feat: safe sync appdata

packages/system/src/index.ts

@@ -38,7 +38,7 @@ export * from "./pow-util";
 export * from "./query-optimizer";
 export * from "./encrypted";
 export * from "./outbox";
-export * from "./range-sync";
+export * from "./sync";
 
 export * from "./impl/nip4";
 export * from "./impl/nip44";

packages/system/src/sync/index.ts

@@ -0,0 +1,7 @@
+export interface HasId {
+  id: string;
+}
+
+export * from "./safe-sync";
+export * from "./range-sync";
+export * from "./json-in-event-sync";

packages/system/src/sync/json-in-event-sync.ts

@@ -0,0 +1,76 @@
+import { SafeSync } from "./safe-sync";
+import { HasId } from ".";
+import { EventExt, EventSigner, NostrEvent, NostrLink, SystemInterface } from "..";
+import debug from "debug";
+import EventEmitter from "eventemitter3";
+import { unixNow } from "@snort/shared";
+
+export interface JsonSyncEvents {
+  change: () => void;
+}
+
+export class JsonEventSync<T extends HasId> extends EventEmitter<JsonSyncEvents> {
+  #log = debug("JsonEventSync");
+  #sync: SafeSync;
+  #json: T;
+
+  constructor(
+    initValue: T,
+    readonly encrypt: boolean,
+  ) {
+    super();
+    this.#sync = new SafeSync();
+    this.#json = initValue;
+
+    this.#sync.on("change", () => this.emit("change"));
+  }
+
+  get json(): Readonly<T> {
+    const ret = { ...this.#json };
+    return Object.freeze(ret);
+  }
+
+  async sync(link: NostrLink, signer: EventSigner, system: SystemInterface) {
+    const res = await this.#sync.sync(link, system);
+    this.#log("Sync result %O", res);
+    if (res) {
+      if (this.encrypt) {
+        this.#json = JSON.parse(await signer.nip4Decrypt(res.content, await signer.getPubKey())) as T;
+      } else {
+        this.#json = JSON.parse(res.content) as T;
+      }
+    }
+  }
+
+  /**
+   * Update the json content in the event
+   * @param val
+   * @param signer
+   */
+  async updateJson(val: T, signer: EventSigner, system: SystemInterface) {
+    this.#log("Updating: %O", val);
+    const next = this.#sync.value ? ({ ...this.#sync.value } as NostrEvent) : undefined;
+    if (!next) {
+      throw new Error("Cannot update with no previous value");
+    }
+
+    next.content = JSON.stringify(val);
+    next.created_at = unixNow();
+
+    const prevTag = next.tags.find(a => a[0] === "previous");
+    if (prevTag) {
+      prevTag[1] = next.id;
+    } else {
+      next.tags.push(["previous", next.id]);
+    }
+    if (this.encrypt) {
+      next.content = await signer.nip4Encrypt(next.content, await signer.getPubKey());
+    }
+    next.id = EventExt.createId(next);
+    const signed = await signer.sign(next);
+
+    await this.#sync.update(signed, system);
+    this.#json = val;
+    this.#json.id = next.id;
+  }
+}

packages/system/src/sync/range-sync.ts

@@ -1,6 +1,6 @@
 import { unixNow } from "@snort/shared";
 import EventEmitter from "eventemitter3";
-import { ReqFilter, RequestBuilder, SystemInterface, TaggedNostrEvent } from ".";
+import { ReqFilter, RequestBuilder, SystemInterface, TaggedNostrEvent } from "..";
 
 /**
  * When nostr was created

packages/system/src/sync/safe-sync.ts

@@ -0,0 +1,101 @@
+import EventEmitter from "eventemitter3";
+import { EventExt, EventType, NostrEvent, NostrLink, RequestBuilder, SystemInterface } from "..";
+
+export interface SafeSyncEvents {
+  change: () => void;
+}
+
+/**
+ * Safely sync replacable events to nostr
+ *
+ * Usefule for the following critical kinds:
+ * 0 (Metadata)
+ * 3 (Contacts)
+ * 10002 (Relays)
+ * 30078 (AppData)
+ */
+export class SafeSync extends EventEmitter<SafeSyncEvents> {
+  #base: NostrEvent | undefined;
+
+  get value() {
+    return this.#base;
+  }
+
+  /**
+   * Fetch the latest version
+   * @param link A link to the kind
+   */
+  async sync(link: NostrLink, system: SystemInterface) {
+    if (link.kind === undefined) {
+      throw new Error("Kind must be set");
+    }
+
+    const rb = new RequestBuilder("sync");
+    const f = rb.withFilter().link(link);
+    if (this.#base) {
+      f.since(this.#base.created_at);
+    }
+    const results = await system.Fetch(rb);
+    const res = results.find(a => link.matchesEvent(a));
+    if (res && res.created_at > (this.#base?.created_at ?? 0)) {
+      this.#base = res;
+      this.emit("change");
+    }
+    return this.#base;
+  }
+
+  /**
+   * Set the base value
+   * @param ev
+   */
+  setBase(ev: NostrEvent) {
+    this.#checkForUpdate(ev, false);
+    this.#base = ev;
+    this.emit("change");
+  }
+
+  /**
+   * Publish an update for this event
+   * @param ev
+   */
+  async update(ev: NostrEvent, system: SystemInterface) {
+    console.debug(this.#base, ev);
+    this.#checkForUpdate(ev, true);
+
+    const link = NostrLink.fromEvent(ev);
+    // always attempt to get a newer version before broadcasting
+    await this.sync(link, system);
+    this.#checkForUpdate(ev, true);
+
+    system.BroadcastEvent(ev);
+    this.#base = ev;
+    this.emit("change");
+  }
+
+  #checkForUpdate(ev: NostrEvent, mustExist: boolean) {
+    if (!this.#base) {
+      if (mustExist) {
+        throw new Error("No previous version detected");
+      } else {
+        return;
+      }
+    }
+    const prevTag = ev.tags.find(a => a[0] === "previous");
+    if (prevTag && prevTag[1] !== this.#base.id) {
+      throw new Error("Previous tag does not match our version");
+    }
+    if (
+      EventExt.getType(ev.kind) !== EventType.Replaceable &&
+      EventExt.getType(ev.kind) !== EventType.ParameterizedReplaceable
+    ) {
+      throw new Error("Not a replacable event kind");
+    }
+    if (this.#base.created_at >= ev.created_at) {
+      throw new Error("Same version, cannot update");
+    }
+    const link = NostrLink.fromEvent(ev);
+    if (!link.matchesEvent(this.#base)) {
+      throw new Error("Invalid event");
+    }
+  }
+}