@rpgjs/physic/dist/index44.js

A deterministic 2D top-down physics library for RPG, sandbox and MMO games

class PredictionController {
  constructor(config) {
    this.config = config;
    this.frameCounter = 0;
    this.history = [];
    this.pendingSnapshot = null;
    this.lastAckFrame = 0;
    this.lastAckTick = 0;
    this.correctionThreshold = config.correctionThreshold ?? 5;
    this.historyTtlMs = config.historyTtlMs ?? 2e3;
    this.maxHistoryEntries = config.maxHistoryEntries ?? 200;
  }
  recordInput(direction, timestamp) {
    const frame = ++this.frameCounter;
    const tick = this.config.getPhysicsTick();
    this.history.push({ frame, tick, timestamp, direction });
    this.trimHistory(timestamp);
    return { frame, tick };
  }
  attachPredictedState(frame, state) {
    const entry = this.history.find((item) => item.frame === frame);
    if (entry) {
      entry.state = state;
    }
  }
  hasPendingInputs() {
    return this.history.length > 0;
  }
  queueServerSnapshot(snapshot) {
    if (this.hasPendingInputs()) {
      this.pendingSnapshot = snapshot;
      return;
    }
    this.applySnapshot(snapshot);
  }
  tryApplyPendingSnapshot() {
    if (!this.pendingSnapshot || this.hasPendingInputs()) {
      return;
    }
    this.applySnapshot(this.pendingSnapshot);
    this.pendingSnapshot = null;
  }
  applyServerAck(ack) {
    if (typeof ack.frame !== "number") {
      return;
    }
    this.lastAckFrame = Math.max(this.lastAckFrame, ack.frame);
    if (typeof ack.serverTick === "number") {
      this.lastAckTick = Math.max(this.lastAckTick, ack.serverTick);
    }
    this.history = this.history.filter((entry) => entry.frame > this.lastAckFrame);
    if (ack.state && !this.hasPendingInputs()) {
      this.applySnapshot(ack.state);
      this.pendingSnapshot = null;
      return;
    }
    if (this.pendingSnapshot && !this.hasPendingInputs()) {
      this.applySnapshot(this.pendingSnapshot);
      this.pendingSnapshot = null;
    }
  }
  cleanup(now) {
    this.trimHistory(now);
  }
  trimHistory(now) {
    const cutoff = now - this.historyTtlMs;
    this.history = this.history.filter((entry) => entry.timestamp >= cutoff);
    if (this.history.length > this.maxHistoryEntries) {
      this.history = this.history.slice(-this.maxHistoryEntries);
    }
  }
  applySnapshot(snapshot) {
    const current = this.config.getCurrentState();
    const dx = current.x - snapshot.x;
    const dy = current.y - snapshot.y;
    const distance = Math.hypot(dx, dy);
    if (distance > this.correctionThreshold) {
      this.config.setAuthoritativeState(snapshot);
      this.history = [];
      return;
    }
    this.history = [];
  }
}
export {
  PredictionController
};
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