If appimage is starting send cached capabilities

Build script runs AppImage and saves capabilities endpoint
output to file.
When AppImage is not started yet - cached file content will be sent.
Otherwise proxy will redirrect to the acctual endpoint.

build-nextcloud-app.sh

@@ -49,6 +49,11 @@ HASH=`./${app_name}/collabora/Collabora_Online.AppImage --version-hash`
 echo "HASH: $HASH"
 sed "s/%LOOLWSD_VERSION_HASH%/$HASH/g" ../proxy.php > ${app_name}/proxy.php
 
+# Fetch capabilities from AppImage for cache
+PID_FILE="/tmp/loolwsd.pid"
+`./${app_name}/collabora/Collabora_Online.AppImage 2>/dev/null` & (sleep 3 && curl "http://localhost:9983/hosting/capabilities" --max-time 10 -o "${app_name}/capabilities.json") || (echo && echo "ERROR: Cannot fetch capabilities!" && echo)
+kill -9 `cat $PID_FILE` 2>/dev/null || (echo && echo "Failed to run Collabora Online Appimage" && echo)
+
 # check if we are building for arm64
 if [[ "$APPIMAGE_URL" =~ "arm64" ]]; then
     echo "Building for arm64"

proxy.php

@@ -206,6 +206,17 @@ function getallheaders()
 if ($request == '' && !$statusOnly)
     errorExit("Missing, required req= parameter");
 
+if (startsWith($request, '/hosting/capabilities') && !isLoolwsdRunning() && file_exists('capabilities.json')) {
+    header('Content-type: application/json');
+    header('Cache-Control: no-store');
+    $capabilities = file_get_contents('capabilities.json');
+    if ($capabilities !== false) {
+        print $capabilities;
+        http_response_code(200);
+        exit();
+    }
+}
+
 // If we can't get a socket open in 3 seconds when that is backed by
 // a dedicated thread, then we have a server missing in action.
 $local = @fsockopen("localhost", 9983, $errno, $errstr, 3);