#define _FILE_OFFSET_BITS 64
#define _LARGEFILE64_SOURCE

#include <Source/RuntimeInternal.hpp>
#include "FS.hpp"
#include "FileStream.Generic.hpp"

#include <sys/types.h>
#include <unistd.h>
#include <fcntl.h>

#if !defined(_AURUNTIME_GENERICFILESTREAM)

namespace Aurora::IO::FS
{
    static const AuUInt64 kFileCopyBlock = 0x4000; // 16KiB
  
    static bool PosixLseek63(int fd, AuUInt64 offset, int whence, AuUInt64 *pOffset)
    {
        if (offset > std::numeric_limits<off_t>::max())
        {
            SysPushErrorIO("int overflow exploit?");
            return false;
        }
        
    #if defined(AURORA_IS_LINUX_DERIVED)
        auto ret = lseek64(fd, offset, whence);
    #elif defined(AURORA_IS_64BIT)
        static_assert(std::numeric_limits<off_t>::max() >= std::numeric_limits<AuInt64>::max(), "unsupported posix os");
        auto ret = lseek(fd, offset, whence); 
    #else
        #error accient 32-bit posix operating systems require 64-bit file awareness
    #endif
        
        if (ret < 0)
        {
            LogWarn("PosixLseek63 IO Error %i", ret);
            SysPushErrorIO("PosixLseek63: %i", ret);
            return false;
        }
        
        if (pOffset)
        {
            *pOffset = ret;
        }
        
        return true;
    }
    
    static AuUInt64 PosixGetOffset(int fd)
    {
        AuUInt64 ret;
        if (!PosixLseek63(fd, 0, SEEK_SET, &ret)) 
        {
            return 0;
        }
        return ret;
    }
    
    static bool PosixSetOffset(int fd, AuUInt64 offset)
    {
        return PosixLseek63(fd, offset, SEEK_SET, nullptr); 
    }
    
    static AuUInt64 PosixGetLength(int fd)
    {
        AuUInt64 ret {}, old {};
        bool status {};
        
        if (!PosixLseek63(fd, 0, SEEK_SET, &old)) 
        {
            return 0;
        }
        
        status  = PosixLseek63(fd, 0, SEEK_END, &ret);
        status &= PosixLseek63(fd, old, SEEK_SET, nullptr);
        
        return status ? ret : 0;
    }
    
    static bool PosixRead(int fd, void *buf, AuUInt32 count, AuUInt32 *pRead)
    {
        auto ret = read(fd, buf, count);
        
        if (ret < 0)
        {
            LogWarn("PosixRead IO Error %i", ret);
            SysPushErrorIO("PosixRead: %i", ret);
            return false;
        }
        
        if (pRead)
        {
            *pRead = ret;
        }
        
        return true;
    }
    
    static bool PosixWrite(int fd, const void *buf, AuUInt32 count, AuUInt32 *pWritten)
    {
        auto ret = write(fd, buf, count);
        
        if (ret < 0)
        {
            LogWarn("PosixWrite IO Error %i", ret);
            SysPushErrorIO("PosixWrite: %i", ret);
            return false;
        }
        
        if (pWritten)
        {
            *pWritten = ret;
        }
        
        return true;
    }
  

    PosixFileStream::~PosixFileStream()
    {
        Close();
    }

    void PosixFileStream::Init(int handle, const AuString &path)
    {
        handle_ = handle;
        path_ = path;
    }
    
    AuUInt64 PosixFileStream::GetOffset()
    {
        if (handle_ == -1)
        {
            SysPushErrorUninitialized();
            return 0;
        }

        return PosixGetOffset(handle_);
    }

    bool PosixFileStream::SetOffset(AuUInt64 offset)
    {
        if (handle_ == -1)
        {
            SysPushErrorUninitialized();
            return 0;
        }
        
        return PosixSetOffset(handle_, offset);
    }

    AuUInt64 PosixFileStream::GetLength()
    {
        if (handle_ == -1)
        {
            SysPushErrorUninitialized();
            return 0;
        }
        
        return PosixGetLength(handle_);
    }

    bool PosixFileStream::Read(const Memory::MemoryViewStreamWrite &parameters)
    {
        if (handle_ == -1)
        {
            SysPushErrorUninitialized();
            return 0;
        }

        auto length = parameters.length;
        AuUInt offset {0};
        while (length)
        {
            AuUInt32 read;

            int blockSize = std::min(kFileCopyBlock, length);

            if (!PosixRead(handle_, &reinterpret_cast<char *>(parameters.ptr)[offset], blockSize, &read))
            {
                SysPushErrorNested("File Error: {}", path_);
                break;
            }
            
            if (read == 0)
            {
                break;
            }

            offset += read;
            length -= read;
        }
        
        if (!offset)
        {
            return false;
        }

        parameters.outVariable = offset;
        return true;
    }
    
    bool PosixFileStream::Write(const Memory::MemoryViewStreamRead &parameters)
    {
        if (handle_ == -1)
        {
            SysPushErrorUninitialized();
            return 0;
        }

        auto length = parameters.length;
        AuUInt offset {0};
        while (length)
        {
            AuUInt32 written;

            int blockSize = std::min(kFileCopyBlock, length);

            if (!PosixWrite(handle_, &reinterpret_cast<const char *>(parameters.ptr)[offset], blockSize, &written))
            {
                SysPushErrorNested("File Error: {}", path_);
                return false;
            }

            if (written != blockSize)
            {
                SysPushErrorIO();
                SysPushErrorNested("File Error: {}", path_);
                break;
            }

            offset += written;
            length -= written;
        }
        
        if (!offset)
        {
            return false;
        }

        parameters.outVariable = offset;
        return true;
    }

    void PosixFileStream::Close()
    {
        int handle;

        if ((handle = std::exchange(handle_, -1)) != -1)
        {
            ::close(handle);
        }
    }

    void PosixFileStream::Flush()
    {
        fsync(handle_);
    }
    
    static IFileStream *OpenNew(const AuString &path, bool read)
    {
        auto pathex = NormalizePathRet(path);

        if (!read)
        {
            CreateDirectories(pathex, true);
        }

        auto fileHandle = open(pathex.c_str(), read ? O_RDONLY : O_RDWR);

        if (fileHandle < 0)
        {
            LogWarn("Couldn't open file: {}", path);
            SysPushErrorIO("Couldn't open file: {}", path);
            return nullptr;
        }

        auto stream = _new PosixFileStream();
        if (!stream)
        {
            close(fileHandle);
            return nullptr;
        }

        stream->Init(fileHandle, pathex);
        return stream;
    }

    AUKN_SYM IFileStream *OpenReadNew(const AuString &path)
    {
        return OpenNew(path, true);
    }

    AUKN_SYM void OpenReadRelease(IFileStream * that)
    {
        SafeDelete<PosixFileStream *>(that);
    }

    AUKN_SYM IFileStream *OpenWriteNew(const AuString &path)
    {
        return OpenNew(path, false);
    }
    
    AUKN_SYM void OpenWriteRelease(IFileStream * that)
    {
        SafeDelete<PosixFileStream *>(that);
    }
}
#endif