/*
    This file is part of the KDE project
    SPDX-FileCopyrightText: 2003 Dominik Seichter <domseichter@web.de>
    SPDX-FileCopyrightText: 2004 Ignacio Castaño <castano@ludicon.com>

    SPDX-License-Identifier: LGPL-2.0-or-later
*/

/* this code supports:
 * reading:
 *     uncompressed and run length encoded indexed, grey and color tga files.
 *     image types 1, 2, 3, 9, 10 and 11.
 *     only RGB color maps with no more than 256 colors.
 *     pixel formats 8, 16, 24 and 32.
 * writing:
 *     uncompressed true color tga files
 */

#include "tga_p.h"
#include "util_p.h"

#include <assert.h>

#include <QDataStream>
#include <QDebug>
#include <QImage>

typedef quint32 uint;
typedef quint16 ushort;
typedef quint8 uchar;

namespace // Private.
{
// Header format of saved files.
uchar targaMagic[12] = {0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0};

enum TGAType {
    TGA_TYPE_INDEXED = 1,
    TGA_TYPE_RGB = 2,
    TGA_TYPE_GREY = 3,
    TGA_TYPE_RLE_INDEXED = 9,
    TGA_TYPE_RLE_RGB = 10,
    TGA_TYPE_RLE_GREY = 11,
};

#define TGA_INTERLEAVE_MASK 0xc0
#define TGA_INTERLEAVE_NONE 0x00
#define TGA_INTERLEAVE_2WAY 0x40
#define TGA_INTERLEAVE_4WAY 0x80

#define TGA_ORIGIN_MASK 0x30
#define TGA_ORIGIN_LEFT 0x00
#define TGA_ORIGIN_RIGHT 0x10
#define TGA_ORIGIN_LOWER 0x00
#define TGA_ORIGIN_UPPER 0x20

/** Tga Header. */
struct TgaHeader {
    uchar id_length;
    uchar colormap_type;
    uchar image_type;
    ushort colormap_index;
    ushort colormap_length;
    uchar colormap_size;
    ushort x_origin;
    ushort y_origin;
    ushort width;
    ushort height;
    uchar pixel_size;
    uchar flags;

    enum {
        SIZE = 18,
    }; // const static int SIZE = 18;
};

static QDataStream &operator>>(QDataStream &s, TgaHeader &head)
{
    s >> head.id_length;
    s >> head.colormap_type;
    s >> head.image_type;
    s >> head.colormap_index;
    s >> head.colormap_length;
    s >> head.colormap_size;
    s >> head.x_origin;
    s >> head.y_origin;
    s >> head.width;
    s >> head.height;
    s >> head.pixel_size;
    s >> head.flags;
    return s;
}

static bool IsSupported(const TgaHeader &head)
{
    if (head.image_type != TGA_TYPE_INDEXED && head.image_type != TGA_TYPE_RGB && head.image_type != TGA_TYPE_GREY && head.image_type != TGA_TYPE_RLE_INDEXED
        && head.image_type != TGA_TYPE_RLE_RGB && head.image_type != TGA_TYPE_RLE_GREY) {
        return false;
    }
    if (head.image_type == TGA_TYPE_INDEXED || head.image_type == TGA_TYPE_RLE_INDEXED) {
        if (head.colormap_length > 256 || head.colormap_size != 24 || head.colormap_type != 1) {
            return false;
        }
    }
    if (head.image_type == TGA_TYPE_RGB || head.image_type == TGA_TYPE_GREY || head.image_type == TGA_TYPE_RLE_RGB || head.image_type == TGA_TYPE_RLE_GREY) {
        if (head.colormap_type != 0) {
            return false;
        }
    }
    if (head.width == 0 || head.height == 0) {
        return false;
    }
    if (head.pixel_size != 8 && head.pixel_size != 16 && head.pixel_size != 24 && head.pixel_size != 32) {
        return false;
    }
    // If the colormap_type field is set to zero, indicating that no color map exists, then colormap_size, colormap_index and colormap_length should be set to zero.
    if (head.colormap_type == 0 && (head.colormap_size != 0 || head.colormap_index != 0 || head.colormap_length != 0)) {
        return false;
    }
    return true;
}

struct Color555 {
    ushort b : 5;
    ushort g : 5;
    ushort r : 5;
};

struct TgaHeaderInfo {
    bool rle;
    bool pal;
    bool rgb;
    bool grey;

