/*
 * Invoke gsmstack() with any kind of burst. Automaticly decode and retrieve
 * information.
 */
#include "system.h"
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include "gsmstack.h"
#include "gsm_constants.h"
#include "interleave.h"
#include "sch.h"
#include "cch.h"

static void out_gsmdecode(char type, int arfcn, int ts, int fn, char *data, int len);

#if 0
static void
diff_decode(char *dst, char *src, int len)
{
	const char *end = src + len;
	unsigned char last;

	src += 3;
	last = 0;
	memset(dst, 0, 3);
	dst += 3;

	while (src < end)
	{
		*dst = !*src ^ last;
		last = *dst;
		src++;
		dst++;
	}
}
#endif

/*
 * Initialize a new GSMSTACK context.
 */
int
GS_new(GS_CTX *ctx)
{
	memset(ctx, 0, sizeof *ctx);
	interleave_init(&ctx->interleave_ctx, 456, 114);
	ctx->fn = -1;
	ctx->bsic = -1;
	ctx->tun_fd = mktun("gsm", ctx->ether_addr);
	if (ctx->tun_fd < 0)
		return -1;

	return 0;
}

/*
 * 142 bit
 */
int
GS_process(GS_CTX *ctx, int ts, int type, const unsigned char *src)
{
	int fn;
	int bsic;
	int ret;
	unsigned char *data;
	int len;

	if (ts != 0)
		return;

	if (type == SCH)
	{
		ret = decode_sch(src, &fn, &bsic);
		if (ret != 0)
			return 0;
		if ((ctx->bsic > 0) && (bsic != ctx->bsic))
			fprintf(stderr, "WARN: BSIC changed.\n");
		//DEBUGF("FN %d, BSIC %d\n", fn, bsic);
		ctx->fn = fn;
		ctx->bsic = bsic;
		/* Reset message concatenator */
		ctx->burst_count = 0;
		return 0;
	}

	/* If we did not get Frame Number yet then return */
	if (ctx->fn < 0)
		return 0;

	ctx->fn++;
	if (type == NORMAL)
	{
		/* Interested in these frame numbers (cch)
 		 * 2-5, 12-15, 22-25, 23-35, 42-45
 		 * 6-9, 16-19, 26-29, 36-39, 46-49
 		 */
		/* Copy content data into new array */
		//DEBUGF("burst count %d\n", ctx->burst_count);
		memcpy(ctx->burst + (116 * ctx->burst_count), src, 58);
		memcpy(ctx->burst + (116 * ctx->burst_count) + 58, src + 58 + 26, 58);
		ctx->burst_count++;
		/* Return if not enough bursts for a full gsm message */
		if (ctx->burst_count < 4)
			return 0;

		ctx->burst_count = 0;
		data = decode_cch(ctx, ctx->burst, &len);
		if (data == NULL)
			return -1;
		//DEBUGF("OK TS %d, len %d\n", ts, len);

		out_gsmdecode(0, 0, ts, ctx->fn - 4, data, len);
		write_interface(ctx->tun_fd, data+1, len-1, ctx->ether_addr);
#if 0
		if (ctx->fn % 51 != 0) && ( (((ctx->fn % 51 + 5) % 10 == 0) || (((ctx->fn % 51) + 1) % 10 ==0) ) )
			ready = 1;
#endif
		
		return 0;
	}
}


/*
 * Output data so that it can be parsed from gsmdeocde.
 */
static void
out_gsmdecode(char type, int arfcn, int ts, int fn, char *data, int len)
{
	char *end = data + len;

	/* FIXME: speed this up by first printing into an array */
	while (data < end)
		printf(" %02.2x", (unsigned char)*data++);
	printf("\n");
	fflush(stdout);
}