view data/fileio/CachedFile.cpp @ 490:c3fb8258e34d

* Make it possible to import an entire session from an RDF document.
  However, at the moment the timings of events appear to be constrained
  by how far the audio decoder has got through its audio file at the
  time the event is queried -- need to investigate.

/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */

/*
    Sonic Visualiser
    An audio file viewer and annotation editor.
    Centre for Digital Music, Queen Mary, University of London.
    This file copyright 2008 QMUL.
    
    This program is free software; you can redistribute it and/or
    modify it under the terms of the GNU General Public License as
    published by the Free Software Foundation; either version 2 of the
    License, or (at your option) any later version.  See the file
    COPYING included with this distribution for more information.
*/

#include "CachedFile.h"

#include "base/TempDirectory.h"
#include "base/ProgressReporter.h"
#include "base/Exceptions.h"

#include "FileSource.h"

#include <QFileInfo>
#include <QSettings>
#include <QVariant>
#include <QMap>
#include <QDir>
#include <QCryptographicHash>

#include "base/Profiler.h"

#include <iostream>

CachedFile::OriginLocalFilenameMap
CachedFile::m_knownGoodCaches;

QString
CachedFile::getLocalFilenameFor(QUrl url)
{
    Profiler p("CachedFile::getLocalFilenameFor");

    QDir dir(getCacheDirectory());

    QString filename =
        QString::fromLocal8Bit
        (QCryptographicHash::hash(url.toString().toLocal8Bit(),
                                  QCryptographicHash::Sha1).toHex());

    return dir.filePath(filename);
}

QString
CachedFile::getCacheDirectory()
{
    QDir dir = TempDirectory::getInstance()->getContainingPath();

    QString cacheDirName("cache");

    QFileInfo fi(dir.filePath(cacheDirName));

    if ((fi.exists() && !fi.isDir()) ||
        (!fi.exists() && !dir.mkdir(cacheDirName))) {

        throw DirectoryCreationFailed(fi.filePath());
    }

    return fi.filePath();
}

CachedFile::CachedFile(QString origin, ProgressReporter *reporter) :
    m_origin(origin),
    m_reporter(reporter),
    m_ok(false)
{
    Profiler p("CachedFile::CachedFile[1]");

    std::cerr << "CachedFile::CachedFile: origin is \""
              << origin.toStdString() << "\"" << std::endl;
    check();
}

CachedFile::CachedFile(QUrl url, ProgressReporter *reporter) :
    m_origin(url.toString()),
    m_reporter(reporter),
    m_ok(false)
{
    Profiler p("CachedFile::CachedFile[2]");

    std::cerr << "CachedFile::CachedFile: url is \""
              << url.toString().toStdString() << "\"" << std::endl;
    check();
}

CachedFile::~CachedFile()
{
}

bool
CachedFile::isOK() const
{
    return m_ok;
}

QString
CachedFile::getLocalFilename() const
{
    return m_localFilename;
}

void
CachedFile::check()
{
    //!!! n.b. obvious race condition here if different CachedFile
    // objects for same url used in more than one thread -- need to
    // lock appropriately.  also consider race condition between
    // separate instances of the program!

    OriginLocalFilenameMap::const_iterator i = m_knownGoodCaches.find(m_origin);
    if (i != m_knownGoodCaches.end()) {
        m_ok = true;
        m_localFilename = i->second;
        return;
    }

    m_localFilename = getLocalFilenameFor(m_origin);

    if (!QFileInfo(m_localFilename).exists()) {
        std::cerr << "CachedFile::check: Local file does not exist, making a note that it hasn't been retrieved" << std::endl;
        updateLastRetrieval(false); // empirically!
    }

    QDateTime lastRetrieval = getLastRetrieval();

    if (lastRetrieval.isValid()) {
        std::cerr << "CachedFile::check: Valid last retrieval at "
                  << lastRetrieval.toString().toStdString() << std::endl;
        // this will not be the case if the file is missing, after
        // updateLastRetrieval(false) was called above
        m_ok = true;
        if (lastRetrieval.addDays(2) < QDateTime::currentDateTime()) { //!!!
            std::cerr << "CachedFile::check: Out of date; trying to retrieve again" << std::endl;
            // doesn't matter if retrieval fails -- we just don't
            // update the last retrieval time

