From b2a8db14b69764e259452277da822f59a85887f7 Mon Sep 17 00:00:00 2001
From: Andras Schmelczer <andras@schmelczer.dev>
Date: Thu, 2 Jan 2025 11:58:06 +0000
Subject: [PATCH] Update files atomically in Obsidian

---
 plugin/src/file-operations/file-operations.ts |  6 +-
 .../obsidian-file-operations.ts               | 62 ++++++++++---------
 2 files changed, 39 insertions(+), 29 deletions(-)

diff --git a/plugin/src/file-operations/file-operations.ts b/plugin/src/file-operations/file-operations.ts
index 1470d79d..910b6d71 100644
--- a/plugin/src/file-operations/file-operations.ts
+++ b/plugin/src/file-operations/file-operations.ts
@@ -7,9 +7,13 @@ export interface FileOperations {
 
 	getModificationTime: (path: RelativePath) => Promise<Date>;
 
+	// Create and write the file if it doesn't exist. Otherwise, it has the same behavior as write.
+	// All parent directories are created if they don't exist.
 	create: (path: RelativePath, newContent: Uint8Array) => Promise<void>;
 
-	// Writes new content to the file at the given path. If the file's content has changed since the expectedContent was read, the write will merge the changes.
+	// Update the file at the given path.
+	// If the file's content is different from `expectedContent`, the a 3-way merge is performed before writing.
+	// If the file no longer exists, the file is not recreated and an empty array is returned.
 	write: (
 		path: RelativePath,
 		expectedContent: Uint8Array,
diff --git a/plugin/src/file-operations/obsidian-file-operations.ts b/plugin/src/file-operations/obsidian-file-operations.ts
index 7f9a47aa..7c30ecda 100644
--- a/plugin/src/file-operations/obsidian-file-operations.ts
+++ b/plugin/src/file-operations/obsidian-file-operations.ts
@@ -2,7 +2,6 @@ import type { Vault } from "obsidian";
 import { normalizePath } from "obsidian";
 import type { FileOperations } from "./file-operations";
 import * as lib from "../../../backend/sync_lib/pkg/sync_lib.js";
-import { isEqualBytes } from "src/utils/is-equal-bytes";
 import type { RelativePath } from "src/database/document-metadata";
 
 export class ObsidianFileOperations implements FileOperations {
@@ -27,33 +26,6 @@ export class ObsidianFileOperations implements FileOperations {
 		return new Date(file.mtime);
 	}
 
-	public async write(
-		path: RelativePath,
-		expectedContent: Uint8Array,
-		newContent: Uint8Array
-	): Promise<Uint8Array> {
-		if (!(await this.vault.adapter.exists(normalizePath(path)))) {
-			// The caller assumed the file exists, but it doesn't, let's not recreate it
-			return new Uint8Array(0);
-		}
-
-		const currentContent = await this.read(path);
-		if (!isEqualBytes(currentContent, expectedContent)) {
-			const result = lib.merge(
-				expectedContent,
-				currentContent,
-				newContent
-			);
-
-			await this.vault.adapter.writeBinary(normalizePath(path), result);
-
-			return result;
-		}
-		await this.vault.adapter.writeBinary(normalizePath(path), newContent);
-
-		return newContent;
-	}
-
 	public async create(
 		path: RelativePath,
 		newContent: Uint8Array
@@ -67,6 +39,40 @@ export class ObsidianFileOperations implements FileOperations {
 		await this.vault.adapter.writeBinary(normalizePath(path), newContent);
 	}
 
+	public async write(
+		path: RelativePath,
+		expectedContent: Uint8Array,
+		newContent: Uint8Array
+	): Promise<Uint8Array> {
+		if (!(await this.vault.adapter.exists(normalizePath(path)))) {
+			// The caller assumed the file exists, but it doesn't, let's not recreate it
+			return new Uint8Array(0);
+		}
+
+		if (lib.isBinary(expectedContent)) {
+			await this.vault.adapter.writeBinary(
+				normalizePath(path),
+				newContent
+			);
+			return newContent;
+		}
+
+		const expetedText = new TextDecoder().decode(expectedContent);
+		const newText = new TextDecoder().decode(newContent);
+
+		const resultText = await this.vault.adapter.process(
+			normalizePath(path),
+			(currentText) => {
+				if (currentText !== expetedText) {
+					return lib.mergeText(expetedText, currentText, newText);
+				}
+
+				return newText;
+			}
+		);
+		return new TextEncoder().encode(resultText);
+	}
+
 	public async remove(path: RelativePath): Promise<void> {
 		if (await this.vault.adapter.exists(normalizePath(path))) {
 			return this.vault.adapter.remove(normalizePath(path));