implement very very simple stream sql support

ixsnake/ixsnake/IXStreamSql.cpp

@@ -2,20 +2,62 @@
  *  IXStreamSql.cpp
  *  Author: Benjamin Sergeant
  *  Copyright (c) 2020 Machine Zone, Inc. All rights reserved.
+ *
+ *  Super simple hacked up version of a stream sql expression,
+ *  that only supports non nested field evaluation
  */
 
 #include "IXStreamSql.h"
+#include <sstream>
+#include <iostream>
 
 namespace snake
 {
     StreamSql::StreamSql(const std::string& sqlFilter)
+        : _valid(false)
     {
-        ;
+        std::string token;
+        std::stringstream tokenStream(sqlFilter);
+        std::vector<std::string> tokens;
+
+        // Split by ' '
+        while (std::getline(tokenStream, token, ' '))
+        {
+            tokens.push_back(token);
+        }
+
+        _valid = tokens.size() == 8;
+        if (!_valid) return;
+
+        _field = tokens[5];
+        _operator = tokens[6];
+        _value = tokens[7];
+
+        // remove single quotes
+        _value = _value.substr(1, _value.size() - 2);
+
+        if (_operator == "LIKE")
+        {
+            _value = _value.substr(1, _value.size() - 2);
+        }
     }
 
-    bool StreamSql::match(const nlohmann::json& pdu)
+    bool StreamSql::valid() const
     {
-        return true;
+        return _valid;
+    }
+
+    bool StreamSql::match(const nlohmann::json& msg)
+    {
+        if (!_valid) return false;
+
+        if (msg.find(_field) == msg.end())
+        {
+            return false;
+        }
+
+        std::string value = msg[_field];
+        return value == _value;
     }
 
 } // namespace snake