/*
 * Geekttrss is a RSS feed reader application on the Android Platform.
 *
 * Copyright (C) 2017-2020 by Frederic-Charles Barthelery.
 *
 * This file is part of Geekttrss.
 *
 * Geekttrss is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Geekttrss is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Geekttrss.  If not, see <http://www.gnu.org/licenses/>.
 */
package com.geekorum.ttrss

import android.annotation.SuppressLint
import android.app.Application
import android.os.Bundle
import android.os.PowerManager
import androidx.activity.viewModels
import androidx.appcompat.app.AppCompatActivity
import androidx.appcompat.app.AppCompatDelegate
import androidx.lifecycle.LiveData
import androidx.lifecycle.ViewModel
import androidx.lifecycle.distinctUntilChanged
import androidx.lifecycle.map
import androidx.lifecycle.observe
import androidx.lifecycle.switchMap
import com.geekorum.geekdroid.battery.BatterySaverLiveData
import com.geekorum.geekdroid.battery.LowBatteryLiveData
import javax.inject.Inject

/**
 * An [android.app.Activity] who switch to Night mode when battery is low or in saving mode.
 */
@SuppressLint("Registered")
open class BatteryFriendlyActivity : AppCompatActivity() {

    private val nightViewModel: ForceNightModeViewModel by viewModels()

    @SuppressLint("WrongConstant")
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        nightViewModel.forceNightMode.observe(this) {
            // we need to reset the local night mode to unspecified
            // otherwise the default night mode is not picked
            val mode =
                if (it) AppCompatDelegate.MODE_NIGHT_YES else AppCompatDelegate.MODE_NIGHT_UNSPECIFIED
            delegate.localNightMode = mode
        }
    }
}

/**
 * Observe the system to know if we should force night mode on all activities
 */
class ForceNightModeViewModel(
    private val batterySaverLiveData: LiveData<Boolean>,
    private val lowBatteryLiveData: LiveData<Boolean>
) : ViewModel() {

    @Inject
    constructor(application: Application, powerManager: PowerManager) : this(
        BatterySaverLiveData(application, powerManager), LowBatteryLiveData(application)
    )

    val forceNightMode = batterySaverLiveData.switchMap { saving ->
        // need to provide a copy of batterySaverLiveData to be observed
        if (saving) batterySaverLiveData.map { it } else lowBatteryLiveData
    }.distinctUntilChanged()

}