/*
 * Copyright (C) 2009 Google Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * 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.
 *     * Neither the name of Google Inc. nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND 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 COPYRIGHT
 * OWNER OR 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 "config.h"
#include "SQLTransactionCoordinator.h"

#include "CString.h"
#include "Database.h"
#include "SQLTransaction.h"
#include <wtf/Deque.h>
#include <wtf/HashMap.h>
#include <wtf/RefPtr.h>

namespace WebCore {

static String getDatabaseIdentifier(SQLTransaction* transaction)
{
    Database* database = transaction->database();
    ASSERT(database);
    return database->stringIdentifier();
}

void SQLTransactionCoordinator::acquireLock(SQLTransaction* transaction)
{
    String dbIdentifier = getDatabaseIdentifier(transaction);

    TransactionsHashMap::iterator it = m_pendingTransactions.find(dbIdentifier);
    if (it == m_pendingTransactions.end()) {
        // No pending transactions for this DB
        TransactionsQueue pendingTransactions;
        pendingTransactions.append(transaction);
        m_pendingTransactions.add(dbIdentifier, pendingTransactions);

        // Start the transaction
        transaction->lockAcquired();
    } else {
        // Another transaction is running on this DB; put this one in the queue
        TransactionsQueue& pendingTransactions = it->second;
        pendingTransactions.append(transaction);
    }
}

void SQLTransactionCoordinator::releaseLock(SQLTransaction* transaction)
{
    if (m_pendingTransactions.isEmpty())
        return;

    String dbIdentifier = getDatabaseIdentifier(transaction);

    TransactionsHashMap::iterator it = m_pendingTransactions.find(dbIdentifier);
    ASSERT(it != m_pendingTransactions.end());
    TransactionsQueue& pendingTransactions = it->second;
    ASSERT(!pendingTransactions.isEmpty());

    // 'transaction' should always be the first transaction in this queue
    ASSERT(pendingTransactions.first().get() == transaction);

    // Remove 'transaction' from the queue of pending transactions
    pendingTransactions.removeFirst();
    if (pendingTransactions.isEmpty()) {
        // No more pending transactions; delete dbIdentifier's queue
        m_pendingTransactions.remove(it);
    } else {
        // We have more pending transactions; start the next one
        pendingTransactions.first()->lockAcquired();
    }
}

void SQLTransactionCoordinator::shutdown()
{
    // Clean up all pending transactions for all databases
    m_pendingTransactions.clear();
}

}