KStarbound/src/main/kotlin/ru/dbotthepony/kstarbound/item/ItemStack.kt

package ru.dbotthepony.kstarbound.item

import com.google.gson.JsonNull
import com.google.gson.JsonObject
import com.google.gson.JsonPrimitive
import com.google.gson.TypeAdapter
import com.google.gson.internal.bind.TypeAdapters
import com.google.gson.stream.JsonReader
import com.google.gson.stream.JsonWriter
import org.classdump.luna.Table
import org.classdump.luna.TableFactory
import ru.dbotthepony.kstarbound.Registry
import ru.dbotthepony.kstarbound.Starbound
import ru.dbotthepony.kstarbound.defs.item.ItemDescriptor
import ru.dbotthepony.kstarbound.defs.item.api.IItemDefinition
import ru.dbotthepony.kommons.gson.consumeNull
import ru.dbotthepony.kommons.io.writeBinaryString
import ru.dbotthepony.kommons.io.writeVarLong
import ru.dbotthepony.kstarbound.Registries
import ru.dbotthepony.kstarbound.json.writeJsonElement
import ru.dbotthepony.kstarbound.lua.from
import java.io.DataOutputStream
import java.util.concurrent.atomic.AtomicLong

/**
 * Base class for instanced items in game
 */
open class ItemStack {
	constructor() {
		this.config = Registries.items.emptyRef
		this.parameters = JsonObject()
	}

	constructor(descriptor: ItemDescriptor) {
		this.config = Registries.items.ref(descriptor.name)
		this.count = descriptor.count
		this.parameters = descriptor.parameters.deepCopy()
	}

	/**
	 * unique number utilized to determine whenever stack has changed
	 */
	var changeset: Long = CHANGESET.incrementAndGet()
		private set

	/**
	 * it uses global atomic long to guarantee stacks having different
	 * changesets throughout entire lifetime of game
	 */
	protected fun bumpVersion() {
		changeset = CHANGESET.incrementAndGet()
	}

	var count: Long = 0L
		set(value) {
			field = value.coerceAtLeast(0L)
		}

	val config: Registry.Ref<IItemDefinition>
	val parameters: JsonObject

	val isEmpty: Boolean
		get() = count <= 0 || config.isEmpty

	val isNotEmpty: Boolean
		get() = count > 0 && config.isPresent

	val maxStackSize: Long
		get() = config.value?.maxStack ?: 0L

	fun grow(amount: Long) {
		count += amount
	}

	fun shrink(amount: Long) {
		count -= amount
	}

	fun createDescriptor(): ItemDescriptor {
		if (isEmpty)
			return ItemDescriptor.EMPTY

		return ItemDescriptor(config.key.left(), count, parameters.deepCopy())
	}

	// faster than creating an item descriptor and writing it (because it avoids copying and allocation)
	fun write(stream: DataOutputStream) {
		if (isEmpty) {
			stream.writeBinaryString("")
			stream.writeVarLong(0L)
			stream.writeJsonElement(JsonNull.INSTANCE)
		} else {
			stream.writeBinaryString(config.key.left())
			stream.writeVarLong(count)
			stream.writeJsonElement(parameters)
		}
	}

	/**
	 * Возвращает null если этот предмет пуст
	 */
	fun conciseToNull(): ItemStack? {
		if (isEmpty) {
			return null
		} else {
			return this
		}
	}

	fun mergeFrom(other: ItemStack, simulate: Boolean) {
		if (isStackable(other)) {
			val newCount = (count + other.count).coerceAtMost(maxStackSize)
			val diff = newCount - count
			other.count -= diff

			if (!simulate)
				count = newCount
		}
	}

	fun lenientEquals(other: Any?): Boolean {
		if (other !is ItemStack)
			return false

		if (isEmpty)
			return other.isEmpty

		return other.count == count && other.config == config
	}

	fun isStackable(other: ItemStack): Boolean {
		if (isEmpty || other.isEmpty)
			return false

		return count != 0L && other.count != 0L && maxStackSize < count && other.config == config && other.parameters == parameters
	}

	override fun equals(other: Any?): Boolean {
		if (other !is ItemStack)
			return false

		if (isEmpty)
			return other.isEmpty

		return other.count == count && other.config == config && other.parameters == parameters
	}

	override fun hashCode(): Int {
		return config.hashCode()
	}

	override fun toString(): String {
		if (isEmpty)
			return "ItemStack.EMPTY"

		return "ItemDescriptor[${config.value?.itemName}, count = $count, params = $parameters]"
	}

	fun copy(): ItemStack {
		if (isEmpty)
			return this

		return ItemStack(ItemDescriptor(config, count, parameters.deepCopy()))
	}

	fun toJson(): JsonObject? {
		if (isEmpty)
			return null

		return JsonObject().also {
			it.add("name", JsonPrimitive(config.key.left()))
			it.add("count", JsonPrimitive(count))
			it.add("parameters", parameters.deepCopy())
		}
	}

	fun toTable(allocator: TableFactory): Table? {
		if (isEmpty) {
			return null
		}

		return allocator.newTable(0, 3).also {
			it.rawset("name", config.key.left())
			it.rawset("count", count)
			it.rawset("parameters", allocator.from(parameters))
		}
	}

	class Adapter(val starbound: Starbound) : TypeAdapter<ItemStack>() {
		override fun write(out: JsonWriter, value: ItemStack?) {
			val json = value?.toJson()

			if (json == null)
				out.nullValue()
			else
				TypeAdapters.JSON_ELEMENT.write(out, json)
		}

		override fun read(`in`: JsonReader): ItemStack {
			if (`in`.consumeNull())
				return EMPTY

			return starbound.item(TypeAdapters.JSON_ELEMENT.read(`in`))
		}
	}

	companion object {
		private val CHANGESET = AtomicLong()

		@JvmField
		val EMPTY = ItemStack()

		fun create(descriptor: ItemDescriptor): ItemStack {
			return EMPTY
		}
	}
}