// @(#)root/base:$Id$
// Author: Rene Brun   28/11/94

/*************************************************************************
 * Copyright (C) 1995-2000, Rene Brun and Fons Rademakers.               *
 * All rights reserved.                                                  *
 *                                                                       *
 * For the licensing terms see $ROOTSYS/LICENSE.                         *
 * For the list of contributors see $ROOTSYS/README/CREDITS.             *
 *************************************************************************/

#ifndef ROOT_TDirectory
#define ROOT_TDirectory


//////////////////////////////////////////////////////////////////////////
//                                                                      //
// TDirectory                                                           //
//                                                                      //
// Describe directory structure in memory.                              //
//                                                                      //
//////////////////////////////////////////////////////////////////////////

#include "TNamed.h"
#include "TClass.h"
#include "TUUID.h"
#include <atomic>

#ifdef R__LESS_INCLUDES
class TList;
#else
#include "TList.h"
#include "TBuffer.h"
// #include "TDatime.h"
#endif

class TBrowser;
class TKey;
class TFile;
namespace ROOT {
namespace Internal {
   struct TDirectoryAtomicAdapter;
}}

class TDirectory : public TNamed {
public:

/** \class TContext
\ingroup Base

TDirectory::TContext keeps track and restore the current directory.
With this tool C++ exceptions will be guaranteed to properly restore the
current directory pointer.

For example code like:

~~~ {.cpp}
   TDirectory *sav = gDirectory;
   mydirectory->cd();
   if (...) {
      ....
      sav->cd();
      return;
   } else if (...) {
      ....
      sav->cd();
      return;
   }
   sav->cd;
   return;
~~~

can be replaced with the simpler and exception safe:

~~~ {.cpp}
   TDirectory::TContext context(gDirectory, mydirectory);
   if (...) {
      ....
      return;
   } else if (...) {
      ....
      return;
   }
   return;
~~~

*/

   class TContext  {
   private:
      std::atomic<TDirectory*> fDirectory{nullptr}; //! Pointer to the previous current directory.
      std::atomic<bool> fActiveDestructor{false};   //! Set to true during the destructor execution
      std::atomic<bool> fDirectoryWait{false};      //! Set to true if a TDirectory might still access this object.
      TContext   *fPrevious{nullptr};               //! Pointer to the next TContext in the implied list of context pointing to fPrevious.
      TContext   *fNext{nullptr};                   //! Pointer to the next TContext in the implied list of context pointing to fPrevious.

      TContext(TContext&) = delete;
      TContext& operator=(TContext&) = delete;

      void CdNull();
      friend class TDirectory;

      void RegisterCurrentDirectory();

   public:
      // Note: the directory pointed to by `previous` must not be already deleted
      // or in the process of being deleted by another thread while this constructor runs.
      TContext(TDirectory *previous, TDirectory *newCurrent) : fDirectory(previous)
      {
         // Store the value of `previous` as the directory to return to when
         // this object is destructed.
         // Then cd to the `newCurrent` directory.
         if (fDirectory)
            (*fDirectory).RegisterContext(this);
         if (newCurrent)
            newCurrent->cd();
         else
            CdNull();
      }
      TContext() : fDirectory(TDirectory::CurrentDirectory().load())
      {
         // Store the current directory so we can restore it
         // later and cd to the new directory.
         RegisterCurrentDirectory();
      }
      TContext(TDirectory *newCurrent) : fDirectory(TDirectory::CurrentDirectory().load())
      {
         // Store the current directory so we can restore it
         // later and cd to the new directory.
         RegisterCurrentDirectory();
         if (newCurrent)
            newCurrent->cd();
         else
            CdNull();
      }
      ~TContext();
   };

protected:

   TObject         *fMother{nullptr};   // pointer to mother of the directory
   TList           *fList{nullptr};     // List of objects in memory
   TUUID            fUUID;              // Unique identifier
   mutable TString  fPathBuffer;        //! Buffer for GetPath() function
   TContext        *fContext{nullptr};  //! Pointer to a list of TContext object pointing to this TDirectory

   using SharedGDirectory_t = std::shared_ptr<std::atomic<TDirectory *>>;

   static SharedGDirectory_t &GetSharedLocalCurrentDirectory();

   std::vector<SharedGDirectory_t> fGDirectories; //! thread local gDirectory pointing to this object.

