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#include "shadercache_p.h"

#include <QtCore/QMutexLocker>

QT_BEGIN_NAMESPACE

namespace Qt3DRender {
namespace Render {

/*!
 * \internal
 *
 * Destroys the ShaderCache and deletes all cached QOpenGLShaderPrograms
 */
ShaderCache::~ShaderCache()
{
    qDeleteAll(m_programHash);
}

/*!
 * \internal
 *
 * Looks up the QOpenGLShaderProgram corresponding to \a dna. Also checks to see if the cache
 * contains a reference to this shader program from the Shader with peerId of \a shaderPeerId.
 * If there is no existing reference for \a shaderPeerId, one is recorded.
 *
 * \return A pointer to the shader program if it is cached, nullptr otherwise
 */
QOpenGLShaderProgram *ShaderCache::getShaderProgramAndAddRef(ProgramDNA dna, Qt3DCore::QNodeId shaderPeerId, bool *wasPresent)
{
    auto shaderProgram = m_programHash.constFind(dna);

    // Some callers may wish to differentiate between a result of null due to
    // not having anything in the cache and a result of null due to the cache
    // containing a program the shaders of which failed to compile.
    if (wasPresent)
        *wasPresent = shaderProgram != m_programHash.constEnd();

    if (shaderProgram != m_programHash.constEnd()) {
        // Ensure we store the fact that shaderPeerId references this shader
        QMutexLocker lock(&m_refsMutex);
        QVector<Qt3DCore::QNodeId> &programRefs = m_programRefs[dna];
        auto it = std::lower_bound(programRefs.begin(), programRefs.end(), shaderPeerId);
        if (*it != shaderPeerId)
            programRefs.insert(it, shaderPeerId);

        m_pendingRemoval.removeOne(dna);

        return *shaderProgram;
    }

    return nullptr;
}

/*!
 * \internal
 *
 * Inserts the \a program in the cache indexed by \a dna and adds a reference to it from
 * \a shaderPeerId. The cache takes ownership of the \a program.
 */
void ShaderCache::insert(ProgramDNA dna, Qt3DCore::QNodeId shaderPeerId, QOpenGLShaderProgram *program)
{
    Q_ASSERT(!m_programHash.contains(dna));
    m_programHash.insert(dna, program);
    QMutexLocker lock(&m_refsMutex);
    Q_ASSERT(!m_programRefs.contains(dna));
    QVector<Qt3DCore::QNodeId> programRefs;
    programRefs.push_back(shaderPeerId);
    m_programRefs.insert(dna, programRefs);
}

/*!
 * \internal
 *
 * Removes a reference to the shader program indexed by \a dna from the Shader with peerId of
 * \a shaderPeerId. If this was the last reference, the dna and corresponding shader are added
 * to a list of items to be removed by the next call to purge.
 */
void ShaderCache::removeRef(ProgramDNA dna, Qt3DCore::QNodeId shaderPeerId)
{
    QMutexLocker lock(&m_refsMutex);
    auto it = m_programRefs.find(dna);
    if (it != m_programRefs.end()) {
        QVector<Qt3DCore::QNodeId> &programRefs = it.value();
        programRefs.removeOne(shaderPeerId);
        if (programRefs.isEmpty())
            m_pendingRemoval.append(dna);
    }
}

/*!
 * \internal
 *
 * Iterates through a list of program dna's and checks to see if they still have no references
 * from Shaders. If so, the dna and corresponding QOpenGLShaderProgram are removed from the cache.
 */
void ShaderCache::purge()
{
    QMutexLocker lock(&m_refsMutex);
    for (const ProgramDNA &dna : qAsConst(m_pendingRemoval)) {
        QVector<Qt3DCore::QNodeId> &programRefs = m_programRefs[dna];
        if (programRefs.isEmpty()) {
            delete m_programHash.take(dna);
            m_programRefs.remove(dna);
        }
    }

    m_pendingRemoval.clear();
}

/*!
 * \internal
 *
 * Deletes all cached shader programs and removes any references
 */
void ShaderCache::clear()
{
    QMutexLocker lock(&m_refsMutex);
    qDeleteAll(m_programHash);
    m_programHash.clear();
    m_programRefs.clear();
    m_pendingRemoval.clear();
}

QOpenGLShaderProgram *ShaderCache::getShaderProgramForDNA(ProgramDNA dna) const
{
    return m_programHash.value(dna, nullptr);
}

QVector<Qt3DCore::QNodeId> ShaderCache::shaderIdsForProgram(ProgramDNA dna) const
{
    return m_programRefs.value(dna);
}

} // namespace Render
} // namespace Qt3DRender

QT_END_NAMESPACE