enable debug

.dockerignore

@@ -0,0 +1,10 @@
+node_modules
+npm-debug.log
+Dockerfile
+.dockerignore
+.git
+.gitignore
+README.md
+*.example
+.env.example
+.labels.example

.env.example

@@ -0,0 +1,43 @@
+# --- Application Configuration ---
+
+# --- VAPID Keys (REQUIRED for Web Push) ---
+# Generate these once using npx web-push generate-vapid-keys (or other tools)
+# Keep the private key SECRET!
+VAPID_PUBLIC_KEY=
+VAPID_PRIVATE_KEY=
+
+# Subject claim for VAPID. Use a 'mailto:' URI or an 'https:' URL identifying your application.
+# Example: mailto:admin@yourdomain.com or https://yourdomain.com/contact
+VAPID_SUBJECT=mailto:admin@virtonline.eu
+
+# Subscription Storage
+SUBSCRIPTIONS_FILE=subscriptions.json
+
+# CORS
+ALLOWED_ORIGINS=https://game-timer.virtonline.eu
+ALLOWED_METHODS=POST,OPTIONS,GET
+ALLOWED_HEADERS=Content-Type,Authorization
+
+# Logging Configuration
+LOG_LEVEL=INFO
+
+# --- Security (Optional) ---
+# If you want to add a simple security layer between Flic and this app.
+# If set, configure Flic's HTTP request to include an "Authorization: Bearer YOUR_SECRET_VALUE" header.
+# use e.g.: openssl rand -hex 32
+FLIC_SECRET=
+
+# --- DNS and Network Configuration ---
+# These settings help with Docker DNS resolution issues (EAI_AGAIN errors)
+
+# Maximum number of retry attempts for failed DNS resolutions
+MAX_NOTIFICATION_RETRIES=3
+
+# Initial delay in milliseconds before first retry (will increase with backoff)
+INITIAL_RETRY_DELAY_MS=1000
+
+# DNS resolution timeout in milliseconds
+DNS_TIMEOUT_MS=5000
+
+# HTTP request timeout in milliseconds
+HTTP_TIMEOUT_MS=10000

.gitignore

@@ -0,0 +1,20 @@
+myenv
+.vscode
+.cursor
+
+# Node.js
+node_modules/
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+.env
+subscriptions.json
+
+# OS generated files
+.DS_Store
+.DS_Store?
+._*
+.Spotlight-V100
+.Trashes
+ehthumbs.db
+Thumbs.db

Dockerfile

@@ -0,0 +1,23 @@
+# Use an official Node.js runtime as a parent image
+# Alpine Linux is chosen for its small size
+FROM node:20-alpine
+
+# Set the working directory in the container
+WORKDIR /app
+
+# Copy package.json and package-lock.json (if available)
+COPY package*.json ./
+
+# Install app dependencies using npm ci for faster, reliable builds
+# Use --only=production to avoid installing devDependencies
+RUN npm ci --only=production
+
+# Copy the rest of the application code
+COPY . .
+
+# Make port 3000 available to the world outside this container
+# This is the port our Node.js app will listen on
+EXPOSE 3000
+
+# Define the command to run your app using CMD which defines your runtime
+CMD [ "node", "server.js" ]

