MultiMC5/launcher/net/HttpMetaCache.h

/* Copyright 2013-2021 MultiMC Contributors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#pragma once
#include <QString>
#include <QMap>
#include <qtimer.h>
#include <memory>

class HttpMetaCache;

class MetaEntry
{
friend class HttpMetaCache;
protected:
    MetaEntry() {}
public:
    bool isStale()
    {
        return stale;
    }
    void setStale(bool stale)
    {
        this->stale = stale;
    }
    QString getFullPath();
    QString getRemoteChangedTimestamp()
    {
        return remote_changed_timestamp;
    }
    void setRemoteChangedTimestamp(QString remote_changed_timestamp)
    {
        this->remote_changed_timestamp = remote_changed_timestamp;
    }
    void setLocalChangedTimestamp(qint64 timestamp)
    {
        local_changed_timestamp = timestamp;
    }
    QString getETag()
    {
        return etag;
    }
    void setETag(QString etag)
    {
        this->etag = etag;
    }
    QString getMD5Sum()
    {
        return md5sum;
    }
    void setMD5Sum(QString md5sum)
    {
        this->md5sum = md5sum;
    }
protected:
    QString baseId;
    QString basePath;
    QString relativePath;
    QString md5sum;
    QString etag;
    qint64 local_changed_timestamp = 0;
    QString remote_changed_timestamp; // QString for now, RFC 2822 encoded time
    bool stale = true;
};

typedef std::shared_ptr<MetaEntry> MetaEntryPtr;

class HttpMetaCache : public QObject
{
    Q_OBJECT
public:
    // supply path to the cache index file
    HttpMetaCache(QString path = QString());
    ~HttpMetaCache();

    // get the entry solely from the cache
    // you probably don't want this, unless you have some specific caching needs.
    MetaEntryPtr getEntry(QString base, QString resource_path);

    // get the entry from cache and verify that it isn't stale (within reason)
    MetaEntryPtr resolveEntry(QString base, QString resource_path,
                              QString expected_etag = QString());

    // add a previously resolved stale entry
    bool updateEntry(MetaEntryPtr stale_entry);

    // evict selected entry from cache
    bool evictEntry(MetaEntryPtr entry);

    void addBase(QString base, QString base_root);

    // (re)start a timer that calls SaveNow later.
    void SaveEventually();
    void Load();
    QString getBasePath(QString base);
public
slots:
    void SaveNow();

private:
    // create a new stale entry, given the parameters
    MetaEntryPtr staleEntry(QString base, QString resource_path);
    struct EntryMap
    {
        QString base_path;
        QMap<QString, MetaEntryPtr> entry_list;
    };
    QMap<QString, EntryMap> m_entries;
    QString m_index_file;
    QTimer saveBatchingTimer;
};