PhysicalConnectivity/src/main/kotlin/net/shadowfacts/phycon/network/block/netswitch/SwitchBlockEntity.kt

package net.shadowfacts.phycon.network.block.netswitch

import net.fabricmc.fabric.api.block.entity.BlockEntityClientSerializable
import net.minecraft.block.BlockState
import net.minecraft.block.entity.BlockEntity
import net.minecraft.nbt.CompoundTag
import net.minecraft.util.Tickable
import net.minecraft.util.math.Direction
import net.shadowfacts.phycon.api.Interface
import net.shadowfacts.phycon.api.frame.EthernetFrame
import net.shadowfacts.phycon.api.util.MACAddress
import net.shadowfacts.phycon.init.PhyBlockEntities
import net.shadowfacts.phycon.network.NetworkUtil
import java.lang.ref.WeakReference

/**
 * @author shadowfacts
 */
class SwitchBlockEntity: BlockEntity(PhyBlockEntities.SWITCH),
	BlockEntityClientSerializable,
	Tickable {

	companion object {
		var SWITCHING_CAPACITY = 256
	}

	val interfaces = Direction.values().map { SwitchInterface(it, WeakReference(this), MACAddress.random()) }

	private val macTable = mutableMapOf<MACAddress, Direction>()
	private var packetsHandledThisTick = 0

//	override fun handle(packet: Packet, itf: Interface) {
//		if (packetsHandledThisTick >= SWITCHING_CAPACITY) {
//			if (packet is ItemStackPacket) {
//				// todo: calculate entity spawn point by finding non-obstructed location
//				val entity = ItemEntity(world!!, pos.x.toDouble(), pos.y + 1.0, pos.z.toDouble(), packet.stack)
//				world!!.spawnEntity(entity)
//			}
//			return
//		}
//
//		packetsHandledThisTick++
//
//		if (packet.destination.isBroadcast) {
////			for (other in interfaces) {
////				if (other == itf) continue
////				sendPacket(packet, other)
////			}
//			flood(packet, itf)
//		} else {
//			val direction = ipTable[packet.destination]
//			if (direction != null) {
//				sendPacket()
////				val dest = findDestination(direction)
////				if (dest != null && packet.destination == dest.macAddress) {
////					sendPacke(packet, dest)
////					return
////				}
//			}
//			flood(packet, itf)
//		}
//	}

	fun interfaceForSide(side: Direction): SwitchInterface {
		return interfaces.find { it.side == side }!!
	}

	private fun handle(frame: EthernetFrame, fromItf: Interface) {
		val itfSide = (fromItf as SwitchInterface).side
		macTable[frame.source] = itfSide

		val knownDir = macTable[frame.destination]
		if (knownDir != null) {
			println("$this ($itfSide, ${fromItf.macAddress}) forwarding $frame to side $knownDir")
			interfaceForSide(knownDir).send(frame)
		} else {
			println("$this ($itfSide, ${fromItf.macAddress}) flooding $frame")
			flood(frame, fromItf)
		}
	}

	private fun flood(frame: EthernetFrame, source: Interface) {
		for (itf in interfaces) {
			if (source == itf) continue
			itf.send(frame)
		}
	}

	private fun findDestination(fromItf: Interface): Interface? {
		val side = (fromItf as SwitchInterface).side
		return NetworkUtil.findConnectedInterface(world!!, pos, side)
	}

	override fun tick() {
		packetsHandledThisTick = 0
	}

	override fun toTag(tag: CompoundTag): CompoundTag {
		tag.putLongArray("InterfaceAddresses", interfaces.map { it.macAddress.address })
		return super.toTag(tag)
	}

	override fun fromTag(state: BlockState, tag: CompoundTag) {
		super.fromTag(state, tag)
		tag.getLongArray("InterfaceAddresses")?.forEachIndexed { i, l ->
			interfaces[i].macAddress = MACAddress(l)
		}
	}

	override fun toClientTag(tag: CompoundTag): CompoundTag {
		tag.putLongArray("InterfaceAddresses", interfaces.map { it.macAddress.address })
		return tag
	}

	override fun fromClientTag(tag: CompoundTag) {
		tag.getLongArray("InterfaceAddresses")?.forEachIndexed { i, l ->
			interfaces[i].macAddress = MACAddress(l)
		}
	}

	class SwitchInterface(
		val side: Direction,
		val switch: WeakReference<SwitchBlockEntity>,
		@JvmField var macAddress: MACAddress,
	): Interface {
		override fun getMACAddress() = macAddress

		override fun receive(frame: EthernetFrame) {
			switch.get()?.handle(frame, this)
		}

		override fun send(frame: EthernetFrame) {
			switch.get()?.findDestination(this)?.receive(frame)
		}
	}

}