/*
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.core.instrument.binder.BaseUnits
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.DevSettings
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,
    devSettings: DevSettings,
    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 reset" }
    }

    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.serverError }
    )

    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",
        statistics
    ) { it.bytesSent.get().toDouble() }
        .baseUnit(BaseUnits.BYTES).register(registry)

    val verifier = TokenVerifier(
        tokenKey = remoteSettings.tokenKey,
        isDisabled = devSettings.disableTokenValidation,
    )

    if (devSettings.disableTokenValidation) {
        LOGGER.warn { "Token validation has been explicitly disabled. This should only be used for testing!" }
    }

    return timeRequest()
        .then(addCommonHeaders(devSettings.sendServerHeader))
        .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, serverSettings, devSettings, 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
        }
    }
}