/**************************************************************/

/*  treebnf: a tree oriented bnf library                      */

/*  Copyright (C) 2024  SysDeer Technologies, LLC             */

/*  Released under GPLv2 and GPLv3; see COPYING.TREEBNF.      */

/**************************************************************/

#include <treebnf/treebnf.h>

#define TBNF_STATE_STACK_SIZE   (512)

/* single token, read-only context */

int tbnf_scan_token(const struct tbnf_scan_ctx * sctx, struct tbnf_token * tok)

{

	int ret  = 0;

	int len  = 0;

	int type = 0;

	int tidx = 0;

	int sidx = sctx->tok_scan_state;

	for (; tidx < sctx->tok_scan_nents; ) {

		if (sctx->tok_scan_tbls[sidx][tidx].tok_scan_fn)

			ret = sctx->tok_scan_tbls[sidx][tidx].tok_scan_fn(sctx);

		if (ret > len) {

			len  = ret;

			type = tidx;

		}

		tidx++;

	}

	tok->tok_type = type;

	tok->tok_len  = len;

	tok->tok_off  = sctx->tok_scan_mark - sctx->tok_scan_base;

	return (len > 0) ? 0 : -1;

}

/* scan up to ntoks tokens, read-write context */

int tbnf_scan_tokens(struct tbnf_scan_ctx * sctx, size_t ntoks, struct tbnf_token * tokv, int any)

{

	int                     ret;

	int *                   state;

	int *                   stcap;

	int                     ststk[TBNF_STATE_STACK_SIZE];

	struct tbnf_scan_tbl *  pentry;

	ret      = 0;

	ntoks    = (ntoks > INT32_MAX) ? INT32_MAX : ntoks;

	state    = ststk;

	state[0] = sctx->tok_scan_state;

	stcap    = &state[TBNF_STATE_STACK_SIZE];

	stcap--;

	/*******************************************************************/

	/* a positive return value that's smaller than the original ntoks, */

	/* in combination with mark < cap, indicates an error while trying */

	/* to obtain the next token.                                       */

	/*******************************************************************/

	for (; ntoks && (sctx->tok_scan_mark < sctx->tok_scan_cap); ) {

		if (tbnf_scan_token(sctx,tokv) < 0)

			return (ret > 0) ? ret : (-1);

		pentry = &sctx->tok_scan_tbls[*state][tokv->tok_type];

		switch (pentry->tok_state_op) {

			case TBNF_STATE_POP:

				if (state == ststk)

					return (-1);

				state--;

				sctx->tok_scan_state = *state;

				break;

			case TBNF_STATE_KEEP:

				break;

			case TBNF_STATE_PUSH:

				if (state == stcap)

					return (-1);

				sctx->tok_scan_state = pentry->tok_state_next;

				*++state             = sctx->tok_scan_state;

				break;

		}

		sctx->tok_scan_type  = tokv->tok_type;

		sctx->tok_scan_mark += tokv->tok_len;

		tokv->tok_any = any;

		tokv++;

		ntoks--;

		ret++;

	}

	return ret;

}