/**
 * @file _httplibcurl.h
 * @brief Declarations for internal class providing libcurl transport.
 *
 * $LicenseInfo:firstyear=2012&license=viewerlgpl$
 * Second Life Viewer Source Code
 * Copyright (C) 2012-2014, 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_LIBCURL_H_
#define	_LLCORE_HTTP_LIBCURL_H_

#include "linden_common.h"		// Modifies curl/curl.h interfaces

#include <curl/curl.h>
#include <curl/multi.h>

#include <set>

#include "httprequest.h"
#include "_httpservice.h"
#include "_httpinternal.h"


namespace LLCore
{


class HttpPolicy;
class HttpOpRequest;
class HttpHeaders;


/// Implements libcurl-based transport 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 HttpLibcurl
{
public:
	HttpLibcurl(HttpService * service);
	virtual ~HttpLibcurl();

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

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

	/// Give cycles to libcurl to run active requests.  Completed
	/// operations (successful or failed) will be retried or handed
	/// over to the reply queue as final responses.
	///
	/// @return			Indication of how long this method is
	///					willing to wait for next service call.
	///
	/// Threading:  called by worker thread.
	HttpService::ELoopSpeed processTransport();

	/// Add request to the active list.  Caller is expected to have
	/// provided us with a reference count on the op to hold the
	/// request.  (No additional references will be added.)
	///
	/// Threading:  called by worker thread.
    void addOp(const opReqPtr_t & op);

	/// One-time call to set the number of policy classes to be
	/// serviced and to create the resources for each.  Value
	/// must agree with HttpPolicy::setPolicies() call.
	///
	/// Threading:  called by init thread.
	void start(int policy_count);

	/// Synchronously stop libcurl operations.  All active requests
	/// are canceled and removed from libcurl's handling.  Easy
	/// handles are detached from their multi handles and released.
	/// Multi handles are also released.  Canceled requests are
	/// completed with canceled status and made available on their
	/// respective reply queues.
	///
	/// Can be restarted with a start() call.
	///
	/// Threading:  called by worker thread.
	void shutdown();

	/// Return global and per-class counts of active requests.
	///
	/// Threading:  called by worker thread.
	int getActiveCount() const;
	int getActiveCountInClass(int policy_class) const;

	/// Attempt to cancel a request identified by handle.
	///
	/// Interface shadows HttpService's method.
	///
	/// @return			True if handle was found and operation canceled.
	///
	/// Threading:  called by worker thread.
	bool cancel(HttpHandle handle);

	/// Informs transport that a particular policy class has had
	/// options changed and so should effect any transport state
	/// change necessary to effect those changes.  Used mainly for
	/// initialization and dynamic option setting.
	///
	/// Threading:  called by worker thread.
	void policyUpdated(int policy_class);

	/// Allocate a curl handle for caller.  May be freed using
	/// either the freeHandle() method or calling curl_easy_cleanup()
	/// directly.
	///
	/// @return			Libcurl handle (CURL *) or NULL on allocation
	///					problem.  Handle will be in curl_easy_reset()
	///					condition.
	///
	/// Threading:  callable by worker thread.
	///
	/// Deprecation:  Expect this to go away after _httpoprequest is
	/// refactored bringing code into this class.
	CURL * getHandle()
		{
			return mHandleCache.getHandle();
		}

protected:
	/// Invoked when libcurl has indicated a request has been processed
	/// to completion and we need to move the request to a new state.
	bool completeRequest(CURLM * multi_handle, CURL * handle, CURLcode status);

	/// Invoked to cancel an active request, mainly during shutdown
	/// and destroy.
    void cancelRequest(const opReqPtr_t &op);
	
protected:
    typedef std::set<opReqPtr_t> active_set_t;

	/// Simple request handle cache for libcurl.
	///
	/// Handle creation is somewhat slow and chunky in libcurl and there's
	/// a pretty good speedup to be had from handle re-use.  So, a simple
	/// vector is kept of 'freed' handles to be reused as needed.  When
	/// that is empty, the first freed handle is kept as a template for
	/// handle duplication.  This is still faster than creation from nothing.
	/// And when that fails, we init fresh from curl_easy_init().
	///
	/// Handles allocated with getHandle() may be freed with either
	/// freeHandle() or curl_easy_cleanup().  Choice may be dictated
	/// by thread constraints.
	///
	/// Threading:  Single-threaded.  May only be used by a single thread,
	/// typically the worker thread.  If freeing requests' handles in an
	/// unknown threading context, use curl_easy_cleanup() for safety.

	class HandleCache
	{
	public:
		HandleCache();
		~HandleCache();

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

	public:
		/// Allocate a curl handle for caller.  May be freed using
		/// either the freeHandle() method or calling curl_easy_cleanup()
		/// directly.
		///
		/// @return			Libcurl handle (CURL *) or NULL on allocation
		///					problem.
		///
		/// Threading:  Single-thread (worker) only.
		CURL * getHandle();

		/// Free a libcurl handle acquired by whatever means.  Thread
		/// safety is left to the caller.
		///
		/// Threading:  Single-thread (worker) only.
		void freeHandle(CURL * handle);

	protected:
		typedef std::vector<CURL *> handle_cache_t;
	
	protected:
		CURL *				mHandleTemplate;		// Template for duplicating new handles
		handle_cache_t		mCache;					// Cache of old handles
	}; // end class HandleCache
	
protected:
	HttpService *		mService;			// Simple reference, not owner
	HandleCache			mHandleCache;		// Handle allocator, owner
	active_set_t		mActiveOps;
	int					mPolicyCount;
	CURLM **			mMultiHandles;		// One handle per policy class
	int *				mActiveHandles;		// Active count per policy class
	bool *				mDirtyPolicy;		// Dirty policy update waiting for stall (per pc)
	
}; // end class HttpLibcurl

}  // end namespace LLCore

#endif // _LLCORE_HTTP_LIBCURL_H_
