feat: expose configurations, add retry, make stable

pi/README.md

@@ -0,0 +1,70 @@
+# noisebell
+
+Monitors a GPIO pin on a Raspberry Pi to detect door open/close events. State changes get POSTed to a webhook endpoint. Current state is available over HTTP.
+
+Runs on NixOS with Tailscale for networking and agenix for secrets.
+
+## Setup
+
+### 1. Hardware config
+
+Replace `hardware-configuration.nix` with the output of `nixos-generate-config --show-hardware-config` on your Pi (or use an appropriate hardware module like `sd-card/sd-image-aarch64.nix`).
+
+### 2. SSH key
+
+Add your SSH public key to `configuration.nix`:
+
+```nix
+users.users.root.openssh.authorizedKeys.keys = [
+  "ssh-ed25519 AAAA..."
+];
+```
+
+### 3. Secrets
+
+Get your Pi's SSH host public key and put it in `secrets/secrets.nix`:
+
+```sh
+ssh-keyscan <pi-ip> | grep ed25519
+```
+
+Then create the encrypted secret files:
+
+```sh
+cd secrets
+agenix -e endpoint-url.age      # paste webhook URL
+agenix -e tailscale-auth-key.age # paste Tailscale auth key
+```
+
+### 4. Deploy
+
+```sh
+nix build .#nixosConfigurations.pi.config.system.build.toplevel
+nixos-rebuild switch --flake .#pi --target-host root@noisebell
+```
+
+## Configuration
+
+Options under `services.noisebell` in `flake.nix`:
+
+| Option | Default | Description |
+|---|---|---|
+| `gpioPin` | 17 | GPIO pin to monitor |
+| `debounceSecs` | 5 | Debounce delay |
+| `port` | 8080 | HTTP status port |
+| `retryAttempts` | 3 | Webhook retry count |
+| `retryBaseDelaySecs` | 1 | Base delay for exponential backoff |
+| `httpTimeoutSecs` | 10 | Timeout for outbound webhook requests |
+| `bindAddress` | `0.0.0.0` | Address to bind the HTTP server to |
+| `activeLow` | `true` | Whether low GPIO level means open (depends on wiring) |
+| `restartDelaySecs` | 5 | Seconds before systemd restarts on failure |
+
+## API
+
+`GET /` — current door state:
+
+```json
+{"status": "open", "timestamp": 1710000000}
+```
+
+State changes (and initial state on startup) are POSTed to the configured endpoint in the same format.