/***
    Copyright (C) 2021 J Reece Wilson (a/k/a "Reece"). All rights reserved.

    File: FileStream.Unix.cpp
    Date: 2021-6-12
    Author: Reece
***/
#define _FILE_OFFSET_BITS 64
#define _LARGEFILE64_SOURCE

#include <Source/RuntimeInternal.hpp>
#include "FS.hpp"
#include "FileStream.Generic.hpp"
#include "FileAdvisory.Unix.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)
        {
            //SysPushErrorIO("PosixLseek63 IO Error: %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;
    }
    
    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;
    }
    
    bool PosixRead(int fd, void *buf, AuUInt32 count, AuUInt32 *pRead)
    {
        auto ret = read(fd, buf, count);
        
        if (ret < 0)
        {
            SysPushErrorIO("PosixRead IO Error: %i", ret);
            return false;
        }
        
        if (pRead)
        {
            *pRead = ret;
        }
        
        return true;
    }

    bool PosixWrite(int fd, const void *buf, AuUInt32 count, AuUInt32 *pWritten)
    {
        auto ret = write(fd, buf, count);
        
        if (ret < 0)
        {
            SysPushErrorIO("PosixWrite IO Error: %i", ret);
            return false;
        }
        
        if (pWritten)
        {
            *pWritten = ret;
        }
        
        return true;
    }
  

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

    bool PosixFileStream::Init(AuSPtr<IIOHandle> pHandle)
    {
        AuCtorCode_t code;
        this->pHandle_ = pHandle;
        return true;
    }
    
    AuUInt64 PosixFileStream::GetOffset()
    {
        AU_LOCK_GUARD(this->spinlock_);
       
        int fd {};
        if (auto pHandle = this->pHandle_)
        {
            if (!pHandle->IsFile())
            {
                SysPushErrorIOResourceRejected();
                return 0;
            }

            if (auto opt = pHandle->GetOSHandleSafe())
            {
                fd = opt.Value();
            }
            else
            {
                SysPushErrorInvalidFd();
                return 0;
            }
        }
        else
        {
            SysPushErrorUninitialized();
            return 0;
        }

        return PosixGetOffset(fd);
    }
    
    bool PosixFileStream::SetOffset(AuUInt64 offset)
    {
        AU_LOCK_GUARD(this->spinlock_);

        int fd {};
        if (auto pHandle = this->pHandle_)
        {
            if (!pHandle->IsFile())
            {
                SysPushErrorIOResourceRejected();
                return 0;
            }

            if (auto opt = pHandle->GetOSHandleSafe())
            {
                fd = opt.Value();
            }
            else
            {
                SysPushErrorInvalidFd();
                return false;
            }
        }
        else
        {
            SysPushErrorUninitialized();
            return false;
        }

        return PosixSetOffset(fd, offset);
    }

    AuUInt64 PosixFileStream::GetLength()
    {
        AU_LOCK_GUARD(this->spinlock_);

        int fd {};
        if (auto pHandle = this->pHandle_)
        {
            if (!pHandle->IsFile())
            {
                // Intentionally suppressed (for the moment)
                // I don't want to fill error stacks up under paths that can handle char-devs by reading until EoS
                // If we do, we could hit an always-throw on AuErrorStack-catch
                // Some users are completely unaware they can access/test the underlying handle
                // Returning zero will do
                return 0;
            }

            if (auto opt = pHandle->GetOSHandleSafe())
            {
                fd = opt.Value();
            }
            else
            {
                SysPushErrorInvalidFd();
                return 0;
            }
        }
        else
        {
            SysPushErrorUninitialized();
            return 0;
        }
        
        return PosixGetLength(fd);
    }

    bool PosixFileStream::Read(const Memory::MemoryViewStreamWrite &parameters)
    {
        AU_LOCK_GUARD(this->spinlock_);
        
        parameters.outVariable = 0;

        if (!this->pHandle_)
        {
            SysPushErrorUninitialized();
            return 0;
        }

        int fd = (int)this->pHandle_->GetOSReadHandleSafe().ValueOr((AuUInt)-1);
        if (fd == -1)
        {
            SysPushErrorIOResourceRejected();
            return 0;
        }

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

            int blockSize = AuMin(kFileCopyBlock, length);

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

            offset += read;
            length -= read;
        }
        
        parameters.outVariable = offset;
        return true;
    }
    
    bool PosixFileStream::Write(const Memory::MemoryViewStreamRead &parameters)
    {
        AU_LOCK_GUARD(this->spinlock_);

        if (!this->pHandle_)
        {
            SysPushErrorUninitialized();
            return 0;
        }

        int fd = this->pHandle_->GetOSWriteHandleSafe().ValueOr((AuUInt)-1);
        if (fd == -1)
        {
            SysPushErrorUninitialized();
            return 0;
        }

        parameters.outVariable = 0;

