mods/grapplehook.js

(function grapplehook() {
    PluginAPI.require("player"); //Require the player
    globalThis.GrappleHookPlugin = {
        oldXYZ: [0, 0, 0], //The previous hook position.
        prev: "NONE", //The previous state
        scaleH: 0.25, //Used for X and Z velocity
        scaleV: 0.15, //((Grapple Y) minus (Player Y)) times scaleV
        lift: 0.4, //Base vertical motion
        crouchToCancel: true //Whether or not crouching should disable the grappling hook.
    };
    PluginAPI.addEventListener("update", () => { //Every client tick
        var player = ModAPI.player.getCorrective(); //Gets the corrective version of the player object. This removes broken proerty suffixes. You usually don't need this, but in my case, I do.
        if (!player.fishEntity) { //If the fish hook does not exist.
            if (GrappleHookPlugin.prev === "GROUND" && (!GrappleHookPlugin.crouchToCancel || !player.isSneaking())) { //If the old state was ground
                GrappleHookPlugin.prev = "NONE"; //Update the state
                var mx = GrappleHookPlugin.oldXYZ[0] - player.posX; //Get delta X
                var my = GrappleHookPlugin.oldXYZ[1] - player.posY; //Get delta Y
                var mz = GrappleHookPlugin.oldXYZ[2] - player.posZ; //Get delta Z
                mx *= GrappleHookPlugin.scaleH; //Multiply by horizontal scale
                my *= GrappleHookPlugin.scaleV; //Multiply by vertical scale
                mz *= GrappleHookPlugin.scaleH; //Multiply by horizontal scale
                player.motionX += mx; //Add x motion
                player.motionY += my + GrappleHookPlugin.lift;  //Add y motion, plus base lift.
                player.motionZ += mz; //Add z motion
            } else {
                GrappleHookPlugin.prev = "NONE";
            }
        } else if (GrappleHookPlugin.prev === "NONE") { //If the hook exists, but the previous state was NONE, update the state.
            GrappleHookPlugin.prev = "AIR";
        }
        if (
            player.fishEntity !== undefined && //If the fish hook exists
            GrappleHookPlugin.prev === "AIR" && //And the hook was previously in the air
            (player.fishEntity.inGround || player.fishEntity.onGround) //And the hook is in the ground
        ) {
            GrappleHookPlugin.oldXYZ = [ //Set old grapple hook position
                player.fishEntity.posX,
                player.fishEntity.posY,
                player.fishEntity.posZ,
            ];
            GrappleHookPlugin.prev = "GROUND";//Update state
        }
    });
})();