/*
Mangadex@Home
Copyright (c) 2020, MangaDex Network
This file is part of MangaDex@Home.

MangaDex@Home 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.

MangaDex@Home 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 this MangaDex@Home.  If not, see <http://www.gnu.org/licenses/>.
*/
package mdnet.server

import io.github.resilience4j.circuitbreaker.CircuitBreakerConfig
import io.github.resilience4j.circuitbreaker.CircuitBreakerRegistry
import io.github.resilience4j.micrometer.tagged.TaggedCircuitBreakerMetrics
import io.micrometer.core.instrument.FunctionCounter
import io.micrometer.prometheus.PrometheusMeterRegistry
import mdnet.cache.ImageStorage
import mdnet.data.Statistics
import mdnet.logging.info
import mdnet.logging.warn
import mdnet.metrics.GeoIpMetricsFilterBuilder
import mdnet.metrics.PostTransactionLabeler
import mdnet.netty.Netty
import mdnet.settings.MetricsSettings
import mdnet.settings.RemoteSettings
import mdnet.settings.ServerSettings
import org.http4k.core.*
import org.http4k.filter.*
import org.http4k.routing.*
import org.http4k.server.Http4kServer
import org.http4k.server.asServer
import org.slf4j.LoggerFactory
import java.time.Duration

fun getServer(
    storage: ImageStorage,
    remoteSettings: RemoteSettings,
    serverSettings: ServerSettings,
    metricsSettings: MetricsSettings,
    statistics: Statistics,
    registry: PrometheusMeterRegistry,
    client: HttpHandler
): Http4kServer {
    val circuitBreakerRegistry = CircuitBreakerRegistry.ofDefaults()
    TaggedCircuitBreakerMetrics
        .ofCircuitBreakerRegistry(circuitBreakerRegistry)
        .bindTo(registry)

    val circuitBreaker = circuitBreakerRegistry.circuitBreaker(
        "upstream",
        CircuitBreakerConfig.custom()
            .slidingWindow(50, 20, CircuitBreakerConfig.SlidingWindowType.COUNT_BASED)
            .permittedNumberOfCallsInHalfOpenState(10)
            .slowCallDurationThreshold(Duration.ofSeconds(20))
            .waitDurationInOpenState(Duration.ofSeconds(20))
            .build()
    )

    circuitBreaker.eventPublisher.onFailureRateExceeded {
        LOGGER.warn { "Circuit breaker has exceeded failure rate" }
    }

    circuitBreaker.eventPublisher.onSlowCallRateExceeded {
        LOGGER.warn { "Circuit breaker has exceeded slow call rate" }
    }

    circuitBreaker.eventPublisher.onReset {
        LOGGER.warn { "Circuit breaker has rest" }
    }

    circuitBreaker.eventPublisher.onStateTransition {
        LOGGER.warn { "Circuit breaker has moved from ${it.stateTransition.fromState} to ${it.stateTransition.toState}" }
    }

    val circuited = ResilienceFilters.CircuitBreak(
        circuitBreaker,
        isError = { r: Response -> !r.status.successful }
    )

    val upstream = ClientFilters.MicrometerMetrics.RequestTimer(registry)
        .then(ClientFilters.SetBaseUriFrom(remoteSettings.imageServer))
        .then(circuited)
        .then(client)

    val imageServer = ImageServer(
        storage = storage,
        upstream = upstream,
        registry = registry
    )

    FunctionCounter.builder(
        "client_sent_bytes",
        statistics,
        { it.bytesSent.get().toDouble() }
    ).register(registry)

    val verifier = TokenVerifier(
        tokenKey = remoteSettings.tokenKey,
    )

    return timeRequest()
        .then(addCommonHeaders())
        .then(catchAllHideDetails())
        .then(
            routes(
                "/{token}/data/{chapterHash}/{fileName}" bind Method.GET to verifier.then(
                    imageServer.handler(
                        dataSaver = false,
                    )
                ),
                "/{token}/data-saver/{chapterHash}/{fileName}" bind Method.GET to verifier.then(
                    imageServer.handler(
                        dataSaver = true,
                    )
                ),
                "/data/{chapterHash}/{fileName}" bind Method.GET to verifier.then(
                    imageServer.handler(
                        dataSaver = false,
                    )
                ),
                "/data-saver/{chapterHash}/{fileName}" bind Method.GET to verifier.then(
                    imageServer.handler(
                        dataSaver = true,
                    )
                ),
                "/prometheus" bind Method.GET to {
                    Response(Status.OK).body(registry.scrape())
                },
            ).withFilter(
                ServerFilters.MicrometerMetrics.RequestTimer(registry, labeler = PostTransactionLabeler())
            ).withFilter(
                GeoIpMetricsFilterBuilder(metricsSettings.enableGeoip, metricsSettings.geoipLicenseKey, registry).build()
            )
        )
        .asServer(Netty(remoteSettings.tls!!, serverSettings, statistics))
}

private val LOGGER = LoggerFactory.getLogger(ImageServer::class.java)

fun timeRequest(): Filter {
    return Filter { next: HttpHandler ->
        { request: Request ->
            val cleanedUri = request.uri.path.replaceBefore("/data", "/{token}")

            LOGGER.info { "Request for $cleanedUri received" }

            val start = System.currentTimeMillis()
            val response = next(request)
            val latency = System.currentTimeMillis() - start

            LOGGER.info { "Request for $cleanedUri completed (TTFB) in ${latency}ms" }

            response
        }
    }
}