/* 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 mozilla.components.lib.crash

import android.app.PendingIntent
import android.content.Context
import android.content.Intent
import androidx.annotation.StyleRes
import androidx.annotation.VisibleForTesting
import androidx.core.content.ContextCompat
import kotlinx.coroutines.CoroutineScope
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.Job
import kotlinx.coroutines.launch
import kotlinx.coroutines.withContext
import mozilla.components.lib.crash.db.CrashDatabase
import mozilla.components.lib.crash.db.insertCrashSafely
import mozilla.components.lib.crash.db.insertReportSafely
import mozilla.components.lib.crash.db.toEntity
import mozilla.components.lib.crash.db.toReportEntity
import mozilla.components.lib.crash.handler.ExceptionHandler
import mozilla.components.lib.crash.notification.CrashNotification
import mozilla.components.lib.crash.prompt.CrashPrompt
import mozilla.components.lib.crash.service.CrashReporterService
import mozilla.components.lib.crash.service.CrashTelemetryService
import mozilla.components.lib.crash.service.SendCrashReportService
import mozilla.components.lib.crash.service.SendCrashTelemetryService
import mozilla.components.concept.base.crash.Breadcrumb
import mozilla.components.concept.base.crash.CrashReporting
import mozilla.components.support.base.log.logger.Logger

/**
 * A generic crash reporter that can report crashes to multiple services.
 *
 * In the `onCreate()` method of your Application class create a `CrashReporter` instance and call `install()`:
 *
 * ```Kotlin
 *   CrashReporter(
 *     services = listOf(
 *       // List the crash reporting services you want to use
 *     )
 *   ).install(this)
 * ```
 *
 * With this minimal setup the crash reporting library will capture "uncaught exception" crashes and "native code"
 * crashes and forward them to the configured crash reporting services.
 *
 * @property enabled Enable/Disable crash reporting.
 *
 * @param services List of crash reporting services that should receive crash reports.
 * @param telemetryServices List of telemetry crash reporting services that should receive crash reports.
 * @param shouldPrompt Whether or not the user should be prompted to confirm sending crash reports.
 * @param enabled Enable/Disable crash reporting.
 * @param promptConfiguration Configuration for customizing the crash reporter prompt.
 * @param nonFatalCrashIntent A [PendingIntent] that will be launched if a non fatal crash (main process not affected)
 *                            happened. This gives the app the opportunity to show an in-app confirmation UI before
 *                            sending a crash report. See component README for details.
 */
@Suppress("TooManyFunctions", "LongParameterList")
class CrashReporter(
    context: Context,
    private val services: List<CrashReporterService> = emptyList(),
    private val telemetryServices: List<CrashTelemetryService> = emptyList(),
    private val shouldPrompt: Prompt = Prompt.NEVER,
    var enabled: Boolean = true,
    internal val promptConfiguration: PromptConfiguration = PromptConfiguration(),
    private val nonFatalCrashIntent: PendingIntent? = null,
    private val scope: CoroutineScope = CoroutineScope(Dispatchers.IO),
    private val maxBreadCrumbs: Int = 30
) : CrashReporting {
    private val database: CrashDatabase by lazy { CrashDatabase.get(context) }

    internal val logger = Logger("mozac/CrashReporter")

    @VisibleForTesting(otherwise = VisibleForTesting.PRIVATE)
    internal val crashBreadcrumbs = ArrayList<Breadcrumb>()

    init {
        if (services.isEmpty() and telemetryServices.isEmpty()) {
            throw IllegalArgumentException("No crash reporter services defined")
        }
    }

    /**
     * Install this [CrashReporter] instance. At this point the component will be setup to collect crash reports.
     */
    fun install(applicationContext: Context): CrashReporter {
        instance = this

        val defaultHandler = Thread.getDefaultUncaughtExceptionHandler()
        val handler = ExceptionHandler(applicationContext, this, defaultHandler)
        Thread.setDefaultUncaughtExceptionHandler(handler)

        return this
    }

    /**
     * Get a copy of the crashBreadCrumbs
     */
    internal fun crashBreadcrumbsCopy(): ArrayList<Breadcrumb> {
        @Suppress("UNCHECKED_CAST")
        return crashBreadcrumbs.clone() as ArrayList<Breadcrumb>
    }

    /**
     * Submit a crash report to all registered services.
     */
    fun submitReport(crash: Crash, then: () -> Unit = {}): Job {
        return scope.launch {
            services.forEach { service ->
                val reportId = when (crash) {
                    is Crash.NativeCodeCrash -> service.report(crash)
                    is Crash.UncaughtExceptionCrash -> service.report(crash)
                }

                if (reportId != null) {
                    database.crashDao().insertReportSafely(service.toReportEntity(crash, reportId))
                }

                val reportUrl = reportId?.let { service.createCrashReportUrl(it) }

                logger.info("Submitted crash to ${service.name} (id=$reportId, url=$reportUrl)")
            }

            logger.info("Crash report submitted to ${services.size} services")
            withContext(Dispatchers.Main) {
                then()
            }
        }
    }

    /**
     * Submit a crash report to all registered telemetry services.
     */
    fun submitCrashTelemetry(crash: Crash, then: () -> Unit = {}): Job {
        return scope.launch {
            telemetryServices.forEach { telemetryService ->
                when (crash) {
                    is Crash.NativeCodeCrash -> telemetryService.record(crash)
                    is Crash.UncaughtExceptionCrash -> telemetryService.record(crash)
                }
            }

            logger.info("Crash report submitted to ${telemetryServices.size} telemetry services")
            withContext(Dispatchers.Main) {
                then()
            }
        }
    }

