Combined output json processing from youtube-dl between subscriptions and one-off downloads

Added workaround for missing video in playlist to one-off downloads

backend/utils.js

@@ -530,6 +530,37 @@ exports.getDirectoriesInDirectory = async (basePath) => {
     }
 }
 
+exports.parseOutputJSON = (output, err) => {
+    let split_output = [];
+    // const output_jsons = [];
+    if (err && !output) {
+        if (!err.stderr.includes('This video is unavailable') && !err.stderr.includes('Private video')) {
+            return null;
+        }
+        logger.info('An error was encountered with at least one video, backup method will be used.')
+        try {
+            split_output = err.stdout.split(/\r\n|\r|\n/);
+        } catch (e) {
+            logger.error('Backup method failed. See error below:');
+            logger.error(e);
+            return null;
+        }
+    }   else {
+        for (const output_item of output) {
+            // we have to do this because sometimes there will be leading characters before the actual json
+            const start_idx = output_item.indexOf('{"');
+            const clean_output = output_item.slice(start_idx, output_item.length);
+            split_output.push(clean_output);
+        }
+    }
+
+    try {
+        return split_output.map(split_output_str => JSON.parse(split_output_str));
+    } catch(e) {
+        return null;
+    }
+}
+
 // objects
 
 function File(id, title, thumbnailURL, isAudio, duration, url, uploader, size, path, upload_date, description, view_count, height, abr) {