/* gprs_ms.cpp
 *
 * Copyright (C) 2015 by Sysmocom s.f.m.c. GmbH
 * Author: Jacob Erlbeck <jerlbeck@sysmocom.de>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 */


#include "gprs_ms.h"

#include "bts.h"
#include "tbf.h"
#include "gprs_debug.h"

#include <time.h>

extern "C" {
	#include <osmocom/core/talloc.h>
	#include <osmocom/core/utils.h>
}

extern void *tall_pcu_ctx;

static int64_t now_msec()
{
	struct timespec ts;
	clock_gettime(CLOCK_MONOTONIC, &ts);

	return int64_t(ts.tv_sec) * 1000 + ts.tv_nsec / 1000000;
}

struct GprsMsDefaultCallback: public GprsMs::Callback {
	virtual void ms_idle(class GprsMs *ms) {
		delete ms;
	}
	virtual void ms_active(class GprsMs *) {}
};

static GprsMsDefaultCallback gprs_default_cb;

GprsMs::Guard::Guard(GprsMs *ms) :
	m_ms(ms ? ms->ref() : NULL)
{
}

GprsMs::Guard::~Guard()
{
	if (m_ms)
		m_ms->unref();
}

void GprsMs::timeout(void *priv_)
{
	GprsMs *ms = static_cast<GprsMs *>(priv_);

	LOGP(DRLCMAC, LOGL_INFO, "Timeout for MS object, TLLI = 0x%08x\n",
		ms->tlli());

	if (ms->m_timer.data) {
		ms->m_timer.data = NULL;
		ms->unref();
	}
}

GprsMs::GprsMs(BTS *bts, uint32_t tlli) :
	m_bts(bts),
	m_cb(&gprs_default_cb),
	m_ul_tbf(NULL),
	m_dl_tbf(NULL),
	m_tlli(tlli),
	m_new_ul_tlli(0),
	m_new_dl_tlli(0),
	m_ta(0),
	m_ms_class(0),
	m_current_cs_ul(1),
	m_current_cs_dl(1),
	m_is_idle(true),
	m_ref(0),
	m_list(this),
	m_delay(0)
{
	LOGP(DRLCMAC, LOGL_INFO, "Creating MS object, TLLI = 0x%08x\n", tlli);

	m_imsi[0] = 0;
	memset(&m_timer, 0, sizeof(m_timer));
	m_timer.cb = GprsMs::timeout;
	m_llc_queue.init();
	if (m_bts) {
		m_current_cs_ul = m_bts->bts_data()->initial_cs_ul;
		if (m_current_cs_ul < 1)
			m_current_cs_ul = 1;

		m_current_cs_dl = m_bts->bts_data()->initial_cs_dl;
		if (m_current_cs_dl < 1)
			m_current_cs_dl = 1;
	}
	m_last_cs_not_low = now_msec();
}

GprsMs::~GprsMs()
{
	LOGP(DRLCMAC, LOGL_INFO, "Destroying MS object, TLLI = 0x%08x\n", tlli());

	if (osmo_timer_pending(&m_timer))
		osmo_timer_del(&m_timer);

	if (m_ul_tbf) {
		m_ul_tbf->set_ms(NULL);
		m_ul_tbf = NULL;
	}

	if (m_dl_tbf) {
		m_dl_tbf->set_ms(NULL);
		m_dl_tbf = NULL;
	}
	m_llc_queue.clear(m_bts);
}

void* GprsMs::operator new(size_t size)
{
	static void *tall_ms_ctx = NULL;
	if (!tall_ms_ctx)
		tall_ms_ctx = talloc_named_const(tall_pcu_ctx, 0, __PRETTY_FUNCTION__);

	return talloc_size(tall_ms_ctx, size);
}

void GprsMs::operator delete(void* p)
{
	talloc_free(p);
}

GprsMs *GprsMs::ref()
{
	m_ref += 1;
	return this;
}

void GprsMs::unref()
{
	OSMO_ASSERT(m_ref >= 0);
	m_ref -= 1;
	if (m_ref == 0)
		update_status();
}

void GprsMs::start_timer()
{
	if (m_delay == 0)
		return;

