/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

package org.mozilla.fenix

import android.annotation.SuppressLint
import android.app.Application
import android.os.Build
import android.os.Build.VERSION.SDK_INT
import android.os.StrictMode
import androidx.appcompat.app.AppCompatDelegate
import androidx.core.content.getSystemService
import io.reactivex.plugins.RxJavaPlugins
import kotlinx.coroutines.Deferred
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.GlobalScope
import kotlinx.coroutines.async
import kotlinx.coroutines.launch
import kotlinx.coroutines.runBlocking
import mozilla.appservices.Megazord
import mozilla.components.concept.push.PushProcessor
import mozilla.components.service.experiments.Experiments
import mozilla.components.service.fretboard.Fretboard
import mozilla.components.service.fretboard.source.kinto.KintoExperimentSource
import mozilla.components.service.fretboard.storage.flatfile.FlatFileExperimentStorage
import mozilla.components.support.base.log.Log
import mozilla.components.support.base.log.logger.Logger
import mozilla.components.support.base.log.sink.AndroidLogSink
import mozilla.components.support.ktx.android.content.isMainProcess
import mozilla.components.support.ktx.android.content.runOnlyInMainProcess
import mozilla.components.support.rusthttp.RustHttpConfig
import mozilla.components.support.rustlog.RustLog
import org.mozilla.fenix.GleanMetrics.ExperimentsMetrics
import org.mozilla.fenix.components.Components
import org.mozilla.fenix.ext.settings
import org.mozilla.fenix.session.NotificationSessionObserver
import org.mozilla.fenix.session.VisibilityLifecycleCallback
import java.io.File

@SuppressLint("Registered")
@Suppress("TooManyFunctions")
open class FenixApplication : Application() {
    lateinit var fretboard: Fretboard
    lateinit var experimentLoader: Deferred<Boolean>
    var experimentLoaderComplete: Boolean = false

    open val components by lazy { Components(this) }

    var visibilityLifecycleCallback: VisibilityLifecycleCallback? = null
        private set

    override fun onCreate() {
        super.onCreate()

        setupApplication()
    }

    open fun setupApplication() {
        setupCrashReporting()
        setDayNightTheme()

        setupMegazord()
        setupLogging()
        registerRxExceptionHandling()
        enableStrictMode()

        if (!isMainProcess()) {
            // If this is not the main process then do not continue with the initialization here. Everything that
            // follows only needs to be done in our app's main process and should not be done in other processes like
            // a GeckoView child process or the crash handling process. Most importantly we never want to end up in a
            // situation where we create a GeckoRuntime from the Gecko child process.
            return
        }

        // Make sure the engine is initialized and ready to use.
        components.core.engine.warmUp()

        // We want to call this function as early as possible, but only once and
        // on the main process, as it uses Gecko to fetch experiments from the server.
        experimentLoader = loadExperiments()

        // Enable the service-experiments component
        if (settings().isExperimentationEnabled) {
            Experiments.initialize(
                applicationContext,
                mozilla.components.service.experiments.Configuration(
                    httpClient = lazy(LazyThreadSafetyMode.NONE) { components.core.client }
                )
            )
        }

        // When the `fenix-test-2019-08-05` experiment is active, record its branch in Glean
        // telemetry. This will be used to validate that the experiment system correctly enrolls
        // clients and segments them into branches. Note that this will not take effect the first
        // time the application has launched, since there won't be enough time for the experiments
        // library to get a list of experiments. It will take effect the second time the
        // application is launched.
        Experiments.withExperiment("fenix-test-2019-08-05") { branchName ->
            ExperimentsMetrics.activeExperiment.set(branchName)
        }

        setupLeakCanary()
        if (settings().isTelemetryEnabled) {
            components.analytics.metrics.start()
        }

        setupPush()

        visibilityLifecycleCallback = VisibilityLifecycleCallback(getSystemService())
        registerActivityLifecycleCallbacks(visibilityLifecycleCallback)

        components.core.sessionManager.register(NotificationSessionObserver(this))

        if ((System.currentTimeMillis() - this.settings().lastPlacesStorageMaintenance) > ONE_DAY_MILLIS) {
            runStorageMaintenance()
        }
    }

    private fun runStorageMaintenance() {
        GlobalScope.launch(Dispatchers.IO) {
            // Bookmarks and history storage sit on top of the same db file so we only need to
            // run maintenance on one - arbitrarily using bookmarks.
            components.core.bookmarksStorage.runMaintenance()
        }
        this.settings().lastPlacesStorageMaintenance = System.currentTimeMillis()
    }

    private fun registerRxExceptionHandling() {
        RxJavaPlugins.setErrorHandler {
            throw it.cause ?: it
        }
    }

    /**
     * Wait until all experiments are loaded
     *
     * This function will cause the caller to block until the experiments are loaded.
     * It could be used in any number of reasons, but the most likely scenario is that
     * a calling function needs to access the loaded experiments and wants to
     * make sure that the experiments are loaded from the server before doing so.
     *
     * Because this function is synchronized, it can only be accessed by one thread
     * at a time. Anyone trying to check the loaded status will wait if someone is
     * already waiting. This is okay because the thread waiting for access to the
     * function will immediately see that the loader is complete upon gaining the
     * opportunity to run the function.
     */
    @Synchronized
    public fun waitForExperimentsToLoad() {