    TgaHeaderInfo(const TgaHeader &tga)
        : rle(false)
        , pal(false)
        , rgb(false)
        , grey(false)
    {
        switch (tga.image_type) {
        case TGA_TYPE_RLE_INDEXED:
            rle = true;
            Q_FALLTHROUGH();
        // no break is intended!
        case TGA_TYPE_INDEXED:
            pal = true;
            break;

        case TGA_TYPE_RLE_RGB:
            rle = true;
            Q_FALLTHROUGH();
        // no break is intended!
        case TGA_TYPE_RGB:
            rgb = true;
            break;

        case TGA_TYPE_RLE_GREY:
            rle = true;
            Q_FALLTHROUGH();
        // no break is intended!
        case TGA_TYPE_GREY:
            grey = true;
            break;

        default:
            // Error, unknown image type.
            break;
        }
    }
};

static QImage::Format imageFormat(const TgaHeader &head)
{
    auto format = QImage::Format_Invalid;
    if (IsSupported(head)) {
        // Bits 0-3 are the numbers of alpha bits (can be zero!)
        const int numAlphaBits = head.flags & 0xf;
        // However alpha exists only in the 32 bit format.
        if ((head.pixel_size == 32) && (head.flags & 0xf)) {
            if (numAlphaBits <= 8) {
                format = QImage::Format_ARGB32;
            }
        }
        else {
            format = QImage::Format_RGB32;
        }
    }
    return format;
}

/*!
 * \brief peekHeader
 * Reads the header but does not change the position in the device.
 */
static bool peekHeader(QIODevice *device, TgaHeader &header)
{
    qint64 oldPos = device->pos();
    QByteArray head = device->read(TgaHeader::SIZE);
    int readBytes = head.size();

    if (device->isSequential()) {
        for (int pos = readBytes - 1; pos >= 0; --pos) {
            device->ungetChar(head[pos]);
        }
    } else {
        device->seek(oldPos);
    }

    if (readBytes < TgaHeader::SIZE) {
        return false;
    }

    QDataStream stream(head);
    stream.setByteOrder(QDataStream::LittleEndian);
    stream >> header;

    return true;
}

static bool LoadTGA(QDataStream &s, const TgaHeader &tga, QImage &img)
{
    img = imageAlloc(tga.width, tga.height, imageFormat(tga));
    if (img.isNull()) {
        qWarning() << "Failed to allocate image, invalid dimensions?" << QSize(tga.width, tga.height);
        return false;
    }

    TgaHeaderInfo info(tga);

    const int numAlphaBits = tga.flags & 0xf;
    uint pixel_size = (tga.pixel_size / 8);
    qint64 size = qint64(tga.width) * qint64(tga.height) * pixel_size;

    if (size < 1) {
        //          qDebug() << "This TGA file is broken with size " << size;
        return false;
    }

    // Read palette.
    static const int max_palette_size = 768;
    char palette[max_palette_size];
    if (info.pal) {
        // @todo Support palettes in other formats!
        const int palette_size = 3 * tga.colormap_length;
        if (palette_size > max_palette_size) {
            return false;
        }
        const int dataRead = s.readRawData(palette, palette_size);
        if (dataRead < 0) {
            return false;
        }
        if (dataRead < max_palette_size) {
            memset(&palette[dataRead], 0, max_palette_size - dataRead);
        }
    }

    // Allocate image.
    uchar *const image = reinterpret_cast<uchar *>(malloc(size));
    if (!image) {
        return false;
    }

    bool valid = true;

    if (info.rle) {
        // Decode image.
        char *dst = (char *)image;
        char *imgEnd = dst + size;
        qint64 num = size;

        while (num > 0 && valid) {
            if (s.atEnd()) {
                valid = false;
                break;
            }

