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.
Let’s implement the client side part.
(function TimescaleCommand() {
ModAPI.meta.title("Timescale Command");
ModAPI.meta.description("use /timescale to control time");
ModAPI.meta.credits("By <author_name>");
ModAPI.addEventListener("sendchatmessage", (event) => { // before a message gets sent to the server
if (event.message.toLowerCase().startsWith("/timescale")) { //if it is the timescale command
var speed = parseFloat(event.message.split(" ")[1]); //get the part of the message after the space
if (!speed) { //If it doesn't exist, set it to 1.
speed = 1;
} else { //If it does exist:
if (speed < 1) { //When the speed is less than 1, round the denominator (1 over x)
speed = 1 / Math.round(1 / speed);
} else {
// When the speed is greater or equal to 1, round the numerator (x over 1)
speed = Math.round(speed);
}
// Set the speed
ModAPI.mc.timer.timerSpeed = speed;
}
// Log the speed to chat
ModAPI.displayToChat("[Timescale] Set world timescale to " + speed.toFixed(2) + ".");
}
});
})()
Now for the serverside part.
(function TimescaleCommand() {
//...
ModAPI.dedicatedServer.appendCode(function () { // Run on the server
globalThis.timeScale = 1n; // Initialize globalThis.timeScale
globalThis.timeScaleDividing = false; // Initialize globalThis.timeScaleDividing
ModAPI.addEventListener("processcommand", (event) => { // when the server receives a command
if (event.command.toLowerCase().startsWith("/timescale")) { // if it is a timescale command
var speed = parseFloat(event.command.split(" ")[1]); // get the second part of the command (the speed of time)
if (!speed) { // If it doesn't exist, set it to 1.
globalThis.timeScale = 1n;
globalThis.timeScaleDividing = false;
} else { // If it does exist:
if (speed < 1) {
// When the speed is less than 1, round the denominator (1 over x)
// And enable division mode
globalThis.timeScaleDividing = true;
globalThis.timeScale = BigInt(Math.round(1 / speed));
} else {
// When the speed is greater or equal to 1, round the numerator (x over 1)
// And disable division mode
globalThis.timeScaleDividing = false;
globalThis.timeScale = BigInt(Math.round(speed));
}
}
if (ModAPI.server) { //If the server is initialized
//Bump the current time forward so the server doesn't try to play catch-up
ModAPI.server.currentTime = ModAPI.hooks.methods[ModAPI.util.getMethodFromPackage("net.minecraft.server.MinecraftServer", "getCurrentTimeMillis")]();
}
//Prevent the command not found error from appearing
event.preventDefault = true;
}
});
//Monkey patch the getCurrentTime function.
const original_getCurrentTime = ModAPI.hooks.methods[ModAPI.util.getMethodFromPackage("net.minecraft.server.MinecraftServer", "getCurrentTimeMillis")];
ModAPI.hooks.methods[ModAPI.util.getMethodFromPackage("net.minecraft.server.MinecraftServer", "getCurrentTimeMillis")] = function () {
if (globalThis.timeScaleDividing) { //If we are in divide mode
return original_getCurrentTime() / globalThis.timeScale; //Return the current time divided by the time scale
} else {
return original_getCurrentTime() * globalThis.timeScale; //Else, return the current time multiplied by the time scale
}
};
});
})()