README.md

@@ -1,3 +1,201 @@
-# flic-webpush-localstack
+# Flic to PWA WebPush Backend
 
-AWS Lambda function using LocalStack in Docker that receives HTTP requests from Flic buttons and sends WebPush notifications.
+This project provides a self-hosted backend service that listens for HTTP requests from Flic smart buttons and triggers Web Push notifications to specific Progressive Web App (PWA) instances. The goal is to allow a Flic button press (Single Click, Double Click, Hold) to trigger actions within the PWA via push messages handled by a Service Worker.
+
+It's designed to be run as a Docker container and integrated with Traefik v3 for SSL termination and routing.
+
+## Features
+
+*   Receives GET requests on `/flic-webhook`.
+*   Uses HTTP headers `Button-Name` and `Timestamp` from the Flic request.
+*   Gets `click_type` from query parameter.
+*   Looks up the target PWA push subscription based on the `Button-Name` header in a JSON file.
+*   Sends a Web Push notification containing the click details (action, button, timestamp) to the corresponding PWA subscription.
+*   Integrates with Traefik v3 via Docker labels.
+*   Configurable via environment variables (`.env` file).
+*   Optional bearer token authentication for securing the Flic webhook endpoint.
+*   CORS configuration for allowing requests (needed if your PWA management interface interacts with this service, although not strictly necessary for the Flic->Backend->PWA push flow itself).
+
+## Prerequisites
+
+*   **Docker:** [Install Docker](https://docs.docker.com/engine/install/)
+*   **Traefik:** A running Traefik v3 instance configured with SSL (Let's Encrypt recommended) and connected to a Docker network named `traefik`. You need to know your certificate resolver name.
+*   **Domain Name:** A domain or subdomain pointing to your Traefik instance (e.g., `webpush.virtonline.eu`). This will be used for the webhook URL.
+*   **Flic Hub/Service:** Configured to send HTTP requests for button actions. You'll need the serial number(s) of your Flic button(s).
+*   **Node.js & npm/npx (Optional):** Needed only locally to generate VAPID keys easily. Not required for running the container.
+*   **PWA Push Subscription Details:** You need to obtain the Push Subscription object (containing `endpoint`, `keys.p256dh`, `keys.auth`) from your PWA after the user grants notification permission.
+
+## System Architecture
+
+### Subscription Flow
+<img src="images/subscription-flow.png" width="600" alt="Subscription Flow">
+
+### Interaction Flow
+<img src="images/interaction-flow.png" width="300" alt="Interaction Flow">
+
+## Project Structure
+
+## Setup
+
+1.  **Clone the Repository:**
+    ```bash
+    git clone https://gitea.virtonline.eu/2HoursProject/flic-webhook-webpush.git
+    cd flic-webhook-webpush
+    ```
+
+2.  **Generate VAPID Keys:**
+    Web Push requires VAPID keys for security. Generate them once and store them into `.env`. You can use `npx`:
+    ```bash
+    npx web-push generate-vapid-keys
+    ```
+    This will output a Public Key and a Private Key.
+
+3.  **Configure Environment Variables:**
+    *   Copy the example `.env` file:
+        ```bash
+        cp .env.example .env
+        ```
+    *   Edit the `.env` file with your specific values:
+        *   `VAPID_PUBLIC_KEY`: The public key generated in step 2. **Your PWA will also need this key** when it subscribes to push notifications.
+        *   `VAPID_PRIVATE_KEY`: The private key generated in step 2. **Keep this secret!**
+        *   `VAPID_SUBJECT`: A `mailto:` or `https:` URL identifying you or your application (e.g., `mailto:admin@yourdomain.com`). Used by push services to contact you.
+        *   `PORT`: (Default: `3000`) The internal port the Node.js app listens on. Traefik will map to this.
+        *   `SUBSCRIPTIONS_FILE`: (Default: `/app/subscriptions.json`) The path *inside the container* where the button-to-subscription mapping is stored.
+        *   `FLIC_SECRET`: (Optional) Set a strong, random secret string if you want to secure the webhook endpoint using Bearer token authentication. Generate with `openssl rand -hex 32` or a password manager.
+        *   `ALLOWED_ORIGINS`: Comma-separated list of domains allowed by CORS. Include your PWA's domain if it needs to interact directly (e.g., for setup). Example: `https://my-pwa.com`.
+        *   `ALLOWED_METHODS`: (Default: `POST,OPTIONS`) Standard methods needed.
+        *   `ALLOWED_HEADERS`: (Default: `Content-Type,Authorization`) Standard headers needed.
+        *   `MAX_NOTIFICATION_RETRIES`: (Default: `3`) Number of retry attempts for failed push notifications. Must be a number.
+        *   `INITIAL_RETRY_DELAY_MS`: (Default: `1000`) Initial delay in milliseconds before first retry. Must be a number.
+        *   `DNS_TIMEOUT_MS`: (Default: `5000`) DNS resolution timeout in milliseconds. Must be a number.
+        *   `HTTP_TIMEOUT_MS`: (Default: `10000`) HTTP request timeout in milliseconds. Must be a number.
+        *   `LOG_LEVEL`: (Default: `info`) Controls verbosity of logs. Valid values are `error`, `warn`, `info`, or `debug`. Use `debug` to see detailed header information and other diagnostic messages.
+        *   `TRAEFIK_SERVICE_HOST`: Your public domain for this service (e.g., `webpush.virtonline.eu`).
+        *   `TRAEFIK_CERT_RESOLVER`: The name of your TLS certificate resolver configured in Traefik (e.g., `le`, `myresolver`).
+
+4.  **Configure Traefik Labels:**
+    *   Copy the example `labels` file:
+        ```bash
+        cp labels.example labels
+        ```
+    *   **Important:** Edit the `labels` file. Replace `${TRAEFIK_SERVICE_HOST}`, `${TRAEFIK_CERT_RESOLVER}`, and `${PORT}` with the *actual values* from your `.env` file, as `docker run` does not substitute variables in label files.
+        *   Example replacement: `Host(\`${TRAEFIK_SERVICE_HOST}\`)` becomes `Host(`webpush.virtonline.eu`)`.
+        *   `traefik.http.routers.flic-webhook.tls.certresolver=${TRAEFIK_CERT_RESOLVER}` becomes `traefik.http.routers.flic-webhook.tls.certresolver=myresolver`.
+        *   `traefik.http.services.flic-webhook.loadbalancer.server.port=${PORT}` becomes `traefik.http.services.flic-webhook.loadbalancer.server.port=3000`.
