PhysicalConnectivity/src/main/kotlin/net/shadowfacts/phycon/util/NetworkUtil.kt

package net.shadowfacts.phycon.util

import net.minecraft.util.math.BlockPos
import net.minecraft.util.math.Direction
import net.minecraft.world.World
import net.shadowfacts.phycon.api.*
import java.util.*

/**
 * @author shadowfacts
 */
object NetworkUtil {

	fun findConnectedInterface(world: World, startPos: BlockPos, startSide: Direction): Interface? {
		var curSide = startSide
		var pos = startPos.offset(startSide)
		var state = world.getBlockState(pos)
		while (state.block is NetworkComponentBlock) {
			val block = state.block as NetworkComponentBlock
			val itf = block.getNetworkInterfaceForSide(curSide.opposite, state, world, pos)
			if (itf != null) {
				return itf
			}
			val connectedSides = block.getNetworkConnectedSides(state, world, pos).filter { it != curSide.opposite }
			if (connectedSides.size == 1) {
				curSide = connectedSides.first()
				pos = pos.offset(curSide)
				if (!world.isChunkLoaded(pos)) {
					// avoid loading unloaded chunks
					return null
				}
				state = world.getBlockState(pos)
			} else {
				return null
			}
		}
		return null
	}

	fun findDestinations(world: World, startPos: BlockPos, direction: Direction? = null): List<PacketSink> {
		val results = LinkedList<PacketSink>()
		val visited = hashSetOf(startPos)
		val queue = LinkedList<BlockPos>()
		if (direction != null) {
			queue.add(startPos.offset(direction))
		} else {
			findEdges(queue, visited, world, startPos, includeNonCables = true)
		}

		while (queue.isNotEmpty()) {
			val pos = queue.pop()

			val sink = PhyAttributes.PACKET_SINK.getFirstOrNull(world, pos)
			if (sink != null) {
				results.add(sink)
			}

			findEdges(queue, visited, world, pos)

			visited.add(pos)
		}

		return results
	}

	private fun findEdges(queue: MutableList<BlockPos>, visited: Set<BlockPos>, world: World, pos: BlockPos, includeNonCables: Boolean = false) {
		val state = world.getBlockState(pos)
		val block = state.block
		if (block is NetworkComponentBlock && (includeNonCables || block is NetworkCableBlock)) {
			val connections = block.getNetworkConnectedSides(state, world, pos)
			for (side in connections) {
				val newPos = pos.offset(side)
				if (newPos !in visited) {
					queue.add(newPos)
				}
			}
		}
	}

}