diff --git a/.vscode/c_cpp_properties.json b/.vscode/c_cpp_properties.json
index 4912fde..25015e2 100644
--- a/.vscode/c_cpp_properties.json
+++ b/.vscode/c_cpp_properties.json
@@ -6,10 +6,10 @@
                 "${workspaceFolder}/**"
             ],
             "defines": [],
-            "compilerPath": "/usr/bin/clang",
+            "compilerPath": "/usr/bin/g++",
             "cStandard": "c17",
             "cppStandard": "c++17",
-            "intelliSenseMode": "linux-clang-x64",
+            "intelliSenseMode": "linux-gcc-x64",
             "configurationProvider": "ms-vscode.cmake-tools"
         }
     ],
diff --git a/.vscode/settings.json b/.vscode/settings.json
index 052b81c..c31a2ab 100644
--- a/.vscode/settings.json
+++ b/.vscode/settings.json
@@ -52,6 +52,25 @@
         "streambuf": "cpp",
         "cinttypes": "cpp",
         "typeinfo": "cpp",
-        "filesystem": "cpp"
-    }
+        "filesystem": "cpp",
+        "csignal": "cpp",
+        "cstring": "cpp",
+        "any": "cpp",
+        "condition_variable": "cpp",
+        "forward_list": "cpp",
+        "list": "cpp",
+        "map": "cpp",
+        "set": "cpp",
+        "unordered_set": "cpp",
+        "fstream": "cpp",
+        "mutex": "cpp",
+        "ranges": "cpp",
+        "semaphore": "cpp",
+        "span": "cpp",
+        "stop_token": "cpp",
+        "thread": "cpp",
+        "valarray": "cpp",
+        "variant": "cpp"
+    },
+    "C_Cpp.errorSquiggles": "enabled"
 }
\ No newline at end of file
diff --git a/CMakeLists.txt b/CMakeLists.txt
index d60fe21..98ac888 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -6,12 +6,20 @@ project(aare
     HOMEPAGE_URL "https://github.com/slsdetectorgroup/aare"
     LANGUAGES C CXX 
 )
-# cmake_policy(SET CMP0135 NEW)
 
-# include(GNUInstallDirs)
+cmake_policy(SET CMP0135 NEW)
+
+
+include(FetchContent)
+
+FetchContent_Declare(json
+    GIT_REPOSITORY https://github.com/nlohmann/json
+    GIT_TAG v3.11.3
+)
+FetchContent_MakeAvailable(json)
+
+find_package(fmt 6 REQUIRED)
 
-# include(cmake/helpers.cmake)
-# default_build_type("Debug")]
 
 set(CMAKE_BUILD_TYPE "Debug")
 
@@ -24,17 +32,8 @@ set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 
 option(USE_SANITIZER "Sanitizers for debugging" ON)
 option(DISABLE_WARNINGS "Disbale compilation warnings" OFF)
-# option(USE_TESTS "Unit tests" OFF)
-# option(USE_PYTHON "Python bindings" OFF)
-# option(TUNE_LOCAL "Tune to exact CPU architecture" OFF)
-# option(BUILD_EXAMPLES "Build examples" OFF)
-# option(DISABLE_LTO "Disable Link Time Optimizations" OFF)
 
 
-# if(NOT APPLE)
-#     set(CMAKE_INSTALL_RPATH $ORIGIN)
-# endif()
-
 set(OPTIONAL_FLAGS "")
 if(DISABLE_WARNINGS)
     set(OPTIONAL_FLAGS "${OPTIONAL_FLAGS} -Wall -Wextra -pedantic -Wno-unused-parameter -Wshadow -Wformat=2 -Wold-style-cast -Wnon-virtual-dtor  -Wfloat-equal -Wconversion -Wlogical-op -Wshift-overflow=2 -Woverloaded-virtual -Winline")
@@ -58,7 +57,6 @@ endif()
 
 
 
-#Enable LTO if available
 include(CheckIPOSupported)
 check_ipo_supported(RESULT LTO_AVAILABLE)
 if((CMAKE_BUILD_TYPE STREQUAL "Release") AND  LTO_AVAILABLE)
@@ -67,9 +65,26 @@ else()
     message(STATUS "Building without link time optimization")
 endif()
 
+set(SUPPRESSED_WARNINGS "-Wno-return-type")
+
+set(CMAKE_CXX_FLAGS  "${OPTIONAL_FLAGS} ${OPTIMIZATION_FLAGS} ${SUPPRESSED_WARNINGS}")
+
 