+
+5.  **Prepare Subscription Mapping File:**
+    *   Edit the `subscriptions.json` file
+    *   Add entries mapping your Flic button's serial number (as a lowercase string key) to the PWA `PushSubscription` object.
+        ```json
+        {
+          "game": { // <-- Replace with your actual Flic Button name (lowercase recommended)
+            "endpoint": "https://your_pwa_push_endpoint...",
+            "expirationTime": null,
+            "keys": {
+              "p256dh": "YOUR_PWA_SUBSCRIPTION_P256DH_KEY",
+              "auth": "YOUR_PWA_SUBSCRIPTION_AUTH_KEY"
+            }
+          }
+          // Add more entries for other buttons if needed
+        }
+        ```
+    *   Ensure this file contains valid JSON.
+
+## Running the Service
+
+1.  **Build the Docker Image:**
+    Make sure you are in the `flic-webhook-webpush` directory.
+    ```bash
+    docker build -t flic-webhook-webpush:latest .
+    ```
+
+2.  **Run the Container:**
+    This command runs the container in detached mode (`-d`), names it, connects it to the `traefik` network, passes environment variables from the `.env` file, applies the Traefik labels from the `labels` file, and mounts the `subscriptions.json` file into the container.
+
+    ```bash
+    docker run -d --name flic-webhook-webpush \
+      --network traefik \
+      --env-file .env \
+      --label-file labels \
+      --mount type=bind,src=./subscriptions.json,dst=/app/subscriptions.json \
+      flic-webhook-webpush:latest
+    ```
+
+3.  **Check Logs:**
+    Monitor the container logs to ensure it started correctly and to see incoming webhook requests or errors.
+    ```bash
+    docker logs -f flic-webhook-webpush
+    ```
+    You should see messages indicating the server started, configuration details, and subscription loading status.
+
+4.  **Verify Traefik:** Check your Traefik dashboard to ensure the `flic-webhook-webpush` service and router are discovered and healthy.
+
+## Flic Button Configuration
+
+In your Flic app or Flic Hub SDK interface:
+
+1.  Select your Flic button.
+2.  Add an "Internet Request" action.
+3.  Fill in the following details:
+    *   Set `GET` method.
+    *   Set URL with query parameter: `https://webpush.virtonline.eu/flic-webhook?click_type=SingleClick`
+    *   Add headers:
+        *   Key: `Authorization`
+        *   Value: `Bearer <FLIC_SECRET>` (Replace `<FLIC_SECRET>` with the actual secret from your `.env` file).
+    *   It should look like this:
+
+    <!-- <img src="images/flic-button-request.png" width="300" alt="Flic Button Request Configuration"> // TODO: Update image -->
+
+    *   Tap on `Save action`.
+4.   Repeat for Double Click and/or Hold events.
+    
+## API Endpoint
+
+*   **`GET /flic-webhook`**
+    *   **Description:** Receives Flic button events.
+    *   **Authentication:** Optional Bearer token via `Authorization` header if `FLIC_SECRET` is configured.
+    *   **Query Parameters:**
+        *   `click_type`: The type of button press (SingleClick, DoubleClick, or Hold)
+    *   **Responses:**
+        *   `200 OK`: Webhook received, push notification sent successfully.
+        *   `400 Bad Request`: Missing `Button-Name` header or `click_type` query parameter.
+        *   `401 Unauthorized`: Missing or invalid Bearer token (if `FLIC_SECRET` is enabled).
+        *   `404 Not Found`: No subscription found in `subscriptions.json` for the given `Button-Name`.
+        *   `410 Gone`: The push subscription associated with the button was rejected by the push service (likely expired or revoked).
+        *   `500 Internal Server Error`: Failed to send the push notification for other reasons.
+
+## Testing the Webhook
+
+Once your service is up and running, you can test the webhook endpoint using curl or any API testing tool:
+
+**Note:** In the command below, replace `a74181969a613c545d66c1e436e75c1e4a6` with your actual FLIC_SECRET value from your .env file.
+
+```bash
+curl -X GET "https://webpush.virtonline.eu/flic-webhook?click_type=SingleClick" \
+  -H "Authorization: Bearer a74181969a613c545d66c1e436e75c1e4a6" \
+  -H "Button-Name: Game" \
+  -H "Timestamp: 2025-03-26T01:10:20Z"
+```
+
+The expected response should be:
+```json
+{"message":"Push notification sent successfully"}
+```
+
+If successful, the above response indicates that:
+1. Your webhook endpoint is properly configured
+2. The button ID was found in your subscriptions.json file
+3. The web push notification was successfully sent to the registered PUSH API endpoint (e.g. https://jmt17.google.com/fcm/send/cf907M...)
+
+If you receive a different response, refer to the Troubleshooting section below.
+
+## Troubleshooting
+
+*   **Check Backend Logs:** `docker logs flic-webhook-webpush`. Look for errors related to configuration, file access, JSON parsing, authentication, or sending push notifications.
+    * To see detailed debug information including all headers received from the Flic button, set `LOG_LEVEL=debug` in your .env file.
+*   **Check Traefik Logs:** `docker logs traefik`. Look for routing errors or certificate issues.
+*   **Verify `.env`:** Ensure all required variables are set correctly, especially VAPID keys and Traefik settings.
+*   **Verify `labels`:** Double-check that variables were correctly substituted manually and match your `.env` and Traefik setup.
+*   **Verify `subscriptions.json`:** Ensure it's valid JSON and the button serial number (key) matches exactly what Flic sends (check backend logs for "Received webhook: Button=..."). Check if the subscription details are correct. Case sensitivity matters for the JSON keys (button serials).
+*   **Check Flic Configuration:** Ensure the URL, Method, Body, and Headers (especially `Content-Type` and `Authorization` if used) are correct in the Flic action setup. Use `curl` or Postman to test the endpoint manually first.
+*   **PWA Service Worker:** Remember that the PWA needs a correctly registered Service Worker to receive and handle the incoming push messages. Ensure the PWA subscribes using the *same* `VAPID_PUBLIC_KEY` configured in the backend's `.env`.

