package ru.dbotthepony.kstarbound.server

import com.google.gson.JsonObject
import io.netty.channel.ChannelHandlerContext
import it.unimi.dsi.fastutil.objects.ObjectOpenHashSet
import kotlinx.coroutines.Job
import kotlinx.coroutines.channels.Channel
import kotlinx.coroutines.delay
import kotlinx.coroutines.future.await
import kotlinx.coroutines.launch
import org.apache.logging.log4j.LogManager
import ru.dbotthepony.kommons.io.ByteKey
import ru.dbotthepony.kommons.util.Either
import ru.dbotthepony.kommons.util.KOptional
import ru.dbotthepony.kommons.vector.Vector2i
import ru.dbotthepony.kommons.vector.Vector3i
import ru.dbotthepony.kstarbound.Globals
import ru.dbotthepony.kstarbound.defs.WarpAction
import ru.dbotthepony.kstarbound.defs.WarpAlias
import ru.dbotthepony.kstarbound.defs.WarpMode
import ru.dbotthepony.kstarbound.defs.WorldID
import ru.dbotthepony.kstarbound.defs.world.CelestialParameters
import ru.dbotthepony.kstarbound.defs.world.VisitableWorldParameters
import ru.dbotthepony.kstarbound.network.Connection
import ru.dbotthepony.kstarbound.network.ConnectionSide
import ru.dbotthepony.kstarbound.network.ConnectionType
import ru.dbotthepony.kstarbound.network.IServerPacket
import ru.dbotthepony.kstarbound.network.packets.ClientContextUpdatePacket
import ru.dbotthepony.kstarbound.network.packets.clientbound.CelestialResponsePacket
import ru.dbotthepony.kstarbound.network.packets.clientbound.PlayerWarpResultPacket
import ru.dbotthepony.kstarbound.network.packets.clientbound.ServerDisconnectPacket
import ru.dbotthepony.kstarbound.server.world.ServerWorldTracker
import ru.dbotthepony.kstarbound.server.world.WorldStorage
import ru.dbotthepony.kstarbound.server.world.LegacyWorldStorage
import ru.dbotthepony.kstarbound.server.world.ServerWorld
import ru.dbotthepony.kstarbound.world.SystemWorldLocation
import ru.dbotthepony.kstarbound.world.UniversePos
import java.util.HashMap
import java.util.UUID
import kotlin.properties.Delegates

// serverside part of connection
class ServerConnection(val server: StarboundServer, type: ConnectionType) : Connection(ConnectionSide.SERVER, type) {
	var tracker: ServerWorldTracker? = null
	var worldStartAcknowledged = false
	var returnWarp: WarpAction? = null

	val world: ServerWorld?
		get() = tracker?.world

	// packets which interact with world must be
	// executed on world's thread
	fun enqueue(task: ServerWorld.() -> Unit) {
		return tracker?.enqueue(task) ?: throw IllegalStateException("Not in world.")
	}

	lateinit var shipWorld: ServerWorld
		private set

	var uuid: UUID? = null

	init {
		connectionID = server.channels.nextConnectionID()

		rpc.add("team.fetchTeamStatus") {
			JsonObject()
		}
	}

	override fun toString(): String {
		val channel = if (hasChannel) channel.remoteAddress().toString() else "<no channel>"
		val world = tracker?.world?.toString() ?: "<not in world>"
		return "ServerConnection[$nickname $uuid ID=$connectionID channel=$channel / $world]"
	}

	fun alias(): String {
		return "$nickname <$connectionID/$uuid>"
	}

	private val shipChunks = HashMap<ByteKey, KOptional<ByteArray>>()
	private val modifiedShipChunks = ObjectOpenHashSet<ByteKey>()
	var shipChunkSource by Delegates.notNull<WorldStorage>()
		private set

	override fun setupLegacy() {
		super.setupLegacy()
		shipChunkSource = LegacyWorldStorage.memory(shipChunks)
	}

