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web/view_history.js

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+/* Copyright 2012 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.
+ */
+
+const DEFAULT_VIEW_HISTORY_CACHE_SIZE = 20;
+
+/**
+ * View History - This is a utility for saving various view parameters for
+ *                recently opened files.
+ *
+ * The way that the view parameters are stored depends on how PDF.js is built,
+ * for 'gulp <flag>' the following cases exist:
+ *  - MOZCENTRAL        - uses sessionStorage.
+ *  - GENERIC or CHROME - uses localStorage, if it is available.
+ */
+class ViewHistory {
+  constructor(fingerprint, cacheSize = DEFAULT_VIEW_HISTORY_CACHE_SIZE) {
+    this.fingerprint = fingerprint;
+    this.cacheSize = cacheSize;
+
+    this._initializedPromise = this._readFromStorage().then(databaseStr => {
+      const database = JSON.parse(databaseStr || "{}");
+      let index = -1;
+      if (!Array.isArray(database.files)) {
+        database.files = [];
+      } else {
+        while (database.files.length >= this.cacheSize) {
+          database.files.shift();
+        }
+
+        for (let i = 0, ii = database.files.length; i < ii; i++) {
+          const branch = database.files[i];
+          if (branch.fingerprint === this.fingerprint) {
+            index = i;
+            break;
+          }
+        }
+      }
+      if (index === -1) {
+        index = database.files.push({ fingerprint: this.fingerprint }) - 1;
+      }
+      this.file = database.files[index];
+      this.database = database;
+    });
+  }
+
+  async _writeToStorage() {
+    const databaseStr = JSON.stringify(this.database);
+
+    if (typeof PDFJSDev !== "undefined" && PDFJSDev.test("MOZCENTRAL")) {
+      sessionStorage.setItem("pdfjs.history", databaseStr);
+      return;
+    }
+    localStorage.setItem("pdfjs.history", databaseStr);
+  }
+
+  async _readFromStorage() {
+    if (typeof PDFJSDev !== "undefined" && PDFJSDev.test("MOZCENTRAL")) {
+      return sessionStorage.getItem("pdfjs.history");
+    }
+    return localStorage.getItem("pdfjs.history");
+  }
+
+  async set(name, val) {
+    await this._initializedPromise;
+    this.file[name] = val;
+    return this._writeToStorage();
+  }
+
+  async setMultiple(properties) {
+    await this._initializedPromise;
+    for (const name in properties) {
+      this.file[name] = properties[name];
+    }
+    return this._writeToStorage();
+  }
+
+  async get(name, defaultValue) {
+    await this._initializedPromise;
+    const val = this.file[name];
+    return val !== undefined ? val : defaultValue;
+  }
+
+  async getMultiple(properties) {
+    await this._initializedPromise;
+    const values = Object.create(null);
+
+    for (const name in properties) {
+      const val = this.file[name];
+      values[name] = val !== undefined ? val : properties[name];
+    }
+    return values;
+  }
+}
+
+export { ViewHistory };