/*
    SPDX-FileCopyrightText: 2017 Nicolas Carion
    SPDX-License-Identifier: GPL-3.0-only OR LicenseRef-KDE-Accepted-GPL
*/

#include "thumbnailcache.hpp"
#include "bin/projectclip.h"
#include "bin/projectitemmodel.h"
#include "core.h"
#include "doc/kdenlivedoc.h"
#include "project/projectmanager.h"
#include <QDir>
#include <QMutexLocker>
#include <list>

std::unique_ptr<ThumbnailCache> ThumbnailCache::instance;
std::once_flag ThumbnailCache::m_onceFlag;

class ThumbnailCache::Cache_t
{
public:
    Cache_t(int maxCost)
        : m_maxCost(maxCost)
    {
    }

    bool contains(const QString &key) const { return m_cache.count(key) > 0; }

    void remove(const QString &key)
    {
        if (!contains(key)) {
            return;
        }
        auto it = m_cache.at(key);
        m_currentCost -= (*it).second.second;
        // Need to erase reference to iterator before erasing what it points to.
        // Fixes BUG 463764.
        m_cache.erase(key);
        m_data.erase(it);
    }

    void insert(const QString &key, const QImage &img, int cost)
    {
        if (cost > m_maxCost) {
            return;
        }
        m_data.push_front({key, {img, cost}});
        auto it = m_data.begin();
        m_cache[key] = it;
        m_currentCost += cost;
        while (m_currentCost > m_maxCost) {
            remove(m_data.back().first);
        }
    }

    QImage get(const QString &key)
    {
        if (!contains(key)) {
            return QImage();
        }
        // when a get operation occurs, we put the corresponding list item in front to remember last access
        std::pair<QString, std::pair<QImage, int>> data;
        auto it = m_cache.at(key);
        std::swap(data, (*it));                                         // take data out without copy
        QImage result = data.second.first;                              // a copy occurs here
        m_data.erase(it);                                               // delete old iterator
        m_cache[key] = m_data.emplace(m_data.begin(), std::move(data)); // reinsert without copy and store iterator
        return result;
    }
    void clear()
    {
        m_data.clear();
        m_cache.clear();
        m_currentCost = 0;
    }
    bool checkIntegrity() const
    {
        if (m_data.size() != m_cache.size()) {
            // Cache is corrupted
            return false;
        }
        for (const auto &d : m_data) {
            if (!contains(d.first)) {
                return false;
            }
        }
        return true;
    }

protected:
    int m_maxCost;
    int m_currentCost{0};

    // The data is stored as (key,(image, cost)) in a std::list that serves as a
    // FIFO queue. If m_maxCost is exceeded, elements are removed from the
    // end of the list until the sum of the costs in the list is less than m_maxCost.
    std::list<std::pair<QString, std::pair<QImage, int>>> m_data;
    // m_cache keeps a mapping from the key to an iterator that represents the
    // item's location in m_data, like a pointer.
    std::unordered_map<QString, decltype(m_data.begin())> m_cache;
};

ThumbnailCache::ThumbnailCache()
    : m_volatileCache(new Cache_t(10000000))
{
}

std::unique_ptr<ThumbnailCache> &ThumbnailCache::get()
{
    std::call_once(m_onceFlag, [] { instance.reset(new ThumbnailCache()); });
    return instance;
}

bool ThumbnailCache::hasThumbnail(const QString &binId, int pos, bool volatileOnly) const
{
    QMutexLocker locker(&m_mutex);
    bool ok = false;
    auto key = pos < 0 ? getAudioKey(binId, &ok).constFirst() : getKey(binId, pos, &ok);
    if (ok && m_volatileCache->contains(key)) {
        return true;
    }
    if (!ok || volatileOnly) {
        return false;
    }
    locker.unlock();
    QDir thumbFolder = getDir(pos < 0, &ok);
    return ok && thumbFolder.exists(key);
}

