/**********************************************************************

   Audacity: A Digital Audio Editor
   Audacity(R) is copyright (c) 1999-2010 Audacity Team.
   License: GPL v2 or later.  See License.txt.

   ProjectSerializer.cpp

*******************************************************************//**

\class ProjectSerializer
\brief a class used to (de)serialize the project catalog

*//********************************************************************/

#include "ProjectSerializer.h"

#include <algorithm>
#include <cstdint>
#include <mutex>
#include <wx/ustring.h>
#include <codecvt>
#include <locale>
#include <deque>

#include <wx/log.h>

#include "BufferedStreamReader.h"

///
/// ProjectSerializer class
///

// Simple "binary xml" format used exclusively for project documents.
//
// It is not intended that the user view or modify the file.
//
// It IS intended that very little work be done during auto save, so numbers
// and strings are written in their native format.  They will be converted
// during recovery.
//
// The file has 3 main sections:
//
//    character size    1 (UTF-8), 2 (UTF-16) or 4 (UTF-32)
//    name dictionary   dictionary of all names used in the document
//    data fields       the "encoded" XML document
//
// If a subtree is added, it will be preceded with FT_Push to tell the decoder
// to preserve the active dictionary.  The decoder will then restore the
// dictionary when an FT_Pop is encountered.  Nesting is unlimited.
//
// To save space, each name (attribute or element) encountered is stored in
// the name dictionary and replaced with the assigned 2-byte identifier.
//
// All strings are in native unicode format, 2-byte or 4-byte.
//
// All name "lengths" are 2-byte signed, so are limited to 32767 bytes long.
// All string/data "lengths" are 4-byte signed.

enum FieldTypes
{
   FT_CharSize,      // type, ID, value
   FT_StartTag,      // type, ID
   FT_EndTag,        // type, ID
   FT_String,        // type, ID, string length, string
   FT_Int,           // type, ID, value
   FT_Bool,          // type, ID, value
   FT_Long,          // type, ID, value
   FT_LongLong,      // type, ID, value
   FT_SizeT,         // type, ID, value
   FT_Float,         // type, ID, value, digits
   FT_Double,        // type, ID, value, digits
   FT_Data,          // type, string length, string
   FT_Raw,           // type, string length, string
   FT_Push,          // type only
   FT_Pop,           // type only
   FT_Name           // type, ID, name length, name
};

// Static so that the dict can be reused each time.
//
// If entries get added later, like when an envelope node (for example)
// is written and then the envelope is later removed, the dict will still
// contain the envelope name, but that's not a problem.

NameMap ProjectSerializer::mNames;
MemoryStream ProjectSerializer::mDict;

TranslatableString ProjectSerializer::FailureMessage( const FilePath &/*filePath*/ )
{
   return 
XO("This recovery file was saved by Audacity 2.3.0 or before.\n"
   "You need to run that version of Audacity to recover the project." );
}

namespace
{
// Aliases for the FIXED-WIDTH integer types that are used in the file
// format.

// Chosen so that among the four build types (32 bit Windows, 64
// bit Windows, 64 bit Mac clang, Linux g++) presently done (3.0.0
// development), we use the narrowest width of the type on any of them, so
// that anything saved on one build will be read back identically on all
// builds. (Although this means that very large values on some systems might
// be saved and then read back with loss.)

// In fact the only types for which this matters are long (only 32 bits on
// 32 and 64 bit Windows) and size_t (only 32 bits on 32 bit Windows).

using UShort = std::uint16_t;
using Int = std::int32_t;

using Long = std::int32_t;   // To save long values
using ULong = std::uint32_t; // To save size_t values

using LongLong = std::int64_t;

// Detect this computer's endianness
bool IsLittleEndian()
{
   const std::uint32_t x = 1u;
   return static_cast<const unsigned char*>(static_cast<const void*>(&x))[0];
   // We will assume the same for other widths!
}
// In C++20 this could be
// constexpr bool IsLittleEndian = (std::endian::native == std::endian::little);
// static_assert( IsLittleEndian || (std::endian::native == std::endian::big),
//    "Oh no!  I'm mixed-endian!" );

// Functions that can read and write native integer types to a canonicalized
// little-endian file format.  (We don't bother to do the same for floating
// point numbers.)

