/*
    SPDX-FileCopyrightText: 2005 Joris Guisson <joris.guisson@gmail.com>
    SPDX-License-Identifier: GPL-2.0-or-later
*/

#include <config-ktcore.h>

#include <cstdio>
#include <cstdlib>
#include <errno.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>

#include <QFile>

#include <KFileItem>
#include <KLocalizedString>

#include "mmapfile.h"
#include <torrent/globals.h>
#include <util/error.h>
#include <util/log.h>

namespace bt
{
MMapFile::MMapFile()
    : fptr(nullptr)
    , data(nullptr)
    , size(0)
    , file_size(0)
    , ptr(0)
    , mode(QIODevice::ReadOnly)
{
}

MMapFile::~MMapFile()
{
    if (fptr)
        close();
}

bool MMapFile::open(const QString &file, QIODevice::OpenModeFlag mode)
{
    // close already open file
    if (fptr && fptr->isOpen()) {
        close();
    }

    // setup flags
    int mmap_flag = 0;
    switch (mode) {
    case QIODevice::ReadOnly:
        mmap_flag = PROT_READ;
        break;
    case QIODevice::WriteOnly:
        mmap_flag = PROT_WRITE;
        break;
    default:
    case QIODevice::ReadWrite:
        mmap_flag = PROT_READ | PROT_WRITE;
        break;
    }

    fptr = new QFile(file);
    // open the file
    if (!(fptr->open(mode))) {
        delete fptr;
        fptr = nullptr;
        return false;
    }

    // read the file size
    this->size = fptr->size();
    this->mode = mode;

    file_size = fptr->size();
    filename = file;

    // mmap the file
#ifndef Q_WS_WIN
    int fd = fptr->handle();
#ifdef HAVE_MMAP64
    data = (Uint8 *)mmap64(0, size, mmap_flag, MAP_SHARED, fd, 0);
#else
    data = (Uint8 *)mmap(nullptr, size, mmap_flag, MAP_SHARED, fd, 0);
#endif
    if (data == MAP_FAILED) {
        ::close(fd);
        data = nullptr;
        fd = -1;
        ptr = 0;
        return false;
    }
    ptr = 0;
    return true;
#else // Q_WS_WIN
    data = (Uint8 *)fptr->map(0, size);

    if (!data) {
        fptr->close();
        delete fptr;
        fptr = nullptr;
        return false;
    }
    ptr = 0;
    return true;
#endif
}

void MMapFile::close()
{
    if (fptr) {
#ifndef Q_WS_WIN
#ifdef HAVE_MUNMAP64
        munmap64(data, size);
#else
        munmap(data, size);
#endif
#else
        fptr->unmap(data);
#endif
        fptr->close();
        delete fptr;
        fptr = nullptr;
        ptr = size = 0;
        data = nullptr;
        filename = QString();
    }
}

void MMapFile::flush()
{
    if (fptr)
#ifndef Q_WS_WIN
        msync(data, size, MS_SYNC);
#else
        FlushViewOfFile(data, size);
#endif
}

Uint32 MMapFile::write(const void *buf, Uint32 buf_size)
{
    if (!fptr || mode == QIODevice::ReadOnly)
        return 0;

    // check if data fits in memory mapping
    if (ptr + buf_size > size)
        throw Error(i18n("Cannot write beyond end of the mmap buffer."));

    Out(SYS_GEN | LOG_DEBUG) << "MMapFile::write : " << (ptr + buf_size) << " " << file_size << endl;
    // enlarge the file if necessary
    if (ptr + buf_size > file_size) {
        growFile(ptr + buf_size);
    }

    // memcpy data
    memcpy(&data[ptr], buf, buf_size);
    // update ptr
    ptr += buf_size;
    // update file size if necessary
    if (ptr >= size)
        size = ptr;

    return buf_size;
}

void MMapFile::growFile(Uint64 new_size)
{
    Out(SYS_GEN | LOG_DEBUG) << "Growing file to " << new_size << " bytes " << endl;
    Uint64 to_write = new_size - file_size;
    // jump to the end of the file
    fptr->seek(fptr->size());

    Uint8 buf[1024];
    memset(buf, 0, 1024);
    // write data until to_write is 0
    while (to_write > 0) {
        ssize_t w = fptr->write((const char *)buf, to_write > 1024 ? 1024 : to_write);
        if (w > 0)
            to_write -= w;
        else if (w < 0)
            break;
    }
    file_size = new_size;
}

Uint32 MMapFile::read(void *buf, Uint32 buf_size)
{
    if (!fptr || mode == QIODevice::WriteOnly)
        return 0;

    // check if we aren't going to read past the end of the file
    Uint32 to_read = ptr + buf_size >= size ? size - ptr : buf_size;
    // read data
    memcpy(buf, data + ptr, to_read);
    ptr += to_read;
    return to_read;
}

Uint64 MMapFile::seek(SeekPos from, Int64 num)
{
    switch (from) {
    case BEGIN:
        if (num > 0)
            ptr = num;
        if (ptr >= size)
            ptr = size - 1;
        break;
    case END: {
        Int64 np = (size - 1) + num;
        if (np < 0) {
            ptr = 0;
            break;
        }
        if (np >= (Int64)size) {
            ptr = size - 1;
            break;
        }
        ptr = np;
    } break;
    case CURRENT: {
        Int64 np = ptr + num;
        if (np < 0) {
            ptr = 0;
            break;
        }
        if (np >= (Int64)size) {
            ptr = size - 1;
            break;
        }
        ptr = np;
    } break;
    }
    return ptr;
}

bool MMapFile::eof() const
{
    return ptr >= size;
}

Uint64 MMapFile::tell() const
{
    return ptr;
}

QString MMapFile::errorString() const
{
    return QString::fromUtf8(strerror(errno));
}

Uint64 MMapFile::getSize() const
{
    return size;
}

Uint8 *MMapFile::getData(Uint64 off)
{
    if (off >= size)
        return nullptr;
    return &data[off];
}
}