            // Get packet header.
            uchar c;
            s >> c;

            uint count = (c & 0x7f) + 1;
            num -= count * pixel_size;
            if (num < 0) {
                valid = false;
                break;
            }

            if (c & 0x80) {
                // RLE pixels.
                assert(pixel_size <= 8);
                char pixel[8];
                const int dataRead = s.readRawData(pixel, pixel_size);
                if (dataRead < (int)pixel_size) {
                    memset(&pixel[dataRead], 0, pixel_size - dataRead);
                }
                do {
                    if (dst + pixel_size > imgEnd) {
                        qWarning() << "Trying to write out of bounds!" << ptrdiff_t(dst) << (ptrdiff_t(imgEnd) - ptrdiff_t(pixel_size));
                        valid = false;
                        break;
                    }

                    memcpy(dst, pixel, pixel_size);
                    dst += pixel_size;
                } while (--count);
            } else {
                // Raw pixels.
                count *= pixel_size;
                const int dataRead = s.readRawData(dst, count);
                if (dataRead < 0) {
                    free(image);
                    return false;
                }

                if ((uint)dataRead < count) {
                    const size_t toCopy = count - dataRead;
                    if (&dst[dataRead] + toCopy > imgEnd) {
                        qWarning() << "Trying to write out of bounds!" << ptrdiff_t(image) << ptrdiff_t(&dst[dataRead]);
                        ;
                        valid = false;
                        break;
                    }

                    memset(&dst[dataRead], 0, toCopy);
                }
                dst += count;
            }
        }
    } else {
        // Read raw image.
        const int dataRead = s.readRawData((char *)image, size);
        if (dataRead < 0) {
            free(image);
            return false;
        }
        if (dataRead < size) {
            memset(&image[dataRead], 0, size - dataRead);
        }
    }

    if (!valid) {
        free(image);
        return false;
    }

    // Convert image to internal format.
    int y_start;
    int y_step;
    int y_end;
    if (tga.flags & TGA_ORIGIN_UPPER) {
        y_start = 0;
        y_step = 1;
        y_end = tga.height;
    } else {
        y_start = tga.height - 1;
        y_step = -1;
        y_end = -1;
    }

    uchar *src = image;

    for (int y = y_start; y != y_end; y += y_step) {
        QRgb *scanline = (QRgb *)img.scanLine(y);

        if (info.pal) {
            // Paletted.
            for (int x = 0; x < tga.width; x++) {
                uchar idx = *src++;
                scanline[x] = qRgb(palette[3 * idx + 2], palette[3 * idx + 1], palette[3 * idx + 0]);
            }
        } else if (info.grey) {
            // Greyscale.
            for (int x = 0; x < tga.width; x++) {
                scanline[x] = qRgb(*src, *src, *src);
                src++;
            }
        } else {
            // True Color.
            if (tga.pixel_size == 16) {
                for (int x = 0; x < tga.width; x++) {
                    Color555 c = *reinterpret_cast<Color555 *>(src);
                    scanline[x] = qRgb((c.r << 3) | (c.r >> 2), (c.g << 3) | (c.g >> 2), (c.b << 3) | (c.b >> 2));
                    src += 2;
                }
            } else if (tga.pixel_size == 24) {
                for (int x = 0; x < tga.width; x++) {
                    scanline[x] = qRgb(src[2], src[1], src[0]);
                    src += 3;
                }
            } else if (tga.pixel_size == 32) {
                for (int x = 0; x < tga.width; x++) {
                    // ### TODO: verify with images having really some alpha data
                    const uchar alpha = (src[3] << (8 - numAlphaBits));
                    scanline[x] = qRgba(src[2], src[1], src[0], alpha);
                    src += 4;
                }
            }
        }
    }

    // Free image.
    free(image);

    return true;
}

} // namespace

TGAHandler::TGAHandler()
{
}

bool TGAHandler::canRead() const
{
    if (canRead(device())) {
        setFormat("tga");
        return true;
    }
    return false;
}

bool TGAHandler::read(QImage *outImage)
{
    // qDebug() << "Loading TGA file!";

    auto d = device();
    TgaHeader tga;
    if (!peekHeader(d, tga) || !IsSupported(tga)) {
        //         qDebug() << "This TGA file is not valid.";
        return false;
    }

    if (d->isSequential()) {
        d->read(TgaHeader::SIZE + tga.id_length);
    } else {
        d->seek(TgaHeader::SIZE + tga.id_length);
    }

    QDataStream s(d);
    s.setByteOrder(QDataStream::LittleEndian);

    // Check image file format.
    if (s.atEnd()) {
        //         qDebug() << "This TGA file is not valid.";
        return false;
    }