// Write native little-endian to little-endian file format
template <typename Number>
void WriteLittleEndian(MemoryStream& out, Number value)
{
   out.AppendData(&value, sizeof(value));
}

// Write native big-endian to little-endian file format
template <typename Number> void WriteBigEndian(MemoryStream& out, Number value)
{
   auto begin = static_cast<unsigned char*>(static_cast<void*>(&value));
   std::reverse(begin, begin + sizeof(value));
   out.AppendData(&value, sizeof(value));
}

// Read little-endian file format to native little-endian
template <typename Number> Number ReadLittleEndian(BufferedStreamReader& in)
{
   Number result;
   in.ReadValue(result);
   return result;
}

// Read little-endian file format to native big-endian
template <typename Number> Number ReadBigEndian(BufferedStreamReader& in)
{
   Number result;
   in.ReadValue(result);
   auto begin = static_cast<unsigned char*>(static_cast<void*>(&result));
   std::reverse(begin, begin + sizeof(result));
   return result;
}

// Choose between implementations!
static const auto WriteUShort =
   IsLittleEndian() ? &WriteLittleEndian<UShort> : &WriteBigEndian<UShort>;
static const auto WriteInt =
   IsLittleEndian() ? &WriteLittleEndian<Int> : &WriteBigEndian<Int>;
static const auto WriteLong =
   IsLittleEndian() ? &WriteLittleEndian<Long> : &WriteBigEndian<Long>;
static const auto WriteULong =
   IsLittleEndian() ? &WriteLittleEndian<ULong> : &WriteBigEndian<ULong>;
static const auto WriteLongLong =
   IsLittleEndian() ? &WriteLittleEndian<LongLong> : &WriteBigEndian<LongLong>;

static const auto ReadUShort =
   IsLittleEndian() ? &ReadLittleEndian<UShort> : &ReadBigEndian<UShort>;
static const auto ReadInt =
   IsLittleEndian() ? &ReadLittleEndian<Int> : &ReadBigEndian<Int>;
static const auto ReadLong =
   IsLittleEndian() ? &ReadLittleEndian<Long> : &ReadBigEndian<Long>;
static const auto ReadULong =
   IsLittleEndian() ? &ReadLittleEndian<ULong> : &ReadBigEndian<ULong>;
static const auto ReadLongLong =
   IsLittleEndian() ? &ReadLittleEndian<LongLong> : &ReadBigEndian<LongLong>;

// Functions to read and write certain lengths -- maybe we will change
// our choices for widths or signedness?

using Length = Int; // Instead, as wide as size_t?
static const auto WriteLength = WriteInt;
static const auto ReadLength = ReadInt;

using Digits = Int; // Instead, just an unsigned char?
static const auto WriteDigits = WriteInt;
static const auto ReadDigits = ReadInt;

class XMLTagHandlerAdapter final
{
public:
   explicit XMLTagHandlerAdapter(XMLTagHandler* handler) noexcept
       : mBaseHandler(handler)
   {
   }

   void EmitStartTag(const std::string_view& name)
   {
      if (mInTag)
         EmitStartTag();

      mCurrentTagName = name;
      mInTag = true;
   }

   void EndTag(const std::string_view& name)
   {
      if (mInTag)
         EmitStartTag();

      if (XMLTagHandler* const handler = mHandlers.back())
         handler->HandleXMLEndTag(name);

      mHandlers.pop_back();
   }

   void WriteAttr(const std::string_view& name, std::string value)
   {
      assert(mInTag);

      if (!mInTag)
         return;

      mAttributes.emplace_back(name, CacheString(std::move(value)));
   }

   template <typename T> void WriteAttr(const std::string_view& name, T value)
   {
      assert(mInTag);