	override fun setupNative() {
		super.setupNative()
		shipChunkSource = WorldStorage.EMPTY
	}

	fun receiveShipChunks(chunks: Map<ByteKey, KOptional<ByteArray>>) {
		check(shipChunks.isEmpty()) { "Already has ship chunks" }
		shipChunks.putAll(chunks)
	}

	private var remoteVersion = 0L

	override fun flush() {
		if (isConnected) {
			val entries = rpc.write()

			if (entries != null || modifiedShipChunks.isNotEmpty() || server2clientGroup.upstream.hasChangedSince(remoteVersion)) {
				val (data, version) = server2clientGroup.write(remoteVersion, isLegacy)
				remoteVersion = version

				channel.write(ClientContextUpdatePacket(
					entries ?: listOf(),
					KOptional(modifiedShipChunks.associateWith { shipChunks[it]!! }),
					KOptional(data)))

				modifiedShipChunks.clear()
			}
		}

		super.flush()
	}

	override fun onChannelClosed() {
		playerEntity = null

		super.onChannelClosed()
		warpQueue.close()
		server.channels.freeConnectionID(connectionID)
		server.channels.connections.remove(this)
		server.freeNickname(nickname)

		announceDisconnect("Connection to remote host is lost.")

		if (::shipWorld.isInitialized) {
			shipWorld.close()
		}

		if (countedTowardsPlayerCount) {
			countedTowardsPlayerCount = false
			server.channels.decrementPlayerCount()
		}
	}

	private val warpQueue = Channel<Pair<WarpAction, Boolean>>(capacity = 10)

	private suspend fun warpEventLoop() {
		while (true) {
			var (request, deploy) = warpQueue.receive()

			if (request is WarpAlias)
				request = request.remap(this)

			LOGGER.info("Trying to warp $this to $request")

			val resolve = request.resolve(this)

			if (resolve.isLimbo) {
				send(PlayerWarpResultPacket(false, request, true))
			} else if (tracker?.world?.worldID == resolve) {
				LOGGER.info("$this tried to warp into world they are already in.")
				send(PlayerWarpResultPacket(true, request, false))
			} else {
				val world = server.worlds[resolve]

				if (world == null) {
					send(PlayerWarpResultPacket(false, request, false))
					continue
				}

				try {
					world.acceptClient(this, request).await()

					if (resolve is WorldID.ShipWorld) {
						val connection = server.channels.connectionByUUID(resolve.uuid)

						if (connection != null) {
							orbitalWarpAction = connection.currentOrbitalWarpAction
						}
					} else {
						orbitalWarpAction = KOptional()
					}
				} catch (err: Throwable) {
					send(PlayerWarpResultPacket(false, request, false))

					if (world == shipWorld) {
						disconnect("ShipWorld refused to accept its owner: $err")
					} else {
						enqueueWarp(returnWarp ?: WarpAlias.OwnShip)
					}
				}
			}
		}
	}

	private val flyShipQueue = Channel<Pair<Vector3i, SystemWorldLocation>>(capacity = 40)

	fun flyShip(system: Vector3i, location: SystemWorldLocation) {
		flyShipQueue.trySend(system to location)
	}

	private var currentOrbitalWarpAction = KOptional<Pair<WarpAction, WarpMode>>()

	// coordinates ship flight
	private suspend fun shipFlightEventLoop() {
		shipWorld.sky.startFlying(true, true)
		var visited = 0

		LOGGER.info("Finding starter world for ${alias()}...")
		val params = Globals.universeServer.findStarterWorldParameters