-set(CMAKE_CXX_FLAGS  "${OPTIONAL_FLAGS} ${OPTIMIZATION_FLAGS}")
 
 add_executable(aare)
 
+target_link_libraries( aare  
+PRIVATE
+ nlohmann_json::nlohmann_json
+PUBLIC
+ fmt::fmt
+)
+
+
+
+
+
 add_subdirectory(src)
+
+
+
diff --git a/README.md b/README.md
index b7ee44c..46b0ba7 100644
--- a/README.md
+++ b/README.md
@@ -1,2 +1,8 @@
 # aare
 Data analysis library for PSI hybrid detectors
+
+
+
+
+## file_io class diagram
+![file_io class diagram](./extra/uml/out/file_io/ClassDiagram.png)
\ No newline at end of file
diff --git a/extra/uml/file_io.pu b/extra/uml/file_io.pu
new file mode 100644
index 0000000..db9b7ef
--- /dev/null
+++ b/extra/uml/file_io.pu
@@ -0,0 +1,36 @@
+@startuml ClassDiagram
+abstract class FileFactory{
+    {static} +getFactory(path):FileFactory
+    {abstract} +loadFile(path):File
+}
+class JsonFileFactory{
+  +loadFile(path):JsonFile
+}
+class RawFileFactory{
+   +loadFile(path):RawFile
+}
+class NumpyFileFactory{
+   +loadFile(path):NumpyFile
+}
+
+abstract File{
+}
+
+class JsonFile{
+}
+class RawFile{
+}
+class NumpyFile{
+}
+
+FileFactory <|-- RawFileFactory
+FileFactory <|-- NumpyFileFactory
+FileFactory <|-- JsonFileFactory
+
+File <|-- JsonFile
+File <|-- RawFile
+File <|-- NumpyFile
+
+FileFactory ..> File
+
+@enduml
\ No newline at end of file
diff --git a/extra/uml/out/file_io/ClassDiagram.png b/extra/uml/out/file_io/ClassDiagram.png
new file mode 100644
index 0000000..f293f85
Binary files /dev/null and b/extra/uml/out/file_io/ClassDiagram.png differ
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 4c44806..bf41f40 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -1,6 +1,7 @@
 add_subdirectory(file_io)
 add_subdirectory(core)
 add_subdirectory(processing)
+add_subdirectory(common)
 
-target_include_directories(aare PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
-target_sources(aare PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/main.cpp)
\ No newline at end of file
+target_include_directories(aare PUBLIC  ${CMAKE_CURRENT_SOURCE_DIR})
+target_sources(aare PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/main.cpp)
diff --git a/src/common/CMakeLists.txt b/src/common/CMakeLists.txt
new file mode 100644
index 0000000..ec461e6
--- /dev/null
+++ b/src/common/CMakeLists.txt
@@ -0,0 +1,7 @@
+target_include_directories(aare PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/include )
+
+target_include_directories(aare PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
+
+
+
+
diff --git a/src/core/include/defs.hpp b/src/common/include/defs.hpp
similarity index 71%
rename from src/core/include/defs.hpp
rename to src/common/include/defs.hpp
index 14218ab..e782527 100644
--- a/src/core/include/defs.hpp
+++ b/src/common/include/defs.hpp
@@ -10,4 +10,5 @@ using dynamic_shape = std::vector<ssize_t>;
 
 enum class DetectorType { Jungfrau, Eiger, Mythen3, Moench };
 
