genosdb-server/conflictResolver.js

GenosDB Server: A persistent Node.js peer for the GenosDB distributed graph database. Provides a reliable file-system storage layer, ensuring data durability and network resilience for your real-time, peer-to-peer applications.

// Maximum allowed future timestamp drift (2 hours)
const MAX_FUTURE_DRIFT_MS = 7200000;

/**
 * Resolves a conflict between a local node and an incoming remote change.
 * Uses Last-Write-Wins (LWW) strategy at the object level.
 *
 * @param {{ value: any, timestamp: any } | null} localNode - Local node.
 * @param {{ value: any, timestamp: any }} remoteChange - Incoming remote change.
 * @param {HybridClock} clock - Hybrid clock to compare timestamps.
 * @returns {{ resolved: boolean, value?: any, timestamp?: any }}
 */
export function resolveConflict(localNode, remoteChange, clock) {
  let ts = remoteChange.timestamp;

  // Cap remote timestamp to prevent excessive future drift
  if (ts?.physical > Date.now() + MAX_FUTURE_DRIFT_MS) {
    ts = { physical: Date.now() + MAX_FUTURE_DRIFT_MS, logical: ts.logical };
  }

  // If local node doesn't exist, accept remote change
  if (!localNode?.timestamp) return { resolved: true, value: remoteChange.value, timestamp: ts };

  // If local timestamp is newer or equal, do not overwrite
  if (clock.compare(ts, localNode.timestamp) <= 0) return { resolved: false };

  // Remote wins: apply LWW at object level
  return { resolved: true, value: remoteChange.value, timestamp: ts };
}