/*
 * Copyright (C) 2012 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"

#if ENABLE(WEB_SOCKETS)

#include "WebSocketExtensionDispatcher.h"

#include <wtf/ASCIICType.h>
#include <wtf/HashMap.h>
#include <wtf/text/CString.h>
#include <wtf/text/StringHash.h>

namespace WebCore {

class ExtensionParser {
public:
    ExtensionParser(const char* start, const char* end)
        : m_current(start)
        , m_end(end)
    {
    }
    bool finished();
    bool parsedSuccessfully();
    const String& currentToken() { return m_currentToken; }

    // The following member functions basically follow the grammer defined
    // in Section 2.2 of RFC 2616.
    bool consumeToken();
    bool consumeQuotedString();
    bool consumeQuotedStringOrToken();
    bool consumeCharacter(char);

private:
    void skipSpaces();

    const char* m_current;
    const char* m_end;
    String m_currentToken;
};

bool ExtensionParser::finished()
{
    return m_current >= m_end;
}

bool ExtensionParser::parsedSuccessfully()
{
    return m_current == m_end;
}

static bool isSeparator(char character)
{
    static const char* separatorCharacters = "()<>@,;:\\\"/[]?={} \t";
    const char* p = strchr(separatorCharacters, character);
    return p && *p;
}

void ExtensionParser::skipSpaces()
{
    while (m_current < m_end && (*m_current == ' ' || *m_current == '\t'))
        ++m_current;
}

bool ExtensionParser::consumeToken()
{
    skipSpaces();
    const char* start = m_current;
    while (m_current < m_end && isASCIIPrintable(*m_current) && !isSeparator(*m_current))
        ++m_current;
    if (start < m_current) {
        m_currentToken = String(start, m_current - start);
        return true;
    }
    return false;
}

bool ExtensionParser::consumeQuotedString()
{
    skipSpaces();
    if (m_current >= m_end || *m_current != '"')
        return false;

    Vector<char> buffer;
    ++m_current;
    while (m_current < m_end && *m_current != '"') {
        if (*m_current == '\\' && ++m_current >= m_end)
            return false;
        buffer.append(*m_current);
        ++m_current;
    }
    if (m_current >= m_end || *m_current != '"')
        return false;
    m_currentToken = String::fromUTF8(buffer.data(), buffer.size());
    ++m_current;
    return true;
}

bool ExtensionParser::consumeQuotedStringOrToken()
{
    // This is ok because consumeQuotedString() doesn't update m_current or
    // makes it same as m_end on failure.
    return consumeQuotedString() || consumeToken();
}

bool ExtensionParser::consumeCharacter(char character)
{
    skipSpaces();
    if (m_current < m_end && *m_current == character) {
        ++m_current;
        return true;
    }
    return false;
}

void WebSocketExtensionDispatcher::reset()
{
    m_processors.clear();
}

void WebSocketExtensionDispatcher::addProcessor(PassOwnPtr<WebSocketExtensionProcessor> processor)
{
    for (size_t i = 0; i < m_processors.size(); ++i) {
        if (m_processors[i]->extensionToken() == processor->extensionToken())
            return;
    }
    ASSERT(processor->handshakeString().length());
    ASSERT(!processor->handshakeString().contains('\n'));
    ASSERT(!processor->handshakeString().contains(static_cast<UChar>('\0')));
    m_processors.append(processor);
}

const String WebSocketExtensionDispatcher::createHeaderValue() const
{
    size_t numProcessors = m_processors.size();
    if (!numProcessors)
        return String();

    StringBuilder builder;
    builder.append(m_processors[0]->handshakeString());
    for (size_t i = 1; i < numProcessors; ++i) {
        builder.append(", ");
        builder.append(m_processors[i]->handshakeString());
    }
    return builder.toString();
}

void WebSocketExtensionDispatcher::appendAcceptedExtension(const String& extensionToken, HashMap<String, String>& extensionParameters)
{
    if (!m_acceptedExtensionsBuilder.isEmpty())
        m_acceptedExtensionsBuilder.append(", ");
    m_acceptedExtensionsBuilder.append(extensionToken);
    // FIXME: Should use ListHashSet to keep the order of the parameters.
    for (HashMap<String, String>::const_iterator iterator = extensionParameters.begin(); iterator != extensionParameters.end(); ++iterator) {
        m_acceptedExtensionsBuilder.append("; ");
        m_acceptedExtensionsBuilder.append(iterator->first);
        if (!iterator->second.isNull()) {
            m_acceptedExtensionsBuilder.append("=");
            m_acceptedExtensionsBuilder.append(iterator->second);
        }
    }
}

void WebSocketExtensionDispatcher::fail(const String& reason)
{
    m_failureReason = reason;
    m_acceptedExtensionsBuilder.clear();
}

bool WebSocketExtensionDispatcher::processHeaderValue(const String& headerValue)
{
    if (!headerValue.length())
        return true;

    // If we don't send Sec-WebSocket-Extensions header, the server should not return the header.
    if (!m_processors.size()) {
        fail("Received unexpected Sec-WebSocket-Extensions header");
        return false;
    }

    const CString headerValueData = headerValue.utf8();
    ExtensionParser parser(headerValueData.data(), headerValueData.data() + headerValueData.length());
    while (!parser.finished()) {
        // Parse extension-token.
        if (!parser.consumeToken()) {
            fail("Sec-WebSocket-Extensions header is invalid");
            return false;
        }
        String extensionToken = parser.currentToken();

        // Parse extension-parameters if exists.
        HashMap<String, String> extensionParameters;
        while (parser.consumeCharacter(';')) {
            if (!parser.consumeToken()) {
                fail("Sec-WebSocket-Extensions header is invalid");
                return false;
            }

            String parameterToken = parser.currentToken();
            if (parser.consumeCharacter('=')) {
                if (parser.consumeQuotedStringOrToken())
                    extensionParameters.add(parameterToken, parser.currentToken());
                else {
                    fail("Sec-WebSocket-Extensions header is invalid");
                    return false;
                }
            } else
                extensionParameters.add(parameterToken, String());
        }
        if (!parser.finished() && !parser.consumeCharacter(',')) {
            fail("Sec-WebSocket-Extensions header is invalid");
            return false;
        }

        size_t index;
        for (index = 0; index < m_processors.size(); ++index) {
            WebSocketExtensionProcessor* processor = m_processors[index].get();
            if (extensionToken == processor->extensionToken()) {
                if (processor->processResponse(extensionParameters)) {
                    appendAcceptedExtension(extensionToken, extensionParameters);
                    break;
                }
                fail(processor->failureReason());
                return false;
            }
        }
        // There is no extension which can process the response.
        if (index == m_processors.size()) {
            fail("Received unexpected extension: " + extensionToken);
            return false;
        }
    }
    return parser.parsedSuccessfully();
}

String WebSocketExtensionDispatcher::acceptedExtensions() const
{
    if (m_acceptedExtensionsBuilder.isEmpty())
        return String();
    return m_acceptedExtensionsBuilder.toStringPreserveCapacity();
}

String WebSocketExtensionDispatcher::failureReason() const
{
    return m_failureReason;
}

} // namespace WebCore

#endif // ENABLE(WEB_SOCKETS)