images/interaction-flow.mmd

@@ -0,0 +1,8 @@
+stateDiagram-v2
+    [*] --> FlicButton : Button Press
+    FlicButton --> Bluetooth : Transmit Signal
+    Bluetooth --> Phone : Receive Signal
+    Phone --> WebhookWebPushService : Send Webhook
+    WebhookWebPushService --> GooglePushAPI : Forward Notification
+    GooglePushAPI --> PWA : Push Notification
+    PWA --> [*] : Handle Notification

images/subscription-flow.mmd

@@ -0,0 +1,7 @@
+stateDiagram-v2
+    [*] --> PWA : User Initiates
+    PWA --> GooglePushAPI : Request Subscription
+    GooglePushAPI --> PWA : Return Subscription Info
+    PWA --> WebhookWebPushService : Store Subscription Info
+    WebhookWebPushService --> PWA : Confirmation
+    [*] --> Complete

labels

@@ -0,0 +1,32 @@
+# Enable Traefik for this container
+traefik.enable=true
+
+# Docker Network
+traefik.docker.network=traefik
+
+# Route requests based on Host
+traefik.http.routers.flic-webhook-webpush.rule=Host(`webpush.virtonline.eu`)
+# Specify the entrypoint ('websecure' for HTTPS)
+traefik.http.routers.flic-webhook-webpush.entrypoints=web-secure
+traefik.http.routers.flic-webhook-webpush.tls=true
+traefik.http.routers.flic-webhook-webpush.tls.certResolver=default
+# Link the router to the service defined below
+traefik.http.routers.flic-webhook-webpush.service=flic-webhook-webpush
+
+# Point the service to the container's port
+traefik.http.services.flic-webhook-webpush.loadbalancer.server.port=3000
+
+# Middleware CORS
+traefik.http.middlewares.cors-headers.headers.accesscontrolallowmethods=POST,GET,OPTIONS
+traefik.http.middlewares.cors-headers.headers.accesscontrolalloworiginlist=https://game-timer.virtonline.eu
+traefik.http.middlewares.cors-headers.headers.accesscontrolallowheaders=Content-Type,Authorization
+traefik.http.middlewares.cors-headers.headers.accesscontrolmaxage=600
+traefik.http.middlewares.cors-headers.headers.addvaryheader=true
+# Apply the middleware to the router
+traefik.http.routers.flic-webhook-webpush.middlewares=cors-headers 
+
+# Middleware Rate Limiting
+traefik.http.middlewares.flic-ratelimit.ratelimit.average=10
+traefik.http.middlewares.flic-ratelimit.ratelimit.burst=20
+# Apply the middleware to the router
+traefik.http.routers.flic-webhook-webpush.middlewares=flic-ratelimit

