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/**
 * @file _httppolicy.h
 * @brief Declarations for internal class enforcing policy decisions.
 *
 * $LicenseInfo:firstyear=2012&license=viewerlgpl$
 * Second Life Viewer Source Code
 * Copyright (C) 2012-2013, Linden Research, Inc.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation;
 * version 2.1 of the License only.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * Linden Research, Inc., 945 Battery Street, San Francisco, CA  94111  USA
 * $/LicenseInfo$
 */

#ifndef _LLCORE_HTTP_POLICY_H_
#define _LLCORE_HTTP_POLICY_H_


#include "httprequest.h"
#include "_httpservice.h"
#include "_httpreadyqueue.h"
#include "_httpretryqueue.h"
#include "_httppolicyglobal.h"
#include "_httppolicyclass.h"
#include "_httpinternal.h"


namespace LLCore
{

class HttpReadyQueue;
class HttpOpRequest;


/// Implements class-based queuing policies for an HttpService instance.
///
/// Threading:  Single-threaded.  Other than for construction/destruction,
/// all methods are expected to be invoked in a single thread, typically
/// a worker thread of some sort.
class HttpPolicy
{
public:
    HttpPolicy(HttpService *);
    virtual ~HttpPolicy();

private:
    HttpPolicy(const HttpPolicy &);             // Not defined
    void operator=(const HttpPolicy &);         // Not defined

public:
    typedef std::shared_ptr<HttpOpRequest> opReqPtr_t;

    /// Threading:  called by init thread.
    HttpRequest::policy_t createPolicyClass();

    /// Cancel all ready and retry requests sending them to
    /// their notification queues.  Release state resources
    /// making further request handling impossible.
    ///
    /// Threading:  called by worker thread
    void shutdown();

    /// Deliver policy definitions and enable handling of
    /// requests.  One-time call invoked before starting
    /// the worker thread.
    ///
    /// Threading:  called by init thread
    void start();

    /// Give the policy layer some cycles to scan the ready
    /// queue promoting higher-priority requests to active
    /// as permited.
    ///
    /// @return         Indication of how soon this method
    ///                 should be called again.
    ///
    /// Threading:  called by worker thread
    HttpService::ELoopSpeed processReadyQueue();

    /// Add request to a ready queue.  Caller is expected to have
    /// provided us with a reference count to hold the request.  (No
    /// additional references will be added.)
    ///
    /// OpRequest is owned by the request queue after this call
    /// and should not be modified by anyone until retrieved
    /// from queue.
    ///
    /// Threading:  called by worker thread
    void addOp(const opReqPtr_t &);

    /// Similar to addOp, used when a caller wants to retry a
    /// request that has failed.  It's placed on a special retry
    /// queue but ordered by retry time not priority.  Otherwise,
    /// handling is the same and retried operations are considered
    /// before new ones but that doesn't guarantee completion
    /// order.
    ///
    /// Threading:  called by worker thread
    void retryOp(const opReqPtr_t &);

    /// Attempt to cancel a previous request.
    /// Shadows HttpService's method as well
    ///
    /// Threading:  called by worker thread
    bool cancel(HttpHandle handle);

    /// When transport is finished with an op and takes it off the
    /// active queue, it is delivered here for dispatch.  Policy
    /// may send it back to the ready/retry queues if it needs another
    /// go or we may finalize it and send it on to the reply queue.
    ///
    /// @return         Returns true of the request is still active
    ///                 or ready after staging, false if has been
    ///                 sent on to the reply queue.
    ///
    /// Threading:  called by worker thread
    bool stageAfterCompletion(const opReqPtr_t &op);

    /// Get a reference to global policy options.  Caller is expected
    /// to do context checks like no setting once running.  These
    /// are done, for example, in @see HttpService interfaces.
    ///
    /// Threading:  called by any thread *but* the object may
    /// only be modified by the worker thread once running.
    HttpPolicyGlobal & getGlobalOptions()
        {
            return mGlobalOptions;
        }

    /// Get a reference to class policy options.  Caller is expected
    /// to do context checks like no setting once running.  These
    /// are done, for example, in @see HttpService interfaces.
    ///
    /// Threading:  called by any thread *but* the object may
    /// only be modified by the worker thread once running and
    /// read accesses by other threads are exposed to races at
    /// that point.
    HttpPolicyClass & getClassOptions(HttpRequest::policy_t pclass);

    /// Get ready counts for a particular policy class
    ///
    /// Threading:  called by worker thread
    int getReadyCount(HttpRequest::policy_t policy_class) const;

    /// Stall (or unstall) a policy class preventing requests from
    /// transitioning to an active state.  Used to allow an HTTP
    /// request policy to empty prior to changing settings or state
    /// that isn't tolerant of changes when work is outstanding.
    ///
    /// Threading:  called by worker thread
    bool stallPolicy(HttpRequest::policy_t policy_class, bool stall);

protected:
    struct ClassState;
    typedef std::vector<ClassState *>   class_list_t;

    HttpPolicyGlobal                    mGlobalOptions;
    class_list_t                        mClasses;
    HttpService *                       mService;               // Naked pointer, not refcounted, not owner
};  // end class HttpPolicy

}  // end namespace LLCore

#endif // _LLCORE_HTTP_POLICY_H_