package ru.dbotthepony.kstarbound.world

import it.unimi.dsi.fastutil.objects.ObjectArrayList
import it.unimi.dsi.fastutil.objects.ObjectArraySet
import it.unimi.dsi.fastutil.objects.ReferenceOpenHashSet
import ru.dbotthepony.kstarbound.world.api.AbstractCell
import ru.dbotthepony.kstarbound.world.api.ICellAccess
import ru.dbotthepony.kstarbound.world.api.ImmutableCell
import ru.dbotthepony.kstarbound.world.api.OffsetCellAccess
import ru.dbotthepony.kstarbound.world.api.TileView
import ru.dbotthepony.kstarbound.world.entities.Entity
import ru.dbotthepony.kstarbound.world.entities.WorldObject
import ru.dbotthepony.kvector.arrays.Object2DArray
import ru.dbotthepony.kvector.util2d.AABB
import ru.dbotthepony.kvector.vector.Vector2d
import kotlin.concurrent.withLock

/**
 * Чанк мира
 *
 * Хранит в себе тайлы и ентити внутри себя
 *
 * Считается, что один тайл имеет форму квадрата и сторона квадрата примерно равна полуметру,
 * что будет называться Starbound Unit
 *
 * Весь игровой мир будет измеряться в Starbound Unit'ах
 */
abstract class Chunk<WorldType : World<WorldType, This>, This : Chunk<WorldType, This>>(
	val world: WorldType,
	val pos: ChunkPos,
) : ICellAccess {
	var changeset = 0
		private set

	var tileChangeset = 0
		private set
	var liquidChangeset = 0
		private set
	var cellChangeset = 0
		private set

	var foregroundChangeset = 0
		private set
	var backgroundChangeset = 0
		private set

	val entities = ReferenceOpenHashSet<Entity>()
	val objects = ReferenceOpenHashSet<WorldObject>()
	protected val subscribers = ObjectArraySet<IChunkListener>()

	// local cells' tile access
	val localBackgroundView = TileView.Background(this)
	val localForegroundView = TileView.Foreground(this)

	// relative world cells access (accessing 0, 0 will lookup cell in world, relative to this chunk)
	val worldView = OffsetCellAccess(world, pos.x * CHUNK_SIZE, pos.y * CHUNK_SIZE)
	val worldBackgroundView = TileView.Background(worldView)
	val worldForegroundView = TileView.Foreground(worldView)

	val aabb = aabbBase + Vector2d(pos.x * CHUNK_SIZE.toDouble(), pos.y * CHUNK_SIZE.toDouble())

	protected val cells = lazy {
		Object2DArray(CHUNK_SIZE, CHUNK_SIZE, AbstractCell.NULL)
	}

	fun loadCells(source: Object2DArray<out AbstractCell>) {
		val ours = cells.value
		source.checkSizeEquals(ours)

		for (x in 0 until CHUNK_SIZE) {
			for (y in 0 until CHUNK_SIZE) {
				ours[x, y] = source[x, y].immutable()
			}
		}
	}

	override fun getCell(x: Int, y: Int): AbstractCell {
		if (!cells.isInitialized())
			return AbstractCell.NULL

		return cells.value[x, y]
	}

	override fun getCellDirect(x: Int, y: Int): AbstractCell {
		return getCell(x, y)
	}

	override fun setCell(x: Int, y: Int, cell: AbstractCell): Boolean {
		val ix = x and CHUNK_SIZE_FF
		val iy = y and CHUNK_SIZE_FF

		if (ix != x || iy != y) return false

		val old = if (cells.isInitialized()) cells.value[ix, iy] else AbstractCell.NULL
		val new = cell.immutable()

		if (old != new) {
			cells.value[ix, iy] = new

			if (old.foreground != new.foreground) {
				foregroundChanges(ix, iy, new)
			}

			if (old.background != new.background) {
				backgroundChanges(ix, iy, new)
			}

			if (old.liquid != new.liquid) {
				liquidChanges(ix, iy, new)
			}

			cellChanges(ix, iy, new)
		}

		return true
	}

	protected open fun foregroundChanges(x: Int, y: Int, cell: ImmutableCell) {
		cellChanges(x, y, cell)
		tileChangeset++
		foregroundChangeset++
	}