package-lock.json

@@ -0,0 +1,926 @@
+{
+    "name": "flic-webhook-webpush",
+    "version": "1.0.0",
+    "lockfileVersion": 3,
+    "requires": true,
+    "packages": {
+        "": {
+            "name": "flic-webhook-webpush",
+            "version": "1.0.0",
+            "license": "MIT",
+            "dependencies": {
+                "cors": "^2.8.5",
+                "dotenv": "^16.4.5",
+                "express": "^4.19.2",
+                "web-push": "^3.6.7"
+            }
+        },
+        "node_modules/accepts": {
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+                "jws": "^4.0.0",
+                "minimist": "^1.2.5"
+            },
+            "bin": {
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+        }
+    }
+}

package.json

@@ -0,0 +1,25 @@
+{
+    "name": "flic-webhook-webpush",
+    "version": "1.0.0",
+    "description": "Backend to receive Flic webhooks and send Web Push notifications",
+    "main": "server.js",
+    "scripts": {
+      "start": "node server.js",
+      "test": "echo \"Error: no test specified\" && exit 1"
+    },
+    "keywords": [
+      "flic",
+      "webpush",
+      "pwa",
+      "webhook",
+      "docker"
+    ],
+    "author": "Your Name",
+    "license": "MIT",
+    "dependencies": {
+      "cors": "^2.8.5",
+      "dotenv": "^16.4.5",
+      "express": "^4.19.2",
+      "web-push": "^3.6.7"
+    }
+  }

