/* 
 * Copyright (C) 2026 Peter Mikkelsen <petermikkelsen10@gmail.com>
 *
 * This file is part of aplwc.
 *
 * Aplwc 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 3 of the License, or
 * (at your option) any later version.
 *
 * Aplwc 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 aplwc.  If not, see <https://www.gnu.org/licenses/>.
 */

#include "aplwc_internal.h"

struct scan_state {
	struct aplwc *aplwc;
	struct string **text;
	size_t offset;
	int skip_number_and_identifier;
};

static void
init_scan_state(struct scan_state *state, struct aplwc *aplwc, struct string **text)
{
	state->aplwc = aplwc;
	state->text = text;
	state->offset = 0;
	state->skip_number_and_identifier = 0;
}

static int
is_space(uint32_t c)
{
	return c == ' ';
}

static int
is_letter(uint32_t c)
{
	return ((c >= 'a') && (c <= 'z')) || ((c >= 'A') && (c <= 'Z'));
}

static int
is_digit(uint32_t c)
{
	return (c >= '0') && (c <= '9');
}

static uint32_t
peek(struct scan_state *state)
{
	return string_char(*state->text, state->offset);
}

static uint32_t 
advance(struct scan_state *state)
{
	state->offset += char_length(*state->text, state->offset);
	state->skip_number_and_identifier = 0;
	return peek(state);
}

static enum aplwc_rc
newsym(struct scan_state *state, size_t from, size_t length, symbol_t *id)
{
	struct string *s;

	if((s = substring(state->aplwc, *state->text, from, length)) == NULL)
		return state->aplwc->last_error;
	return getsym(state->aplwc, s, id);
}

static void
skip_space(struct scan_state *state)
{
	while(is_space(peek(state)))
		advance(state);
}

#define T tokens->tokens[token_index]

static enum aplwc_rc
single_sym(struct scan_state *state, struct token_list *tokens, size_t token_index, int check_only)
{
	uint32_t c;
	size_t start;
	symbol_t sym;
	enum aplwc_rc rc;

	MEMPTRS(state->aplwc, 1);
	MEMPTR(0, tokens);

	rc = APLWC_OK;
	c = peek(state);
	start = state->offset;

	switch(c){
	case 0x2190: T.tag = TOKEN_TAG_LEFT_ARROW; break;
	case 0x22C4: T.tag = TOKEN_TAG_DIAMOND; break;
	case 0x2207: T.tag = TOKEN_TAG_DEL; break;
	case 0x2336: T.tag = TOKEN_TAG_IBEAM; break;
	case 0x2395: T.tag = TOKEN_TAG_QUAD; break;
	case '\n':   T.tag = TOKEN_TAG_NEWLINE; break;
	case '(':    T.tag = TOKEN_TAG_LEFT_PAREN; break;
	case ')':    T.tag = TOKEN_TAG_RIGHT_PAREN; break;
	default:
		T.tag = TOKEN_TAG_UNKNOWN_SYM;
		if(!check_only){
			if((rc = newsym(state, start, 1, &sym)) != APLWC_OK)
				goto end;
			T.data.symbol = sym;
		}
		break;
	}

	advance(state);
end:
	MEMPTRS_EXIT(state->aplwc);
	return rc;
}

static enum aplwc_rc
identifier(struct scan_state *state, struct token_list *tokens, size_t token_index, int check_only)
{
	uint32_t c;
	size_t start, len;
	enum aplwc_rc rc;
	symbol_t sym;

	MEMPTRS(state->aplwc, 1);
	MEMPTR(0, tokens);

	rc = APLWC_INVALID_SYNTAX;

	if(state->skip_number_and_identifier || (!is_letter(peek(state))))
		goto end;

	start = state->offset;
	len = 0;
	do{
		c = advance(state);
		len++;
	}while(is_letter(c) || is_digit(c) || (c == '_'));