	protected open fun backgroundChanges(x: Int, y: Int, cell: ImmutableCell) {
		cellChanges(x, y, cell)
		tileChangeset++
		backgroundChangeset++
	}

	protected open fun liquidChanges(x: Int, y: Int, cell: ImmutableCell) {
		cellChanges(x, y, cell)
		liquidChangeset++
	}

	protected open fun cellChanges(x: Int, y: Int, cell: ImmutableCell) {
		changeset++
		cellChangeset++

		subscribers.forEach { it.cellChanges(x, y, cell) }
	}

	protected inline fun forEachNeighbour(block: (This) -> Unit) {
		world.chunkMap[pos.left]?.let(block)
		world.chunkMap[pos.right]?.let(block)
		world.chunkMap[pos.top]?.let(block)
		world.chunkMap[pos.bottom]?.let(block)
		world.chunkMap[pos.topLeft]?.let(block)
		world.chunkMap[pos.topRight]?.let(block)
		world.chunkMap[pos.bottomLeft]?.let(block)
		world.chunkMap[pos.bottomRight]?.let(block)
	}

	override fun randomLongFor(x: Int, y: Int): Long {
		return world.randomLongFor(x or pos.x shl CHUNK_SIZE_BITS, y or pos.y shl CHUNK_SIZE_BITS)
	}

	fun addListener(subscriber: IChunkListener) {
		subscribers.add(subscriber)
	}

	fun removeListener(subscriber: IChunkListener) {
		subscribers.remove(subscriber)
	}

	fun addEntity(entity: Entity) {
		world.lock.withLock {
			if (!entities.add(entity)) {
				throw IllegalArgumentException("Already having having entity $entity")
			}

			changeset++
			subscribers.forEach { it.onEntityAdded(entity) }
		}
	}

	fun transferEntity(entity: Entity, otherChunk: Chunk<*, *>) {
		world.lock.withLock {
			if (otherChunk == this)
				throw IllegalArgumentException("what?")

			if (this::class.java != otherChunk::class.java) {
				throw IllegalArgumentException("Incompatible types: $this !is $otherChunk")
			}

			if (!entities.add(entity)) {
				throw IllegalArgumentException("Already containing $entity")
			}

			changeset++
			otherChunk.subscribers.forEach { it.onEntityRemoved(entity) }
			subscribers.forEach { it.onEntityAdded(entity) }

			if (!otherChunk.entities.remove(entity)) {
				throw IllegalStateException("Unable to remove $entity from $otherChunk after transfer")
			}
		}
	}

	fun removeEntity(entity: Entity) {
		world.lock.withLock {
			if (!entities.remove(entity)) {
				throw IllegalArgumentException("Already not having entity $entity")
			}

			changeset++
			subscribers.forEach { it.onEntityRemoved(entity) }
		}
	}

	override fun toString(): String {
		return "${this::class.simpleName}(pos=$pos, entityCount=${entities.size}, world=$world)"
	}

	fun addObject(obj: WorldObject) {
		world.lock.withLock {
			if (!objects.add(obj))
				throw IllegalStateException("$this already has object $obj!")

			if (!world.objects.add(obj))
				throw IllegalStateException("World $world already has object $obj!")

			obj.spawn(world)
			subscribers.forEach { it.onObjectAdded(obj) }
		}
	}

	fun removeObject(obj: WorldObject) {
		world.lock.withLock {
			if (!objects.remove(obj))
				throw IllegalStateException("$this does not have object $obj!")

			if (!world.objects.remove(obj))
				throw IllegalStateException("World $world does not have object $obj!")

			subscribers.forEach { it.onObjectRemoved(obj) }
		}
	}

	open fun remove() {
		world.lock.withLock {
			for (obj in ObjectArrayList(objects)) {
				if (!world.objects.remove(obj)) {
					throw IllegalStateException("World $world does not have object $obj!")
				}
			}

			for (ent in ObjectArrayList(entities)) {
				ent.chunk = null
			}
		}
	}

	open fun think() {

	}

	companion object {
		private val aabbBase = AABB(
			Vector2d.ZERO,
			Vector2d(CHUNK_SIZE.toDouble(), CHUNK_SIZE.toDouble()),
		)
	}
}