JSON message parsing for contract control messages. (#166)

src/msg/json/controlmsg_json.cpp

@@ -0,0 +1,58 @@
+#include "../../pchheader.hpp"
+#include "../controlmsg_common.hpp"
+#include "controlmsg_json.hpp"
+
+namespace msg::controlmsg::json
+{
+    // JSON separators
+    constexpr const char *SEP_COMMA = "\",\"";
+    constexpr const char *SEP_COLON = "\":\"";
+    constexpr const char *SEP_COMMA_NOQUOTE = ",\"";
+    constexpr const char *SEP_COLON_NOQUOTE = "\":";
+
+    // Message types
+    constexpr const char *MSGTYPE_HANDSHAKE_CHALLENGE = "handshake_challenge";
+
+    /**
+     * Parses a json control message sent by the contract.
+     * @param d Jsoncons document to which the parsed json should be loaded.
+     * @param message The message to parse.
+     *                Accepted message format:
+     *                {
+     *                  'type': '<message type>'
+     *                  ...
+     *                }
+     * @return 0 on successful parsing. -1 for failure.
+     */
+    int parse_control_message(jsoncons::json &d, std::string_view message)
+    {
+        try
+        {
+            d = jsoncons::json::parse(message, jsoncons::strict_json_parsing());
+        }
+        catch (const std::exception &e)
+        {
+            LOG_DEBUG << "User json message parsing failed.";
+            return -1;
+        }
+
+        // Check existence of msg type field.
+        if (!d.contains(msg::controlmsg::FLD_TYPE) || !d[msg::controlmsg::FLD_TYPE].is<std::string>())
+        {
+            LOG_DEBUG << "User json message 'type' missing or invalid.";
+            return -1;
+        }
+
+        return 0;
+    }
+
+    /**
+     * Extracts the message 'type' value from the json document.
+     */
+    int extract_type(std::string &extracted_type, const jsoncons::json &d)
+    {
+        extracted_type = d[msg::controlmsg::FLD_TYPE].as<std::string>();
+        return 0;
+    }
+
+} // namespace msg::controlmsg::json