move electron update logic into own file, tidy tidy tidy

Signed-off-by: Michael Telatynski <7t3chguy@gmail.com>

electron_app/src/updater.js

@@ -0,0 +1,65 @@
+const { app, autoUpdater, ipcMain } = require('electron');
+
+const UPDATE_POLL_INTERVAL_MS = 60 * 60 * 1000;
+const INITIAL_UPDATE_DELAY_MS = 30 * 1000;
+
+function installUpdate() {
+    // for some reason, quitAndInstall does not fire the
+    // before-quit event, so we need to set the flag here.
+    global.appQuitting = true;
+    autoUpdater.quitAndInstall();
+}
+
+function pollForUpdates() {
+    try {
+        autoUpdater.checkForUpdates();
+    } catch (e) {
+        console.log('Couldn\'t check for update', e);
+    }
+}
+
+module.exports = {};
+module.exports.start = function startAutoUpdate(updateBaseUrl) {
+    if (updateBaseUrl.slice(-1) !== '/') {
+        updateBaseUrl = updateBaseUrl + '/';
+    }
+    try {
+        // For reasons best known to Squirrel, the way it checks for updates
+        // is completely different between macOS and windows. On macOS, it
+        // hits a URL that either gives it a 200 with some json or
+        // 204 No Content. On windows it takes a base path and looks for
+        // files under that path.
+        if (process.platform === 'darwin') {
+            // include the current version in the URL we hit. Electron doesn't add
+            // it anywhere (apart from the User-Agent) so it's up to us. We could
+            // (and previously did) just use the User-Agent, but this doesn't
+            // rely on NSURLConnection setting the User-Agent to what we expect,
+            // and also acts as a convenient cache-buster to ensure that when the
+            // app updates it always gets a fresh value to avoid update-looping.
+            autoUpdater.setFeedURL(`${updateBaseUrl}macos/?localVersion=${encodeURIComponent(app.getVersion())}`);
+
+        } else if (process.platform === 'win32') {
+            autoUpdater.setFeedURL(`${updateBaseUrl}win32/${process.arch}/`);
+        } else {
+            // Squirrel / electron only supports auto-update on these two platforms.
+            // I'm not even going to try to guess which feed style they'd use if they
+            // implemented it on Linux, or if it would be different again.
+            console.log('Auto update not supported on this platform');
+        }
+        // We check for updates ourselves rather than using 'updater' because we need to
+        // do it in the main process (and we don't really need to check every 10 minutes:
+        // every hour should be just fine for a desktop app)
+        // However, we still let the main window listen for the update events.
+        // We also wait a short time before checking for updates the first time because
+        // of squirrel on windows and it taking a small amount of time to release a
+        // lock file.
+        setTimeout(pollForUpdates, INITIAL_UPDATE_DELAY_MS);
+        setInterval(pollForUpdates, UPDATE_POLL_INTERVAL_MS);
+    } catch (err) {
+        // will fail if running in debug mode
+        console.log('Couldn\'t enable update checking', err);
+    }
+}
+
+ipcMain.on('install_update', installUpdate);
+ipcMain.on('checkForUpdates', pollForUpdates);