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[jolly bay]

Sounds like you'll need to raycast, possibly every few ticks or so. Start with this:

!!timer

[lean valve]

Fabric itself does not include APIs to schedule something in the future.

DO NOT use threads or java.util.Timer. (This can cause a crash!) Instead:

• If you are making a block do something in the future: world.scheduleBlockTick + override scheduledTick in your Block.
• If you are making a custom tickable stuff (usually block entity/entity) do something in the future/periodically: see below, but instead of Mixin just implement yourself
• If you are making a vanilla tickable thing (world, server, etc) do something in the future/periodically: use the following mixin.

@Mixin(StuffToTick.class) // ServerWorld, MinecraftServer, etc
public class StuffTimer implements StuffTimerAccess {
    @Unique
    private long ticksUntilSomething;

    @Inject(method = "tick", at = @At("TAIL"))
    private void onTick(CallbackInfo ci) { // Fix parameters as needed
        if (--this.ticksUntilSomething == 0L) {
            doSomething();
            // If you want to repeat this, reset ticksUntilSomething here.
        }
    }

    @Override
    public void yourmod_setTimer(long ticksUntilSomething) {
        this.ticksUntilSomething = ticksUntilSomething;
    }
}

public interface StuffTimerAccess {
    void yourmod_setTimer(long ticksUntilSomething);
}

Usage:

MinecraftServer server;
((StuffTimerAccess) server).yourmod_setTimer(100L); // do something after 100 ticks

[jolly bay]

Well, you're gonna have to play around with it some then.

Help with builds failing you might get. Just writing code for you isn't something you'll find here.