QImage ThumbnailCache::getAudioThumbnail(const QString &binId, bool volatileOnly) const
{
    QMutexLocker locker(&m_mutex);
    bool ok = false;
    auto key = getAudioKey(binId, &ok).constFirst();
    if (ok && m_volatileCache->contains(key)) {
        return m_volatileCache->get(key);
    }
    if (!ok || volatileOnly) {
        return QImage();
    }
    QDir thumbFolder = getDir(true, &ok);
    if (ok && thumbFolder.exists(key)) {
        if (std::find(m_storedOnDisk[binId].begin(), m_storedOnDisk[binId].end(), -1) != m_storedOnDisk[binId].end()) {
            m_storedOnDisk[binId].push_back(-1);
        }
        locker.unlock();
        return QImage(thumbFolder.absoluteFilePath(key));
    }
    return QImage();
}

const QList<QUrl> ThumbnailCache::getAudioThumbPath(const QString &binId) const
{
    bool ok = false;
    auto key = getAudioKey(binId, &ok);
    QDir thumbFolder = getDir(true, &ok);
    QList<QUrl> pathList;
    if (ok) {
        for (const QString &p : qAsConst(key)) {
            if (thumbFolder.exists(p)) {
                pathList << QUrl::fromLocalFile(thumbFolder.absoluteFilePath(p));
            }
        }
    }
    return pathList;
}

QImage ThumbnailCache::getThumbnail(QString hash, const QString &binId, int pos, bool volatileOnly) const
{
    if (hash.isEmpty()) {
        return QImage();
    }
    hash.append(QString("#%1.jpg").arg(pos));
    QMutexLocker locker(&m_mutex);
    if (m_volatileCache->contains(hash)) {
        return m_volatileCache->get(hash);
    }
    if (volatileOnly) {
        return QImage();
    }
    bool ok = false;
    QDir thumbFolder = getDir(false, &ok);
    if (ok && thumbFolder.exists(hash)) {
        if (m_storedOnDisk.find(binId) == m_storedOnDisk.end() ||
            std::find(m_storedOnDisk[binId].begin(), m_storedOnDisk[binId].end(), pos) == m_storedOnDisk[binId].end()) {
            m_storedOnDisk[binId].push_back(pos);
        }
        locker.unlock();
        return QImage(thumbFolder.absoluteFilePath(hash));
    }
    locker.unlock();
    return QImage();
}

QImage ThumbnailCache::getThumbnail(const QString &binId, int pos, bool volatileOnly) const
{
    QMutexLocker locker(&m_mutex);
    bool ok = false;
    auto key = getKey(binId, pos, &ok);
    if (ok && m_volatileCache->contains(key)) {
        return m_volatileCache->get(key);
    }
    if (!ok || volatileOnly) {
        return QImage();
    }
    QDir thumbFolder = getDir(false, &ok);
    if (ok && thumbFolder.exists(key)) {
        if (m_storedOnDisk.find(binId) == m_storedOnDisk.end() ||
            std::find(m_storedOnDisk[binId].begin(), m_storedOnDisk[binId].end(), pos) == m_storedOnDisk[binId].end()) {
            m_storedOnDisk[binId].push_back(pos);
        }
        locker.unlock();
        return QImage(thumbFolder.absoluteFilePath(key));
    }
    return QImage();
}

void ThumbnailCache::storeThumbnail(const QString &binId, int pos, const QImage &img, bool persistent)
{
    QMutexLocker locker(&m_mutex);
    bool ok = false;
    const QString key = getKey(binId, pos, &ok);
    if (!ok) {
        return;
    }
    // if volatile cache also contains this entry, update it
    if (m_volatileCache->contains(key)) {
        m_volatileCache->remove(key);
    } else {
        m_storedVolatile[binId].push_back(pos);
    }
    m_volatileCache->insert(key, img, (int)img.sizeInBytes());
    if (persistent) {
        QDir thumbFolder = getDir(false, &ok);
        if (ok) {
            if (m_storedOnDisk.find(binId) == m_storedOnDisk.end() ||
                std::find(m_storedOnDisk[binId].begin(), m_storedOnDisk[binId].end(), pos) == m_storedOnDisk[binId].end()) {
                m_storedOnDisk[binId].push_back(pos);
            }
            locker.unlock();
            if (!img.save(thumbFolder.absoluteFilePath(key))) {
                qDebug() << ".............\n!!!!!!!! ERROR SAVING THUMB in: " << thumbFolder.absoluteFilePath(key);
            }
        }
    }
}

bool ThumbnailCache::checkIntegrity() const
{
    return m_volatileCache->checkIntegrity();
}