-enum class TimingMode {Auto, Trigger};
\ No newline at end of file
+enum class TimingMode {Auto, Trigger};
+DetectorType StringTo(std::string_view name);
\ No newline at end of file
diff --git a/src/file_io/CMakeLists.txt b/src/file_io/CMakeLists.txt
index 5fab7d8..f402919 100644
--- a/src/file_io/CMakeLists.txt
+++ b/src/file_io/CMakeLists.txt
@@ -1,5 +1,14 @@
-target_include_directories(aare PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
-set(FILE_IO_SOURCES "File.cpp" "FileFactory.cpp" "RawFileFactory.cpp")
+target_include_directories(aare PUBLIC "${CMAKE_CURRENT_SOURCE_DIR}/file")
+target_include_directories(aare PUBLIC "${CMAKE_CURRENT_SOURCE_DIR}/file_factory")
+target_include_directories(aare PUBLIC "${CMAKE_CURRENT_SOURCE_DIR}")
+
+set(FILE_IO_SOURCES "file/File.cpp"
+                    "file/JsonFile.cpp"
+                    "file_factory/FileFactory.cpp"
+                    "file_factory/JsonFileFactory.cpp"
+                    "file_factory/RawFileFactory.cpp"
+                    "helpers.cpp"
+                    )
 # append ${CMAKE_CURRENT_SOURCE_DIR} to the list of sources using for loop
 foreach(FILE_IO_SOURCE ${FILE_IO_SOURCES})
     list(APPEND FILE_IO_SOURCES_WITH_PATH "${CMAKE_CURRENT_SOURCE_DIR}/${FILE_IO_SOURCE}")
diff --git a/src/file_io/File.hpp b/src/file_io/File.hpp
deleted file mode 100644
index 8bbaf5c..0000000
--- a/src/file_io/File.hpp
+++ /dev/null
@@ -1,29 +0,0 @@
-#pragma once
-
-#include <filesystem>
-#include "defs.hpp"
-
-class File
-{
-private:
-    // std::unique_ptr<FileWrapper> fp;
-public:
-    // File();
-    // ~File();
-    size_t total_frames{};
-    ssize_t rows{};
-    ssize_t cols{};
-    uint8_t bitdepth{};
-    DetectorType type{};
-
-    inline size_t bytes_per_frame() const{
-        //TODO: ask if this is correct
-        return rows*cols*bitdepth/8;
-        
-    }
-    inline size_t pixels() const{
-        return rows*cols;
-    }
-    // size_t total_frames();
-
-};
diff --git a/src/file_io/FileFactory.cpp b/src/file_io/FileFactory.cpp
deleted file mode 100644
index bd0e8ef..0000000
--- a/src/file_io/FileFactory.cpp
+++ /dev/null
@@ -1,31 +0,0 @@
-#include "FileFactory.hpp"
-#include "File.hpp"
-#include "RawFileFactory.hpp"
-#include "JsonFileFactory.hpp"
-#include <iostream>
-
-File FileFactory::loadFile(std::filesystem::path fpath){
-    // check if file exists
-    if(!std::filesystem::exists(fpath)){
-        throw std::runtime_error("File does not exist");
-    }
-
-    File ret;
-    // check if extension is raw
-    if(fpath.extension() == ".raw"){
-        std::cout<<"Loading raw file"<<std::endl;
-    }
-    // json
-    else if(fpath.extension() == ".json"){
-        std::cout<<"Loading json file"<<std::endl;
-        JsonFileFactory jff = JsonFileFactory();
-        
-
-    }
-    //check if extension is numpy
-    else if(fpath.extension() == ".npy"){
-        std::cout<<"Loading numpy file"<<std::endl;
-    }
-    // TODO: determine file type
-    return ret ;
-}
\ No newline at end of file
diff --git a/src/file_io/FileFactory.hpp b/src/file_io/FileFactory.hpp
deleted file mode 100644
index 781f90c..0000000
--- a/src/file_io/FileFactory.hpp
+++ /dev/null
@@ -1,12 +0,0 @@
-#pragma once
-#include <filesystem>
-#include "File.hpp"
-
-class FileFactory{
-    // Class that will be used to create File objects
-    // follows the factory pattern
-public:
-    // virtual File createFile() = 0;
-    // virtual int deleteFile() = 0;
-    File loadFile(std::filesystem::path); //TODO: add option to load all file to memory or keep it on disk
-};
diff --git a/src/file_io/JsonFileFactory.hpp b/src/file_io/JsonFileFactory.hpp
deleted file mode 100644
index d44bb13..0000000
--- a/src/file_io/JsonFileFactory.hpp
+++ /dev/null
@@ -1,10 +0,0 @@
-#include "FileFactory.hpp"
-
-class JsonFileFactory: FileFactory
-{
-private:
-    /* data */
-public:
-
-};
-
diff --git a/src/file_io/File.cpp b/src/file_io/file/File.cpp