   std::atomic<size_t> fContextPeg{0};  //! Counter delaying the TDirectory destructor from finishing.
   mutable std::atomic_flag fSpinLock;  //! MSVC doesn't support = ATOMIC_FLAG_INIT;

   static Bool_t fgAddDirectory;        //!flag to add histograms, graphs,etc to the directory

          Bool_t  cd1(const char *path);
   static Bool_t  Cd1(const char *path);

           void   CleanTargets();
           void   FillFullPath(TString& buf) const;
           void   RegisterContext(TContext *ctxt);
           void   RegisterGDirectory(SharedGDirectory_t &ptr);
           void   UnregisterContext(TContext *ctxt);
           void   BuildDirectory(TFile* motherFile, TDirectory* motherDir);

   friend class TContext;
   friend struct ROOT::Internal::TDirectoryAtomicAdapter;

protected:
   TDirectory(const TDirectory &directory) = delete;  //Directories cannot be copied
   void operator=(const TDirectory &) = delete; //Directories cannot be copied

public:

   TDirectory();
   TDirectory(const char *name, const char *title, Option_t *option = "", TDirectory* motherDir = nullptr);
   virtual ~TDirectory();
   static  void        AddDirectory(Bool_t add=kTRUE);
   static  Bool_t      AddDirectoryStatus();
   virtual void        Append(TObject *obj, Bool_t replace = kFALSE);
   virtual void        Add(TObject *obj, Bool_t replace = kFALSE) { Append(obj,replace); }
   virtual Int_t       AppendKey(TKey *) {return 0;}
           void        Browse(TBrowser *b) override;
   virtual void        Build(TFile* motherFile = nullptr, TDirectory* motherDir = nullptr) { BuildDirectory(motherFile, motherDir); }
           void        Clear(Option_t *option="") override;
   virtual TObject    *CloneObject(const TObject *obj, Bool_t autoadd = kTRUE);
   virtual void        Close(Option_t *option="");
   static std::atomic<TDirectory*> &CurrentDirectory();  // Return the current directory for this thread.
           void        Copy(TObject &) const override { MayNotUse("Copy(TObject &)"); }
   virtual Bool_t      cd();
   virtual Bool_t      cd(const char *path);
   virtual void        DeleteAll(Option_t *option="");
           void        Delete(const char *namecycle="") override;
           void        Draw(Option_t *option="") override;
   virtual TKey       *FindKey(const char * /*keyname*/) const {return nullptr;}
   virtual TKey       *FindKeyAny(const char * /*keyname*/) const {return nullptr;}
           TObject    *FindObject(const char *name) const override;
           TObject    *FindObject(const TObject *obj) const override;
   virtual TObject    *FindObjectAny(const char *name) const;
   virtual TObject    *FindObjectAnyFile(const char * /*name*/) const {return nullptr;}
   virtual TObject    *Get(const char *namecycle);
   /// See documentation of TDirectoryFile::Get(const char *namecycle)
   template <class T> inline T* Get(const char* namecycle)
   {
      return static_cast<T*>(GetObjectChecked(namecycle, TClass::GetClass<T>()));
   }
   virtual TDirectory *GetDirectory(const char *namecycle, Bool_t printError = false, const char *funcname = "GetDirectory");
   /// Get an object with proper type checking. If the object doesn't exist in the file or if the type doesn't match,
   /// a `nullptr` is returned. Also see TDirectory::Get().
   template <class T> inline void GetObject(const char* namecycle, T*& ptr)
   {
      ptr = (T *)GetObjectChecked(namecycle, TClass::GetClass<T>());
   }
   virtual void       *GetObjectChecked(const char *namecycle, const char* classname);
   virtual void       *GetObjectChecked(const char *namecycle, const TClass* cl);
   virtual void       *GetObjectUnchecked(const char *namecycle);
   virtual Int_t       GetBufferSize() const {return 0;}
   virtual TFile      *GetFile() const { return nullptr; }
   virtual TKey       *GetKey(const char * /*name */, Short_t /* cycle */=9999) const {return nullptr;}
   virtual TList      *GetList() const { return fList; }
   virtual TList      *GetListOfKeys() const { return nullptr; }
           TObject    *GetMother() const { return fMother; }
           TDirectory *GetMotherDir() const { return !fMother ? nullptr : dynamic_cast<TDirectory*>(fMother); }
   virtual Int_t       GetNbytesKeys() const { return 0; }
   virtual Int_t       GetNkeys() const { return 0; }
   virtual Long64_t    GetSeekDir() const { return 0; }
   virtual Long64_t    GetSeekParent() const { return 0; }
   virtual Long64_t    GetSeekKeys() const { return 0; }
