Added Langevin thermostat, with json config features

.gitignore

@@ -0,0 +1,6 @@
+notebooks
+*.txt
+*.rst
+*.json
+.vscode
+a.out

config.h

@@ -1,9 +1,71 @@
 #ifndef CONFIG_H
 #define CONFIG_H
 
-class Config {
-    public:
-        static constexpr float samplingTemperature = 0.3;
-};
+#include <fstream>
+#include "json.hpp"
+
+using json = nlohmann::json;
+
+float samplingTemperature;
+std::vector<float> samplingTemperatures;
+int numSteps;
+int numParticles;
+int outputPeriod;
+std::string runType;
+std::string systemName;
+std::string rst;
+bool isRstPresent;
+float tauValue;
+
+void setDefaultConfig() {
+    samplingTemperature = 0.3;
+    samplingTemperatures = {0.3f, 2.0f};
+    numSteps = 1000;
+    numParticles = 10;
+    outputPeriod = 100;
+    runType = "nve";
+    systemName = "1D_Smit";
+    tauValue = 0.01f;
+    isRstPresent = false;
+
+}
+
+void getConfigFromFile(std::string fileName) {
+
+    std::ifstream jsonFileObject(fileName);
+    json data = json::parse(jsonFileObject);
+
+    if(data.contains("temperature"))
+        samplingTemperature = data["temperature"];
+
+    if(data.contains("num_steps"))
+        numSteps = data["num_steps"];
+
+    if(data.contains("output_period"))
+        outputPeriod = data["output_period"];
+
+    if(data.contains("run_type"))
+        runType = data["run_type"];
+
+    if(data.contains("system"))
+        systemName = data["system"];
+
+    if(data.contains("tau"))
+        tauValue = data["tau"];
+
+    if(data.contains("rst")) {
+        isRstPresent = true;
+        rst = data["rst"];
+    }
+
+    if(data.contains("num_particles"))
+        numParticles = data["num_particles"];
+
+    // if(data.contains("temperatures"))
+    //     samplingTemperatures = data["temperatures"];
+
+
+}
+
 
 #endif