package net.shadowfacts.phycon.network.block.terminal

import alexiil.mc.lib.attributes.item.GroupedItemInv
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.block.BlockState
import net.minecraft.entity.ItemEntity
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.nbt.ListTag
import net.minecraft.network.PacketByteBuf
import net.minecraft.screen.ScreenHandler
import net.minecraft.server.network.ServerPlayerEntity
import net.minecraft.text.LiteralText
import net.minecraft.util.Tickable
import net.shadowfacts.phycon.api.packet.Packet
import net.shadowfacts.phycon.api.util.MACAddress
import net.shadowfacts.phycon.init.PhyBlockEntities
import net.shadowfacts.phycon.network.DeviceBlockEntity
import net.shadowfacts.phycon.network.block.netinterface.InterfaceBlockEntity
import net.shadowfacts.phycon.network.packet.*
import net.shadowfacts.phycon.util.fromTag
import net.shadowfacts.phycon.util.toTag
import java.util.*
import kotlin.math.min

/**
 * @author shadowfacts
 */
class TerminalBlockEntity: DeviceBlockEntity(PhyBlockEntities.TERMINAL), InventoryChangedListener, BlockEntityClientSerializable, Tickable {

	companion object {
		val LOCATE_REQUEST_TIMEOUT = 40 // ticks
	}

	private val inventoryCache = mutableMapOf<MACAddress, GroupedItemInv>()
	val internalBuffer = TerminalBufferInventory(18)

	private val pendingRequests = LinkedList<StackLocateRequest>()

	private var observers = 0
	val cachedNetItems = ItemStackCollections.intMap()
	var cachedSortedNetItems = listOf<ItemStack>()
	var counter = 0

	init {
		internalBuffer.addListener(this)
	}

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

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

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

	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.sourceInterface)
			if (request.totalResultAmount >= request.amount || counter - request.timestamp >= LOCATE_REQUEST_TIMEOUT || request.results.size >= inventoryCache.size) {
				pendingRequests.remove(request)
				stackLocateRequestCompleted(request)
			}
		}
	}

	private fun handleItemStack(packet: ItemStackPacket) {
		val remaining = internalBuffer.insertFromNetwork(packet.stack)
		if (!remaining.isEmpty) {
			// todo: calculate entity spawn point by finding non-obstructed location
			val entity = ItemEntity(world!!, pos.x.toDouble(), pos.y + 1.0, pos.z.toDouble(), remaining)
			world!!.spawnEntity(entity)
		}
	}

	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 }
			}
		}
		// todo: is the map necessary or is just the sorted list enough?
		cachedSortedNetItems = cachedNetItems.object2IntEntrySet().sortedByDescending { it.intValue }.map {
			val stack = it.key.copy()
			stack.count = it.intValue
			stack
		}
	}

	fun addObserver() {
		observers++
	}

	fun removeObserver() {
		observers--
	}

	override fun tick() {
		if (observers > 0 && (++counter % 20) == 0) {
			if (world!!.isClient) {
				println(cachedNetItems)
			} else {
				updateNetItems()
				sync()
			}
		}
	}

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

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

				override fun getDisplayName() = LiteralText("Terminal")

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

	fun requestItem(stack: ItemStack, amount: Int = stack.count) {
		pendingRequests.add(StackLocateRequest(stack, amount, counter))
		sendToSingle(LocateStackPacket(stack, macAddress))
	}

	private fun stackLocateRequestCompleted(request: StackLocateRequest) {
		// todo: also sort results by interface priority
		val sortedResults = request.results.sortedByDescending { it.first }.toMutableList()
		var amountRequested = 0
		while (amountRequested < request.amount && sortedResults.isNotEmpty()) {
			val (sourceAmount, sourceInterface) = sortedResults.removeAt(0)
			val amountToRequest = min(sourceAmount, request.amount - amountRequested)
			amountRequested += amountToRequest
			sendToSingle(ExtractStackPacket(request.stack, amountToRequest, macAddress, sourceInterface.macAddress))
		}
	}

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

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

	override fun fromTag(state: BlockState, tag: CompoundTag) {
		super.fromTag(state, tag)
		internalBuffer.fromTag(tag.getList("InternalBuffer", 10))
	}

	override fun toClientTag(tag: CompoundTag): CompoundTag {
		tag.put("InternalBuffer", internalBuffer.toTag())
		val list = ListTag()
		tag.put("CachedNetItems", list)
		for ((stack, amount) in cachedNetItems) {
			val entryTag = stack.toTag(CompoundTag())
			entryTag.putInt("NetAmount", amount)
			list.add(entryTag)
		}
		return tag
	}

	override fun fromClientTag(tag: CompoundTag) {
		tag.getList("InternalBuffer", 10)?.also { list ->
			if (list.isNotEmpty()) {
				internalBuffer.fromTag(list)
			} else {
				// todo: should this clear or just do nothing?
				internalBuffer.clear()
			}
		}
		val list = tag.getList("CachedNetItems", 10)
		cachedNetItems.clear()
		for (entryTag in list) {
			val stack = ItemStack.fromTag(entryTag as CompoundTag)
			val netAmount = entryTag.getInt("NetAmount")
			cachedNetItems[stack] = netAmount
		}
		cachedSortedNetItems = cachedNetItems.object2IntEntrySet().sortedByDescending { it.intValue }.map {
			val stack = it.key.copy()
			stack.count = it.intValue
			stack
		}
	}

}

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