From b24d06028139559cab955f58e71c0829fd240c25 Mon Sep 17 00:00:00 2001
From: Laurent Cozic <laurent@cozic.net>
Date: Wed, 9 Sep 2020 12:25:31 +0100
Subject: [PATCH] All: Got clock sync to work on mobile

---
 .../lib/file-api-driver-dropbox.js            |  2 +-
 ReactNativeClient/lib/file-api.js             | 34 ++++++++++++++-----
 2 files changed, 27 insertions(+), 9 deletions(-)

diff --git a/ReactNativeClient/lib/file-api-driver-dropbox.js b/ReactNativeClient/lib/file-api-driver-dropbox.js
index 876208821..f16c2dd33 100644
--- a/ReactNativeClient/lib/file-api-driver-dropbox.js
+++ b/ReactNativeClient/lib/file-api-driver-dropbox.js
@@ -44,7 +44,7 @@ class FileApiDriverDropbox {
 	metadataToStat_(md, path) {
 		const output = {
 			path: path,
-			updated_time: md.server_modified ? new Date(md.server_modified) : new Date(),
+			updated_time: md.server_modified ? (new Date(md.server_modified)).getTime() : Date.now(),
 			isDir: md['.tag'] === 'folder',
 		};
 
diff --git a/ReactNativeClient/lib/file-api.js b/ReactNativeClient/lib/file-api.js
index 52200673d..f188eac60 100644
--- a/ReactNativeClient/lib/file-api.js
+++ b/ReactNativeClient/lib/file-api.js
@@ -63,6 +63,31 @@ class FileApi {
 		this.remoteDateMutex_ = new Mutex();
 	}
 
+
+	async fetchRemoteDateOffset_() {
+		const tempFile = `${this.tempDirName()}/timeCheck${Math.round(Math.random() * 1000000)}.txt`;
+		const startTime = Date.now();
+		await this.put(tempFile, 'timeCheck');
+
+		// Normally it should be possible to read the file back immediately but
+		// just in case, read it in a loop.
+		const loopStartTime = Date.now();
+		let stat = null;
+		while (Date.now() - loopStartTime < 5000) {
+			stat = await this.stat(tempFile);
+			if (stat) break;
+			await time.msleep(200);
+		}
+
+		if (!stat) throw new Error('Timed out trying to get sync target clock time');
+
+		this.delete(tempFile); // No need to await for this call
+
+		const endTime = Date.now();
+		const expectedTime = Math.round((endTime + startTime) / 2);
+		return stat.updated_time - expectedTime;
+	}
+
 	// Approximates the current time on the sync target. It caches the time offset to
 	// improve performance.
 	async remoteDate() {
@@ -77,17 +102,10 @@ class FileApi {
 				// Another call might have refreshed the time while we were waiting for the mutex,
 				// so check again if we need to refresh.
 				if (shouldSyncTime()) {
-					const tempFile = `${this.tempDirName()}/timeCheck${Math.random() * 10000}.txt`;
-					const startTime = Date.now();
-					await this.put(tempFile, 'timeCheck');
-					const stat = await this.stat(tempFile);
-					const endTime = Date.now();
-					const expectedTime = Math.round((endTime + startTime) / 2);
-					this.remoteDateOffset_ = stat.updated_time.getTime() - expectedTime;
+					this.remoteDateOffset_ = await this.fetchRemoteDateOffset_();
 					// The sync target clock should rarely change but the device one might,
 					// so we need to refresh relatively frequently.
 					this.remoteDateNextCheckTime_ = Date.now() + 10 * 60 * 1000;
-					this.delete(tempFile); // No need to await for this call
 				}
 			} catch (error) {
 				this.logger().warn('Could not retrieve remote date - defaulting to device date:', error);