PhysicalConnectivity/src/main/kotlin/net/shadowfacts/phycon/block/terminal/TerminalBlockEntity.kt

package net.shadowfacts.phycon.block.terminal

import alexiil.mc.lib.attributes.item.GroupedItemInvView
import alexiil.mc.lib.attributes.item.ItemStackCollections
import alexiil.mc.lib.attributes.item.ItemStackUtil
import net.fabricmc.fabric.api.block.entity.BlockEntityClientSerializable
import net.fabricmc.fabric.api.screenhandler.v1.ExtendedScreenHandlerFactory
import net.minecraft.entity.player.PlayerEntity
import net.minecraft.entity.player.PlayerInventory
import net.minecraft.inventory.Inventory
import net.minecraft.inventory.InventoryChangedListener
import net.minecraft.item.ItemStack
import net.minecraft.nbt.CompoundTag
import net.minecraft.network.PacketByteBuf
import net.minecraft.screen.ScreenHandler
import net.minecraft.server.network.ServerPlayerEntity
import net.minecraft.text.TranslatableText
import net.minecraft.util.Tickable
import net.minecraft.util.math.Direction
import net.shadowfacts.phycon.api.Interface
import net.shadowfacts.phycon.api.packet.Packet
import net.shadowfacts.phycon.api.util.IPAddress
import net.shadowfacts.phycon.init.PhyBlockEntities
import net.shadowfacts.phycon.block.DeviceBlockEntity
import net.shadowfacts.phycon.util.NetworkUtil
import net.shadowfacts.phycon.component.*
import net.shadowfacts.phycon.packet.*
import java.lang.ref.WeakReference
import java.util.*
import kotlin.math.min
import kotlin.properties.Delegates

/**
 * @author shadowfacts
 */
class TerminalBlockEntity: DeviceBlockEntity(PhyBlockEntities.TERMINAL),
	InventoryChangedListener,
	BlockEntityClientSerializable,
	Tickable,
	ItemStackPacketHandler,
	NetworkStackDispatcher<TerminalBlockEntity.PendingInsertion> {

	companion object {
		// the locate/insertion timeouts are only 1 tick because that's long enough to hear from every device on the network
		// in a degraded state (when there's latency in the network), not handling interface priorities correctly is acceptable
		val LOCATE_REQUEST_TIMEOUT: Long = 1 // ticks
		val INSERTION_TIMEOUT: Long = 1
	}

	private val inventoryCache = mutableMapOf<IPAddress, GroupedItemInvView>()
	val internalBuffer = TerminalBufferInventory(18)

	private val pendingRequests = LinkedList<StackLocateRequest>()
	override val pendingInsertions = mutableListOf<PendingInsertion>()
	override val dispatchStackTimeout = INSERTION_TIMEOUT

	private var observers = 0
	val cachedNetItems = ItemStackCollections.intMap()

	// todo: multiple players could have the terminal open simultaneously
	var netItemObserver: WeakReference<NetItemObserver>? = null

	init {
		internalBuffer.addListener(this)
	}

	override fun findDestination(): Interface? {
		for (dir in Direction.values()) {
			val itf = NetworkUtil.findConnectedInterface(world!!, pos, dir)
			if (itf != null) {
				return itf
			}
		}
		return null
	}

	override fun handle(packet: Packet) {
		when (packet) {
			is ReadInventoryPacket -> handleReadInventory(packet)
			is DeviceRemovedPacket -> handleDeviceRemoved(packet)
			is StackLocationPacket -> handleStackLocation(packet)
			is ItemStackPacket -> handleItemStack(packet)
			is CapacityPacket -> handleCapacity(packet)
		}
	}

	private fun handleReadInventory(packet: ReadInventoryPacket) {
		inventoryCache[packet.source] = packet.inventory
		updateAndSync()
	}

	private fun handleDeviceRemoved(packet: DeviceRemovedPacket) {
		inventoryCache.remove(packet.source)
		updateAndSync()
	}

	private fun handleStackLocation(packet: StackLocationPacket) {
		val request = pendingRequests.firstOrNull {
			ItemStackUtil.areEqualIgnoreAmounts(it.stack, packet.stack)
		}
		if (request != null) {
			request.results.add(packet.amount to packet.stackProvider)
			if (request.isFinishable(counter)) {
				stackLocateRequestCompleted(request)
			}
		}
	}

	override fun doHandleItemStack(packet: ItemStackPacket): ItemStack {
		val remaining = internalBuffer.insertFromNetwork(packet.stack)