    QImage img;
    bool result = LoadTGA(s, tga, img);

    if (result == false) {
        //         qDebug() << "Error loading TGA file.";
        return false;
    }

    *outImage = img;
    return true;
}

bool TGAHandler::write(const QImage &image)
{
    QDataStream s(device());
    s.setByteOrder(QDataStream::LittleEndian);

    QImage img(image);
    const bool hasAlpha = img.hasAlphaChannel();
    if (hasAlpha && img.format() != QImage::Format_ARGB32) {
        img = img.convertToFormat(QImage::Format_ARGB32);
    } else if (!hasAlpha && img.format() != QImage::Format_RGB32) {
        img = img.convertToFormat(QImage::Format_RGB32);
    }
    if (img.isNull()) {
        qDebug() << "TGAHandler::write: image conversion to 32 bits failed!";
        return false;
    }
    static constexpr quint8 originTopLeft = TGA_ORIGIN_UPPER + TGA_ORIGIN_LEFT; // 0x20
    static constexpr quint8 alphaChannel8Bits = 0x08;

    for (int i = 0; i < 12; i++) {
        s << targaMagic[i];
    }

    // write header
    s << quint16(img.width()); // width
    s << quint16(img.height()); // height
    s << quint8(hasAlpha ? 32 : 24); // depth (24 bit RGB + 8 bit alpha)
    s << quint8(hasAlpha ? originTopLeft + alphaChannel8Bits : originTopLeft);   // top left image (0x20) + 8 bit alpha (0x8)

    for (int y = 0; y < img.height(); y++) {
        auto ptr = reinterpret_cast<QRgb *>(img.scanLine(y));
        for (int x = 0; x < img.width(); x++) {
            auto color = *(ptr + x);
            s << quint8(qBlue(color));
            s << quint8(qGreen(color));
            s << quint8(qRed(color));
            if (hasAlpha) {
                s << quint8(qAlpha(color));
            }
        }
    }

    return true;
}

bool TGAHandler::supportsOption(ImageOption option) const
{
    if (option == QImageIOHandler::Size) {
        return true;
    }
    if (option == QImageIOHandler::ImageFormat) {
        return true;
    }
    return false;
}

QVariant TGAHandler::option(ImageOption option) const
{
    QVariant v;

    if (option == QImageIOHandler::Size) {
        if (auto d = device()) {
            TgaHeader header;
            if (peekHeader(d, header) && IsSupported(header)) {
                v = QVariant::fromValue(QSize(header.width, header.height));
            }
        }
    }

    if (option == QImageIOHandler::ImageFormat) {
        if (auto d = device()) {
            TgaHeader header;
            if (peekHeader(d, header) && IsSupported(header)) {
                v = QVariant::fromValue(imageFormat(header));
            }
        }
    }

    return v;
}

bool TGAHandler::canRead(QIODevice *device)
{
    if (!device) {
        qWarning("TGAHandler::canRead() called with no device");
        return false;
    }

    qint64 oldPos = device->pos();
    QByteArray head = device->read(TgaHeader::SIZE);
    int readBytes = head.size();

    if (device->isSequential()) {
        for (int pos = readBytes - 1; pos >= 0; --pos) {
            device->ungetChar(head[pos]);
        }
    } else {
        device->seek(oldPos);
    }

    if (readBytes < TgaHeader::SIZE) {
        return false;
    }

    TgaHeader tga;
    if (!peekHeader(device, tga)) {
        qWarning("TGAHandler::canRead() error while reading the header");
        return false;
    }

    return IsSupported(tga);
}

QImageIOPlugin::Capabilities TGAPlugin::capabilities(QIODevice *device, const QByteArray &format) const
{
    if (format == "tga") {
        return Capabilities(CanRead | CanWrite);
    }
    if (!format.isEmpty()) {
        return {};
    }
    if (!device->isOpen()) {
        return {};
    }

    Capabilities cap;
    if (device->isReadable() && TGAHandler::canRead(device)) {
        cap |= CanRead;
    }
    if (device->isWritable()) {
        cap |= CanWrite;
    }
    return cap;
}

QImageIOHandler *TGAPlugin::create(QIODevice *device, const QByteArray &format) const
{
    QImageIOHandler *handler = new TGAHandler;
    handler->setDevice(device);
    handler->setFormat(format);
    return handler;
}

#include "moc_tga_p.cpp"