	if (!m_timer.data)
		m_timer.data = ref();

	osmo_timer_schedule(&m_timer, m_delay, 0);
}

void GprsMs::stop_timer()
{
	if (!m_timer.data)
		return;

	osmo_timer_del(&m_timer);
	m_timer.data = NULL;
	unref();
}

void GprsMs::attach_tbf(struct gprs_rlcmac_tbf *tbf)
{
	if (tbf->direction == GPRS_RLCMAC_DL_TBF)
		attach_dl_tbf(static_cast<gprs_rlcmac_dl_tbf *>(tbf));
	else
		attach_ul_tbf(static_cast<gprs_rlcmac_ul_tbf *>(tbf));
}

void GprsMs::attach_ul_tbf(struct gprs_rlcmac_ul_tbf *tbf)
{
	if (m_ul_tbf == tbf)
		return;

	LOGP(DRLCMAC, LOGL_INFO, "Attaching TBF to MS object, TLLI = 0x%08x, TBF = %s\n",
		tlli(), tbf->name());

	Guard guard(this);

	if (m_ul_tbf)
		detach_tbf(m_ul_tbf);

	m_ul_tbf = tbf;

	if (tbf)
		stop_timer();
}

void GprsMs::attach_dl_tbf(struct gprs_rlcmac_dl_tbf *tbf)
{
	if (m_dl_tbf == tbf)
		return;

	LOGP(DRLCMAC, LOGL_INFO, "Attaching TBF to MS object, TLLI = 0x%08x, TBF = %s\n",
		tlli(), tbf->name());

	Guard guard(this);

	if (m_dl_tbf)
		detach_tbf(m_dl_tbf);

	m_dl_tbf = tbf;

	if (tbf)
		stop_timer();
}

void GprsMs::detach_tbf(gprs_rlcmac_tbf *tbf)
{
	if (m_ul_tbf && tbf == static_cast<gprs_rlcmac_tbf *>(m_ul_tbf))
		m_ul_tbf = NULL;
	else if (m_dl_tbf && tbf == static_cast<gprs_rlcmac_tbf *>(m_dl_tbf))
		m_dl_tbf = NULL;
	else
		return;

	LOGP(DRLCMAC, LOGL_INFO, "Detaching TBF from MS object, TLLI = 0x%08x, TBF = %s\n",
		tlli(), tbf->name());

	if (tbf->ms() == this)
		tbf->set_ms(NULL);

	if (!m_dl_tbf && !m_dl_tbf)
		start_timer();

	update_status();
}

void GprsMs::update_status()
{
	if (m_ref > 0)
		return;

	if (is_idle() && !m_is_idle) {
		m_is_idle = true;
		m_cb->ms_idle(this);
		/* this can be deleted by now, do not access it */
		return;
	}

	if (!is_idle() && m_is_idle) {
		m_is_idle = false;
		m_cb->ms_active(this);
	}
}

void GprsMs::set_tlli(uint32_t tlli)
{
	if (tlli == m_tlli || tlli == m_new_ul_tlli)
		return;

	if (tlli != m_new_dl_tlli) {
		LOGP(DRLCMAC, LOGL_INFO,
			"Modifying MS object, UL TLLI: 0x%08x -> 0x%08x, "
			"not yet confirmed\n",
			this->tlli(), tlli);
		m_new_ul_tlli = tlli;
		return;
	}

	LOGP(DRLCMAC, LOGL_INFO,
		"Modifying MS object, TLLI: 0x%08x -> 0x%08x, "
		"already confirmed partly\n",
		m_tlli, tlli);

	m_tlli = tlli;
	m_new_dl_tlli = 0;
	m_new_ul_tlli = 0;
}

bool GprsMs::confirm_tlli(uint32_t tlli)
{
	if (tlli == m_tlli || tlli == m_new_dl_tlli)
		return false;

	if (tlli != m_new_ul_tlli) {
		/* The MS has not sent a message with the new TLLI, which may
		 * happen according to the spec [TODO: add reference]. */

		LOGP(DRLCMAC, LOGL_INFO,
			"The MS object cannot fully confirm an unexpected TLLI: 0x%08x, "
			"partly confirmed\n", tlli);
		/* Use the network's idea of TLLI as candidate, this does not
		 * change the result value of tlli() */
		m_new_dl_tlli = tlli;
		return false;
	}

