/*    Copyright 2012 10gen Inc.
 *
 *    Licensed under the Apache License, Version 2.0 (the "License");
 *    you may not use this file except in compliance with the License.
 *    You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 *    Unless required by applicable law or agreed to in writing, software
 *    distributed under the License is distributed on an "AS IS" BASIS,
 *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *    See the License for the specific language governing permissions and
 *    limitations under the License.
 */

#pragma once

#include <boost/scoped_array.hpp>
#include <string>

#include "mongo/base/disallow_copying.h"
#include "mongo/base/status.h"
#include "mongo/base/string_data.h"
#include "mongo/client/export_macros.h"
#include "mongo/stdx/functional.h"

namespace mongo {

/**
 * Base class for the client side of a SASL authentication conversation.
 *
 * To use, create an instance, then use setParameter() to configure the authentication
 * parameters.  Once all parameters are set, call initialize() to initialize the client state
 * machine.  Finally, use repeated calls to step() to generate messages to send to the server
 * and process server responses.
 *
 * The required parameters vary by mechanism, but all mechanisms require parameterServiceName,
 * parameterServiceHostname, parameterMechanism and parameterUser.  All of the required
 * parameters must be UTF-8 encoded strings with no embedded NUL characters.  The
 * parameterPassword parameter is not constrained.
 */
class SaslClientSession {
    MONGO_DISALLOW_COPYING(SaslClientSession);

public:
    typedef stdx::function<SaslClientSession*(const std::string&)> SaslClientSessionFactoryFn;
    static SaslClientSessionFactoryFn create;

    /**
     * Identifiers of parameters used to configure a SaslClientSession.
     */
    enum Parameter {
        parameterServiceName = 0,
        parameterServiceHostname,
        parameterMechanism,
        parameterUser,
        parameterPassword,
        numParameters  // Must be last
    };

    SaslClientSession();
    virtual ~SaslClientSession();

    /**
     * Sets the parameter identified by "id" to "value".
     *
     * The value of "id" must be one of the legal values of Parameter less than numParameters.
     * May be called repeatedly for the same value of "id", with the last "value" replacing
     * previous values.
     *
     * The session object makes and owns a copy of the data in "value".
     */
    virtual void setParameter(Parameter id, const StringData& value);

    /**
     * Returns true if "id" identifies a parameter previously set by a call to setParameter().
     */
    virtual bool hasParameter(Parameter id);

    /**
     * Returns the value of a previously set parameter.
     *
     * If parameter "id" was never set, returns an empty StringData.  Note that a parameter may
     * be explicitly set to StringData(), so use hasParameter() to distinguish those cases.
     *
     * The session object owns the storage behind the returned StringData, which will remain
     * valid until setParameter() is called with the same value of "id", or the session object
     * goes out of scope.
     */
    virtual StringData getParameter(Parameter id);

    /**
     * Initializes a session for use.
     *
     * Call exactly once, after setting any parameters you intend to set via setParameter().
     */
    virtual Status initialize() = 0;

    /**
     * Takes one step of the SASL protocol on behalf of the client.
     *
     * Caller should provide data from the server side of the conversation in "inputData", or an
     * empty StringData() if none is available.  If the client should make a response to the
     * server, stores the response into "*outputData".
     *
     * Returns Status::OK() on success.  Any other return value indicates a failed
     * authentication, though the specific return value may provide insight into the cause of
     * the failure (e.g., ProtocolError, AuthenticationFailed).
     *
     * In the event that this method returns Status::OK(), consult the value of isDone() to
     * determine if the conversation has completed.  When step() returns Status::OK() and
     * isDone() returns true, authentication has completed successfully.
     */
    virtual Status step(const StringData& inputData, std::string* outputData) = 0;

    /**
     * Returns true if the authentication completed successfully.
     */
    virtual bool isDone() const = 0;

private:
    /**
     * Buffer object that owns data for a single parameter.
     */
    struct DataBuffer {
        boost::scoped_array<char> data;
        size_t size;
    };

    /// Buffers for each of the settable parameters.
    DataBuffer _parameters[numParameters];
};

}  // namespace mongo
