EaglerForgeInjector/docs/tutorials/timescale.md

Timescale Mod with ModAPI

This mod will cover adding a new command that controls the speed that Eaglercraft runs at. This tutorial assumes that you have some knowledge on how to use BigInt in JavaScript.

Let's get our basic template code down:

(function TimescaleCommand() {
    ModAPI.meta.title("Timescale Command");
    ModAPI.meta.description("use /timescale to control time");
    ModAPI.meta.credits("By <author_name>");
})()

Our mod is going to be split into 2 distinct parts: client-side and server-side. The client will modify ModAPI.mc.timer.timerSpeed when a /timescale command is sent, while the server will set the timescale to a global variable, and then modify net.minecraft.server.MinecraftServer's getCurrentTimeMillis() to change the rate calculations happen at on the server.

However, there is a slight logistical problem: the server gets the time in milliseconds as a JavaScript BigInt, which means we can't just multiply it by a number, we have to either multiply or divide it by another BigInt.

var x = 1n * 1.0; //TypeError

var x = 1n * 1n; //Success

To allow us to both speed up and slow down time, we'll need to check if the speed inputted is greater or equal to 1. If it is, we round it and then convert it to a BigInt, which we'll store on the globalThis object. If it's less we'll need to find the speed to the power of -1, or 1 / speed. We can then round this value and convert that to a BigInt to store on globalThis. We'll also set globalThis.timeScaleDividing to true, to signal to replaced getCurrentTimeMillis() to divide by the BigInt speed factor instead of multiply.

Finally, due to our BigInt rounding shenanigans on the server, we have to replicate the rounding inaccuracy on the client.