/* soft-modem B-channel based on spandsp library */

#include <unistd.h>

#include <osmocom/core/utils.h>
#include <osmocom/core/bits.h>
#include <osmocom/core/logging.h>

#include <spandsp/telephony.h>
#include <spandsp/g711.h>
#include <spandsp/logging.h>

#include <spandsp/alloc.h>
#include <spandsp/at_interpreter.h>
#include <spandsp/async.h>
#include <spandsp/data_modems.h>

#include "bchan.h"
#include "errno.h"

/***********************************************************************
 * spandsp callbacks
 ***********************************************************************/

static int cb_at_tx_handler(void *user_data, const uint8_t *buf, size_t len)
{
	/* write to stdout for now */
	return write(1, buf, len);
}

static int cb_modem_ctrl_hdlr(data_modems_state_t *ms, void *user_data, int op, const char *num)
{
	printf("MODEM CONTROL: %s\n", at_modem_control_to_str(op));
	switch (op) {
	case AT_MODEM_CONTROL_CALL:
		data_modems_call_event(ms, AT_CALL_EVENT_CONNECTED);
		break;
	case AT_MODEM_CONTROL_ANSWER:
		data_modems_call_event(ms, AT_CALL_EVENT_ANSWERED);
		break;
	}
	return 0;
}

static void cb_put_msg(void *user_data, const uint8_t msg[], int len)
{
	if (len < 0)
		printf("Status %s\n", signal_status_to_str(len));
	else
		printf("Put %d '%s'\n", len, msg);
}

static int cb_get_msg(void *user_data, uint8_t msg[], int len)
{
	return 0;
}

/***********************************************************************
 * bchan integration
 ***********************************************************************/

struct spandsp_priv {
	data_modems_state_t *ms;
	g711_state_t *g711;
};

static int spandsp_init(struct call_state *cst)
{
	struct spandsp_priv *rpp;
	logging_state_t *logging;

	rpp = cst->priv = talloc_zero(cst, struct spandsp_priv);
	if (!rpp)
		return -ENOMEM;

	rpp->ms = data_modems_init(NULL, false, cb_at_tx_handler, NULL, cb_modem_ctrl_hdlr,
				   NULL, cb_put_msg, cb_get_msg, rpp);
	OSMO_ASSERT(rpp->ms);
	logging = data_modems_get_logging_state(rpp->ms);
	span_log_set_level(logging, SPAN_LOG_DEBUG | SPAN_LOG_SHOW_TAG | SPAN_LOG_SHOW_SAMPLE_TIME);
	span_log_set_tag(logging, "modem");
	/* this is the default, but calling it now applies above-mentioned log level */
	data_modems_set_modem_type(rpp->ms, DATA_MODEM_V8, 0, 0);
	//data_modems_set_modem_type(rpp->ms, DATA_MODEM_BELL103, 0, 0);
	rpp->g711 = g711_init(NULL, G711_ALAW);
	data_modems_call_event(rpp->ms, AT_CALL_EVENT_ANSWERED);

	return 0;
}

static void spandsp_rx(struct call_state *cst, const uint8_t *data, size_t len)
{
	struct spandsp_priv *rpp = cst->priv;
	int16_t s16_buf[len];
	uint8_t tx_buf[len];
	int rc;

	/* mISDN/CAPI bit order != spandsp order */
	osmo_revbytebits_buf((uint8_t *)data, len);

	/* A-law -> S16 */
	rc = g711_decode(rpp->g711, s16_buf, data, len);
	OSMO_ASSERT(rc == len);

	rc = data_modems_rx(rpp->ms, s16_buf, len);
	OSMO_ASSERT(rc == 0);

	/* generate respective number of output samples and transmit them */
	rc = data_modems_tx(rpp->ms, s16_buf, len);
	OSMO_ASSERT(rc == len);

	/* A-law <- S16 */
	rc = g711_encode(rpp->g711, tx_buf, s16_buf, len);
	OSMO_ASSERT(rc == len);

	/* mISDN/CAPI bit order != spandsp order */
	osmo_revbytebits_buf(tx_buf, len);

	bchan_call_tx(cst, tx_buf, len);
}

static void spandsp_fini(struct call_state *cst)
{
	struct spandsp_priv *rpp = cst->priv;
	g711_free(rpp->g711);
	data_modems_free(rpp->ms);
	talloc_free(rpp);
	cst->priv = NULL;
}

static void spandsp_log_cb(void *user_data, int level, const char *text)
{
	LOGP(DCAPI, LOGL_INFO, text);
}

static struct bchan_handler bch_spandsp = {
	.name = "spandsp",
	.cfg = {
		.proto = { CAPI_B1_64k_TRANSPARENT, CAPI_B2_TRANSPARENT, CAPI_B3_TRANSPARENT },
		.ncpi = NULL,
		.max_b_data_blocks = 10,
		.max_b_data_len = 32,
	},
	.ops = {
		.init = spandsp_init,
		.rx_data = spandsp_rx,
		.fini = spandsp_fini,
	},
};

static void *span_alloc_cb(size_t size)
{
	return talloc_size(g_ctx, size);
}

static void span_free_cb(void *ptr)
{
	talloc_free(ptr);
}

static __attribute__((constructor)) void hdlr_spandsp_init(void)
{
	/* memory allocator */
	span_mem_allocators(span_alloc_cb, NULL, span_free_cb, NULL, NULL);

	/* logging */
	//span_set_message_handler(spandsp_log_cb, NULL);

	bchan_handler_register(&bch_spandsp);
}