FileDialog Microservice

Update

The use of a file-provider was deemed to be a better design since this microservice does not need to go through the servemanager layer. See async/paraview!102

Goal

A simple service that allows to browse the filesystem and create/delete directories

FileDialog microservice design

Keep the Model-View-Controller design of the current pqFileDialog but adapt it to the micro-services design idea.

Steps:

1. Bring pqFileModel in since it has the required logic already in-place but remove Qt bits (mainly usage of QString).
2. View, and Controller will by handled by python/trame (since they interact with the user), FileModel will be wrapped for python.
3. The actual FileMicroService will be only used internally.

Note: We can have an explicit async function Update() that updates the model (FileModel1) or all "getters" can become async functions (FileModel2)

class FileModel1:
{
    public:

        void SetCurrentPath(std::string path=".")

        void Initialize();

        std::string GetCurrentPath();
        std::vector<std::string> GetCurrentPathListing();
        /**
         Push current directory to the server and fetch directory listing.
         It will be wrapped as:

        async def Update() -> bool 
        **/
        rxcpp::observable<bool>  Update() {return StatusSubject.get_observable();}

     private:
       vtkFileMicroService FileMicroService;
       rxcpp::subject<bool> StatusSubject;

       std::string CurrentPath;
       std::vector<std::string> CurrentPathListing;
};

void Initialize()
{
    FileMicroService.SetSession(...);
        
    FileService.GetObservable().subscribe([this]vtkVPFileInformation fileInfo)
    {
        this->CurrentPath = fileInfo.GetCurrentPath();
        this->CurrentPathListing = fileInfo.GetPathListing();
        StatusSubject.get_subscriber().on_next(true);
    });
}

// FileModel2 all "getters" are async functions (`FileModel2`)

class FileModel2:
{
    public:

        void SetCurrentPath(std::string path=".")

        void Initialize();

        // will we wrapped as async def GetCurrentPath() -> AsyncIterator[str]
        rxcpp::observable<std::string> GetCurrentPath()
        {   return this->CurrentPathSubject.get_observable();}

        // will we wrapped as async def GetCurrentPathListing() -> AsyncIterator[list[str]]
        rxcpp::observable< std::vector<std::string> > GetCurrentPathListing()
        {   return this->CurrentPathListing.get_observable();}

    private:
        vtkFileMicroService FileMicroService;
        rxcpp::subject<std::string> CurrentPathSubject;
        rxcpp::subject<std::vector<std::string>> CurrentPathListingSubject;
};

void Initialize()
{
    FileMicroService.SetSession(...);
        
    FileService.GetObservable().subscribe([]vtkVPFileInformation fileInfo)
    {
        std::string currentPath = fileInfo.GetCurrentPath();
        std::vector<std::string> pathListing = fileInfo.GetPathListing();
        CurrentPathSubject.get_subscriber().on_next(currentPath);
        CurrentPathListing.get_subscriber().on_next(pathListing);

    });
}

class vtkFileMicroService :
{
        public:
        void SetSession(Session* session);
        Session* GetSession();

        void SetCurrentPath(std::string path);

        rxcpp::observable<vtkPVFileInformation> GetObservable() 
        { return this->FileInformationSubject.get_observable(); }

        private:
           rxcpp::subject<vtkPVFileInformation> FileInformationSubject;

}
void SetCurrentPath(std::string path)
{
    vtkPVFileInformation fileInfoRequest;
    // populate fileInfo attributes and flags based on path
    populate(fielInfoRequest)

    auto packet = vtkRemoteObjectProvider::GatherInformation(fileInfoRequest);
    auto eventual = this->Session->SendRequest(DATA_SERVER,packet);
    eventual.GetObservable()
    .observe_on(/* appropriate coordination */) // to avoid blocking
    subscribe([this](vtkPacket packet){
        vtkPVFileInformation fileInfoResponse;
        vtkRemoteObjectProvider::ParseResponse(packet, fileInfoResponse)
        this->FileInformationSubject.get_subscriber().on_next(fileInfoResponse);
    });
}