// Copyright (C) 2018 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only

#include "../shared/examplefw.h"
#include <qmath.h>

QByteArray loadHdr(const QString &fn, QSize *size)
{
    QFile f(fn);
    if (!f.open(QIODevice::ReadOnly)) {
        qWarning("Failed to open %s", qPrintable(fn));
        return QByteArray();
    }

    char sig[256];
    f.read(sig, 11);
    if (strncmp(sig, "#?RADIANCE\n", 11))
        return QByteArray();

    QByteArray buf = f.readAll();
    const char *p = buf.constData();
    const char *pEnd = p + buf.size();

    // Process lines until the empty one.
    QByteArray line;
    while (p < pEnd) {
        char c = *p++;
        if (c == '\n') {
            if (line.isEmpty())
                break;
            if (line.startsWith(QByteArrayLiteral("FORMAT="))) {
                const QByteArray format = line.mid(7).trimmed();
                if (format != QByteArrayLiteral("32-bit_rle_rgbe")) {
                    qWarning("HDR format '%s' is not supported", format.constData());
                    return QByteArray();
                }
            }
            line.clear();
        } else {
            line.append(c);
        }
    }
    if (p == pEnd) {
        qWarning("Malformed HDR image data at property strings");
        return QByteArray();
    }

    // Get the resolution string.
    while (p < pEnd) {
        char c = *p++;
        if (c == '\n')
            break;
        line.append(c);
    }
    if (p == pEnd) {
        qWarning("Malformed HDR image data at resolution string");
        return QByteArray();
    }

    int w = 0, h = 0;
    // We only care about the standard orientation.
    if (!sscanf(line.constData(), "-Y %d +X %d", &h, &w)) {
        qWarning("Unsupported HDR resolution string '%s'", line.constData());
        return QByteArray();
    }
    if (w <= 0 || h <= 0) {
        qWarning("Invalid HDR resolution");
        return QByteArray();
    }

    // output is RGBA32F
    const int blockSize = 4 * sizeof(float);
    QByteArray data;
    data.resize(w * h * blockSize);

    typedef unsigned char RGBE[4];
    RGBE *scanline = new RGBE[w];

    for (int y = 0; y < h; ++y) {
        if (pEnd - p < 4) {
            qWarning("Unexpected end of HDR data");
            delete[] scanline;
            return QByteArray();
        }

        scanline[0][0] = *p++;
        scanline[0][1] = *p++;
        scanline[0][2] = *p++;
        scanline[0][3] = *p++;

        if (scanline[0][0] == 2 && scanline[0][1] == 2 && scanline[0][2] < 128) {
            // new rle, the first pixel was a dummy
            for (int channel = 0; channel < 4; ++channel) {
                for (int x = 0; x < w && p < pEnd; ) {
                    unsigned char c = *p++;
                    if (c > 128) { // run
                        if (p < pEnd) {
                            int repCount = c & 127;
                            c = *p++;
                            while (repCount--)
                                scanline[x++][channel] = c;
                        }
                    } else { // not a run
                        while (c-- && p < pEnd)
                            scanline[x++][channel] = *p++;
                    }
                }
            }
        } else {
            // old rle
            scanline[0][0] = 2;
            int bitshift = 0;
            int x = 1;
            while (x < w && pEnd - p >= 4) {
                scanline[x][0] = *p++;
                scanline[x][1] = *p++;
                scanline[x][2] = *p++;
                scanline[x][3] = *p++;

                if (scanline[x][0] == 1 && scanline[x][1] == 1 && scanline[x][2] == 1) { // run
                    int repCount = scanline[x][3] << bitshift;
                    while (repCount--) {
                        memcpy(scanline[x], scanline[x - 1], 4);
                        ++x;
                    }
                    bitshift += 8;
                } else { // not a run
                    ++x;
                    bitshift = 0;
                }
            }
        }

        // adjust for -Y orientation
        float *fp = reinterpret_cast<float *>(data.data() + (h - 1 - y) * blockSize * w);
        for (int x = 0; x < w; ++x) {
            float d = qPow(2.0f, float(scanline[x][3]) - 128.0f);
            // r, g, b, a
            *fp++ = scanline[x][0] / 256.0f * d;
            *fp++ = scanline[x][1] / 256.0f * d;
            *fp++ = scanline[x][2] / 256.0f * d;
            *fp++ = 1.0f;
        }
    }

    delete[] scanline;

    if (size)
        *size = QSize(w, h);

    return data;
}

static float vertexData[] =
{ // Y up, CCW
  -0.5f,   0.5f,   0.0f, 0.0f,
  -0.5f,  -0.5f,   0.0f, 1.0f,
  0.5f,   -0.5f,   1.0f, 1.0f,
  0.5f,   0.5f,    1.0f, 0.0f
};

static quint16 indexData[] =
{
    0, 1, 2, 0, 2, 3
};

struct {
    QList<QRhiResource *> releasePool;
    QRhiBuffer *vbuf = nullptr;
    QRhiBuffer *ibuf = nullptr;
    QRhiBuffer *ubuf = nullptr;
    QRhiTexture *tex = nullptr;
    QRhiSampler *sampler = nullptr;
    QRhiShaderResourceBindings *srb = nullptr;
    QRhiGraphicsPipeline *ps = nullptr;
    QRhiResourceUpdateBatch *initialUpdates = nullptr;
    QMatrix4x4 winProj;
} d;

void Window::customInit()
{
    if (!m_r->isTextureFormatSupported(QRhiTexture::RGBA32F))
        qWarning("RGBA32F texture format is not supported");