similarity index 100%
rename from src/file_io/File.cpp
rename to src/file_io/file/File.cpp
diff --git a/src/file_io/file/File.hpp b/src/file_io/file/File.hpp
new file mode 100644
index 0000000..9680348
--- /dev/null
+++ b/src/file_io/file/File.hpp
@@ -0,0 +1,46 @@
+#pragma once
+
+#include <filesystem>
+#include "defs.hpp"
+#include <fmt/core.h>
+
+class File
+{
+public:
+    std::filesystem::path base_path;
+    std::string base_name,ext;
+    int findex, n_subfiles;
+    size_t total_frames{};
+
+    std::string version;
+    DetectorType type;
+    TimingMode timing_mode;
+    int subfile_rows, subfile_cols;
+
+
+
+
+    ssize_t rows{};
+    ssize_t cols{};
+    uint8_t bitdepth{};
+    DetectorType type{};
+    // File();
+    // ~File();
+    
+
+    inline size_t bytes_per_frame() const{
+        return rows*cols*bitdepth/8;
+        
+    }
+    inline size_t pixels() const{
+        return rows*cols;
+    }
+    inline std::filesystem::path master_fname() {
+    return base_path / fmt::format("{}_master_{}{}", base_name, findex, ext);
+    }
+    inline std::filesystem::path data_fname(int mod_id, int file_id) {
+        return base_path / fmt::format("{}_d{}_f{}_{}.raw", base_name, mod_id, file_id, findex);
+    }
+    // size_t total_frames();
+
+};
diff --git a/src/file_io/RawFileFactory.cpp b/src/file_io/file/JsonFile.cpp
similarity index 100%
rename from src/file_io/RawFileFactory.cpp
rename to src/file_io/file/JsonFile.cpp
diff --git a/src/file_io/file/JsonFile.hpp b/src/file_io/file/JsonFile.hpp
new file mode 100644
index 0000000..8a90306
--- /dev/null
+++ b/src/file_io/file/JsonFile.hpp
@@ -0,0 +1,6 @@
+#pragma once
+
+class JsonFile: public File
+{
+    
+};
\ No newline at end of file
diff --git a/src/file_io/file_factory/FileFactory.cpp b/src/file_io/file_factory/FileFactory.cpp
new file mode 100644
index 0000000..b323ec0
--- /dev/null
+++ b/src/file_io/file_factory/FileFactory.cpp
@@ -0,0 +1,41 @@
+#include "FileFactory.hpp"
+#include "File.hpp"
+#include "RawFileFactory.hpp"
+#include "JsonFileFactory.hpp"
+#include <iostream>
+
+
+
+FileFactory FileFactory::getFactory(std::filesystem::path fpath){
+    // check if file exists
+    if(!std::filesystem::exists(fpath)){
+        throw std::runtime_error("File does not exist");
+    }
+
+    if(fpath.extension() == ".raw"){
+        std::cout<<"Loading raw file"<<std::endl;
+        throw std::runtime_error("Raw file not implemented");
+    }
+    else if(fpath.extension() == ".json"){
+        std::cout<<"Loading json file"<<std::endl;
+        return JsonFileFactory(fpath);
+    }
+    //check if extension is numpy
+    else if(fpath.extension() == ".npy"){
+        std::cout<<"Loading numpy file"<<std::endl;
+        throw std::runtime_error("Numpy file not implemented");
+    }
+    
+    throw std::runtime_error("Unsupported file type");    
+}
+
+void FileFactory::parse_fname(File& file) {
+    file.base_path = fpath.parent_path();
+    file.base_name = fpath.stem();
+    file.ext = fpath.extension();
+
+    auto pos = file.base_name.rfind("_");
+    file.findex = std::stoi(file.base_name.substr(pos + 1));
+    pos = file.base_name.find("_master_");
+    file.base_name.erase(pos);
+}
diff --git a/src/file_io/file_factory/FileFactory.hpp b/src/file_io/file_factory/FileFactory.hpp
new file mode 100644
index 0000000..247afd4
--- /dev/null
+++ b/src/file_io/file_factory/FileFactory.hpp
@@ -0,0 +1,21 @@
+#pragma once
+#include <filesystem>
+#include "File.hpp"
+
+class FileFactory{
+    // Class that will be used to create File objects
+    // follows the factory pattern
+    protected:
+    std::filesystem::path fpath;
+public:
+    static FileFactory getFactory(std::filesystem::path);
+    // virtual int deleteFile() = 0;
+    virtual File loadFile(){};//TODO: add option to load all file to memory or keep it on disk
+    virtual void parse_metadata(File&){};
