.clock.domain.interactor.ClockPickerInteractor
import com.android.customization.picker.clock.shared.ClockSize
import com.android.customization.picker.clock.ui.view.ClockViewFactory
import com.android.themepicker.R
import kotlinx.coroutines.CoroutineDispatcher
import kotlinx.coroutines.ExperimentalCoroutinesApi
import kotlinx.coroutines.Job
import kotlinx.coroutines.delay
import kotlinx.coroutines.flow.Flow
import kotlinx.coroutines.flow.SharingStarted
import kotlinx.coroutines.flow.StateFlow
import kotlinx.coroutines.flow.flatMapLatest
import kotlinx.coroutines.flow.flowOn
import kotlinx.coroutines.flow.map
import kotlinx.coroutines.flow.mapLatest
import kotlinx.coroutines.flow.mapNotNull
import kotlinx.coroutines.flow.stateIn
import kotlinx.coroutines.launch

/**
 * Clock carousel view model that provides data for the carousel of clock previews. When there is
 * only one item, we should show a single clock preview instead of a carousel.
 */
class ClockCarouselViewModel(
    private val interactor: ClockPickerInteractor,
    private val backgroundDispatcher: CoroutineDispatcher,
    private val clockViewFactory: ClockViewFactory,
    private val resources: Resources,
    private val logger: ThemesUserEventLogger,
) : ViewModel() {
    @OptIn(ExperimentalCoroutinesApi::class)
    val allClocks: StateFlow<List<ClockCarouselItemViewModel>> =
        interactor.allClocks
            .mapLatest { allClocks ->
                // Delay to avoid the case that the full list of clocks is not initiated.
                delay(CLOCKS_EVENT_UPDATE_DELAY_MILLIS)
                allClocks.map {
                    val contentDescription =
                        resources.getString(
                            R.string.select_clock_action_description,
                            clockViewFactory.getController(it.clockId).config.description
                        )
                    ClockCarouselItemViewModel(it.clockId, it.isSelected, contentDescription)
                }
            }
            // makes sure that the operations above this statement are executed on I/O dispatcher
            // while parallelism limits the number of threads this can run on which makes sure that
            // the flows run sequentially
            .flowOn(backgroundDispatcher.limitedParallelism(1))
            .stateIn(viewModelScope, SharingStarted.Eagerly, emptyList())

    val selectedClockSize: Flow<ClockSize> = interactor.selectedClockSize

    val seedColor: Flow<Int?> = interactor.seedColor

    fun getClockCardColorResId(isDarkThemeEnabled: Boolean): Flow<Int> {
        return interactor.seedColor.map {
            it.let { seedColor ->
                // if seedColor is null, default clock color is selected
                if (seedColor == null) {
                    if (isDarkThemeEnabled) {
                        // In dark mode, use darkest surface container color
                        com.android.wallpaper.R.color.system_surface_container_high
                    } else {
                        // In light mode, use lightest surface container color
                        com.android.wallpaper.R.color.system_surface_bright
                    }
                } else {
                    val luminance = Color.luminance(seedColor)
                    if (isDarkThemeEnabled) {
                        if (luminance <= CARD_COLOR_CHANGE_LUMINANCE_THRESHOLD_DARK_THEME) {
                            com.android.wallpaper.R.color.system_surface_bright
                        } else {
                            com.android.wallpaper.R.color.system_surface_container_high
                        }
                    } else {
                        if (luminance <= CARD_COLOR_CHANGE_LUMINANCE_THRESHOLD_LIGHT_THEME) {
                            com.android.wallpaper.R.color.system_surface_bright
                        } else {
                            com.android.wallpaper.R.color.system_surface_container_highest
                        }
                    }
                }
            }
        }
    }

    @OptIn(ExperimentalCoroutinesApi::class)
    val selectedIndex: Flow<Int> =
        allClocks
            .flatMapLatest { allClockIds ->
                interactor.selectedClockId.map { selectedClockId ->
                    val index = allClockIds.indexOfFirst { it.clockId == selectedClockId }
                    /** Making sure there is no active [setSelectedClockJob] */
                    val isSetClockIdJobActive = setSelectedClockJob?.isActive == true
                    if (index >= 0 && !isSetClockIdJobActive) {
                        index
                    } else {
                        null
                    }
                }
            }
            .mapNotNull { it }

    private var setSelectedClockJob: Job? = null
    fun setSelectedClock(clockId: String) {
        setSelectedClockJob?.cancel()
        setSelectedClockJob =
            viewModelScope.launch(backgroundDispatcher) {
                interactor.setSelectedClock(clockId)
                logger.logClockApplied(clockId)
            }
    }

    class Factory(
        private val interactor: ClockPickerInteractor,
        private val backgroundDispatcher: CoroutineDispatcher,
        private val clockViewFactory: ClockViewFactory,
        private val resources: Resources,
        private val logger: ThemesUserEventLogger,
    ) : ViewModelProvider.Factory {
        override fun <T : ViewModel> create(modelClass: Class<T>): T {
            @Suppress("UNCHECKED_CAST")
            return ClockCarouselViewModel(
                interactor = interactor,
                backgroundDispatcher = backgroundDispatcher,
                clockViewFactory = clockViewFactory,
                resources = resources,
                logger = logger,
            )
                as T
        }
    }

    companion object {
        const val CLOCKS_EVENT_UPDATE_DELAY_MILLIS: Long = 100
        const val CARD_COLOR_CHANGE_LUMINANCE_THRESHOLD_LIGHT_THEME: Float = 0.85f
        const val CARD_COLOR_CHANGE_LUMINANCE_THRESHOLD_DARK_THEME: Float = 0.03f
    }
}