server.js

@@ -0,0 +1,353 @@
+const express = require('express');
+const webpush = require('web-push');
+const cors = require('cors');
+const fs = require('fs');
+const path = require('path');
+const dns = require('dns'); // Add DNS module
+
+// Load environment variables from .env file
+require('dotenv').config();
+
+// --- Configuration ---
+const port = process.env.PORT || 3000;
+const vapidPublicKey = process.env.VAPID_PUBLIC_KEY;
+const vapidPrivateKey = process.env.VAPID_PRIVATE_KEY;
+const vapidSubject = process.env.VAPID_SUBJECT; // mailto: or https:
+const subscriptionsFilePath = process.env.SUBSCRIPTIONS_FILE || path.join(__dirname, 'subscriptions.json');
+const flicSecret = process.env.FLIC_SECRET; // Optional Bearer token secret for Flic webhook
+// Note: We are NOT adding specific authentication for the /subscribe endpoint in this version.
+// Consider adding API key or other auth if exposing this publicly.
+const allowedOrigins = (process.env.ALLOWED_ORIGINS || "").split(',').map(origin => origin.trim()).filter(origin => origin);
+const allowedMethods = (process.env.ALLOWED_METHODS || "POST,OPTIONS,GET").split(',').map(method => method.trim()).filter(method => method);
+const allowedHeaders = (process.env.ALLOWED_HEADERS || "Content-Type,Authorization").split(',').map(header => header.trim()).filter(header => header);
+// Retry configuration for DNS resolution issues
+const maxRetries = parseInt(process.env.MAX_NOTIFICATION_RETRIES || 3, 10);
+const initialRetryDelay = parseInt(process.env.INITIAL_RETRY_DELAY_MS || 1000, 10); // 1 second
+// HTTP request timeout configuration
+const httpTimeout = parseInt(process.env.HTTP_TIMEOUT_MS || 10000, 10); // 10 seconds
+// Logging level configuration
+const LOG_LEVEL = (process.env.LOG_LEVEL || 'info').toLowerCase();
+
+// --- Logging Utility ---
+const LogLevels = {
+  error: 0,
+  warn: 1,
+  info: 2,
+  debug: 3
+};
+
+const logger = {
+  error: (...args) => {
+    console.error(...args);
+  },
+  warn: (...args) => {
+    if (LogLevels[LOG_LEVEL] >= LogLevels.warn) {
+      console.warn(...args);
+    }
+  },
+  info: (...args) => {
+    if (LogLevels[LOG_LEVEL] >= LogLevels.info) {
+      console.log(...args);
+    }
+  },
+  debug: (...args) => {
+    if (LogLevels[LOG_LEVEL] >= LogLevels.debug) {
+      console.log('DEBUG -', ...args);
+    }
+  }
+};
+
+// Configure global HTTP agent with timeouts to prevent hanging requests
+const https = require('https');
+const http = require('http');
+
+// Custom HTTPS agent with timeout
+const httpsAgent = new https.Agent({
+  keepAlive: true,
+  timeout: httpTimeout,
+  maxSockets: 50, // Limit concurrent connections
+});
+
+// Apply the agent to the webpush module if possible
+// Note: The web-push library might use its own agent, but this is a precaution
+https.globalAgent = httpsAgent;
+
+// --- Validation ---
+if (!vapidPublicKey || !vapidPrivateKey || !vapidSubject) {
+  logger.error('Error: VAPID_PUBLIC_KEY, VAPID_PRIVATE_KEY, and VAPID_SUBJECT must be set in the environment variables.');
+  process.exit(1);
+}
+
+// --- Web Push Setup ---
+webpush.setVapidDetails(
+  vapidSubject,
+  vapidPublicKey,
+  vapidPrivateKey
+);
+
+// Configure DNS settings for more reliable resolution in containerized environments
+// These settings can help with temporary DNS resolution failures
+dns.setDefaultResultOrder('ipv4first'); // Prefer IPv4 to avoid some IPv6 issues in containers
+const dnsTimeout = parseInt(process.env.DNS_TIMEOUT_MS || 5000, 10);
+dns.setServers(dns.getServers()); // Reset DNS servers (can help in some Docker environments)
+
+// You can optionally configure a specific DNS server if needed:
+// Example: dns.setServers(['8.8.8.8', '1.1.1.1']);
+
+// --- Utility function for retrying web push notifications with exponential backoff ---
+async function sendWebPushWithRetry(subscription, payload, retryCount = 0, delay = initialRetryDelay) {
+  try {
+    return await webpush.sendNotification(subscription, payload);
+  } catch (error) {
+    // Check if the error is a DNS resolution error that might be temporary
+    const isDnsError = error.code === 'EAI_AGAIN' || 
+                       error.code === 'ENOTFOUND' || 
+                       error.code === 'ETIMEDOUT';
+    
+    if (isDnsError && retryCount < maxRetries) {
+      console.log(`DNS resolution failed (${error.code}). Retrying notification in ${delay}ms (attempt ${retryCount + 1}/${maxRetries})...`);
+      
+      // Wait for the delay
+      await new Promise(resolve => setTimeout(resolve, delay));
+      
+      // Exponential backoff with jitter
+      const nextDelay = delay * (1.5 + Math.random() * 0.5);
+      
+      // Retry recursively with increased count and delay
+      return sendWebPushWithRetry(subscription, payload, retryCount + 1, nextDelay);
+    }
+    
+    // If we've exhausted retries or it's not a DNS error, rethrow
+    throw error;
+  }
+}
+
+// --- Subscription Loading and Management ---