        // Do we know that we are already complete?
        if (!experimentLoaderComplete) {
            // No? Have we completed since the last call?
            if (!experimentLoader.isCompleted) {
                // No? Well, let's wait.
                runBlocking {
                    experimentLoader.await()
                }
            }
            // Set this so we don't have to wait on the next call.
            experimentLoaderComplete = true
        }
    }

    protected open fun setupLeakCanary() {
        // no-op, LeakCanary is disabled by default
    }

    open fun toggleLeakCanary(newValue: Boolean) {
        // no-op, LeakCanary is disabled by default
    }

    private fun setupLogging() {
        // We want the log messages of all builds to go to Android logcat
        Log.addSink(AndroidLogSink())
        // We want rust logging to go through the log sinks.
        // This has to happen after initializing the megazord.
        RustLog.enable()
    }

    private fun loadExperiments(): Deferred<Boolean> {
        val experimentsFile = File(filesDir, EXPERIMENTS_JSON_FILENAME)
        val experimentSource = KintoExperimentSource(
            EXPERIMENTS_BASE_URL,
            EXPERIMENTS_BUCKET_NAME,
            EXPERIMENTS_COLLECTION_NAME,
            components.core.client
        )
        // TODO add ValueProvider to keep clientID in sync with Glean when ready
        fretboard = Fretboard(experimentSource, FlatFileExperimentStorage(experimentsFile))

        return GlobalScope.async(Dispatchers.IO) {
            fretboard.loadExperiments()
            Logger.debug("Bucket is ${fretboard.getUserBucket(this@FenixApplication)}")
            Logger.debug("Experiments active: ${fretboard.getExperimentsMap(this@FenixApplication)}")
            fretboard.updateExperiments()
            return@async true
        }
    }

    private fun setupPush() {
        // Sets the PushFeature as the singleton instance for push messages to go to.
        // We need the push feature setup here to deliver messages in the case where the service
        // starts up the app first.
        components.backgroundServices.push?.let { autoPushFeature ->
            Logger.info("AutoPushFeature is configured, initializing it...")

            // Install the AutoPush singleton to receive messages.
            PushProcessor.install(autoPushFeature)

            // Initialize the service. This could potentially be done in a coroutine in the future.
            autoPushFeature.initialize()
        }
    }

    private fun setupCrashReporting() {
        components
            .analytics
            .crashReporter
            .install(this)
    }

    /**
     * Initiate Megazord sequence! Megazord Battle Mode!
     *
     * The application-services combined libraries are known as the "megazord". The default megazord
     * contains several features that fenix doesn't need, and so we swap out with a customized fenix-specific
     * version of the megazord. The best explanation for what this is, and why it's done is the a-s
     * documentation on the topic:
     * - https://github.com/mozilla/application-services/blob/master/docs/design/megazords.md
     * - https://mozilla.github.io/application-services/docs/applications/consuming-megazord-libraries.html
     */
    private fun setupMegazord() {
        // Note: This must be called as soon as possible
        Megazord.init()
        // This (and enabling RustLog) may be delayed if needed for performance reasons
        RustHttpConfig.setClient(lazy { components.core.client })
    }

    override fun onTrimMemory(level: Int) {
        super.onTrimMemory(level)
        runOnlyInMainProcess {
            components.core.sessionManager.onLowMemory()
        }
    }

    @SuppressLint("WrongConstant")
    // Suppressing erroneous lint warning about using MODE_NIGHT_AUTO_BATTERY, a likely library bug
    private fun setDayNightTheme() {
        val settings = this.settings()
        when {
            settings.shouldUseLightTheme -> {
                AppCompatDelegate.setDefaultNightMode(
                    AppCompatDelegate.MODE_NIGHT_NO
                )
            }
            settings.shouldUseDarkTheme -> {
                AppCompatDelegate.setDefaultNightMode(
                    AppCompatDelegate.MODE_NIGHT_YES
                )
            }
            SDK_INT < Build.VERSION_CODES.P && settings.shouldUseAutoBatteryTheme -> {
                AppCompatDelegate.setDefaultNightMode(
                    AppCompatDelegate.MODE_NIGHT_AUTO_BATTERY
                )
            }
            SDK_INT >= Build.VERSION_CODES.P && settings.shouldFollowDeviceTheme -> {
                AppCompatDelegate.setDefaultNightMode(
                    AppCompatDelegate.MODE_NIGHT_FOLLOW_SYSTEM
                )
            }
            // First run of app no default set, set the default to Follow System for 28+ and Normal Mode otherwise
            else -> {
                if (SDK_INT >= Build.VERSION_CODES.P) {
                    AppCompatDelegate.setDefaultNightMode(
                        AppCompatDelegate.MODE_NIGHT_FOLLOW_SYSTEM
                    )
                    settings.shouldFollowDeviceTheme = true
                } else {
                    AppCompatDelegate.setDefaultNightMode(
                        AppCompatDelegate.MODE_NIGHT_NO
                    )
                    settings.shouldUseLightTheme = true
                }
            }
        }
    }

    private fun enableStrictMode() {
        if (BuildConfig.DEBUG) {
            StrictMode.setThreadPolicy(
                StrictMode.ThreadPolicy.Builder()
                    .detectAll()
                    .penaltyLog()
                    .build()
            )
            var builder = StrictMode.VmPolicy.Builder()
                .detectLeakedSqlLiteObjects()
                .detectLeakedClosableObjects()
                .detectLeakedRegistrationObjects()
                .detectActivityLeaks()
                .detectFileUriExposure()
                .penaltyLog()
            if (SDK_INT >= Build.VERSION_CODES.O) builder =
                builder.detectContentUriWithoutPermission()
            if (SDK_INT >= Build.VERSION_CODES.P) builder = builder.detectNonSdkApiUsage()
            StrictMode.setVmPolicy(builder.build())
        }
    }

    companion object {
        private const val ONE_DAY_MILLIS = 24 * 60 * 60 * 1000
    }
}