Refactor file write streams (#877)

A lot of code is repeated in various different ways in order to handle
streaming content to files without overwriting them, whether it's from
web resources or local streams.

Refactor the handling of these streams to all use the same utility
function for creating a write stream, and for the places downloading
urls use the same downloadFile function.

packages/controller/src/routes.ts

@@ -553,30 +553,16 @@ async function uploadMod(req: Request, res: Response) {
 		}
 
 		const modsDirectory = req.app.locals.controller.config.get("controller.mods_directory");
-		let tempFilename = filename.replace(/(\.zip)?$/, ".tmp.zip");
+		const filePath = path.join(modsDirectory, filename);
+		const [tempFilePath, writeStream] = await lib.createTempWriteStream(filePath);
 
-		let writeStream;
 		try {
-
-			while (true) {
-				try {
-					writeStream = fs.createWriteStream(path.join(modsDirectory, tempFilename), { flags: "wx" });
-					await events.once(writeStream, "open");
-					break;
-				} catch (err: any) {
-					if (err.code === "EEXIST") {
-						tempFilename = await lib.findUnusedName(modsDirectory, tempFilename, ".tmp.zip");
-					} else {
-						throw err;
-					}
-				}
-			}
 			stream.pipe(writeStream);
 			await finished(writeStream);
 
-			const modInfo = await lib.ModInfo.fromModFile(path.join(modsDirectory, tempFilename));
+			const modInfo = await lib.ModInfo.fromModFile(tempFilePath);
 			checkModName(modInfo.filename);
-			await fs.rename(path.join(modsDirectory, tempFilename), path.join(modsDirectory, modInfo.filename));
+			await fs.rename(tempFilePath, path.join(modsDirectory, modInfo.filename));
 			req.app.locals.controller.modStore.addMod(modInfo);
 			mods.push(modInfo.toJSON());
 
@@ -586,15 +572,13 @@ async function uploadMod(req: Request, res: Response) {
 			stream.resume();
 
 			// Attempt to clean up.
-			if (writeStream) {
-				writeStream.destroy();
-			}
+			writeStream.destroy();
 
 			try {
-				await fs.unlink(path.join(modsDirectory, tempFilename));
+				await fs.unlink(tempFilePath);
 			} catch (unlinkErr: any) {
 				if (unlinkErr.code !== "ENOENT") {
-					logger.error(`Error removing ${tempFilename}: ${unlinkErr.message}`);
+					logger.error(`Error removing ${tempFilePath}: ${unlinkErr.message}`);
 				}
 			}
 		}