void ThumbnailCache::saveCachedThumbs(const std::unordered_map<QString, std::vector<int>> &keys)
{
    bool ok;
    QDir thumbFolder = getDir(false, &ok);
    if (!ok) {
        return;
    }
    QMutexLocker locker(&m_mutex);
    for (auto &key : keys) {
        bool ok;
        for (const auto &pos : key.second) {
            if (m_storedOnDisk.find(key.first) == m_storedOnDisk.end() ||
                std::find(m_storedOnDisk[key.first].begin(), m_storedOnDisk[key.first].end(), pos) == m_storedOnDisk[key.first].end()) {
                const QString thumbKey = getKey(key.first, pos, &ok);
                if (!ok) {
                    continue;
                }
                if (!thumbFolder.exists(thumbKey) && m_volatileCache->contains(thumbKey)) {
                    QImage img = m_volatileCache->get(thumbKey);
                    if (!img.save(thumbFolder.absoluteFilePath(thumbKey))) {
                        qDebug() << "// Error writing thumbnails to " << thumbFolder.absolutePath();
                        break;
                    } else {
                        m_storedOnDisk[key.first].push_back(pos);
                    }
                }
            }
        }
    }
}

void ThumbnailCache::invalidateThumbsForClip(const QString &binId)
{
    QMutexLocker locker(&m_mutex);
    if (m_storedVolatile.find(binId) != m_storedVolatile.end()) {
        bool ok = false;
        for (int pos : m_storedVolatile.at(binId)) {
            auto key = getKey(binId, pos, &ok);
            if (ok) {
                m_volatileCache->remove(key);
            }
        }
        m_storedVolatile.erase(binId);
    }
    bool ok = false;
    // Video thumbs
    QStringList files;
    if (m_storedOnDisk.find(binId) != m_storedOnDisk.end()) {
        // Remove persistent cache
        for (const auto &pos : m_storedOnDisk.at(binId)) {
            if (pos >= 0) {
                auto key = getKey(binId, pos, &ok);
                if (ok) {
                    files << key;
                }
            }
        }
        m_storedOnDisk.erase(binId);
    }
    // Release mutex before deleting files
    locker.unlock();
    if (!files.isEmpty()) {
        QDir thumbFolder = getDir(false, &ok);
        if (ok) {
            while (!files.isEmpty()) {
                thumbFolder.remove(files.takeFirst());
            }
        }
    }
}

void ThumbnailCache::clearCache()
{
    QMutexLocker locker(&m_mutex);
    m_volatileCache->clear();
    m_storedVolatile.clear();
    m_storedOnDisk.clear();
}

// static
QString ThumbnailCache::getKey(const QString &binId, int pos, bool *ok)
{
    if (binId.isEmpty()) {
        *ok = false;
        return QString();
    }
    auto binClip = pCore->projectItemModel()->getClipByBinID(binId);
    *ok = binClip != nullptr && binClip->statusReady();
    if (!*ok) {
        return QString();
    }
    return binClip->hashForThumbs() + QLatin1Char('#') + QString::number(pos) + QStringLiteral(".jpg");
}

// static
QStringList ThumbnailCache::getAudioKey(const QString &binId, bool *ok)
{
    auto binClip = pCore->projectItemModel()->getClipByBinID(binId);
    if (binClip == nullptr) {
        *ok = false;
        qWarning() << "[BUG] Could not find binClip for binId" << binId;
        return {};
    } else {
        *ok = true;
        QString streams = binClip->getProducerProperty(QStringLiteral("kdenlive:active_streams"));
        if (streams == QString::number(INT_MAX)) {
            // activate all audio streams
            QList<int> streamIxes = binClip->audioStreams().keys();
            if (streamIxes.size() > 1) {
                QStringList streamsList;
                for (const int st : qAsConst(streamIxes)) {
                    streamsList << QString("%1_%2.png").arg(binClip->hash()).arg(st);
                }
                return streamsList;
            }
        }
        if (streams.size() < 2) {
            int audio = binClip->getProducerIntProperty(QStringLiteral("audio_index"));
            if (audio > -1) {
                return {QString("%1_%2.png").arg(binClip->hash()).arg(audio)};
            }
            return {binClip->hash() + QStringLiteral(".png")};
        }
        QStringList streamsList;
        QStringList streamIndexes = streams.split(QLatin1Char(';'));
        for (const QString &st : qAsConst(streamIndexes)) {
            streamsList << QString("%1_%2.png").arg(binClip->hash(), st);
        }
        return streamsList;
    }
}

// static
const QDir ThumbnailCache::getDir(bool audio, bool *ok)
{
    return pCore->projectManager()->cacheDir(audio, ok);
}
