Feature/documentation topic (#822)

- Implement documentation topic that can be used to query documentation using the network API.
- Implement a way to pass arguments to lua scripts using json (rather than formatting entire lua string clientside)
- Implement ability to attach callback to lua script executions
- Implement abillity to transport return values from lua scripts back to network API clients.
- Do not initialize server interface on slave nodes.
- Implement Dictionary -> json converter using nlohmann json library

include/openspace/scripting/scriptengine.h

@@ -32,6 +32,9 @@
 #include <ghoul/lua/luastate.h>
 #include <ghoul/misc/boolean.h>
 #include <mutex>
+#include <queue>
+#include <optional>
+#include <functional>
 
 namespace openspace { class SyncBuffer; }
 
@@ -47,8 +50,15 @@ namespace openspace::scripting {
  */
 class ScriptEngine : public Syncable, public DocumentationGenerator {
 public:
+    using ScriptCallback = std::optional<std::function<void(ghoul::Dictionary)>>;
     BooleanType(RemoteScripting);
 
+    struct QueueItem {
+        std::string script;
+        RemoteScripting remoteScripting;
+        ScriptCallback callback;
+    };
+
     static constexpr const char* OpenSpaceLibraryName = "openspace";
 
     ScriptEngine();
@@ -71,7 +81,7 @@ public:
     void addLibrary(LuaLibrary library);
     bool hasLibrary(const std::string& name);
 
-    bool runScript(const std::string& script);
+    bool runScript(const std::string& script, ScriptCallback callback = ScriptCallback());
     bool runScriptFile(const std::string& filename);
 
     bool writeLog(const std::string& script);
@@ -81,13 +91,12 @@ public:
     virtual void decode(SyncBuffer* syncBuffer) override;
     virtual void postSync(bool isMaster) override;
 
-    void queueScript(const std::string &script, RemoteScripting remoteScripting);
-
-    void setLogFile(const std::string& filename, const std::string& type);
-
-    std::vector<std::string> cachedScripts();
+    void queueScript(const std::string& script, RemoteScripting remoteScripting,
+        ScriptCallback cb = ScriptCallback());
 
     std::vector<std::string> allLuaFunctions() const;
+    
+    std::string generateJson() const override;
 
 private:
     BooleanType(Replace);
@@ -100,23 +109,20 @@ private:
     void addBaseLibrary();
     void remapPrintFunction();
 
-    std::string generateJson() const override;
-
     ghoul::lua::LuaState _state;
     std::vector<LuaLibrary> _registeredLibraries;
 
+    std::queue<QueueItem> _incomingScripts;
 
-    //sync variables
-    std::mutex _mutex;
-    std::vector<std::pair<std::string, bool>> _queuedScripts;
-    std::vector<std::string> _receivedScripts;
-    std::string _currentSyncedScript;
+    // Slave scripts are mutex protected since decode and rendering may
+    // happen asynchronously.
+    std::mutex _slaveScriptsMutex;
+    std::queue<std::string> _slaveScriptQueue;
+    std::queue<QueueItem> _masterScriptQueue;
 
-    //parallel variables
-    //std::map<std::string, std::map<std::string, std::string>> _cachedScripts;
-    //std::mutex _cachedScriptsMutex;
+    std::vector<std::string> _scriptsToSync;
 
-    //logging variables
+    // Logging variables
     bool _logFileExists = false;
     bool _logScripts = true;
     std::string _logType;