1 files changed, 140 insertions, 0 deletions
diff --git a/src/main/java/de/hysky/skyblocker/utils/scheduler/Scheduler.java b/src/main/java/de/hysky/skyblocker/utils/scheduler/Scheduler.java
new file mode 100644
index 00000000..0f44cf93
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+++ b/src/main/java/de/hysky/skyblocker/utils/scheduler/Scheduler.java
@@ -0,0 +1,140 @@
+package de.hysky.skyblocker.utils.scheduler;
+
+import com.mojang.brigadier.Command;
+import it.unimi.dsi.fastutil.ints.AbstractInt2ObjectMap;
+import it.unimi.dsi.fastutil.ints.Int2ObjectOpenHashMap;
+import net.fabricmc.fabric.api.client.command.v2.FabricClientCommandSource;
+import net.minecraft.client.MinecraftClient;
+import net.minecraft.client.gui.screen.Screen;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.function.Supplier;
+
+/**
+ * A scheduler for running tasks at a later time. Tasks will be run synchronously on the main client thread. Use the instance stored in {@link #INSTANCE}. Do not instantiate this class.
+ */
+public class Scheduler {
+    private static final Logger LOGGER = LoggerFactory.getLogger(Scheduler.class);
+    public static final Scheduler INSTANCE = new Scheduler();
+    private int currentTick = 0;
+    private final AbstractInt2ObjectMap<List<ScheduledTask>> tasks = new Int2ObjectOpenHashMap<>();
+
+    protected Scheduler() {
+    }
+
+    /**
+     * Schedules a task to run after a delay.
+     *
+     * @param task  the task to run
+     * @param delay the delay in ticks
+     */
+    public void schedule(Runnable task, int delay) {
+        if (delay >= 0) {
+            addTask(new ScheduledTask(task), currentTick + delay);
+        } else {
+            LOGGER.warn("Scheduled a task with negative delay");
+        }
+    }
+
+    /**
+     * Schedules a task to run every period ticks.
+     *
+     * @param task   the task to run
+     * @param period the period in ticks
+     */
+    public void scheduleCyclic(Runnable task, int period) {
+        if (period > 0) {
+            addTask(new CyclicTask(task, period), currentTick);
+        } else {
+            LOGGER.error("Attempted to schedule a cyclic task with period lower than 1");
+        }
+    }
+
+    public static Command<FabricClientCommandSource> queueOpenScreenCommand(Supplier<Screen> screenSupplier) {
+        return context -> INSTANCE.queueOpenScreen(screenSupplier);
+    }
+
+    /**
+     * Schedules a screen to open in the next tick. Used in commands to avoid screen immediately closing after the command is executed.
+     *
+     * @param screenSupplier the supplier of the screen to open
+     * @see #queueOpenScreenCommand(Supplier)
+     */
+    public int queueOpenScreen(Supplier<Screen> screenSupplier) {
+        MinecraftClient.getInstance().send(() -> MinecraftClient.getInstance().setScreen(screenSupplier.get()));
+        return Command.SINGLE_SUCCESS;
+    }
+
+    public void tick() {
+        if (tasks.containsKey(currentTick)) {
+            List<ScheduledTask> currentTickTasks = tasks.get(currentTick);
+            //noinspection ForLoopReplaceableByForEach (or else we get a ConcurrentModificationException)
+            for (int i = 0; i < currentTickTasks.size(); i++) {
+                ScheduledTask task = currentTickTasks.get(i);
+                if (!runTask(task)) {
+                    tasks.computeIfAbsent(currentTick + 1, key -> new ArrayList<>()).add(task);
+                }
+            }
+            tasks.remove(currentTick);
+        }
+        currentTick += 1;
+    }
+
+    /**
+     * Runs the task if able.
+     *
+     * @param task the task to run
+     * @return {@code true} if the task is run, and {@link false} if task is not run.
+     */
+    protected boolean runTask(Runnable task) {
+        task.run();
+        return true;
+    }
+
+    private void addTask(ScheduledTask scheduledTask, int schedule) {
+        if (tasks.containsKey(schedule)) {
+            tasks.get(schedule).add(scheduledTask);
+        } else {
+            List<ScheduledTask> list = new ArrayList<>();
+            list.add(scheduledTask);
+            tasks.put(schedule, list);
+        }
+    }
+
+    /**
+     * A task that runs every period ticks. More specifically, this task reschedules itself to run again after period ticks every time it runs.
+     */
+    protected class CyclicTask extends ScheduledTask {
+        private final int period;
+
+        CyclicTask(Runnable inner, int period) {
+            super(inner);
+            this.period = period;
+        }
+
+        @Override
+        public void run() {
+            super.run();
+            addTask(this, currentTick + period);
+        }
+    }
+
+    /**
+     * A task that runs at a specific tick, relative to {@link #currentTick}.
+     */
+    protected static class ScheduledTask implements Runnable {
+        private final Runnable inner;
+
+        public ScheduledTask(Runnable inner) {
+            this.inner = inner;
+        }
+
+        @Override
+        public void run() {
+            inner.run();
+        }
+    }
+}