node-haxball/examples/api_structure/replayModifier.js

The most powerful and lightweight API that allows you to develop your original Haxball(www.haxball.com) host, client, and standalone applications both on node.js and browser environments and also includes every possible hack and functionality that you can

// This is a demonstration of replay file modification using this API.
// This example is for node.js. If you want this to work for browser, you need to create a file selector instead of require("fs").

const { OperationType, VariableType, ConnectionState, AllowFlags, Direction, CollisionFlags, CameraFollow, BackgroundType, GamePlayState, BanEntryType, Callback, Utils, Room, Replay, Query, Library, RoomConfig, Plugin, Renderer, Errors, Language, EventFactory, Impl } = require("node-haxball")();
const fs = require("fs");

// read the replay file.
var replayData = Replay.readAll(fs.readFileSync("replayfile.hbr2", null));

// remove all players whose id is not 28.
replayData.roomData.players = replayData.roomData.players.filter((x)=>x.id==28);

// remove the discs that belong to other players.
// the replay file must have the game initially started, otherwise roomData.gameState will become undefined.
replayData.roomData.gameState.physicsState.discs = replayData.roomData.gameState.physicsState.discs.filter((x)=>x.playerId==null || x.playerId==28);

// remove all the events that belong to other players and also remove all the events that are not input events.
replayData.events = replayData.events.filter((x)=>(x.byId==28 && x.eventType==OperationType.SendInput));

// since there is only one player left, make it the room owner.
replayData.roomData.players[0].id = 0;

// also update the player's disc to reflect the id change.
replayData.roomData.players[0].disc.playerId = 0;

// also update all the events to reflect the id change.
replayData.events.forEach((x)=>{x.byId = 0});

// write the modified replay file.
fs.writeFileSync("optimized_replayfile.hbr2", Replay.writeAll(replayData));