lndconnect: update to Zeus 0.7.1

- Generate lndconnect URLs with protocol `c-lightning-rest` for clightning.
  (Zeus now auto-detects the lightning implementation by the URL protocol.)
- Use improved QR code format (via qrencode)  .

docs/services.md

@@ -143,7 +143,7 @@ The default password location is `$secretsDir/rtl-password`.
 See: [Secrets dir](./configuration.md#secrets-dir)
 
 # Use Zeus (mobile lightning wallet) via Tor
-1. Install [Zeus](https://zeusln.app)
+1. Install [Zeus](https://zeusln.app) (version ≥ 0.7.1)
 
 2. Edit your `configuration.nix`
 
@@ -186,17 +186,14 @@ See: [Secrets dir](./configuration.md#secrets-dir)
    ```
 
 5. Configure Zeus
-   - Add a new node
-   - Select `Scan lndconnect config` (at the bottom) and scan the QR code
-   - For clightning: Set `Node interface` to `c-lightning-REST`
+   - Add a new node and scan the QR code
    - Click `Save node config`
    - Start sending and stacking sats privately
 
 ### Additional lndconnect features
-- Create plain text URLs or QR code images
+- Create a plain text URL:
   ```bash
   lndconnect --url
-  lndconnect --image
   ```
 - Set a custom host. By default, `lndconnect` detects the system's external IP and uses it as the host.
   ```bash

modules/lndconnect.nix

@@ -82,6 +82,7 @@ let
   mkLndconnect = {
     name,
     shebang ? "#!${pkgs.stdenv.shell} -e",
+    isClightning ? false,
     port,
     macaroonPath,
     enableOnion,
@@ -93,12 +94,39 @@ let
   # https://github.com/LN-Zap/lndconnect/issues/25
   pkgs.hiPrio (pkgs.writeScriptBin name ''
     ${shebang}
-    exec ${config.nix-bitcoin.pkgs.lndconnect}/bin/lndconnect \
+    url=$(
+      ${getExe config.nix-bitcoin.pkgs.lndconnect} --url \
         ${optionalString enableOnion "--host=$(cat ${config.nix-bitcoin.onionAddresses.dataDir}/${onionService})"} \
         --port=${toString port} \
         ${if enableOnion || certPath == null then "--nocert" else "--tlscertpath='${certPath}'"} \
         --adminmacaroonpath='${macaroonPath}' \
         --configfile=/dev/null "$@"
+    )
+
+    ${optionalString isClightning
+      # - Change URL procotcol to c-lightning-rest
+      # - Encode macaroon as hex (in uppercase) instead of base 64.
+      #   Because `macaroon` is always the last URL fragment, the
+      #   sed replacement below works correctly.
+      ''
+        macaroonHex=$(${getExe pkgs.xxd} -p -u -c 99999 '${macaroonPath}')
+        url=$(
+          echo "$url" | ${getExe pkgs.gnused} "
+            s|^lndconnect|c-lightning-rest|
+            s|macaroon=.*|macaroon=$macaroonHex|
+          ";
+        )
+      ''
+    }
+
+    # If --url is in args
+    if [[ " $* " =~ " --url " ]]; then
+      echo "$url"
+    else
+      # This UTF-8 encoding yields a smaller, more convenient output format
+      # compared to the native lndconnect output
+      echo -n "$url" | ${getExe pkgs.qrencode} -t UTF8 -o -
+    fi
   '');
 
   operatorName = config.nix-bitcoin.operator.name;
@@ -144,6 +172,7 @@ in {
           environment.systemPackages = [(
             mkLndconnect {
               name = "lndconnect-clightning";
+              isClightning = true;
               enableOnion = clightning-rest.lndconnect.onion;
               onionService = "${operatorName}/clightning-rest";
               port = clightning-rest.port;