      if (!mInTag)
         return;

      mAttributes.emplace_back(name, XMLAttributeValueView(value));
   }

   void WriteData(std::string value)
   {
      if (mInTag)
         EmitStartTag();

      if (XMLTagHandler* const handler = mHandlers.back())
         handler->HandleXMLContent(CacheString(std::move(value)));
   }

   void WriteRaw(std::string)
   {
      // This method is intentionally left empty.
      // The only data that is serialized by FT_Raw
      // is the boilerplate code like <?xml > and <!DOCTYPE>
      // which are ignored
   }

   bool Finalize()
   {
      if (mInTag)
      {
         EmitStartTag();
         EndTag(mCurrentTagName);
      }

      return mBaseHandler != nullptr;
   }

private:
   void EmitStartTag()
   {
      if (mHandlers.empty())
      {
         mHandlers.push_back(mBaseHandler);
      }
      else
      {
         if (XMLTagHandler* const handler = mHandlers.back())
            mHandlers.push_back(handler->HandleXMLChild(mCurrentTagName));
         else
            mHandlers.push_back(NULL);
      }

      if (XMLTagHandler*& handler = mHandlers.back())
      {
         if (!handler->HandleXMLTag(mCurrentTagName, mAttributes))
         {
            handler = nullptr;

            if (mHandlers.size() == 1)
               mBaseHandler = nullptr;
         }
      }

      mStringsCache.clear();
      mAttributes.clear();
      mInTag = false;
   }

   std::string_view CacheString(std::string string)
   {
      mStringsCache.emplace_back(std::move(string));
      return mStringsCache.back();
   }

   XMLTagHandler* mBaseHandler;

   std::vector<XMLTagHandler*> mHandlers;

   std::string_view mCurrentTagName;

   std::deque<std::string> mStringsCache;
   AttributesList mAttributes;

   bool mInTag { false };
};

// template<typename BaseCharType>
// std::string FastStringConvertFromAscii(const BaseCharType* begin, const BaseCharType* end)
// {
// 
// }

template<typename BaseCharType>
std::string FastStringConvert(const void* bytes, int bytesCount)
{
   constexpr int charSize = sizeof(BaseCharType);

   assert(bytesCount % charSize == 0);

   const auto begin = static_cast<const BaseCharType*>(bytes);
   const auto end = begin + bytesCount / charSize;

   const bool isAscii = std::all_of(
      begin, end,
      [](BaseCharType c)
      { return static_cast<std::make_unsigned_t<BaseCharType>>(c) < 0x7f; });

   if (isAscii)
      return std::string(begin, end);
   
   return std::wstring_convert<std::codecvt_utf8<BaseCharType>, BaseCharType>()
      .to_bytes(begin, end);
}
} // namespace

ProjectSerializer::ProjectSerializer(size_t allocSize)
{
   static std::once_flag flag;
   std::call_once(flag, []{
      // Just once per run, store header information in the unique static
      // dictionary that will be written into each project that is saved.
      // Store the size of "wxStringCharType" so we can convert during recovery
      // in case the file is used on a system with a different character size.
      char size = sizeof(wxStringCharType);
      mDict.AppendByte(FT_CharSize);
      mDict.AppendData(&size, 1);
   });

   mDictChanged = false;
}

ProjectSerializer::~ProjectSerializer()
{
}

void ProjectSerializer::StartTag(const wxString & name)
{
   mBuffer.AppendByte(FT_StartTag);
   WriteName(name);
}

void ProjectSerializer::EndTag(const wxString & name)
{
   mBuffer.AppendByte(FT_EndTag);
   WriteName(name);
}

void ProjectSerializer::WriteAttr(const wxString & name, const wxChar *value)
{
   WriteAttr(name, wxString(value));
}

void ProjectSerializer::WriteAttr(const wxString & name, const wxString & value)
{
   mBuffer.AppendByte(FT_String);
   WriteName(name);

   const Length len = value.length() * sizeof(wxStringCharType);
   WriteLength( mBuffer, len );
   mBuffer.AppendData(value.wx_str(), len);
}

void ProjectSerializer::WriteAttr(const wxString & name, int value)
{
   mBuffer.AppendByte(FT_Int);
   WriteName(name);

