Allow check intervals as low as 10 seconds

- Switch from Chrome alarms (30s min) to setTimeout loops
- Config now uses checkIntervalSeconds instead of minutes
- Default: 15 seconds, minimum: 10 seconds
- Prevents overlapping checks with isChecking flag
- Updated popup UI to show seconds

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

chrome-extension/background.js

@@ -2,7 +2,7 @@
 
 const DEFAULT_CONFIG = {
   discordWebhook: "",
-  checkIntervalMinutes: 1,
+  checkIntervalSeconds: 15, // Now in SECONDS, not minutes!
   enabled: true,
   urls: [
     "https://www.pokemoncenter.com/category/tcg-cards?sort=relevance"
@@ -16,37 +16,62 @@ const DEFAULT_CONFIG = {
 let knownProducts = {};
 let config = DEFAULT_CONFIG;
 let persistentTabId = null; // Keep tab open for faster refreshes
+let checkLoopRunning = false; // Prevent multiple loops
+let isChecking = false; // Prevent overlapping checks
 
 // Initialize
 chrome.runtime.onInstalled.addListener(() => {
   console.log("Pokemon Stock Monitor installed");
-  loadConfig();
-  loadProducts();
-  setupAlarm();
+  loadConfig().then(() => {
+    loadProducts();
+    startCheckLoop();
+  });
 });
 
 // Load on startup
 chrome.runtime.onStartup.addListener(() => {
-  loadConfig();
-  loadProducts();
-  setupAlarm();
-});
-
-// Handle alarm
-chrome.alarms.onAlarm.addListener((alarm) => {
-  if (alarm.name === "stockCheck") {
-    runStockCheck();
-  }
-});
-
-// Setup periodic alarm
-function setupAlarm() {
-  // Chrome minimum is 0.5 minutes (30 seconds) for packed extensions
-  const interval = Math.max(0.5, config.checkIntervalMinutes);
-  chrome.alarms.create("stockCheck", {
-    periodInMinutes: interval
+  loadConfig().then(() => {
+    loadProducts();
+    startCheckLoop();
   });
-  console.log(`Alarm set for every ${interval} minute(s) (${interval * 60} seconds)`);
+});
+
+// Start the check loop (uses setTimeout to bypass Chrome's 30-sec alarm minimum)
+function startCheckLoop() {
+  if (checkLoopRunning) {
+    console.log("Check loop already running");
+    return;
+  }
+  checkLoopRunning = true;
+  console.log(`Starting check loop: every ${config.checkIntervalSeconds} seconds`);
+  scheduleNextCheck();
+}
+
+function scheduleNextCheck() {
+  if (!config.enabled || !checkLoopRunning) {
+    checkLoopRunning = false;
+    console.log("Check loop stopped");
+    return;
+  }
+
+  const intervalMs = Math.max(10, config.checkIntervalSeconds) * 1000; // Min 10 seconds
+
+  setTimeout(async () => {
+    if (!isChecking && config.enabled) {
+      isChecking = true;
+      try {
+        await runStockCheck();
+      } finally {
+        isChecking = false;
+      }
+    }
+    scheduleNextCheck();
+  }, intervalMs);
+}
+
+function stopCheckLoop() {
+  checkLoopRunning = false;
+  console.log("Check loop stopped");
 }
 
 // Load config from storage
@@ -61,7 +86,11 @@ async function loadConfig() {
 // Save config to storage
 async function saveConfig() {
   await chrome.storage.local.set({ config });
-  setupAlarm(); // Reset alarm with new interval
+  // Restart loop with new interval
+  stopCheckLoop();
+  if (config.enabled) {
+    startCheckLoop();
+  }
 }
 
 // Load known products from storage
@@ -381,9 +410,11 @@ chrome.runtime.onMessage.addListener((message, sender, sendResponse) => {
 setTimeout(() => {
   loadConfig().then(() => {
     loadProducts().then(() => {
-      if (config.enabled && config.discordWebhook) {
+      if (config.enabled) {
+        console.log(`Check interval: ${config.checkIntervalSeconds} seconds`);
         runStockCheck();
+        startCheckLoop();
       }
     });
   });
-}, 5000);
+}, 3000);