/*
* This file is part of KDevelop
*
* Copyright 2007-2009 David Nolden <david.nolden.kdevelop@art-master.de>
* Copyright 2016 Milian Wolff <mail@milianw.de>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU Library General Public License as
* published by the Free Software Foundation; either version 2 of the
* License, or (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public
* License along with this program; if not, write to the
* Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
#include "urlparselock.h"

#include <QHash>
#include <QMutex>

using namespace KDevelop;

namespace
{
struct PerUrlData
{
    PerUrlData()
        // TODO: make this non-recursive
        : mutex(QMutex::Recursive)
        , ref(0)
    {}
    QMutex mutex;
    // how many people are (trying to) parse this url
    // we use this to delete the entry once noone needs it anymore
    uint ref;
};

// this mutex protects the parsingUrls
// NOTE: QBasicMutex is safe to initialize statically
QBasicMutex parsingUrlsMutex;

// Hash of urls that are currently being parsed and their protection data
using ParsingUrls = QHash<IndexedString, PerUrlData*>;
ParsingUrls& parsingUrls()
{
    // delay initialization of the hash until it's needed
    static ParsingUrls parsingUrls;
    return parsingUrls;
}

}

UrlParseLock::UrlParseLock(const IndexedString& url)
    : m_url(url)
{
  QMutexLocker lock(&parsingUrlsMutex);

  // NOTE: operator[] default-initializes the ptr to zero for us when not available
  auto& perUrlData = parsingUrls()[url];
  if (!perUrlData) {
    // if that was the case, we are the first to parse this url, create an entry
    perUrlData = new PerUrlData;
  }

  // always increment the refcount
  ++perUrlData->ref;

  // now lock the url, but don't do so while blocking the global mutex
  auto& mutex = perUrlData->mutex;
  lock.unlock();

  mutex.lock();
}

UrlParseLock::~UrlParseLock()
{
  QMutexLocker lock(&parsingUrlsMutex);

  // find the entry for this url
  auto& urls = parsingUrls();
  auto it = urls.find(m_url);
  Q_ASSERT(it != urls.end()); // it must exist
  auto& perUrlData = it.value();

  // unlock the per-url mutex
  perUrlData->mutex.unlock();

  // decrement the refcount
  --perUrlData->ref;
  if (perUrlData->ref == 0) {
    // and cleanup, if possible
    delete perUrlData;
    urls.erase(it);
  }
}