	LOGP(DRLCMAC, LOGL_INFO,
		"Modifying MS object, TLLI: 0x%08x confirmed\n", tlli);

	m_tlli = tlli;
	m_new_dl_tlli = 0;
	m_new_ul_tlli = 0;

	return true;
}

void GprsMs::set_imsi(const char *imsi)
{
	if (!imsi) {
		LOGP(DRLCMAC, LOGL_ERROR, "Expected IMSI!\n");
		return;
	}

	if (imsi[0] && strlen(imsi) < 3) {
		LOGP(DRLCMAC, LOGL_ERROR, "No valid IMSI '%s'!\n",
			imsi);
		return;
	}

	if (strcmp(imsi, m_imsi) == 0)
		return;

	LOGP(DRLCMAC, LOGL_INFO,
		"Modifying MS object, TLLI = 0x%08x, IMSI '%s' -> '%s'\n",
		tlli(), m_imsi, imsi);

	strncpy(m_imsi, imsi, sizeof(m_imsi));
	m_imsi[sizeof(m_imsi) - 1] = '\0';
}

void GprsMs::set_ta(uint8_t ta_)
{
	if (ta_ == m_ta)
		return;

	LOGP(DRLCMAC, LOGL_INFO,
		"Modifying MS object, TLLI = 0x%08x, TA %d -> %d\n",
		tlli(), m_ta, ta_);

	m_ta = ta_;
}

void GprsMs::set_ms_class(uint8_t ms_class_)
{
	if (ms_class_ == m_ms_class)
		return;

	LOGP(DRLCMAC, LOGL_INFO,
		"Modifying MS object, TLLI = 0x%08x, MS class %d -> %d\n",
		tlli(), m_ms_class, ms_class_);

	m_ms_class = ms_class_;
}

void GprsMs::update_error_rate(gprs_rlcmac_tbf *tbf, int error_rate)
{
	struct gprs_rlcmac_bts *bts_data;
	int64_t now;
	uint8_t max_cs_ul = 4, max_cs_dl = 4;

	OSMO_ASSERT(m_bts != NULL);
	bts_data = m_bts->bts_data();

	if (error_rate < 0)
		return;

	now = now_msec();

	if (bts_data->max_cs_ul)
		max_cs_ul = bts_data->max_cs_ul;

	if (bts_data->max_cs_dl)
		max_cs_dl = bts_data->max_cs_dl;

	/* TODO: Support different CS values for UL and DL */

	if (error_rate > bts_data->cs_adj_upper_limit) {
		if (m_current_cs_dl > 1) {
			m_current_cs_dl -= 1;
			m_current_cs_ul = m_current_cs_dl;
			LOGP(DRLCMACDL, LOGL_INFO,
				"MS (IMSI %s): High error rate %d%%, "
				"reducing CS level to %d\n",
				imsi(), error_rate, m_current_cs_dl);
			m_last_cs_not_low = now;
		}
	} else if (error_rate < bts_data->cs_adj_lower_limit) {
		if (m_current_cs_dl < max_cs_dl) {
		       if (now - m_last_cs_not_low > 1000) {
			       m_current_cs_dl += 1;
			       if (m_current_cs_dl <= max_cs_ul)
				       m_current_cs_ul = m_current_cs_dl;

			       LOGP(DRLCMACDL, LOGL_INFO,
				       "MS (IMSI %s): Low error rate %d%%, "
				       "increasing CS level to %d\n",
				       imsi(), error_rate, m_current_cs_dl);
			       m_last_cs_not_low = now;
		       } else {
			       LOGP(DRLCMACDL, LOGL_DEBUG,
				       "MS (IMSI %s): Low error rate %d%%, "
				       "ignored (within blocking period)\n",
				       imsi(), error_rate);
		       }
		}
	} else {
		LOGP(DRLCMACDL, LOGL_DEBUG,
			"MS (IMSI %s): Medium error rate %d%%, ignored\n",
			imsi(), error_rate);
		m_last_cs_not_low = now;
	}
}