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** Copyright (C) 2019 The Qt Company Ltd.
** Contact: https://www.qt.io/licensing/
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** This file is part of Qt Quick 3D.
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** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3 or (at your option) any later version
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** the Free Software Foundation and appearing in the file LICENSE.GPL3
** included in the packaging of this file. Please review the following
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#include "qssgrendershadermetadata_p.h"

#include <QPair>
#include <QJsonDocument>
#include <QJsonArray>
#include <QJsonObject>
#include <QJsonValue>

#include <QtDebug>

// Example snippet based on viewProperties.glsllib
// The comment in the ifdefed block is necessary to keep weird shader compilers (Vivante) happy.

// #ifdef QQ3D_SHADER_META
// /*{
//    "uniforms": [ { "type": "mat44", "name": "qt_viewProjectionMatrix" },
//                  { "type": "mat4", "name": "qt_viewMatrix" },
//                  { "type": "vec2", "name": "qt_cameraProperties" },
//                  { "type": "vec3", "name": "qt_cameraPosition", "condition": "!SSAO_CUSTOM_MATERIAL_GLSLLIB" }
//    ]
// }*/
// #endif // QQ3D_SHADER_META

namespace QSSGRenderShaderMetadata {

const char *shaderMetaStart() { return "#ifdef QQ3D_SHADER_META"; }
const char *shaderMetaEnd() { return "#endif"; }

Uniform::Condition Uniform::conditionFromString(const QString &condition)
{
    if (condition.isEmpty())
        return Uniform::Condition::None;

    if (condition.at(0) == QChar::fromLatin1('!'))
        return Uniform::Negated;

    return Uniform::Regular;
}

QSSGShaderGeneratorStage InputOutput::stageFromString(const QString &stage)
{
    if (stage == QLatin1String("vertex")) {
        return QSSGShaderGeneratorStage::Vertex;
    } else if (stage == QLatin1String("fragment"))
        return QSSGShaderGeneratorStage::Fragment;
    else {
        qWarning("Unknown stage in shader metadata: %s, assuming vertex", qPrintable(stage));
        return QSSGShaderGeneratorStage::Vertex;
    }
}

ShaderMetaData getShaderMetaData(const QByteArray &data)
{
    ShaderMetaData result;
    if (data.isEmpty())
        return result;

    int jsonStart = 0, jsonEnd = 0;
    for ( ; ; ) {
        jsonStart = data.indexOf(shaderMetaStart(), jsonEnd);
        if (jsonStart)
            jsonEnd = data.indexOf(shaderMetaEnd(), jsonStart);

        if (jsonEnd) // adjust start position
            jsonStart += int(strlen(shaderMetaStart()));

        if (jsonStart <= 0 || jsonEnd <= 0)
            break;

        const int size = jsonEnd - jsonStart;
        // /*{"inputs":[]}*/ => 17
        if (size < 17) {
            qWarning("Shader metadata section found, but content to small to be valid!");
            break;
        }

        QByteArray jsonData = data.mid(jsonStart, size).trimmed();
        if (!jsonData.startsWith(QByteArrayLiteral("/*{"))) {
            qWarning("Missing /*{ prefix");
            break;
        }
        if (!jsonData.endsWith(QByteArrayLiteral("}*/"))) {
            qWarning("Missing }*/ suffix");
            break;
        }
        jsonData = jsonData.mid(2, jsonData.count() - 4);

        QJsonParseError error;
        const auto doc = QJsonDocument::fromJson(jsonData, &error);
        if (error.error != QJsonParseError::NoError) {
            qWarning() << "Shader metadata parse error at offset: " << error.offset;
            break;
        }

        static const auto toUniform = [](const QJsonObject &uObj) {
            Uniform uniform;
            auto it = uObj.constBegin();
            const auto end = uObj.constEnd();
            if (it != end) {
                it = uObj.constFind(QLatin1String("type"));
                uniform.type = (it != end) ? it->toString().toLatin1() : QByteArray();
                it = uObj.constFind(QLatin1String("name"));
                uniform.name = (it != end) ? it->toString().toLatin1() : QByteArray();

