/*
 * filesystemwatcher.cpp
 * Copyright 2011-2014, Thorbjørn Lindeijer <bjorn@lindeijer.nl>
 *
 * This file is part of libtiled.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *    1. Redistributions of source code must retain the above copyright notice,
 *       this list of conditions and the following disclaimer.
 *
 *    2. Redistributions in binary form must reproduce the above copyright
 *       notice, this list of conditions and the following disclaimer in the
 *       documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
 * EVENT SHALL THE CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "filesystemwatcher.h"

#include <QDebug>
#include <QFile>
#include <QFileSystemWatcher>
#include <QStringList>

namespace Tiled {

FileSystemWatcher::FileSystemWatcher(QObject *parent) :
    QObject(parent),
    mWatcher(new QFileSystemWatcher(this))
{
    mChangedPathsTimer.setInterval(500);
    mChangedPathsTimer.setSingleShot(true);

    connect(mWatcher, &QFileSystemWatcher::fileChanged,
            this, &FileSystemWatcher::onFileChanged);
    connect(mWatcher, &QFileSystemWatcher::directoryChanged,
            this, &FileSystemWatcher::onDirectoryChanged);

    connect(&mChangedPathsTimer, &QTimer::timeout,
            this, &FileSystemWatcher::pathsChangedTimeout);
}

void FileSystemWatcher::setEnabled(bool enabled)
{
    if (mEnabled == enabled)
        return;

    mEnabled = enabled;

    if (enabled) {
        const auto files = mWatchCount.keys();
        if (!files.isEmpty())
            mWatcher->addPaths(files);
    } else {
        clearInternal();
        mChangedPathsTimer.stop();
    }
}

void FileSystemWatcher::addPaths(const QStringList &paths)
{
    QStringList pathsToAdd;
    pathsToAdd.reserve(paths.size());

    for (const QString &path : paths) {
        // Just silently ignore the request when the file doesn't exist
        if (!QFile::exists(path))
            continue;

        QMap<QString, int>::iterator entry = mWatchCount.find(path);
        if (entry == mWatchCount.end()) {
            if (mEnabled)
                pathsToAdd.append(path);

            mWatchCount.insert(path, 1);
        } else {
            // Path is already being watched, increment watch count
            ++entry.value();
        }
    }

    if (!pathsToAdd.isEmpty())
        mWatcher->addPaths(pathsToAdd);
}

void FileSystemWatcher::removePaths(const QStringList &paths)
{
    QStringList pathsToRemove;
    pathsToRemove.reserve(paths.size());

    for (const QString &path : paths) {
        QMap<QString, int>::iterator entry = mWatchCount.find(path);
        if (entry == mWatchCount.end()) {
            if (QFile::exists(path))
                qWarning() << "FileSystemWatcher: Path was never added:" << path;
            continue;
        }

        // Decrement watch count
        --entry.value();

        if (entry.value() == 0) {
            mWatchCount.erase(entry);

            if (mEnabled)
                pathsToRemove.append(path);
        }
    }

    if (!pathsToRemove.isEmpty())
        mWatcher->removePaths(pathsToRemove);
}

void FileSystemWatcher::clearInternal()
{
    const QStringList files = mWatcher->files();
    if (!files.isEmpty())
        mWatcher->removePaths(files);

    const QStringList directories = mWatcher->directories();
    if (!directories.isEmpty())
        mWatcher->removePaths(directories);
}

void FileSystemWatcher::clear()
{
    clearInternal();
    mWatchCount.clear();
}

void FileSystemWatcher::onFileChanged(const QString &path)
{
    mChangedPaths.insert(path);
    mChangedPathsTimer.start();

    emit fileChanged(path);
}

void FileSystemWatcher::onDirectoryChanged(const QString &path)
{
    mChangedPaths.insert(path);
    mChangedPathsTimer.start();

    emit directoryChanged(path);
}

void FileSystemWatcher::pathsChangedTimeout()
{
    const auto changedPaths = mChangedPaths.values();

    // If the file was replaced, the watcher is automatically removed and needs
    // to be re-added to keep watching it for changes. This happens commonly
    // with applications that do atomic saving.
    for (const QString &path : changedPaths) {
        if (mWatchCount.contains(path) && !mWatcher->files().contains(path)) {
            if (QFile::exists(path))
                mWatcher->addPath(path);
        }
    }


    emit pathsChanged(changedPaths);

    mChangedPaths.clear();
}

} // namespace Tiled

#include "moc_filesystemwatcher.cpp"