    /**
     * Submit a caught exception report to all registered services.
     */
    override fun submitCaughtException(throwable: Throwable): Job {
        /*
         * if stacktrace is empty, replace throwable with UnexpectedlyMissingStacktrace exception so
         * we can figure out which module is submitting caught exception reports without a stacktrace.
         */
        var reportThrowable = throwable
        if (throwable.stackTrace.isEmpty()) {
            reportThrowable = CrashReporterException.UnexpectedlyMissingStacktrace("Missing Stacktrace", throwable)
        }

        logger.info("Caught Exception report submitted to ${services.size} services")
        return scope.launch {
            services.forEach {
                it.report(reportThrowable, crashBreadcrumbsCopy())
            }
        }
    }

    /**
     * Add a crash breadcrumb to all registered services with breadcrumb support.
     *
     * ```Kotlin
     *   crashReporter.recordCrashBreadcrumb(
     *       Breadcrumb("Settings button clicked", data, "UI", Level.INFO, Type.USER)
     *   )
     * ```
     */
    override fun recordCrashBreadcrumb(breadcrumb: Breadcrumb) {
        if (crashBreadcrumbs.size >= maxBreadCrumbs) {
            crashBreadcrumbs.removeAt(0)
        }

        crashBreadcrumbs.add(breadcrumb)
    }

    internal fun onCrash(context: Context, crash: Crash) {
        if (!enabled) {
            return
        }

        logger.info("Received crash: $crash")

        database.crashDao().insertCrashSafely(crash.toEntity())

        if (telemetryServices.isNotEmpty()) {
            sendCrashTelemetry(context, crash)
        }

        // If crash is native code and non fatal then the view will handle the user prompt
        if (shouldSendIntent(crash)) {
            // App has registered a pending intent
            sendNonFatalCrashIntent(context, crash)
            return
        }

        if (services.isNotEmpty()) {
            if (CrashPrompt.shouldPromptForCrash(shouldPrompt, crash)) {
                showPromptOrNotification(context, crash)
            } else {
                sendCrashReport(context, crash)
            }
        }
    }

    @VisibleForTesting(otherwise = VisibleForTesting.PRIVATE)
    internal fun sendNonFatalCrashIntent(context: Context, crash: Crash) {
        logger.info("Invoking non-fatal PendingIntent")

        val additionalIntent = Intent()
        crash.fillIn(additionalIntent)
        nonFatalCrashIntent?.send(context, 0, additionalIntent)
    }

    private fun showPromptOrNotification(context: Context, crash: Crash) {
        if (services.isEmpty()) {
            return
        }

        if (CrashNotification.shouldShowNotificationInsteadOfPrompt(crash)) {
            // If this is a fatal crash taking down the app then we may not be able to show a crash reporter
            // prompt on Android Q+. Unfortunately it's not possible to easily determine if we can launch an
            // activity here. So instead we fallback to just showing a notification
            // https://developer.android.com/preview/privacy/background-activity-starts
            logger.info("Showing notification")
            val notification = CrashNotification(context, crash, promptConfiguration)
            notification.show()
        } else {
            logger.info("Showing prompt")
            showPrompt(context, crash)
        }
    }

    @VisibleForTesting(otherwise = VisibleForTesting.PRIVATE)
    internal fun sendCrashReport(context: Context, crash: Crash) {
        ContextCompat.startForegroundService(context, SendCrashReportService.createReportIntent(context, crash))
    }

    @VisibleForTesting(otherwise = VisibleForTesting.PRIVATE)
    internal fun sendCrashTelemetry(context: Context, crash: Crash) {
        ContextCompat.startForegroundService(context, SendCrashTelemetryService.createReportIntent(context, crash))
    }

    @VisibleForTesting
    internal fun showPrompt(context: Context, crash: Crash) {
        val prompt = CrashPrompt(context, crash)
        prompt.show()
    }

    private fun shouldSendIntent(crash: Crash): Boolean {
        return if (nonFatalCrashIntent == null) {
            // If the app has not registered any intent then we can't send one.
            false
        } else {
            // If this is a non-fatal native code crash then we can recover and can notify the app
            crash is Crash.NativeCodeCrash && !crash.isFatal
        }
    }

    internal fun getCrashReporterServiceById(id: String): CrashReporterService? {
        return services.firstOrNull { it.id == id }
    }

    enum class Prompt {
        /**
         * Never prompt the user. Always submit crash reports immediately.
         */
        NEVER,

        /**
         * Only prompt the user for native code crashes.
         */
        ONLY_NATIVE_CRASH,

        /**
         * Always prompt the user for confirmation before sending crash reports.
         */
        ALWAYS
    }

    /**
     * Configuration for the crash reporter prompt.
     */
    data class PromptConfiguration(
        internal val appName: String = "App",
        internal val organizationName: String = "Mozilla",
        internal val message: String? = null,
        @StyleRes internal val theme: Int = R.style.Theme_Mozac_CrashReporter
    )

    companion object {
        @Volatile
        private var instance: CrashReporter? = null

        @VisibleForTesting
        internal fun reset() {
            instance = null
        }

        internal val requireInstance: CrashReporter
            get() = instance ?: throw IllegalStateException(
                "You need to call install() on your CrashReporter instance from Application.onCreate().")
    }
}

/**
 * A base class for exceptions describing crash reporter exception.
 */
internal abstract class CrashReporterException(message: String, cause: Throwable?) : Exception(message, cause) {
    /**
     * Stacktrace was expected to be present, but it wasn't.
     */
    internal class UnexpectedlyMissingStacktrace(
        message: String,
        cause: Throwable?
    ) : CrashReporterException(message, cause)
}
