SilverBullet pivot to become an offline-first PWA (#403)
This commit is contained in:
Zef Hemel
@@ -0,0 +1,243 @@
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import type { SpacePrimitives } from "../common/spaces/space_primitives.ts";
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import {
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SpaceSync,
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SyncStatus,
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SyncStatusItem,
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} from "../common/spaces/sync.ts";
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import { EventHook } from "../plugos/hooks/event.ts";
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import { KVStore } from "../plugos/lib/kv_store.ts";
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// Keeps the current sync snapshot
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const syncSnapshotKey = "syncSnapshot";
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// Keeps the start time of an ongoing sync, is reset once the sync is done
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const syncStartTimeKey = "syncStartTime";
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// Keeps the last time an activity was registered, used to detect if a sync is still alive and whether a new one should be started already
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const syncLastActivityKey = "syncLastActivity";
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// maximum time between two activities before we consider a sync crashed
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const syncMaxIdleTimeout = 1000 * 20; // 20s
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// How often to sync the whole space
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const syncInterval = 10 * 1000; // Every 10s
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/**
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* The SyncService primarily wraps the SpaceSync engine but also coordinates sync between
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* different browser tabs. It is using the KVStore to keep track of sync state.
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*/
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export class SyncService {
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spaceSync: SpaceSync;
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lastReportedSyncStatus = Date.now();
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constructor(
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private localSpacePrimitives: SpacePrimitives,
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private remoteSpace: SpacePrimitives,
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private kvStore: KVStore,
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private eventHook: EventHook,
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private isSyncCandidate: (path: string) => boolean,
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) {
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this.spaceSync = new SpaceSync(
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this.localSpacePrimitives,
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this.remoteSpace!,
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{
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conflictResolver: this.plugAwareConflictResolver.bind(this),
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isSyncCandidate: this.isSyncCandidate,
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onSyncProgress: (status) => {
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this.registerSyncProgress(status).catch(console.error);
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},
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},
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);
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eventHook.addLocalListener("editor:pageLoaded", async (name) => {
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await this.syncFile(`${name}.md`);
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});
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eventHook.addLocalListener("page:saved", async (name) => {
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await this.syncFile(`${name}.md`);
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});
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}
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async isSyncing(): Promise<boolean> {
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const startTime = await this.kvStore.get(syncStartTimeKey);
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if (!startTime) {
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return false;
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}
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// Sync is running, but is it still alive?
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const lastActivity = await this.kvStore.get(syncLastActivityKey)!;
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if (Date.now() - lastActivity > syncMaxIdleTimeout) {
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// It's been too long since the last activity, let's consider this one crashed and
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// reset the sync start state
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await this.kvStore.del(syncStartTimeKey);
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return false;
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}
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return true;
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}
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async hasInitialSyncCompleted(): Promise<boolean> {
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// Initial sync has happened when sync progress has been reported at least once, but the syncStartTime has been reset (which happens after sync finishes)
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return !!(!(await this.kvStore.get(syncStartTimeKey)) &&
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(await this.kvStore.get(syncLastActivityKey)));
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}
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async registerSyncStart(): Promise<void> {
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// Assumption: this is called after an isSyncing() check
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await this.kvStore.set(syncStartTimeKey, Date.now());
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await this.kvStore.set(syncLastActivityKey, Date.now());
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}
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async registerSyncProgress(status?: SyncStatus): Promise<void> {
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// Emit a sync event at most every 10s
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if (status && this.lastReportedSyncStatus < Date.now() - 10000) {
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this.eventHook.dispatchEvent("sync:progress", status);
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this.lastReportedSyncStatus = Date.now();
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await this.saveSnapshot(status.snapshot);
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}
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await this.kvStore.set(syncLastActivityKey, Date.now());
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}
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async registerSyncStop(): Promise<void> {
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await this.registerSyncProgress();
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await this.kvStore.del(syncStartTimeKey);
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}
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async getSnapshot(): Promise<Map<string, SyncStatusItem>> {
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const snapshot = (await this.kvStore.get(syncSnapshotKey)) || {};
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return new Map<string, SyncStatusItem>(
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Object.entries(snapshot),
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);
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}
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start() {
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this.syncSpace().catch(
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console.error,
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);
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setInterval(async () => {
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try {
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const lastActivity = (await this.kvStore.get(syncLastActivityKey)) || 0;
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if (lastActivity && Date.now() - lastActivity > syncInterval) {