                it = uObj.constFind(QLatin1String("condition"));
                const QString conditionString = (it != end) ? it->toString() : QString();
                uniform.condition = Uniform::conditionFromString(conditionString);
                if (uniform.condition == Uniform::Negated)
                    uniform.conditionName = conditionString.mid(1).toLatin1();
                else if (uniform.condition == Uniform::Regular)
                    uniform.conditionName = conditionString.toLatin1();
            }
            return uniform;
        };

        static const auto toInputOutput = [](const QJsonObject &uObj) {
            InputOutput inOutVar;
            auto it = uObj.constBegin();
            const auto end = uObj.constEnd();
            if (it != end) {
                it = uObj.constFind(QLatin1String("type"));
                inOutVar.type = (it != end) ? it->toString().toLatin1() : QByteArray();
                it = uObj.constFind(QLatin1String("name"));
                inOutVar.name = (it != end) ? it->toString().toLatin1() : QByteArray();
                it = uObj.constFind(QLatin1String("stage"));
                inOutVar.stage = InputOutput::stageFromString((it != end) ? it->toString() : QString());
            }
            return inOutVar;
        };

        const QJsonObject obj = doc.object();
        auto it = obj.constBegin();
        const auto end = obj.constEnd();
        if (it != end) {
            // Uniforms
            it = obj.constFind(QLatin1String("uniforms"));
            if (it != obj.constEnd()) {
                // Check if it's an array or a single object
                if (it->type() == QJsonValue::Array) {
                    const auto uniformArray = it->toArray();
                    for (const auto valueRef : uniformArray) {
                        if (!valueRef.isObject())
                            continue;

                        const QJsonObject obj = valueRef.toObject();
                        const auto uniform = toUniform(obj);
                        if (!uniform.type.isEmpty() && !uniform.name.isEmpty()) {
                            result.uniforms.push_back(uniform);
                        } else {
                            qWarning("Invalid uniform, skipping");
                        }
                    }
                } else if (it->type() == QJsonValue::Object) {
                    const auto uniform = toUniform(it->toObject());
                    if (!uniform.type.isEmpty() && !uniform.name.isEmpty())
                        result.uniforms.push_back(uniform);
                    else
                        qWarning("Invalid uniform, skipping");
                }
            }

            // Inputs
            it = obj.constFind(QLatin1String("inputs"));
            if (it != end) {
                if (it->type() == QJsonValue::Array) {
                    for (const auto valueRef : it->toArray()) {
                        if (!valueRef.isObject())
                            continue;
                        const auto inOutVar = toInputOutput(valueRef.toObject());
                        if (!inOutVar.type.isEmpty() && !inOutVar.name.isEmpty())
                            result.inputs.push_back(inOutVar);
                        else
                            qWarning("Invalid input variable, skipping");
                    }
                } else if (it->type() == QJsonValue::Object) {
                    const QJsonObject obj = it->toObject();
                    const auto inOutVar = toInputOutput(obj);
                    if (!inOutVar.type.isEmpty() && !inOutVar.name.isEmpty()) {
                        result.inputs.push_back(inOutVar);
                    } else {
                        qWarning("Invalid input variable, skipping");
                    }
                }
            }

            // Outputs
            it = obj.constFind(QLatin1String("outputs"));
            if (it != end) {
                if (it->type() == QJsonValue::Array) {
                    for (const auto valueRef : it->toArray()) {
                        if (!valueRef.isObject())
                            continue;
                        const auto inOutVar = toInputOutput(valueRef.toObject());
                        if (!inOutVar.type.isEmpty() && !inOutVar.name.isEmpty())
                            result.outputs.push_back(inOutVar);
                        else
                            qWarning("Invalid output variable, skipping");
                    }
                } else if (it->type() == QJsonValue::Object) {
                    const QJsonObject inputJObj = it->toObject();
                    const auto inOutVar = toInputOutput(inputJObj);
                    if (!inOutVar.type.isEmpty() && !inOutVar.name.isEmpty()) {
                        result.outputs.push_back(inOutVar);
                    } else {
                        qWarning("Invalid output variable, skipping");
                    }
                }
            }
        }
    }

    return result;
}

} // namespace