package net.minecraft.client.renderer.chunk;

import it.unimi.dsi.fastutil.objects.ObjectArrayList;
import java.util.List;
import java.util.ListIterator;
import net.fabricmc.api.EnvType;
import net.fabricmc.api.Environment;
import net.minecraft.world.phys.Vec3;

@Environment(EnvType.CLIENT)
public class SectionTaskDynamicQueue {
	private static final int MAX_RECOMPILE_QUOTA = 2;
	private int recompileQuota = 2;
	private final List<SectionRenderDispatcher.RenderSection.SectionTask> tasks = new ObjectArrayList<>();

	public synchronized void add(final SectionRenderDispatcher.RenderSection.SectionTask task) {
		this.tasks.add(task);
	}

	public synchronized SectionRenderDispatcher.RenderSection.SectionTask poll(final Vec3 cameraPos) {
		int bestInitialCompileTaskIndex = -1;
		int bestRecompileTaskIndex = -1;
		double bestInitialCompileDistance = Double.MAX_VALUE;
		double bestRecompileDistance = Double.MAX_VALUE;
		ListIterator<SectionRenderDispatcher.RenderSection.SectionTask> iterator = this.tasks.listIterator();

		while (iterator.hasNext()) {
			int taskIndex = iterator.nextIndex();
			SectionRenderDispatcher.RenderSection.SectionTask task = (SectionRenderDispatcher.RenderSection.SectionTask)iterator.next();
			if (task.isCancelled.get()) {
				iterator.remove();
			} else {
				double distance = task.getRenderOrigin().distToCenterSqr(cameraPos);
				if (!task.isRecompile() && distance < bestInitialCompileDistance) {
					bestInitialCompileDistance = distance;
					bestInitialCompileTaskIndex = taskIndex;
				}

				if (task.isRecompile() && distance < bestRecompileDistance) {
					bestRecompileDistance = distance;
					bestRecompileTaskIndex = taskIndex;
				}
			}
		}

		boolean hasRecompileTask = bestRecompileTaskIndex >= 0;
		boolean hasInitialCompileTask = bestInitialCompileTaskIndex >= 0;
		if (!hasRecompileTask || hasInitialCompileTask && (this.recompileQuota <= 0 || !(bestRecompileDistance < bestInitialCompileDistance))) {
			this.recompileQuota = 2;
			return this.removeTaskByIndex(bestInitialCompileTaskIndex);
		} else {
			this.recompileQuota--;
			return this.removeTaskByIndex(bestRecompileTaskIndex);
		}
	}

	public int size() {
		return this.tasks.size();
	}

	private SectionRenderDispatcher.RenderSection.SectionTask removeTaskByIndex(final int taskIndex) {
		return taskIndex >= 0 ? (SectionRenderDispatcher.RenderSection.SectionTask)this.tasks.remove(taskIndex) : null;
	}

	public synchronized void clear() {
		for (SectionRenderDispatcher.RenderSection.SectionTask task : this.tasks) {
			task.cancel();
		}

		this.tasks.clear();
	}
}