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// It's been a while since the last activity, let's sync the whole space
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// The reason to do this check is that there may be multiple tabs open each with their sync cycle
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await this.syncSpace();
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}
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} catch (e: any) {
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console.error(e);
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}
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}, syncInterval / 2); // check every half the sync cycle because actually running the sync takes some time therefore we don't want to wait for the full cycle
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}
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async syncSpace(): Promise<number> {
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if (await this.isSyncing()) {
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console.log("Already syncing");
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return 0;
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}
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await this.registerSyncStart();
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let operations = 0;
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const snapshot = await this.getSnapshot();
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try {
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operations = await this.spaceSync!.syncFiles(snapshot);
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this.eventHook.dispatchEvent("sync:success", operations);
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} catch (e: any) {
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this.eventHook.dispatchEvent("sync:error", e.message);
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console.error("Sync error", e);
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}
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await this.saveSnapshot(snapshot);
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await this.registerSyncStop();
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return operations;
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}
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async syncFile(name: string) {
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if (await this.isSyncing()) {
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// console.log("Already syncing");
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return;
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}
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if (!this.isSyncCandidate(name)) {
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return;
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}
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await this.registerSyncStart();
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console.log("Syncing file", name);
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const snapshot = await this.getSnapshot();
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try {
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let localHash: number | undefined = undefined;
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let remoteHash: number | undefined = undefined;
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try {
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localHash =
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(await this.localSpacePrimitives.getFileMeta(name)).lastModified;
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} catch {
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// Not present
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}
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try {
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// This is wasteful, but Netlify (silverbullet.md) doesn't support OPTIONS call (404s) so we'll just fetch the whole file
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const { meta } = await this.remoteSpace!.readFile(name);
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remoteHash = meta.lastModified;
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} catch (e: any) {
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if (e.message === "Not found") {
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// File doesn't exist remotely, that's ok
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} else {
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throw e;
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}
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}
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await this.spaceSync!.syncFile(snapshot, name, localHash, remoteHash);
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this.eventHook.dispatchEvent("sync:success");
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} catch (e: any) {
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this.eventHook.dispatchEvent("sync:error", e.message);
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console.error("Sync error", e);
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}
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await this.saveSnapshot(snapshot);
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await this.registerSyncStop();
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}
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async saveSnapshot(snapshot: Map<string, SyncStatusItem>) {
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await this.kvStore.set(syncSnapshotKey, Object.fromEntries(snapshot));
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}
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public async plugAwareConflictResolver(
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name: string,
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snapshot: Map<string, SyncStatusItem>,
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primary: SpacePrimitives,
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secondary: SpacePrimitives,
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): Promise<number> {
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if (!name.startsWith("_plug/")) {
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const operations = await SpaceSync.primaryConflictResolver(
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name,
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snapshot,
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primary,
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secondary,
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);
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if (operations > 0) {
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// Something happened -> conflict copy generated, let's report it
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await this.eventHook.dispatchEvent("sync:conflict", name);
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}
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return operations;
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}
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console.log(
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"[sync]",
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"Conflict in plug",
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name,
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"will pick the version from secondary and be done with it.",
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);
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const fileMeta = await primary.getFileMeta(name);
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// Read file from secondary
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const { data } = await secondary.readFile(
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name,
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);
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// Write file to primary
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const newMeta = await primary.writeFile(
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name,
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data,
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false,
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fileMeta.lastModified,
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);
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// Update snapshot
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snapshot.set(name, [
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newMeta.lastModified,
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fileMeta.lastModified,
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]);
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return 1;
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}
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}
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