		// this happens outside the normal update loop because by receiving the item stack packet
		// we "know" how much the count in the source inventory has changed
		updateAndSync()

		return remaining
	}

	private fun updateAndSync() {
		updateNetItems()
		// syncs the internal buffer to the client
		sync()
		// syncs the open container (if any) to the client
		netItemObserver?.get()?.netItemsChanged()
	}

	private fun updateNetItems() {
		cachedNetItems.clear()
		for (inventory in inventoryCache.values) {
			for (stack in inventory.storedStacks) {
				val amount = inventory.getAmount(stack)
				cachedNetItems.mergeInt(stack, amount) { a, b -> a + b }
			}
		}
	}

	private fun beginInsertions() {
		if (world!!.isClient) return

		for (slot in 0 until internalBuffer.size()) {
			if (internalBuffer.getMode(slot) != TerminalBufferInventory.Mode.TO_NETWORK) continue
			if (pendingInsertions.any { it.bufferSlot == slot }) continue
			val stack = internalBuffer.getStack(slot)
			dispatchItemStack(stack) { insertion ->
				insertion.bufferSlot = slot
			}
		}
	}

	private fun finishPendingRequests() {
		if (world!!.isClient) return
		if (pendingRequests.isEmpty()) return

		val finishable = pendingRequests.filter { it.isFinishable(counter) }
		// stackLocateRequestCompleted removes the object from pendingRequests
		finishable.forEach(::stackLocateRequestCompleted)
	}

	override fun tick() {
		super.tick()

		if (!world!!.isClient) {
			finishPendingRequests()
			finishTimedOutPendingInsertions()
		}

		if (counter % 20 == 0L && !world!!.isClient) {
			beginInsertions()
		}
	}

	fun onActivate(player: PlayerEntity) {
		if (!world!!.isClient) {
			updateAndSync()

			inventoryCache.clear()
			sendPacket(RequestInventoryPacket(ipAddress))
			val factory = object: ExtendedScreenHandlerFactory {
				override fun createMenu(syncId: Int, playerInv: PlayerInventory, player: PlayerEntity): ScreenHandler {
					return TerminalScreenHandler(syncId, playerInv, this@TerminalBlockEntity)
				}

				override fun getDisplayName() = TranslatableText("block.phycon.terminal")

				override fun writeScreenOpeningData(player: ServerPlayerEntity, buf: PacketByteBuf) {
					buf.writeBlockPos(this@TerminalBlockEntity.pos)
				}
			}
			player.openHandledScreen(factory)
		}
	}

	fun requestItem(stack: ItemStack, amount: Int = stack.count) {
		val request = StackLocateRequest(stack, amount, counter)
		pendingRequests.add(request)
		// locate packets are sent immediately instead of being added to a queue
		// otherwise the terminal UI feels sluggish and unresponsive
		sendPacket(LocateStackPacket(stack, ipAddress))
	}

	private fun stackLocateRequestCompleted(request: StackLocateRequest) {
		pendingRequests.remove(request)

		val sortedResults = request.results.toMutableList()
		sortedResults.sortWith { a, b ->
			// sort results first by provider priority, and then by the count that it can provide
			if (a.second.providerPriority == b.second.providerPriority) {
				b.first - a.first
			} else {
				b.second.providerPriority - a.second.providerPriority
			}
		}
		var amountRequested = 0
		while (amountRequested < request.amount && sortedResults.isNotEmpty()) {
			val (sourceAmount, sourceInterface) = sortedResults.removeAt(0)
			val amountToRequest = min(sourceAmount, request.amount - amountRequested)
			amountRequested += amountToRequest
			sendPacket(ExtractStackPacket(request.stack, amountToRequest, ipAddress, sourceInterface.ipAddress))
		}
	}

	override fun createPendingInsertion(stack: ItemStack) = PendingInsertion(stack, counter)

	override fun finishInsertion(insertion: PendingInsertion): ItemStack {
		val remaining = super.finishInsertion(insertion)
		internalBuffer.setStack(insertion.bufferSlot, remaining)

		// as with extracting, we "know" the new amounts and so can update instantly without actually sending out packets
		updateAndSync()

		return remaining
	}

	override fun onInventoryChanged(inv: Inventory) {
		if (inv == internalBuffer && world != null && !world!!.isClient) {
			markDirty()
			sync()
		}
	}

	override fun toCommonTag(tag: CompoundTag) {
		super.toCommonTag(tag)
		tag.put("InternalBuffer", internalBuffer.toTag())
	}

	override fun fromCommonTag(tag: CompoundTag) {
		super.fromCommonTag(tag)
		internalBuffer.fromTag(tag.getCompound("InternalBuffer"))
	}
	interface NetItemObserver {
		fun netItemsChanged()
	}

	class PendingInsertion(stack: ItemStack, timestamp: Long): NetworkStackDispatcher.PendingInsertion<PendingInsertion>(stack, timestamp) {
		var bufferSlot by Delegates.notNull<Int>()
	}

}

data class StackLocateRequest(
		val stack: ItemStack,
		val amount: Int,
		val timestamp: Long,
		var results: MutableSet<Pair<Int, NetworkStackProvider>> = mutableSetOf()
) {
	val totalResultAmount: Int
		get() = results.fold(0) { acc, (amount, _) -> acc + amount }

	fun isFinishable(currentTimestamp: Long): Boolean {
		// we can't check totalResultAmount >= amount because we need to hear back from all network stack providers to
		// correctly sort by priority
		return currentTimestamp - timestamp >= TerminalBlockEntity.LOCATE_REQUEST_TIMEOUT
	}
}