   virtual const char *GetPathStatic() const;
   virtual const char *GetPath() const;
   TUUID               GetUUID() const {return fUUID;}
           Bool_t      IsBuilt() const { return fList != nullptr; }
           Bool_t      IsFolder() const override { return kTRUE; }
   virtual Bool_t      IsModified() const { return kFALSE; }
   virtual Bool_t      IsWritable() const { return kFALSE; }
           void        ls(Option_t *option="") const override;
   virtual TDirectory *mkdir(const char *name, const char *title="", Bool_t returnExistingDirectory = kFALSE);
   virtual TFile      *OpenFile(const char * /*name*/, Option_t * /*option*/ = "",
                            const char * /*ftitle*/ = "", Int_t /*compress*/ = 1,
                            Int_t /*netopt*/ = 0) {return nullptr;}
           void        Paint(Option_t *option="") override;
           void        Print(Option_t *option="") const override;
   virtual void        Purge(Short_t /*nkeep*/=1) {}
   virtual void        pwd() const;
   virtual void        ReadAll(Option_t * /*option*/="") {}
   virtual Int_t       ReadKeys(Bool_t /*forceRead*/=kTRUE) {return 0;}
   virtual Int_t       ReadTObject(TObject * /*obj*/, const char * /*keyname*/) {return 0;}
   virtual TObject    *Remove(TObject*);
           void        RecursiveRemove(TObject *obj) override;
   virtual void        rmdir(const char *name);
   virtual void        Save() {}
   virtual Int_t       SaveObjectAs(const TObject * /*obj*/, const char * /*filename*/="", Option_t * /*option*/="") const;
   virtual void        SaveSelf(Bool_t /*force*/ = kFALSE) {}
   virtual void        SetBufferSize(Int_t /* bufsize */) {}
   virtual void        SetModified() {}
   virtual void        SetMother(TObject *mother) {fMother = (TObject*)mother;}
           void        SetName(const char* newname) override;
   virtual void        SetTRefAction(TObject * /*ref*/, TObject * /*parent*/) {}
   virtual void        SetSeekDir(Long64_t) {}
   virtual void        SetWritable(Bool_t) {}
           Int_t       Sizeof() const override {return 0;}
   virtual Int_t       Write(const char * /*name*/=nullptr, Int_t /*opt*/=0, Int_t /*bufsize*/=0) override {return 0;}
   virtual Int_t       Write(const char * /*name*/=nullptr, Int_t /*opt*/=0, Int_t /*bufsize*/=0) const override {return 0;}
   virtual Int_t       WriteTObject(const TObject *obj, const char *name =nullptr, Option_t * /*option*/="", Int_t /*bufsize*/ =0);
private:
/// \cond HIDDEN_SYMBOLS
           Int_t       WriteObject(void *obj, const char* name, Option_t *option="", Int_t bufsize=0); // Intentionally not implemented.
/// \endcond
public:
   /// \brief Write an object with proper type checking.
   /// \param[in] obj Pointer to an object to be written.
   /// \param[in] name Name of the object in the file.
   /// \param[in] option Options. See TDirectory::WriteTObject.
   /// \param[in] bufsize Buffer size. See TDirectory::WriteTObject.
   ///
   /// This overload takes care of instances of classes that are not derived
   /// from TObject. The method redirects to TDirectory::WriteObjectAny.
   template <typename T>
   inline std::enable_if_t<!std::is_base_of<TObject, T>::value, Int_t>
   WriteObject(const T *obj, const char *name, Option_t *option = "", Int_t bufsize = 0)
   {
      return WriteObjectAny(obj, TClass::GetClass<T>(), name, option, bufsize);
   }
   /// \brief Write an object with proper type checking.
   /// \param[in] obj Pointer to an object to be written.
   /// \param[in] name Name of the object in the file.
   /// \param[in] option Options. See TDirectory::WriteTObject.
   /// \param[in] bufsize Buffer size. See TDirectory::WriteTObject.
   ///
   /// This overload takes care of instances of classes that are derived from
   /// TObject. The method redirects to TDirectory::WriteTObject.
   template <typename T>
   inline std::enable_if_t<std::is_base_of<TObject, T>::value, Int_t>
   WriteObject(const T *obj, const char *name, Option_t *option = "", Int_t bufsize = 0)
   {
      return WriteTObject(obj, name, option, bufsize);
   }
   virtual Int_t       WriteObjectAny(const void *, const char * /*classname*/, const char * /*name*/, Option_t * /*option*/="", Int_t /*bufsize*/ =0) {return 0;}
   virtual Int_t       WriteObjectAny(const void *, const TClass * /*cl*/, const char * /*name*/, Option_t * /*option*/="", Int_t /*bufsize*/ =0) {return 0;}
   virtual void        WriteDirHeader() {}
   virtual void        WriteKeys() {}