+let subscriptions = {}; // In-memory cache of subscriptions
+
+function loadSubscriptions() {
+    if (!fs.existsSync(subscriptionsFilePath)) {
+        logger.warn(`Warning: Subscriptions file not found at ${subscriptionsFilePath}. Creating an empty file.`);
+        try {
+            fs.writeFileSync(subscriptionsFilePath, '{}', 'utf8');
+            subscriptions = {};
+        } catch (err) {
+            logger.error(`Error: Could not create subscriptions file at ${subscriptionsFilePath}.`, err);
+            // Exit or continue with empty object depending on desired robustness
+             process.exit(1); // Exit if we can't even create the file
+        }
+    } else {
+        try {
+            const data = fs.readFileSync(subscriptionsFilePath, 'utf8');
+            subscriptions = JSON.parse(data || '{}'); // Handle empty file case
+            logger.info(`Loaded ${Object.keys(subscriptions).length} subscriptions from ${subscriptionsFilePath}`);
+        } catch (err) {
+            logger.error(`Error reading or parsing subscriptions file at ${subscriptionsFilePath}. Please ensure it's valid JSON. Using empty cache.`, err);
+            // Continue with empty subscriptions, but log the error
+            subscriptions = {};
+        }
+    }
+}
+
+function saveSubscriptions() {
+    try {
+        fs.writeFileSync(subscriptionsFilePath, JSON.stringify(subscriptions, null, 2), 'utf8'); // Pretty print JSON
+        logger.info(`Subscriptions successfully saved to ${subscriptionsFilePath}`);
+    } catch (err) {
+        logger.error(`Error writing subscriptions file: ${subscriptionsFilePath}`, err);
+        // Note: The in-memory object is updated, but persistence failed.
+    }
+}
+
+// Initial load
+loadSubscriptions();
+
+
+// --- Express App Setup ---
+const app = express();
+
+// --- CORS Middleware ---
+const corsOptions = {
+  origin: (origin, callback) => {
+    if (!origin || allowedOrigins.length === 0 || allowedOrigins.includes(origin)) {
+      callback(null, true);
+    } else {
+      console.warn(`CORS: Blocked origin: ${origin}`);
+      callback(new Error('Not allowed by CORS'));
+    }
+  },
+  methods: allowedMethods,
+  allowedHeaders: allowedHeaders,
+  optionsSuccessStatus: 204 // For pre-flight requests
+};
+app.use(cors(corsOptions));
+// Enable pre-flight requests for all relevant routes
+app.options('/flic-webhook', cors(corsOptions));
+app.options('/subscribe', cors(corsOptions));
+
+
+// --- Body Parsing Middleware ---
+app.use(express.json());
+
+// --- Authentication Middleware (For Flic Webhook Only) ---
+const authenticateFlicRequest = (req, res, next) => {
+  // Only apply auth if flicSecret is configured
+  if (!flicSecret) {
+    return next();
+  }
+
+  const authHeader = req.headers.authorization;
+  if (!authHeader || !authHeader.startsWith('Bearer ')) {
+    logger.warn('Auth (Flic): Missing or malformed Authorization header');
+    return res.status(401).json({ message: 'Unauthorized: Missing or malformed Bearer token' });
+  }
+
+  const token = authHeader.split(' ')[1];
+  if (token !== flicSecret) {
+    logger.warn('Auth (Flic): Invalid Bearer token received');
+    return res.status(401).json({ message: 'Unauthorized: Invalid token' });
+  }
+
+  logger.debug('Auth (Flic): Request authenticated successfully.');
+  next();
+};
+
+app.post('/subscribe', async (req, res) => {
+    const { button_id, subscription } = req.body;
+    
+    logger.debug('All headers received:');
+    Object.keys(req.headers).forEach(headerName => {
+      logger.debug(`  ${headerName}: ${req.headers[headerName]}`);
+    });
+
+    logger.info(`Received subscription request for button: ${button_id}`);
+
+    // Basic Validation
+    if (!button_id || typeof button_id !== 'string' || button_id.trim() === '') {
+        logger.warn('Subscription Error: Missing or invalid button_id');
+        return res.status(400).json({ message: 'Bad Request: Missing or invalid button_id' });
+    }
+    if (!subscription || typeof subscription !== 'object' || !subscription.endpoint || !subscription.keys || !subscription.keys.p256dh || !subscription.keys.auth) {
+        logger.warn('Subscription Error: Missing or invalid subscription object structure');
+        return res.status(400).json({ message: 'Bad Request: Missing or invalid subscription object' });
+    }
+
+    const normalizedButtonId = button_id.toLowerCase(); // Use lowercase for consistency
+
+    // Update in-memory store
+    subscriptions[normalizedButtonId] = subscription;
+    logger.info(`Subscription for button ${normalizedButtonId} added/updated in memory.`);
+
+    // Persist to file
+    try {
+        saveSubscriptions(); // Call the save function
+        res.status(201).json({ message: `Subscription saved successfully for button ${normalizedButtonId}` });
+    } catch (err) // Catch potential synchronous errors from saveSubscriptions (though unlikely with writeFileSync)
+    {