            //!!! but we do want an additional last-attempted
            // timestamp so as to ensure we aren't retrying the
            // retrieval every single time if it isn't working

            if (retrieve()) {
                std::cerr << "CachedFile::check: Retrieval succeeded" << std::endl;
                updateLastRetrieval(true);
            } else {
                std::cerr << "CachedFile::check: Retrieval failed, will try again later (using existing file for now)" << std::endl;
            }                
        }
    } else {
        std::cerr << "CachedFile::check: No valid last retrieval" << std::endl;
        // there is no acceptable file
        if (retrieve()) {
            std::cerr << "CachedFile::check: Retrieval succeeded" << std::endl;
            m_ok = true;
            updateLastRetrieval(true);
        } else {
            std::cerr << "CachedFile::check: Retrieval failed, remaining in invalid state" << std::endl;
            // again, we don't need to do anything here -- the last
            // retrieval timestamp is already invalid
        }
    }

    if (m_ok) {
        m_knownGoodCaches[m_origin] = m_localFilename;
    }
}

bool
CachedFile::retrieve()
{
    //!!! need to work by retrieving the file to another name, and
    //!!! then "atomically" moving it to its proper place (I'm not
    //!!! sure we can do an atomic move to replace an existing file
    //!!! using Qt classes, but a plain delete then copy is probably
    //!!! good enough)

    FileSource fs(m_origin, m_reporter);

    if (!fs.isOK() || !fs.isAvailable()) {
        std::cerr << "CachedFile::retrieve: ERROR: FileSource reported unavailable or failure" << std::endl;
        return false;
    }

    fs.waitForData();

    if (!fs.isOK()) {
        std::cerr << "CachedFile::retrieve: ERROR: FileSource reported failure during receive" << std::endl;
        return false;
    }

    QString tempName = fs.getLocalFilename();
    QFile tempFile(tempName);
    if (!tempFile.exists()) {
        std::cerr << "CachedFile::retrieve: ERROR: FileSource reported success, but local temporary file \"" << tempName.toStdString() << "\" does not exist" << std::endl;
        return false;
    }

    QFile previous(m_localFilename);
    if (previous.exists()) {
        if (!previous.remove()) {
            std::cerr << "CachedFile::retrieve: ERROR: Failed to remove previous copy of cached file at \"" << m_localFilename.toStdString() << "\"" << std::endl;
            return false;
        }
    }

    //!!! This is not ideal, could leave us with nothing (old file
    //!!! removed, new file not able to be copied in because e.g. no
    //!!! disk space left)

    if (!tempFile.copy(m_localFilename)) {
        std::cerr << "CachedFile::retrieve: ERROR: Failed to copy newly retrieved file from \"" << tempName.toStdString() << "\" to \"" << m_localFilename.toStdString() << "\"" << std::endl;
        return false;
    }

    std::cerr << "CachedFile::retrieve: Successfully copied newly retrieved file \"" << tempName.toStdString() << "\" to its home at \"" << m_localFilename.toStdString() << "\"" << std::endl;

    return true;
}

QDateTime
CachedFile::getLastRetrieval()
{
    QSettings settings;
    settings.beginGroup("FileCache");

    QString key("last-retrieval-times");

    QMap<QString, QVariant> timeMap = settings.value(key).toMap();
    QDateTime lastTime = timeMap[m_localFilename].toDateTime();

    settings.endGroup();
    return lastTime;
}

void
CachedFile::updateLastRetrieval(bool successful)
{
    //!!! note !successful does not mean "we failed to update the
    //!!! file" (and so it remains the same as before); it means "the
    //!!! file is not there at all"
    
    QSettings settings;
    settings.beginGroup("FileCache");

    QString key("last-retrieval-times");

    QMap<QString, QVariant> timeMap = settings.value(key).toMap();

    QDateTime dt;
    if (successful) dt = QDateTime::currentDateTime();

    timeMap[m_localFilename] = dt;
    settings.setValue(key, timeMap);

    settings.endGroup();
}