   static Bool_t       Cd(const char *path);
   static void         DecodeNameCycle(const char *namecycle, char *name, Short_t &cycle, const size_t namesize = 0);

   ClassDefOverride(TDirectory,5)  //Describe directory structure in memory
};

namespace ROOT {
namespace Internal {
   /// \brief Internal class used in the implementation of `gDirectory`
   /// The objects of type `TDirectoryAtomicAdapter` should only be used inside the
   /// thread that created them.  The intent is for those objects to be used indirectly
   /// through the macro `gDirectory` and solely as temporary objects.
   /// For example:
   /// ```
   ///   gDirectory = newvalue;
   ///   gDirectory->ls();
   ///   TDirectory *current = gDirectory;
   /// ```
   /// Note that:
   /// ```
   ///   auto dir = gDirectory;
   /// ```
   /// currently behaves "unexpectedly" as changing `dir` will also change `gDirectory`:
   /// ```
   ///   dir = newvalue;
   /// ```
   /// leads to
   /// ```
   ///   gDirectory == newvalue
   /// ```
   /// To prevent this we would need a new mechanism such that the type
   /// used by `auto` in that case is `TDirectory*` rather than the `Internal`
   /// type `TDirectoryAtomicAdapter`.
   struct TDirectoryAtomicAdapter {
      // The shared pointer's lifetime is that of the thread creating this object
      // (with the default constructor)
      TDirectory::SharedGDirectory_t &fValue;

      TDirectoryAtomicAdapter() : fValue(TDirectory::GetSharedLocalCurrentDirectory()) {}

      template <typename T>
      explicit operator T*() const {
         return (T *)fValue->load();
      }

      operator TDirectory*() const {
         return fValue->load();
      }

      operator bool() const { return fValue->load() != nullptr; }

      bool operator==(const TDirectory *other) const {
         return fValue->load() == other;
      }

      bool operator!=(const TDirectory *other) const {
         return fValue->load() != other;
      }

      bool operator==(TDirectory *other) const {
         return fValue->load() == other;
      }

      bool operator!=(TDirectory *other) const {
         return fValue->load() != other;
      }

      TDirectory *operator=(TDirectory *newvalue) {
         if (newvalue) {
            newvalue->RegisterGDirectory(fValue);
         }
         fValue->exchange(newvalue);
         return newvalue;
      }

      TDirectory *operator->() const { return fValue->load(); }
   };
} // Internal
} // ROOT
#define gDirectory (::ROOT::Internal::TDirectoryAtomicAdapter{})

#endif