node-haxball/examples/plugins/autoPlay_followBall_inmemory.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

module.exports = function(API){
  const { OperationType, VariableType, ConnectionState, AllowFlags, Direction, CollisionFlags, CameraFollow, BackgroundType, GamePlayState, BanEntryType, Callback, Utils, Room, Replay, Query, Library, RoomConfig, Plugin, Renderer, Errors, Language, EventFactory, Impl } = API;

  Object.setPrototypeOf(this, Plugin.prototype);
  Plugin.call(this, "autoPlay_followBall_inmemory", false, { // "autoPlay_followBall_inmemory" is plugin's name, "false" means "not activated after initialization". Every plugin should have a unique name.
    version: "0.4",
    author: "abc",
    description: `This is an auto-playing bot that always follows the ball blindly, and kicks it whenever it is nearby without any direction checking. This bot creates a fake player(id=65535) in host's memory and controls it using fake events.`,
    allowFlags: AllowFlags.CreateRoom // We allow this plugin to be activated on CreateRoom only.
  });

  this.defineVariable({
    name: "minCoordAlignDelta",
    description: "Minimum delta value for coordinate alignment", 
    type: VariableType.Number,
    value: 0.5, 
    range: {
      min: 0,
      max: 10,
      step: 0.5
    }
  });

  this.defineVariable({
    name: "minKickDistance",
    description: "Minimum distance between ball and bot player for the bot player to start kicking the ball", 
    type: VariableType.Number,
    value: 8, 
    range: {
      min: 0,
      max: 15,
      step: 0.5
    }
  });

  var that = this, oldKeyState = 0;

  this.onPluginActiveChange = function(plugin, customData){
    if (plugin.name!=that.name)
      return;
    if (that.active)
      that.room.fakePlayerJoin(/*id:*/ 65535, /*name:*/ "in-memory-bot", /*flag:*/ "tr", /*avatar:*/ "XX", /*conn:*/ "fake-ip-do-not-believe-it", /*auth:*/ "fake-auth-do-not-believe-it");
    else
      that.room.fakePlayerLeave(65535);
  };

  this.onGameTick = function(customData){

    // ensure extrapolation of the room state before calculating stuff.
    that.room.extrapolate();

    // get the original data object of the next bot
    var cp = that.room.getPlayer(65535);
    var playerDisc = cp?.disc?.ext;

    // coordinates: playerDisc.pos.x, playerDisc.pos.y
    // speed: playerDisc.speed.x, playerDisc.speed.y
    // radius: playerDisc.radius

    if (!playerDisc) // check or else error occurs after changing a player's team to spectators, if the player is not actually in the game, or the game is stopped.
      return;

    // get the extrapolated game state object
    var { state, gameState, gameStateExt } = that.room;
    gameState = gameStateExt || gameState;

    // get the original extrapolated data object of the ball
    var ball = gameState.physicsState.discs[0];

    // get the coordinates of the ball
    var {x, y} = ball?.pos || {};

    // if ball is not reachable, do nothing.
    if (x==null || isNaN(x) || !isFinite(x) || y==null || isNaN(y) || !isFinite(y)) // check 
      return;

    // speed: playerDisc.speed.x, playerDisc.speed.y
    // radius: playerDisc.radius

    // calculate delta difference for both x and y axis.
    var deltaX = x - playerDisc.pos.x, deltaY = y - playerDisc.pos.y, dirX, dirY, kick;

    // x direction:
    if (Math.abs(deltaX) < that.minCoordAlignDelta) // we can omit small delta.
      dirX = 0;
    else 
      dirX = Math.sign(deltaX); // direction is +1 or -1, depending on the delta difference

    // y direction
    if (Math.abs(deltaY) < that.minCoordAlignDelta) // we can omit small delta.
      dirY = 0;
    else
      dirY = Math.sign(deltaY); // direction is +1 or -1, depending on the delta difference

    // kick is true if the distance between ball and player is less than minKickDistance
    kick = (deltaX * deltaX + deltaY * deltaY < (playerDisc.radius + ball.radius + that.minKickDistance) * (playerDisc.radius + ball.radius + that.minKickDistance));

    // apply current keys
    var newKeyState = Utils.keyState(dirX, dirY, kick);
    Utils.runAfterGameTick(()=>{ // this is just a way of doing this outside onGameTick callback.
      // sending keystate on EVERY game tick causes desync when you deactivate game's browser tab. 
      // this happens because requestAnimationFrame is being used. 
      // therefore, we are trying to limit consequent sending.
      if (newKeyState!=oldKeyState || kick!=cp.isKicking){ // isKicking: whether x key is active in-game (the circle around players is painted white if isKicking is true)
        if ((newKeyState==oldKeyState) && kick && !cp.isKicking) // if keyStates are the same and we are trying to kick, but the x key is not active in game,
          that.room.fakeSendPlayerInput(/*input:*/ newKeyState & -17, /*byId:*/ 65535); // we have to release x key before pressing it again. (newKeyState & -17) changes only the 5th(kick) bit of newKeyState to 0.
        that.room.fakeSendPlayerInput(/*input:*/ newKeyState, /*byId:*/ 65535); // unlike room.setKeyState, this function directly emits a keystate message.
        oldKeyState = newKeyState;
      }
    });
  };
};