refactor: Query emits Filters

packages/shared/src/feed-cache.ts

@@ -1,6 +1,7 @@
 import debug from "debug";
-import { removeUndefined, unixNowMs, unwrap } from "./utils";
+import { removeUndefined, unixNowMs } from "./utils";
 import { DexieTableLike } from "./dexie-like";
+import EventEmitter from "eventemitter3";
 
 type HookFn = () => void;
 
@@ -9,14 +10,17 @@ export interface KeyedHookFilter {
   fn: HookFn;
 }
 
+export interface FeedCacheEvents {
+  change: (keys: Array<string>) => void;
+}
+
 /**
  * Dexie backed generic hookable store
  */
-export abstract class FeedCache<TCached> {
-  #name: string;
-  #hooks: Array<KeyedHookFilter> = [];
+export abstract class FeedCache<TCached> extends EventEmitter<FeedCacheEvents> {
+  readonly name: string;
   #snapshot: Array<TCached> = [];
-  #changed = true;
+  #log: ReturnType<typeof debug>;
   #hits = 0;
   #miss = 0;
   protected table?: DexieTableLike<TCached>;
@@ -24,21 +28,22 @@ export abstract class FeedCache<TCached> {
   protected cache: Map<string, TCached> = new Map();
 
   constructor(name: string, table?: DexieTableLike<TCached>) {
-    this.#name = name;
+    super();
+    this.name = name;
     this.table = table;
+    this.#log = debug(name);
     setInterval(() => {
-      debug(this.#name)(
+      this.#log(
         "%d loaded, %d on-disk, %d hooks, %d% hit",
         this.cache.size,
         this.onTable.size,
-        this.#hooks.length,
+        this.listenerCount("change"),
         ((this.#hits / (this.#hits + this.#miss)) * 100).toFixed(1),
       );
     }, 30_000);
-  }
-
-  get name() {
-    return this.#name;
+    this.on("change", () => {
+      this.#snapshot = this.takeSnapshot();
+    });
   }
 
   async preload() {
@@ -49,28 +54,25 @@ export abstract class FeedCache<TCached> {
     }
   }
 
-  keysOnTable() {
-    return [...this.onTable];
-  }
-
   hook(fn: HookFn, key: string | undefined) {
-    if (!key) {
-      return () => {
-        //noop
+    if (key) {
+      const handle = (keys: Array<string>) => {
+        if (keys.includes(key)) {
+          fn();
+        }
       };
+      this.on("change", handle);
+      return () => this.off("change", handle);
     }
 
-    this.#hooks.push({
-      key,
-      fn,
-    });
     return () => {
-      const idx = this.#hooks.findIndex(a => a.fn === fn);
-      if (idx >= 0) {
-        this.#hooks.splice(idx, 1);
-      }
+      // noop
     };
   }
+  
+  keysOnTable() {
+    return [...this.onTable];
+  }
 
   getFromCache(key?: string) {
     if (key) {
@@ -89,7 +91,7 @@ export abstract class FeedCache<TCached> {
       const cached = await this.table.get(key);
       if (cached) {
         this.cache.set(this.key(cached), cached);
-        this.notifyChange([key]);
+        this.emit("change", [key]);
         return cached;
       }
     }
@@ -120,7 +122,7 @@ export abstract class FeedCache<TCached> {
         console.error(e);
       }
     }
-    this.notifyChange([k]);
+    this.emit("change", [k]);
   }
 
   async bulkSet(obj: Array<TCached> | Readonly<Array<TCached>>) {
@@ -133,7 +135,10 @@ export abstract class FeedCache<TCached> {
       }
     }
     obj.forEach(v => this.cache.set(this.key(v), v));
-    this.notifyChange(obj.map(a => this.key(a)));
+    this.emit(
+      "change",
+      obj.map(a => this.key(a)),
+    );
   }
 
   /**
@@ -156,7 +161,7 @@ export abstract class FeedCache<TCached> {
       }
       return "no_change";
     })();
-    debug(this.#name)("Updating %s %s %o", k, updateType, m);
+    this.#log("Updating %s %s %o", k, updateType, m);
     if (updateType !== "no_change") {
       const updated = {
         ...existing,
@@ -184,8 +189,11 @@ export abstract class FeedCache<TCached> {
       fromCache.forEach(a => {
         this.cache.set(this.key(a), a);
       });
-      this.notifyChange(fromCache.map(a => this.key(a)));
-      debug(this.#name)(`Loaded %d/%d in %d ms`, fromCache.length, keys.length, (unixNowMs() - start).toLocaleString());
+      this.emit(
+        "change",
+        fromCache.map(a => this.key(a)),
+      );
+      this.#log(`Loaded %d/%d in %d ms`, fromCache.length, keys.length, (unixNowMs() - start).toLocaleString());
       return mapped.filter(a => !a.has).map(a => a.key);
     }
 
@@ -197,23 +205,12 @@ export abstract class FeedCache<TCached> {
     await this.table?.clear();
     this.cache.clear();
     this.onTable.clear();
-    this.#changed = true;
-    this.#hooks.forEach(h => h.fn());
   }
 
   snapshot() {
-    if (this.#changed) {
-      this.#snapshot = this.takeSnapshot();
-      this.#changed = false;
-    }
     return this.#snapshot;
   }
 
-  protected notifyChange(keys: Array<string>) {
-    this.#changed = true;
-    this.#hooks.filter(a => keys.includes(a.key) || a.key === "*").forEach(h => h.fn());
-  }
-
   abstract key(of: TCached): string;
   abstract takeSnapshot(): Array<TCached>;
 }