		// visit all since randomly trying to find specific world is not healthy performance wise
		val found = server.universe.findRandomWorld(params.tries, params.range, visitAll = true, predicate = {
			if (++visited % 600 == 0) {
				LOGGER.info("Still finding starter world for ${alias()}...")
			}

			val parameters = server.universe.parameters(it) ?: return@findRandomWorld false
			if (parameters.visitableParameters == null) return@findRandomWorld false
			if (!params.starterWorld.test(parameters.visitableParameters!!)) return@findRandomWorld false

			val children = ArrayList<VisitableWorldParameters>()

			for (child in server.universe.children(it.system())) {
				val p = server.universe.parameters(child)

				if (p?.visitableParameters != null) {
					children.add(p.visitableParameters!!)
				}

				for (child2 in server.universe.children(child)) {
					val p2 = server.universe.parameters(child2)

					if (p2?.visitableParameters != null) {
						children.add(p2.visitableParameters!!)
					}
				}
			}

			params.requiredSystemWorlds.all { predicate -> children.any { predicate.test(it) } }
		})

		if (found == null) {
			LOGGER.fatal("Unable to find starter world for $this!")
			disconnect("Unable to find starter world")
			return
		}

		LOGGER.info("Found appropriate starter world at $found for ${alias()}")

		var world = server.loadSystemWorld(found.location).await()
		var ship = world.addClient(this, location = SystemWorldLocation.Celestial(found)).await()
		shipWorld.sky.stopFlyingAt(ship.location.skyParameters(world))
		shipCoordinate = found

		run {
			val action = ship.location.orbitalAction(world)
			orbitalWarpAction = action

			for (client in shipWorld.clients) {
				client.client.orbitalWarpAction = action
			}
		}

		var currentFlightJob: Job? = null

		while (true) {
			val (system, location) = flyShipQueue.receive()

			if (system == world.location) {
				// fly ship in current system
				currentFlightJob?.cancel()
				val flight = world.flyShip(this, location)

				shipWorld.mailbox.execute {
					shipWorld.sky.startFlying(false)
				}

				currentFlightJob = scope.launch {
					val coords = flight.await()
					val action = coords.orbitalAction(world)
					currentOrbitalWarpAction = action

					for (client in shipWorld.clients) {
						client.client.orbitalWarpAction = action
					}

					val sky = coords.skyParameters(world)

					shipWorld.mailbox.execute {
						shipWorld.sky.stopFlyingAt(sky)
					}
				}

				currentOrbitalWarpAction = KOptional()

				for (client in shipWorld.clients) {
					client.client.orbitalWarpAction = KOptional()
				}
			} else {
				// we need to travel to other system
				val exists = server.universe.parameters(UniversePos(system)) != null

				if (!exists)
					continue

				currentFlightJob?.cancel()
				world.removeClient(this)

				shipWorld.mailbox.execute {
					shipWorld.sky.startFlying(true)
				}

				LOGGER.info("${alias()} is flying to new system: ${UniversePos(system)}")
				val newSystem = server.loadSystemWorld(system)

				shipCoordinate = UniversePos(system)
				currentOrbitalWarpAction = KOptional()

				for (client in shipWorld.clients) {
					client.client.orbitalWarpAction = KOptional()
				}

				world = newSystem.await()
				ship = world.addClient(this).await()

				val newParams = ship.location.skyParameters(world)

				shipWorld.mailbox.execute {
					shipWorld.sky.stopFlyingAt(newParams)
				}

				// this seems to be way too big isn't it?
				delay((Globals.universeServer.queuedFlightWaitTime * 1000.0).toLong())
			}
		}
	}

	val celestialRequestQueue = Channel<Either<Vector2i, Vector3i>>(capacity = 100)

	fun pushCelestialRequests(requests: Iterable<Either<Vector2i, Vector3i>>) {
		requests.forEach {
			celestialRequestQueue.trySend(it)
		}
	}

	private suspend fun handleCelestialRequests(requests: Collection<Either<Vector2i, Vector3i>>) {
		val responses = ArrayList<Either<CelestialResponsePacket.ChunkData, CelestialResponsePacket.SystemData>>()

		for (request in requests) {
			if (request.isLeft) {
				val chunkPos = request.left()
				responses.add(Either.left(server.universe.getChunk(chunkPos)?.toNetwork() ?: continue))
			} else {
				val systemPos = UniversePos(request.right())
				val map = HashMap<Int, CelestialResponsePacket.PlanetData>()