+
+    // inline fs::path master_fname() const {
+    // return base_path / fmt::format("{}_master_{}{}", base_name, findex, ext);}
+
+    void parse_fname(File&);
+
+};
diff --git a/src/file_io/file_factory/JsonFileFactory.cpp b/src/file_io/file_factory/JsonFileFactory.cpp
new file mode 100644
index 0000000..e62082f
--- /dev/null
+++ b/src/file_io/file_factory/JsonFileFactory.cpp
@@ -0,0 +1,56 @@
+#include "JsonFileFactory.hpp"
+#include "JsonFile.hpp"
+#include "helpers.hpp"
+#include <iostream>
+#include <fstream>
+
+#include <nlohmann/json.hpp>
+
+using json = nlohmann::json;
+
+
+
+JsonFileFactory::JsonFileFactory(std::filesystem::path fpath){
+    if(not is_master_file(fpath))
+        throw std::runtime_error("Json file is not a master file");
+    this->fpath = fpath;
+}
+
+void JsonFileFactory::parse_metadata(File& file){
+    std::cout<<"Parsing metadata"<<std::endl;
+    std::ifstream ifs(file.master_fname());
+    json j;
+    ifs >> j;
+    double v = j["Version"];
+    file.version = fmt::format("{:.1f}", v);
+    file.type = StringTo<DetectorType>(j["Detector Type"].get<std::string>());
+    file.timing_mode = StringTo<TimingMode>(j["Timing Mode"].get<std::string>());
+    file.total_frames = j["Frames in File"];
+    file.subfile_cols = j["Pixels"]["x"];
+    file.subfile_rows = j["Pixels"]["y"];
+    if (type_ == DetectorType::Moench)
+        bitdepth_ = 16;
+    else
+        bitdepth_ = j["Dynamic Range"];
+
+    // only Eiger had quad
+    if (type_ == DetectorType::Eiger) {
+        quad_ = (j["Quad"] == 1);
+    }
+
+
+
+
+}
+
+File JsonFileFactory::loadFile(){
+    std::cout<<"Loading json file"<<std::endl;
+    JsonFile file = JsonFile();
+    this->parse_fname(file);
+    this->parse_metadata(file);
+
+
+
+
+    return file;
+}
\ No newline at end of file
diff --git a/src/file_io/file_factory/JsonFileFactory.hpp b/src/file_io/file_factory/JsonFileFactory.hpp
new file mode 100644
index 0000000..410db1c
--- /dev/null
+++ b/src/file_io/file_factory/JsonFileFactory.hpp
@@ -0,0 +1,13 @@
+#include "FileFactory.hpp"
+
+class JsonFileFactory: public FileFactory
+{
+private:
+    /* data */
+public:
+    File loadFile() override;
+    void parse_metadata(File&) override;
+    JsonFileFactory(std::filesystem::path fpath);
+
+};
+
diff --git a/src/file_io/file_factory/RawFileFactory.cpp b/src/file_io/file_factory/RawFileFactory.cpp
new file mode 100644
index 0000000..e69de29
diff --git a/src/file_io/RawFileFactory.hpp b/src/file_io/file_factory/RawFileFactory.hpp
similarity index 100%
rename from src/file_io/RawFileFactory.hpp
rename to src/file_io/file_factory/RawFileFactory.hpp
diff --git a/src/file_io/helpers.cpp b/src/file_io/helpers.cpp
new file mode 100644
index 0000000..6b58ea3
--- /dev/null
+++ b/src/file_io/helpers.cpp
@@ -0,0 +1,11 @@
+#include "helpers.hpp"
+
+
+bool is_master_file(std::filesystem::path fpath) {
+    std::string stem = fpath.stem();
+    if (stem.find("_master_") != std::string::npos)
+        return true;
+    else
+        return false;
+}
+
diff --git a/src/file_io/helpers.hpp b/src/file_io/helpers.hpp
new file mode 100644
index 0000000..0dd86fa
--- /dev/null
+++ b/src/file_io/helpers.hpp
@@ -0,0 +1,8 @@
+#pragma once
+
+#include "File.hpp"
+#include <filesystem>
+#include <fmt/core.h>
+
+bool is_master_file(std::filesystem::path fpath);
+
diff --git a/src/main.cpp b/src/main.cpp
index 27c632b..e90319f 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -1,10 +1,10 @@
 // Your First C++ Program
 #include <iostream>
-#include "file_io/FileFactory.hpp"
+#include "file_io/file_factory/FileFactory.hpp"
 
 
 int main() {
-    FileFactory fileFactory=FileFactory();
-    std::filesystem::path p = std::filesystem::current_path();
-    File f = fileFactory.loadFile(p/"test.raw");
+    FileFactory fileFactory=FileFactory::getFactory(std::filesystem::current_path()/"test.json");
+
+    File f = fileFactory.loadFile();
 }