+        // saveSubscriptions already logs the error, but we send a 500 response
+        res.status(500).json({ message: 'Internal Server Error: Failed to save subscription to file' });
+    }
+});
+
+// --- Flic Webhook Endpoint (GET only) ---
+// Apply Flic-specific authentication to this route
+app.get('/flic-webhook', authenticateFlicRequest, async (req, res) => {
+  // Get buttonName from Header 'Button-Name' and timestamp from Header 'Timestamp'
+  const buttonName = req.headers['button-name'];
+  const timestamp = req.headers['timestamp'];
+  // Get click_type from query parameter instead of request body
+  const click_type = req.query.click_type;
+
+  // Log all headers received from Flic
+  logger.debug('All headers received:');
+  Object.keys(req.headers).forEach(headerName => {
+    logger.debug(`  ${headerName}: ${req.headers[headerName]}`);
+  });
+
+  logger.info(`Received GET webhook: Button=${buttonName}, Type=${click_type}, Timestamp=${timestamp || 'N/A'}`);
+
+  // Basic validation
+  if (!buttonName || !click_type) {
+    logger.warn(`Webhook Error: Missing Button-Name header or click_type query parameter`);
+    return res.status(400).json({ message: 'Bad Request: Missing Button-Name header or click_type query parameter' });
+  }
+
+  const normalizedButtonName = buttonName.toLowerCase(); // Use lowercase for lookup consistency
+
+  // Find the subscription associated with this normalized button name
+  const subscription = subscriptions[normalizedButtonName];
+
+  if (!subscription) {
+    logger.warn(`Webhook: No subscription found for button ID: ${normalizedButtonName} (original: ${buttonName})`);
+    return res.status(404).json({ message: `Not Found: No subscription configured for button ${normalizedButtonName}` });
+  }
+
+  // --- Send Web Push Notification ---
+  const payload = JSON.stringify({
+    title: 'Flic Button Action',
+    body: `Button ${normalizedButtonName}: ${click_type}`, // Simplified body
+    data: {
+        action: click_type,
+        button: normalizedButtonName, // Send normalized button name
+        timestamp: timestamp || new Date().toISOString()
+    }
+    // icon: '/path/to/icon.png'
+  });
+
+  try {
+    logger.debug(`Subscription endpoint: ${subscription.endpoint}`);
+    logger.info(`Sending push notification for ${normalizedButtonName} to endpoint: ${subscription.endpoint.substring(0, 40)}...`);
+    await sendWebPushWithRetry(subscription, payload);
+    logger.info(`Push notification sent successfully for button ${normalizedButtonName}.`);
+    res.status(200).json({ message: 'Push notification sent successfully' });
+  } catch (error) {
+    logger.error(`Error sending push notification for button ${normalizedButtonName}:`, error.body || error.message || error);
+
+    if (error.statusCode === 404 || error.statusCode === 410) {
+      logger.warn(`Subscription for button ${normalizedButtonName} is invalid or expired (404/410). Removing it.`);
+      // Optionally remove the stale subscription
+      delete subscriptions[normalizedButtonName];
+      saveSubscriptions(); // Attempt to save the updated list
+      res.status(410).json({ message: 'Subscription Gone' });
+    } else {
+      res.status(500).json({ message: 'Internal Server Error: Failed to send push notification' });
+    }
+  }
+});
+
+// --- Start Server ---
+// Use http.createServer to allow graceful shutdown
+const server = http.createServer(app);
+
+server.listen(port, () => {
+  logger.info(`Flic Webhook to WebPush server listening on port ${port}`);
+  logger.info(`Allowed Origins: ${allowedOrigins.length > 0 ? allowedOrigins.join(', ') : '(Any)'}`);
+  logger.info(`Allowed Methods: ${allowedMethods.join(', ')}`);
+  logger.info(`Allowed Headers: ${allowedHeaders.join(', ')}`);
+  logger.info(`Flic Webhook Auth: ${flicSecret ? 'Enabled (Bearer Token)' : 'Disabled'}`);
+  logger.info(`Subscription Endpoint Auth: Disabled`);
+  logger.info(`Subscriptions File: ${subscriptionsFilePath}`);
+  logger.info(`Push Notification Retry Config: ${maxRetries} retries, ${initialRetryDelay}ms initial delay`);
+  logger.info(`DNS Config: IPv4 first, timeout ${dnsTimeout}ms`);
+  logger.info(`HTTP Timeout: ${httpTimeout}ms`);
+  logger.info(`Log Level: ${LOG_LEVEL.toUpperCase()}`);
+});
+
+// --- Graceful Shutdown ---
+const closeGracefully = (signal) => {
+    logger.info(`${signal} signal received: closing HTTP server`);
+    server.close(() => {
+        logger.info('HTTP server closed');
+        // Perform any other cleanup here if needed
+        process.exit(0);
+    });
+
+    // Force close server after 10 seconds
+    setTimeout(() => {
+        logger.error('Could not close connections in time, forcefully shutting down');
+        process.exit(1);
+    }, 10000); // 10 seconds timeout - This is a literal so no need to parse
+}
+
+process.on('SIGTERM', () => closeGracefully('SIGTERM'));
+process.on('SIGINT', () => closeGracefully('SIGINT')); // Handle Ctrl+C