   WriteInt( mBuffer, value );
}

void ProjectSerializer::WriteAttr(const wxString & name, bool value)
{
   mBuffer.AppendByte(FT_Bool);
   WriteName(name);

   mBuffer.AppendByte(value);
}

void ProjectSerializer::WriteAttr(const wxString & name, long value)
{
   mBuffer.AppendByte(FT_Long);
   WriteName(name);

   WriteLong( mBuffer, value );
}

void ProjectSerializer::WriteAttr(const wxString & name, long long value)
{
   mBuffer.AppendByte(FT_LongLong);
   WriteName(name);

   WriteLongLong( mBuffer, value );
}

void ProjectSerializer::WriteAttr(const wxString & name, size_t value)
{
   mBuffer.AppendByte(FT_SizeT);
   WriteName(name);

   WriteULong( mBuffer, value );
}

void ProjectSerializer::WriteAttr(const wxString & name, float value, int digits)
{
   mBuffer.AppendByte(FT_Float);
   WriteName(name);

   mBuffer.AppendData(&value, sizeof(value));
   WriteDigits( mBuffer, digits );
}

void ProjectSerializer::WriteAttr(const wxString & name, double value, int digits)
{
   mBuffer.AppendByte(FT_Double);
   WriteName(name);

   mBuffer.AppendData(&value, sizeof(value));
   WriteDigits( mBuffer, digits );
}

void ProjectSerializer::WriteData(const wxString & value)
{
   mBuffer.AppendByte(FT_Data);

   Length len = value.length() * sizeof(wxStringCharType);
   WriteLength( mBuffer, len );
   mBuffer.AppendData(value.wx_str(), len);
}

void ProjectSerializer::Write(const wxString & value)
{
   mBuffer.AppendByte(FT_Raw);
   Length len = value.length() * sizeof(wxStringCharType);
   WriteLength( mBuffer, len );
   mBuffer.AppendData(value.wx_str(), len);
}

void ProjectSerializer::WriteName(const wxString & name)
{
   wxASSERT(name.length() * sizeof(wxStringCharType) <= SHRT_MAX);
   UShort id;

   auto nameiter = mNames.find(name);
   if (nameiter != mNames.end())
   {
      id = nameiter->second;
   }
   else
   {
      // mNames is static.  This appends each name to static mDict only once
      // in each run.
      UShort len = name.length() * sizeof(wxStringCharType);

      id = mNames.size();
      mNames[name] = id;

      mDict.AppendByte(FT_Name);
      WriteUShort( mDict, id );
      WriteUShort( mDict, len );
      mDict.AppendData(name.wx_str(), len);

      mDictChanged = true;
   }

   WriteUShort( mBuffer, id );
}

const MemoryStream &ProjectSerializer::GetDict() const
{
   return mDict;
}

const MemoryStream& ProjectSerializer::GetData() const
{
   return mBuffer;
}

bool ProjectSerializer::IsEmpty() const
{
   return mBuffer.GetSize() == 0;
}

bool ProjectSerializer::DictChanged() const
{
   return mDictChanged;
}

// See ProjectFileIO::LoadProject() for explanation of the blockids arg
bool ProjectSerializer::Decode(BufferedStreamReader& in, XMLTagHandler* handler)
{
   if (handler == nullptr)
      return false;