    QSize size;
    QByteArray floatData = loadHdr(QLatin1String(":/OpenfootageNET_fieldairport-512.hdr"), &size);
    Q_ASSERT(!floatData.isEmpty());
    qDebug() << size;

    d.vbuf = m_r->newBuffer(QRhiBuffer::Immutable, QRhiBuffer::VertexBuffer, sizeof(vertexData));
    d.vbuf->create();
    d.releasePool << d.vbuf;

    d.ibuf = m_r->newBuffer(QRhiBuffer::Immutable, QRhiBuffer::IndexBuffer, sizeof(indexData));
    d.ibuf->create();
    d.releasePool << d.ibuf;

    d.ubuf = m_r->newBuffer(QRhiBuffer::Dynamic, QRhiBuffer::UniformBuffer, 68);
    d.ubuf->create();
    d.releasePool << d.ubuf;

    d.tex = m_r->newTexture(QRhiTexture::RGBA32F, size);
    d.releasePool << d.tex;
    d.tex->create();

    d.sampler = m_r->newSampler(QRhiSampler::Linear, QRhiSampler::Linear, QRhiSampler::None,
                                QRhiSampler::ClampToEdge, QRhiSampler::ClampToEdge);
    d.releasePool << d.sampler;
    d.sampler->create();

    d.srb = m_r->newShaderResourceBindings();
    d.releasePool << d.srb;
    d.srb->setBindings({
        QRhiShaderResourceBinding::uniformBuffer(0, QRhiShaderResourceBinding::VertexStage | QRhiShaderResourceBinding::FragmentStage, d.ubuf),
        QRhiShaderResourceBinding::sampledTexture(1, QRhiShaderResourceBinding::FragmentStage, d.tex, d.sampler)
    });
    d.srb->create();

    d.ps = m_r->newGraphicsPipeline();
    d.releasePool << d.ps;
    d.ps->setShaderStages({
        { QRhiShaderStage::Vertex, getShader(QLatin1String(":/texture.vert.qsb")) },
        { QRhiShaderStage::Fragment, getShader(QLatin1String(":/texture.frag.qsb")) }
    });
    QRhiVertexInputLayout inputLayout;
    inputLayout.setBindings({
        { 4 * sizeof(float) }
    });
    inputLayout.setAttributes({
        { 0, 0, QRhiVertexInputAttribute::Float2, 0 },
        { 0, 1, QRhiVertexInputAttribute::Float2, 2 * sizeof(float) }
    });
    d.ps->setVertexInputLayout(inputLayout);
    d.ps->setShaderResourceBindings(d.srb);
    d.ps->setRenderPassDescriptor(m_rp);
    d.ps->create();

    d.initialUpdates = m_r->nextResourceUpdateBatch();
    d.initialUpdates->uploadStaticBuffer(d.vbuf, vertexData);
    d.initialUpdates->uploadStaticBuffer(d.ibuf, indexData);

    qint32 flip = 1;
    d.initialUpdates->updateDynamicBuffer(d.ubuf, 64, 4, &flip);

    QRhiTextureUploadDescription desc({ 0, 0, { floatData.constData(), quint32(floatData.size()) } });
    d.initialUpdates->uploadTexture(d.tex, desc);
}

void Window::customRelease()
{
    qDeleteAll(d.releasePool);
    d.releasePool.clear();
}

void Window::customRender()
{
    QRhiCommandBuffer *cb = m_sc->currentFrameCommandBuffer();
    QRhiResourceUpdateBatch *u = m_r->nextResourceUpdateBatch();
    if (d.initialUpdates) {
        u->merge(d.initialUpdates);
        d.initialUpdates->release();
        d.initialUpdates = nullptr;
    }

    if (d.winProj != m_proj) {
        d.winProj = m_proj;
        QMatrix4x4 mvp = m_proj;
        mvp.scale(2.5f);
        u->updateDynamicBuffer(d.ubuf, 0, 64, mvp.constData());
    }

    const QSize outputSizeInPixels = m_sc->currentPixelSize();
    cb->beginPass(m_sc->currentFrameRenderTarget(), m_clearColor, { 1.0f, 0 }, u);
    cb->setGraphicsPipeline(d.ps);
    cb->setViewport({ 0, 0, float(outputSizeInPixels.width()), float(outputSizeInPixels.height()) });
    cb->setShaderResources();
    const QRhiCommandBuffer::VertexInput vbufBinding(d.vbuf, 0);
    cb->setVertexInput(0, 1, &vbufBinding, d.ibuf, 0, QRhiCommandBuffer::IndexUInt16);
    cb->drawIndexed(6);
    cb->endPass();
}
