/*
 * ============LICENSE_START=======================================================
 * dcaegen2-collectors-veshv
 * ================================================================================
 * Copyright (C) 2018-2019 NOKIA
 * ================================================================================
 * 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.
 * ============LICENSE_END=========================================================
 */
package org.onap.dcae.collectors.veshv.main

import org.onap.dcae.collectors.veshv.api.ServersFactory
import org.onap.dcae.collectors.veshv.config.api.ConfigurationModule
import org.onap.dcae.collectors.veshv.config.api.ConfigurationStateListener
import org.onap.dcae.collectors.veshv.config.api.model.HvVesConfiguration
import org.onap.dcae.collectors.veshv.healthcheck.api.HealthDescription
import org.onap.dcae.collectors.veshv.healthcheck.api.HealthState
import org.onap.dcae.collectors.veshv.main.metrics.MicrometerMetrics
import org.onap.dcae.collectors.veshv.main.servers.HealthCheckServer
import org.onap.dcae.collectors.veshv.ssl.boundary.SslContextFactory
import org.onap.dcae.collectors.veshv.domain.logging.ServiceContext
import org.onap.dcae.collectors.veshv.utils.ServerHandle
import org.onap.dcae.collectors.veshv.utils.logging.Logger
import org.onap.dcae.collectors.veshv.utils.registerShutdownHook
import reactor.core.publisher.Mono
import reactor.core.scheduler.Schedulers
import java.time.Duration
import java.util.concurrent.atomic.AtomicReference


private const val VES_HV_PACKAGE = "org.onap.dcae.collectors.veshv"
private val logger = Logger("$VES_HV_PACKAGE.main")

private val hvVesServer = AtomicReference<ServerHandle>()
private val sslContextFactory = SslContextFactory()
private val maxCloseTime = Duration.ofSeconds(10)

fun main(args: Array<String>) {
    val configStateListener = object : ConfigurationStateListener {
        override fun retrying() {
            HealthState.INSTANCE.changeState(HealthDescription.RETRYING_FOR_DYNAMIC_CONFIGURATION)
        }
    }
    val configurationModule = ConfigurationModule(configStateListener)
    HealthCheckServer.start(configurationModule.healthCheckPort(args)).block()
    configurationModule
            .hvVesConfigurationUpdates(args, ServiceContext::mdc)
            .publishOn(Schedulers.single(Schedulers.elastic()))
            .doOnNext {
                logger.info(ServiceContext::mdc) { "Using updated configuration for new connections" }
                HealthState.INSTANCE.changeState(HealthDescription.HEALTHY)
            }
            .doOnError {
                logger.error(ServiceContext::mdc) { "Failed to create configuration: ${it.message}" }
                logger.withDebug(ServiceContext::mdc) { log("Detailed stack trace: ", it) }
                HealthState.INSTANCE.changeState(HealthDescription.DYNAMIC_CONFIGURATION_NOT_FOUND)
            }
            .flatMap(::startServer)
            .doOnError(::logServerStartFailed)
            .then()
            .block()
}

private fun startServer(config: HvVesConfiguration): Mono<ServerHandle> =
        stopRunningServer()
                .timeout(maxCloseTime)
                .then(deferredVesServer(config))
                .doOnNext {
                    registerShutdownHook { shutdownGracefully(it) }
                    hvVesServer.set(it)
                }

private fun deferredVesServer(config: HvVesConfiguration) = Mono.defer {
    Logger.setLogLevel(VES_HV_PACKAGE, config.logLevel)
    logger.debug(ServiceContext::mdc) { "Configuration: $config" }
    ServersFactory.createHvVesServer(
            config,
            sslContextFactory,
            MicrometerMetrics.INSTANCE
    ).start()
}

private fun stopRunningServer() = Mono.defer {
    hvVesServer.get()?.close() ?: Mono.empty()
}

internal fun shutdownGracefully(serverHandle: ServerHandle,
                                healthState: HealthState = HealthState.INSTANCE) {
    logger.debug(ServiceContext::mdc) { "Graceful shutdown started" }
    healthState.changeState(HealthDescription.SHUTTING_DOWN)
    serverHandle.close().block(maxCloseTime)
    logger.info(ServiceContext::mdc) { "Graceful shutdown completed" }
}

private fun logServerStartFailed(ex: Throwable) =
        logger.withError(ServiceContext::mdc) { log("Failed to start a server", ex) }