feat: integrate AI-driven selection panel with context-aware text summarization and quiz generation features.

src/NexusReader.Infrastructure/Helpers/JsonRepairHelper.cs

@@ -0,0 +1,69 @@
+using System.Text;
+using System.Text.RegularExpressions;
+
+namespace NexusReader.Infrastructure.Helpers;
+
+public static class JsonRepairHelper
+{
+    public static string Repair(string json)
+    {
+        if (string.IsNullOrWhiteSpace(json)) return json;
+        json = json.Trim();
+
+        // 1. If it doesn't end with } or ], it's definitely truncated
+        if (!json.EndsWith("}") && !json.EndsWith("]"))
+        {
+            // Try to find the last "clean" closing point before the truncation
+            // We look for a comma, a closing brace, or a closing bracket that is followed by noise
+            int lastGoodComma = json.LastIndexOf(',');
+            int lastGoodBrace = json.LastIndexOf('}');
+            int lastGoodBracket = json.LastIndexOf(']');
+
+            int cutoff = Math.Max(lastGoodComma, Math.Max(lastGoodBrace, lastGoodBracket));
+            
+            if (cutoff > 0)
+            {
+                // Prune the "garbage" at the end
+                json = json.Substring(0, cutoff);
+            }
+            
+            // Now apply the standard stack-based closing logic
+            var stack = new Stack<char>();
+            bool inString = false;
+            bool escaped = false;
+
+            foreach (char c in json)
+            {
+                if (escaped) { escaped = false; continue; }
+                if (c == '\\') { escaped = true; continue; }
+                if (c == '"') { inString = !inString; continue; }
+                if (inString) continue;
+
+                if (c == '{' || c == '[') stack.Push(c);
+                else if (c == '}' || c == ']')
+                {
+                    if (stack.Count > 0)
+                    {
+                        var last = stack.Peek();
+                        if ((c == '}' && last == '{') || (c == ']' && last == '['))
+                            stack.Pop();
+                    }
+                }
+            }
+
+            var builder = new StringBuilder(json);
+            if (inString) builder.Append('"');
+
+            while (stack.Count > 0)
+            {
+                var c = stack.Pop();
+                if (c == '{') builder.Append("}");
+                else if (c == '[') builder.Append("]");
+            }
+            
+            return builder.ToString();
+        }
+
+        return json;
+    }
+}