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web/generic_signature_storage.js

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+/* Copyright 2025 Mozilla Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { getUuid } from "pdfjs-lib";
+
+const KEY_STORAGE = "pdfjs.signature";
+
+class SignatureStorage {
+  // TODO: Encrypt the data in using a password and add a UI for entering it.
+  // We could use the Web Crypto API for this (see https://bradyjoslin.com/blog/encryption-webcrypto/
+  // for an example).
+
+  #eventBus;
+
+  #signatures = null;
+
+  #signal = null;
+
+  constructor(eventBus, signal) {
+    this.#eventBus = eventBus;
+    this.#signal = signal;
+  }
+
+  #save() {
+    localStorage.setItem(
+      KEY_STORAGE,
+      JSON.stringify(Object.fromEntries(this.#signatures))
+    );
+  }
+
+  async getAll() {
+    if (this.#signal) {
+      window.addEventListener(
+        "storage",
+        ({ key }) => {
+          if (key === KEY_STORAGE) {
+            this.#signatures = null;
+            this.#eventBus?.dispatch("storedsignatureschanged", {
+              source: this,
+            });
+          }
+        },
+        { signal: this.#signal }
+      );
+      this.#signal = null;
+    }
+    if (!this.#signatures) {
+      this.#signatures = new Map();
+      const data = localStorage.getItem(KEY_STORAGE);
+      if (data) {
+        for (const [key, value] of Object.entries(JSON.parse(data))) {
+          this.#signatures.set(key, value);
+        }
+      }
+    }
+    return this.#signatures;
+  }
+
+  async isFull() {
+    // Only allow 5 signatures to be saved.
+    return (await this.size()) === 5;
+  }
+
+  async size() {
+    return (await this.getAll()).size;
+  }
+
+  async create(data) {
+    if (await this.isFull()) {
+      return null;
+    }
+    const uuid = getUuid();
+    this.#signatures.set(uuid, data);
+    this.#save();
+
+    return uuid;
+  }
+
+  async delete(uuid) {
+    const signatures = await this.getAll();
+    if (!signatures.has(uuid)) {
+      return false;
+    }
+    signatures.delete(uuid);
+    this.#save();
+
+    return true;
+  }
+}
+
+export { SignatureStorage };