				for (planet in server.universe.children(systemPos)) {
					val planetData = server.universe.parameters(planet) ?: continue
					val children = HashMap<Int, CelestialParameters>()

					for (satellite in server.universe.children(planet)) {
						children[satellite.satelliteOrbit] = server.universe.parameters(satellite) ?: continue
					}

					map[planet.planetOrbit] = CelestialResponsePacket.PlanetData(planetData, children)
				}

				responses.add(Either.right(CelestialResponsePacket.SystemData(systemPos.location, map)))
			}
		}

		send(CelestialResponsePacket(responses))
	}

	// protects from malicious actors
	private suspend fun celestialRequestsHandler() {
		while (true) {
			val next = celestialRequestQueue.receive()
			val requests = ArrayList<Either<Vector2i, Vector3i>>()
			requests.add(next)

			while (true) {
				val tryNext = celestialRequestQueue.tryReceive().getOrNull() ?: break
				requests.add(tryNext)
			}

			handleCelestialRequests(requests)
		}
	}

	fun enqueueWarp(destination: WarpAction, deploy: Boolean = false) {
		warpQueue.trySend(destination to deploy)
	}

	fun tick() {
		if (!isConnected || !channel.isOpen)
			return

		flush()
	}

	private var announcedDisconnect = true

	private fun announceDisconnect(reason: String) {
		if (!announcedDisconnect && nickname.isNotBlank()) {
			if (reason.isBlank()) {
				server.chat.systemMessage("Player '$nickname' disconnected")
			} else {
				server.chat.systemMessage("Player '$nickname' disconnected ($reason)")
			}

			announcedDisconnect = true
		}
	}

	override fun disconnect(reason: String) {
		announceDisconnect(reason)

		if (channel.isOpen) {
			// send pending updates
			flush()
		}

		tracker?.remove()
		tracker = null

		if (::shipWorld.isInitialized) {
			shipWorld.close()
		}

		if (channel.isOpen) {
			// say goodbye
			channel.write(ServerDisconnectPacket(reason))
			channel.flush()
			channel.close()
		}
	}

	override fun channelRead(ctx: ChannelHandlerContext, msg: Any) {
		if (msg is IServerPacket) {
			try {
				msg.play(this)
			} catch (err: Throwable) {
				LOGGER.error("Failed to handle serverbound packet $msg", err)
				disconnect("Incoming packet caused an exception: $err")
			}
		} else {
			LOGGER.error("Unknown serverbound packet type $msg")
			disconnect("Unknown serverbound packet type $msg")
		}
	}

	private var countedTowardsPlayerCount = false

	override fun inGame() {
		announcedDisconnect = false
		server.chat.systemMessage("Player '$nickname' connected")
		countedTowardsPlayerCount = true
		server.channels.incrementPlayerCount()

		if (isLegacy) {
			scope.launch { celestialRequestsHandler() }

			ServerWorld.load(server, shipChunkSource, WorldID.ShipWorld(uuid!!)).thenAccept {
				if (!isConnected || !channel.isOpen) {
					LOGGER.warn("$this disconnected before loaded their ShipWorld")
					it.close()
				} else {
					shipWorld = it
					shipWorld.thread.start()
					enqueueWarp(WarpAlias.OwnShip)
					shipUpgrades = shipUpgrades.addCapability("planetTravel")
					shipUpgrades = shipUpgrades.addCapability("teleport")
					shipUpgrades = shipUpgrades.copy(maxFuel = 10000, shipLevel = 1)
					scope.launch { warpEventLoop() }
					scope.launch { shipFlightEventLoop() }

					if (server.channels.connections.size > 1) {
						enqueueWarp(WarpAction.Player(server.channels.connections.first().uuid!!))
					}
				}
			}.exceptionally {
				LOGGER.error("Error while initializing shipworld for $this", it)
				disconnect("Error while initializing shipworld for player: $it")
				null
			}
		}
	}

	companion object {
		private val LOGGER = LogManager.getLogger()
	}
}