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

            int blockSize = AuMin(AuUInt(kFileCopyBlock), length);

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

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

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

        parameters.outVariable = offset;
        return true;
    }

    void PosixFileStream::Close()
    {
        auto pHandle = this->pHandle_;
        AuResetMember(this->pHandle_);

        if (AuExchange(this->bMadeTemporary, false))
        {
            if (pHandle)
            {
                ::unlink(pHandle->GetPath().c_str());
            }
        }
    }

    void PosixFileStream::Flush()
    {
        if (!this->pHandle_)
        {
            SysPushErrorUninitialized();
            return;
        }

        int fd = this->pHandle_->GetOSWriteHandleSafe().ValueOr((AuUInt)-1);
        if (fd == -1)
        {
            SysPushErrorIOResourceRejected();
            return;
        }

        ::fsync(fd);
    }

    void PosixFileStream::WriteEoS()
    {
        if (!this->pHandle_)
        {
            SysPushErrorUninitialized();
            return;
        }

        int fd = this->pHandle_->GetOSWriteHandleSafe().ValueOr((AuUInt)-1);
        if (fd == -1)
        {
            SysPushErrorIOResourceRejected();
            return;
        }
        
        ::ftruncate(fd, GetOffset());
    }

    void PosixFileStream::MakeTemporary()
    {
        this->bMadeTemporary = true;
    }
    
    int PosixFileStream::GetUnixHandle()
    {
        return this->pHandle_ ?
            (int)this->pHandle_->GetOSWriteHandleSafe().ValueOr(this->pHandle_->GetOSReadHandleSafe().ValueOr((AuUInt)-1)) :
            -1;
    }

    AuSPtr<IIOHandle> PosixFileStream::GetHandle()
    {
        return this->pHandle_;
    }

    AUKN_SYM AuSPtr<IFileStream> OpenBlockingFileStreamFromHandle(AuSPtr<IIOHandle> pIOHandle)
    {
        auto pStream = AuMakeShared<PosixFileStream>();
        if (!pStream)
        {
            SysPushErrorMemory();
            return nullptr;
        }

        pStream->Init(pIOHandle);
        return pStream;
    }

    static IFileStream *OpenNewEx(const AuString &path,
                                  EFileOpenMode openMode,
                                  EFileAdvisoryLockLevel lock,
                                  bool bCheck)
    {
        try
        {
            auto pHandle = AuIO::IOHandleShared();
            if (!pHandle)
            {
                SysPushErrorMemory();
                return nullptr;
            }

            AuIO::IIOHandle::HandleCreate createhandle(path);
            createhandle.eAdvisoryLevel = lock;
            createhandle.eMode = openMode;
            createhandle.bFailIfNonEmptyFile = bCheck;
            createhandle.bDirectIOMode = false;
            createhandle.bAsyncHandle = false;

            if (!pHandle->InitFromPath(createhandle))
            {
                SysPushErrorNested();
                return nullptr;
            }

            auto pStream = _new PosixFileStream();
            if (!pStream)
            {
                SysPushErrorMemory();
                return nullptr;
            }

            pStream->Init(pHandle);
            return pStream;
        }
        catch (...)
        {
            return nullptr;
        }
    }

    AUKN_SYM IFileStream *CreateNew(const AuString &path)
    {
        return OpenNewEx(path, EFileOpenMode::eWrite, EFileAdvisoryLockLevel::eBlockReadWrite, true);
    }

    AUKN_SYM void CreateRelease(IFileStream *that)
    {
        AuSafeDelete<PosixFileStream *>(that);
    }

    AUKN_SYM IFileStream *OpenNew(const AuString &path, EFileOpenMode openMode, EFileAdvisoryLockLevel lock)
    {
        return OpenNewEx(path, openMode, lock, false);
    }

    AUKN_SYM void OpenRelease(IFileStream *that)
    {
        AuSafeDelete<PosixFileStream *>(that);
    }

    AUKN_SYM IFileStream *OpenReadNew(const AuString &path, EFileAdvisoryLockLevel level)
    {
        return OpenNewEx(path, EFileOpenMode::eRead, level, false);
    }

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

    AUKN_SYM IFileStream *OpenWriteNew(const AuString &path, EFileAdvisoryLockLevel level)
    {
        return OpenNewEx(path, EFileOpenMode::eWrite, level, false);
    }

    AUKN_SYM void OpenWriteRelease(IFileStream *that)
    {
        AuSafeDelete<PosixFileStream *>(that);
    }
}
#endif