comparison data/fileio/CachedFile.cpp @ 465:63b8ba45d953

* stub out persistent cacheing class, as I've decided I don't like the
  way things were going with trying to incorporate all this logic into
  the already too big FileSource class

+/* -*- 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 <QFileInfo>
+#include <QSettings>
+#include <QVariant>
+#include <QMap>
+#include <QDir>
+#include <QCryptographicHash>
+
+QString
+CachedFile::getLocalFilenameFor(QUrl url)
+{
+    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(QUrl url, ProgressReporter *reporter) :
+    m_url(url),
+    m_localFilename(getLocalFilenameFor(url)),
+    m_ok(false)
+{
+    refresh();
+}
+
+bool
+CachedFile::isOK() const
+{
+    return m_ok;
+}
+
+QString
+CachedFile::getLocalFilename() const
+{
+    return m_localFilename;
+}
+
+void
+CachedFile::refresh()
+{
+    //!!! 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
+
+    if (!QFileInfo(m_localFilename).exists()) {
+        updateLastRetrieval(false); // empirically!
+    }
+
+    QDateTime lastRetrieval = getLastRetrieval();
+
+    if (lastRetrieval.isValid()) {
+        // 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()) { //!!!
+            // 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()) {
+                updateLastRetrieval(true);
+            }
+        }
+    } else {
+        // there is no acceptable file
+        if (retrieve()) {
+            m_ok = true;
+            updateLastRetrieval(true);
+        } else {
+            // again, we don't need to do anything here -- the last
+            // retrieval timestamp is already invalid
+        }
+    }
+}
+
+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)
+
+
+
+
+}
+
+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();
+}
+
+