/* This file is part of the KDE project
   Copyright (C) 2003 Dominik Seichter <domseichter@web.de>
   Copyright (C) 2004 Ignacio Castaño <castano@ludicon.com>

   This program is free software; you can redistribute it and/or
   modify it under the terms of the Lesser GNU General Public
   License as published by the Free Software Foundation; either
   version 2 of the License, or (at your option) any later version.
*/

/* 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, 15, 24 and 32.
 * writing:
 *     uncompressed true color tga files
 */

#include "tga.h"

#include <assert.h>

#include <QtGui/QImage>
#include <QtCore/QDataStream>

#include <kdebug.h>

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 )
			{
				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;
		}
		return true;
	}

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

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

		TgaHeaderInfo( const TgaHeader & tga ) : rle(false), pal(false), rgb(false), grey(false), supported(true)
		{
			switch( tga.image_type ) {
				case TGA_TYPE_RLE_INDEXED:
					rle = true;
					// no break is intended!
				case TGA_TYPE_INDEXED:
					if( tga.colormap_type!=1 || tga.colormap_size!=24 || tga.colormap_length>256 ) {
						supported = false;
					}
					pal = true;
					break;

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

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

				default:
					// Error, unknown image type.
					supported = false;
			}
		}
	};



	static bool LoadTGA( QDataStream & s, const TgaHeader & tga, QImage &img )
	{
		// Create image.
		img = QImage( tga.width, tga.height, QImage::Format_RGB32 );

		TgaHeaderInfo info(tga);
		if( !info.supported ) {
			// File not supported.
  			kDebug(399) << "This TGA file is not supported.";
			return false;
		}

                // Bits 0-3 are the numbers of alpha bits (can be zero!)
                const int numAlphaBits = tga.flags & 0xf;
                // However alpha exists only in the 32 bit format.
		if( ( tga.pixel_size == 32 ) && ( tga.flags & 0xf ) ) {
			img = QImage( tga.width, tga.height, QImage::Format_ARGB32 );
		}

		uint pixel_size = (tga.pixel_size/8);
		uint size = tga.width * tga.height * pixel_size;

		if (size < 1)
		{
			kDebug(399) << "This TGA file is broken with size " << size;
			return false;
		}

		// Read palette.
		char palette[768];
		if( info.pal ) {
			// @todo Support palettes in other formats!
			s.readRawData( palette, 3 * tga.colormap_length );
		}

		// Allocate image.
		uchar * const image = new uchar[size];

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

			while (num > 0) {
				// Get packet header.
				uchar c;
				s >> c;

				uint count = (c & 0x7f) + 1;
				num -= count * pixel_size;

				if (c & 0x80) {
					// RLE pixels.
                                        assert(pixel_size <= 8);
					char pixel[8];
					s.readRawData( pixel, pixel_size );
					do {
						memcpy(dst, pixel, pixel_size);
						dst += pixel_size;
					} while (--count);
				}
				else {
					// Raw pixels.
					count *= pixel_size;
					s.readRawData( dst, count );
					dst += count;
				}
			}
		}
		else {
			// Read raw image.
			s.readRawData( (char *)image, size );
		}

		// Convert image to internal format.
		int y_start, y_step, 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.
		delete [] image;

		return true;
	}

} // namespace


TGAHandler::TGAHandler()
{
}

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

bool TGAHandler::read(QImage *outImage)
{
    //kDebug(399) << "Loading TGA file!";

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


    // Read image header.
    TgaHeader tga;
    s >> tga;
    s.device()->seek( TgaHeader::SIZE + tga.id_length );

    // Check image file format.
    if( s.atEnd() ) {
        kDebug(399) << "This TGA file is not valid.";
        return false;
    }

    // Check supported file types.
    if( !IsSupported(tga) ) {
        kDebug(399) << "This TGA file is not supported.";
        return false;
    }


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

    if( result == false ) {
        kDebug(399) << "Error loading TGA file.";
        return false;
    }


    *outImage = img;
    return true;
}

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

    const QImage& img = image;
    const bool hasAlpha = (img.format() == QImage::Format_ARGB32);
    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 ? 0x24 : 0x20 ); // top left image (0x20) + 8 bit alpha (0x4)

    for( int y = 0; y < img.height(); y++ )
        for( int x = 0; x < img.width(); x++ ) {
            const QRgb color = img.pixel( x, y );
            s << quint8( qBlue( color ) );
            s << quint8( qGreen( color ) );
            s << quint8( qRed( color ) );
            if( hasAlpha )
                s << quint8( qAlpha( color ) );
        }

    return true;
}

QByteArray TGAHandler::name() const
{
    return "tga";
}

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

    qint64 oldPos = device->pos();
    QByteArray head = device->readLine(64);
    int readBytes = head.size();

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

    const QRegExp regexp("^.\x01[\x01-\x03\x09-\x0b]\x01{3}.[\x01\x18]");
    QString data(head);

    return data.contains(regexp);
}


class TGAPlugin : public QImageIOPlugin
{
public:
    QStringList keys() const;
    Capabilities capabilities(QIODevice *device, const QByteArray &format) const;
    QImageIOHandler *create(QIODevice *device, const QByteArray &format = QByteArray()) const;
};

QStringList TGAPlugin::keys() const
{
    return QStringList() << "tga" << "TGA";
}

QImageIOPlugin::Capabilities TGAPlugin::capabilities(QIODevice *device, const QByteArray &format) const
{
    if (format == "tga" || format == "TGA")
        return Capabilities(CanRead | CanWrite);
    if (!format.isEmpty())
        return 0;
    if (!device->isOpen())
        return 0;

    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;
}

Q_EXPORT_STATIC_PLUGIN(TGAPlugin)
Q_EXPORT_PLUGIN2(tga, TGAPlugin)
