From fc0ea36cf32fbd52b87e94813c6022d015074f40 Mon Sep 17 00:00:00 2001
From: Elian Doran <contact@eliandoran.me>
Date: Mon, 29 Dec 2025 14:06:59 +0200
Subject: [PATCH] chore(pdfjs): first attempt at intercepting store

---
 packages/pdfjs-viewer/src/custom.ts    | 24 +++++++++++++++++++++---
 packages/pdfjs-viewer/src/typings.d.ts | 14 ++++++++++++++
 2 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/packages/pdfjs-viewer/src/custom.ts b/packages/pdfjs-viewer/src/custom.ts
index 060ed0c1c..96b8986c9 100644
--- a/packages/pdfjs-viewer/src/custom.ts
+++ b/packages/pdfjs-viewer/src/custom.ts
@@ -1,4 +1,4 @@
-const LOG_EVENT_BUS = true;
+const LOG_EVENT_BUS = false;
 
 async function main() {
     // Wait for the PDF viewer application to be available.
@@ -11,12 +11,14 @@ async function main() {
         patchEventBus();
     }
     app.eventBus.on("documentloaded", () => {
-        manageSave(app);
+        interceptViewHistory();
+        manageSave();
     });
     await app.initializedPromise;
 };
 
-function manageSave(app: typeof window.PDFViewerApplication) {
+function manageSave() {
+    const app = window.PDFViewerApplication;
     const storage = app.pdfDocument.annotationStorage;
     let timeout = null;
 
@@ -49,6 +51,22 @@ function manageSave(app: typeof window.PDFViewerApplication) {
     });
 }
 
+function interceptViewHistory() {
+    const app = window.PDFViewerApplication;
+    let activeFingerprint: string = app.pdfDocument.fingerprints[0];
+
+    const store = app.store;
+    store._writeToStorage = async function() {
+        const fileEntry = store.database.files?.find(f => f.fingerprint === activeFingerprint);
+        const databaseStr = JSON.stringify(fileEntry);
+        console.log("Write attempt.", databaseStr);
+    }
+    store._readFromStorage = async function() {
+        console.log("Read attempt", activeFingerprint);
+        return "{}";
+    }
+}
+
 function patchEventBus() {
     const eventBus = window.PDFViewerApplication.eventBus;
     const originalDispatch = eventBus.dispatch.bind(eventBus);
diff --git a/packages/pdfjs-viewer/src/typings.d.ts b/packages/pdfjs-viewer/src/typings.d.ts
index 040300890..9370df20a 100644
--- a/packages/pdfjs-viewer/src/typings.d.ts
+++ b/packages/pdfjs-viewer/src/typings.d.ts
@@ -1,6 +1,19 @@
 import type { PDFDocumentProxy } from "pdfjs-dist";
 
 declare global {
+    /**
+     * @source https://github.com/mozilla/pdf.js/blob/master/web/view_history.js
+     */
+    interface ViewHistory {
+        database: {
+            files?: {
+                fingerprint: string;
+            }[];
+        },
+        _writeToStorage: () => Promise<void>;
+        _readFromStorage: () => Promise<string>;
+    }
+
     interface Window {
         PDFViewerApplication?: {
             initializedPromise: Promise<void>;
@@ -9,6 +22,7 @@ declare global {
                 on(event: string, listener: (...args: any[]) => void): void;
                 dispatch(event: string, data?: any): void;
             };
+            store: ViewHistory;
         };
     }
 }