/*
 * \brief  RAM management
 * \author Norman Feske
 * \date   2013-10-14
 */

/*
 * Copyright (C) 2013 Genode Labs GmbH
 *
 * This file is part of the Genode OS framework, which is distributed
 * under the terms of the GNU General Public License version 2.
 */

#ifndef _INCLUDE__CLI_MONITOR__RAM_H_
#define _INCLUDE__CLI_MONITOR__RAM_H_

/* Genode includes */
#include <ram_session/connection.h>

class Ram
{
	private:

		typedef Genode::size_t size_t;

		Genode::Lock mutable _lock;
		Genode::Ram_session &_ram = *Genode::env()->ram_session();
		Genode::Ram_session_capability _ram_cap = Genode::env()->ram_session_cap();
		Genode::Signal_context_capability _yield_sigh;
		Genode::Signal_context_capability _resource_avail_sigh;

		size_t _preserve;

		void _validate_preservation()
		{
			if (_ram.avail() < _preserve)
				Genode::Signal_transmitter(_yield_sigh).submit();

			/* verify to answer outstanding resource requests too */
			if (_ram.avail() > _preserve)
				Genode::Signal_transmitter(_resource_avail_sigh).submit();
		}

	public:

		struct Status
		{
			size_t quota, used, avail, preserve;
			Status(size_t quota, size_t used, size_t avail, size_t preserve)
			: quota(quota), used(used), avail(avail), preserve(preserve) { }
		};

		Ram(size_t                            preserve,
		    Genode::Signal_context_capability yield_sigh,
		    Genode::Signal_context_capability resource_avail_sigh)
		:
			_yield_sigh(yield_sigh),
			_resource_avail_sigh(resource_avail_sigh),
			_preserve(preserve)
		{ }

		size_t preserve() const
		{
			Genode::Lock::Guard guard(_lock);

			return _preserve;
		}

		void preserve(size_t preserve)
		{
			Genode::Lock::Guard guard(_lock);

			_preserve = preserve;

			_validate_preservation();
		}

		Status status() const
		{
			Genode::Lock::Guard guard(_lock);

			return Status(_ram.quota(), _ram.used(), _ram.avail(), _preserve);
		}

		void validate_preservation()
		{
			Genode::Lock::Guard guard(_lock);

			_validate_preservation();
		}

		/**
		 * Exception type
		 */
		class Transfer_quota_failed { };

		/**
		 * \throw Transfer_quota_failed
		 */
		void withdraw_from(Genode::Ram_session_capability from, size_t amount)
		{
			Genode::Lock::Guard guard(_lock);

			int const ret =
				Genode::Ram_session_client(from).transfer_quota(_ram_cap, amount);

			if (ret != 0)
				throw Transfer_quota_failed();

			Genode::Signal_transmitter(_resource_avail_sigh).submit();
		}

		/**
		 * \throw Transfer_quota_failed
		 */
		void transfer_to(Genode::Ram_session_capability to, size_t amount)
		{
			Genode::Lock::Guard guard(_lock);

			if (_ram.avail() < (_preserve + amount)) {
				Genode::Signal_transmitter(_yield_sigh).submit();
				throw Transfer_quota_failed();
			}

			int const ret = _ram.transfer_quota(to, amount);

			if (ret != 0)
				throw Transfer_quota_failed();
		}

		/**
		 * Return singleton object
		 */
		static Ram &ram();
};

#endif /* _INCLUDE__CLI_MONITOR__RAM_H_ */