Hooks: Make sure that original task is properly detected

On modify event uses UUID of the original task being modified
to determine which line should be interpreted as modification
of the task.

This was achieved by searching by a substring in a specific JSON
format, which, consenquently, failed on JSON strings of other (valid)
formats.

src/Hooks.cpp

@@ -317,7 +317,6 @@ void Hooks::onModify (const Task& before, std::vector <Task>& tasks)
   {
     // Prepare invariants.
     std::string beforeJSON = before.composeJSON ();
-    std::string uuidPattern = "\"uuid\":\"" + before.get ("uuid") + "\"";
 
     // Convert vector of tasks to a vector of strings.
     std::vector <std::string> input;
@@ -345,7 +344,7 @@ void Hooks::onModify (const Task& before, std::vector <Task>& tasks)
         {
           if (status == 0)
           {
-            if (line->find (uuidPattern) != std::string::npos)
+            if (JSONContainsUUID((*line), before.get("uuid")))
               input[1] = *line;                 // [1] original'
             else
               input.push_back (*line);          // [n > 1] extras
@@ -460,6 +459,31 @@ bool Hooks::isJSON (const std::string& input) const
   return false;
 }
 
+////////////////////////////////////////////////////////////////////////////////
+// This method assumes that input has already been validated with isJSON method
+bool Hooks::JSONContainsUUID(const std::string& input, const std::string& uuid) const
+{
+   bool foundUUID = false;
+
+   // Parse the whole thing.
+   json::object* root_obj = (json::object*) (json::parse (input));
+
+   // For each object element...
+   json_object_iter i;
+   for (i  = root_obj->_data.begin ();
+        i != root_obj->_data.end ();
+        ++i)
+   {
+     // If the attribute is a recognized column.
+     std::string type = Task::attributes[i->first];
+     if (type == "string" && i->first == "uuid" &&
+         json::decode (unquoteText (i->second->dump ())) == uuid)
+       foundUUID = true;
+   }
+
+   return foundUUID;
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 int Hooks::callHookScript (
   const std::string& script,

src/Hooks.h

@@ -52,6 +52,7 @@ public:
 private:
   std::vector <std::string> scripts (const std::string&);
   bool isJSON (const std::string&) const;
+  bool JSONContainsUUID (const std::string&, const std::string&) const;
   int callHookScript (const std::string&, const std::vector <std::string>&, std::vector <std::string>&);
 
 private: