/****************************************************************************
**
** Copyright (C) 2012 Nokia Corporation and/or its subsidiary(-ies).
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** This file is part of the Declarative module of the Qt Toolkit.
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** file. Please review the following information to ensure the GNU Lesser
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** Alternatively, this file may be used under the terms of the GNU General
** Public License version 3.0 as published by the Free Software Foundation
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** file. Please review the following information to ensure the GNU General
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****************************************************************************/

#include "qetcprovider.h"

#include <QtDebug>
#include <QFile>

#include <qopenglfunctions.h>
#include <qopenglcontext.h>

QT_BEGIN_NAMESPACE

typedef struct {
    char aName[6];
    unsigned short iBlank;
    /* NB: Beware endianess issues here. */
    unsigned char iPaddedWidthMSB;
    unsigned char iPaddedWidthLSB;
    unsigned char iPaddedHeightMSB;
    unsigned char iPaddedHeightLSB;
    unsigned char iWidthMSB;
    unsigned char iWidthLSB;
    unsigned char iHeightMSB;
    unsigned char iHeightLSB;
} ETCHeader;


unsigned short getWidth(ETCHeader *pHeader)
{
    return (pHeader->iWidthMSB << 8) | pHeader->iWidthLSB;
}

unsigned short getHeight(ETCHeader *pHeader)
{
    return (pHeader->iHeightMSB << 8) | pHeader->iHeightLSB;
}

unsigned short getPaddedWidth(ETCHeader *pHeader)
{
    return (pHeader->iPaddedWidthMSB << 8) | pHeader->iPaddedWidthLSB;
}

unsigned short getPaddedHeight(ETCHeader *pHeader)
{
    return (pHeader->iPaddedHeightMSB << 8) | pHeader->iPaddedHeightLSB;
}

enum {GL_ETC1_RGB8_OES=0x8d64};

EtcTexture::EtcTexture()
    : m_texture_id(0)
{

}

EtcTexture::~EtcTexture()
{
    if (m_texture_id)
        glDeleteTextures(1, &m_texture_id);
}


void EtcTexture::bind()
{
    if (m_texture_id) {
        glBindTexture(GL_TEXTURE_2D, m_texture_id);
        return;
    }

#ifdef ETC_DEBUG
    printf("EtcTextureProvider: about to update that texture...\n");
#endif

    glGenTextures(1, &m_texture_id);

    glBindTexture(GL_TEXTURE_2D, m_texture_id);

#ifdef ETC_DEBUG
    qDebug() << "glCompressedTexImage2D, width: " << m_size.width() << "height" << m_size.height() <<
                "paddedWidth: " << m_paddedSize.width() << "paddedHeight: " << m_paddedSize.height();
#endif

    QOpenGLContext *ctx = QOpenGLContext::currentContext();
    Q_ASSERT(ctx != 0);
    ctx->functions()->glCompressedTexImage2D(GL_TEXTURE_2D, 0, GL_ETC1_RGB8_OES,
                                             m_size.width(), m_size.height(), 0,
                                             (m_paddedSize.width() * m_paddedSize.height()) >> 1,
                                             m_data.data() + 16);

    // Gracefully fail in case of an error...
    GLuint error = glGetError();
    if (error != GL_NO_ERROR) {
        qDebug () << "glCompressedTexImage2D for compressed texture failed, error: " << error;
        glBindTexture(GL_TEXTURE_2D, 0);
        glDeleteTextures(1, &m_texture_id);
        m_texture_id = 0;
        return;
    }
    updateBindOptions(true);
}

QSize EtcTexture::textureSize() const
{
    return m_size;
}


class QEtcTextureFactory : public QDeclarativeTextureFactory
{
public:
    QByteArray m_data;
    QSize m_size;
    QSize m_paddedSize;

    QSize textureSize() const {
        return m_size;
    }

    int textureByteCount() const {
        return m_data.size();
    }

    QSGTexture *createTexture() const {
        EtcTexture *texture = new EtcTexture;
        texture->m_data = m_data;
        texture->m_size = m_size;
        texture->m_paddedSize = m_paddedSize;
        return texture;
    }

};


QDeclarativeTextureFactory *QEtcProvider::requestTexture(const QString &id, QSize *size, const QSize &requestedSize)
{
    Q_UNUSED(requestedSize);
    QEtcTextureFactory *ret = 0;

    size->setHeight(0);
    size->setWidth(0);

    QFile file(id);
#ifdef ETC_DEBUG
    qDebug() << "requestTexture opening file: " << id;
#endif
    if (file.open(QIODevice::ReadOnly)) {
        ret = new QEtcTextureFactory;
        ret->m_data = file.readAll();
        if (!ret->m_data.isEmpty()) {
            ETCHeader *pETCHeader = NULL;
            pETCHeader = (ETCHeader *)ret->m_data.data();
            size->setHeight(getHeight(pETCHeader));
            size->setWidth(getWidth(pETCHeader));
            ret->m_size = *size;
            ret->m_paddedSize.setHeight(getPaddedHeight(pETCHeader));
            ret->m_paddedSize.setWidth(getPaddedWidth(pETCHeader));
        }
        else {
            delete ret;
            ret = 0;
        }
    }

#ifdef ETC_DEBUG
    if (ret)
        qDebug() << "requestTexture returning: " << ret->m_data.length() << ", bytes; width: " << size->width() << ", height: " << size->height();
    else
        qDebug () << "File not found.";
#endif

    return ret;
}

QT_END_NAMESPACE