   XMLTagHandlerAdapter adapter(handler);

   std::vector<char> bytes;
   IdMap mIds;
   std::vector<IdMap> mIdStack;
   char mCharSize = 0;

   mIds.clear();

   struct Error{}; // exception type for short-range try/catch
   auto Lookup = [&mIds]( UShort id ) -> std::string_view
   {
      auto iter = mIds.find( id );
      if (iter == mIds.end())
      {
         throw Error{};
      }

      return iter->second;
   };

   int64_t stringsCount = 0;
   int64_t stringsLength = 0;

   auto ReadString = [&mCharSize, &in, &bytes, &stringsCount, &stringsLength](int len) -> std::string
   {
      bytes.reserve( len );
      auto data = bytes.data();
      in.Read( data, len );

      stringsCount++;
      stringsLength += len;
      
      switch (mCharSize)
      {
         case 1:
            return std::string(bytes.data(), len);

         case 2:
            return FastStringConvert<char16_t>(bytes.data(), len);

         case 4:
            return FastStringConvert<char32_t>(bytes.data(), len);

         default:
            wxASSERT_MSG(false, wxT("Characters size not 1, 2, or 4"));
         break;
      }

      return {};
   };

   try
   {
      while (!in.Eof())
      {
         UShort id;

         switch (in.GetC())
         {
            case FT_Push:
            {
               mIdStack.push_back(mIds);
               mIds.clear();
            }
            break;

            case FT_Pop:
            {
               mIds = mIdStack.back();
               mIdStack.pop_back();
            }
            break;

            case FT_Name:
            {
               id = ReadUShort( in );
               auto len = ReadUShort( in );
               mIds[id] = ReadString(len);
            }
            break;

            case FT_StartTag:
            {
               id = ReadUShort( in );

               adapter.EmitStartTag(Lookup(id));
            }
            break;

            case FT_EndTag:
            {
               id = ReadUShort( in );

               adapter.EndTag(Lookup(id));
            }
            break;

            case FT_String:
            {
               id = ReadUShort( in );
               int len = ReadLength( in );
               
               adapter.WriteAttr(Lookup(id), ReadString(len));
            }
            break;

            case FT_Float:
            {
               float val;

               id = ReadUShort( in );
               in.Read(&val, sizeof(val));
               /* int dig = */ReadDigits(in);

               adapter.WriteAttr(Lookup(id), val);
            }
            break;

            case FT_Double:
            {
               double val;

               id = ReadUShort( in );
               in.Read(&val, sizeof(val));
               /*int dig = */ReadDigits(in);

               adapter.WriteAttr(Lookup(id), val);
            }
            break;

            case FT_Int:
            {
               id = ReadUShort( in );
               int val = ReadInt( in );

               adapter.WriteAttr(Lookup(id), val);
            }
            break;

            case FT_Bool:
            {
               unsigned char val;

               id = ReadUShort( in );
               in.Read(&val, 1);

               adapter.WriteAttr(Lookup(id), val);
            }
            break;

            case FT_Long:
            {
               id = ReadUShort( in );
               long val = ReadLong( in );

               adapter.WriteAttr(Lookup(id), val);
            }
            break;

            case FT_LongLong:
            {
               id = ReadUShort( in );
               long long val = ReadLongLong( in );
               adapter.WriteAttr(Lookup(id), val);
            }
            break;

            case FT_SizeT:
            {
               id = ReadUShort( in );
               size_t val = ReadULong( in );

               adapter.WriteAttr(Lookup(id), val);
            }
            break;

            case FT_Data:
            {
               int len = ReadLength( in );
               adapter.WriteData(ReadString(len));
            }
            break;

            case FT_Raw:
            {
               int len = ReadLength( in );
               adapter.WriteRaw(ReadString(len));
            }
            break;

            case FT_CharSize:
            {
               in.Read(&mCharSize, 1);
            }
            break;

            default:
               wxASSERT(true);
            break;
         }
      }
   }
   catch( const Error& )
   {
      // Document was corrupt, or platform differences in size or endianness
      // were not well canonicalized
      return false;
   }

   wxLogInfo(
      "Loaded %lld string %f Kb in size", stringsCount, stringsLength / 1024.0);

   return adapter.Finalize();
}