	T.tag = TOKEN_TAG_IDENTIFIER;
	if(!check_only){
		if((rc = newsym(state, start, len, &sym)) != APLWC_OK)
			goto end;
		T.data.symbol = sym;
	}

	state->skip_number_and_identifier = 1;
	rc = APLWC_OK;
end:
	MEMPTRS_EXIT(state->aplwc);
	return rc;
}

static enum aplwc_rc
keyword(struct scan_state *state, struct token_list *tokens, size_t token_index, int check_only)
{
	uint32_t c;
	size_t start, len;
	enum aplwc_rc rc;
	symbol_t sym;
	enum keyword kw;

	MEMPTRS(state->aplwc, 1);
	MEMPTR(0, tokens);

	rc = APLWC_INVALID_SYNTAX;

	if(peek(state) != ':')
		goto end;
	c = advance(state);

	start = state->offset;
	len = 0;
	do{
		c = advance(state);
		len++;
	}while(is_letter(c));

	rc = APLWC_OK;
	T.tag = TOKEN_TAG_KEYWORD;
	if(!check_only){
		if((rc = newsym(state, start, len, &sym)) != APLWC_OK)
			goto end;

		for(kw = 0; kw < N_KWDS; kw++){
			if(sym == state->aplwc->keyword_symbols[kw]){
				T.data.keyword = kw;
				break;
			}
		}
		if(kw == N_KWDS)
			rc = APLWC_INVALID_SYNTAX;

	}
end:
	MEMPTRS_EXIT(state->aplwc);
	return rc;
}

static enum aplwc_rc
number(struct scan_state *state, struct token_list *tokens, size_t token_index, int check_only)
{
	uint32_t c;
	int has_digits;
	enum aplwc_rc rc;

	MEMPTRS(state->aplwc, 1);
	MEMPTR(0, tokens);

	UNUSED_PARAMETER(check_only);

	rc = APLWC_INVALID_SYNTAX;
	c = peek(state);

	if(state->skip_number_and_identifier)
		goto end;

	has_digits = 0;

	if(c == 0xAF) /* High minus */
		c = advance(state);
	
	if(is_digit(c)){ /* integer part */
		has_digits = 1;	
		do
			c = advance(state);
		while(is_digit(c));
	}

	if(c == '.'){
		c = advance(state);

		if(is_digit(c)){ /* fractional part */
			has_digits = 1;
			do
				c = advance(state);
			while(is_digit(c));
		}
	}

	if(has_digits == 0)
		goto end;

	T.tag = TOKEN_TAG_NUMBER;
	state->skip_number_and_identifier = 1;
	rc = APLWC_OK;
end:
	MEMPTRS_EXIT(state->aplwc);
	return rc;
}

static enum aplwc_rc
text(struct scan_state *state, struct token_list *tokens, size_t token_index, int check_only)
{
	uint32_t c;
	enum aplwc_rc rc;

	MEMPTRS(state->aplwc, 1);
	MEMPTR(0, tokens);

	UNUSED_PARAMETER(check_only);

	rc = APLWC_INVALID_SYNTAX;;
	c = peek(state);
	if(c != '\'')
		goto end;

	do
		c = advance(state);
	while((c != '\n') && (c != 0) && (c != '\''));

	if(c == '\'')
		advance(state);
	else
		goto end;

	T.tag = TOKEN_TAG_TEXT;
	rc = APLWC_OK;
end:
	MEMPTRS_EXIT(state->aplwc);
	return rc;
}

static enum aplwc_rc
comment(struct scan_state *state, struct token_list *tokens, size_t token_index, int check_only)
{
	uint32_t c;
	enum aplwc_rc rc;

	MEMPTRS(state->aplwc, 1);
	MEMPTR(0, tokens);

	UNUSED_PARAMETER(check_only);

	rc = APLWC_INVALID_SYNTAX;
	c = peek(state);
	if(c != 0x235D)
		goto end;

	do
		c = advance(state);
	while(c != '\n');

	T.tag = TOKEN_TAG_COMMENT;
	rc = APLWC_OK;
end:
	MEMPTRS_EXIT(state->aplwc);
	return rc;
}

static enum aplwc_rc
next_token(struct scan_state *state, struct token_list *tokens, size_t token_index, int check_only)
{
	enum aplwc_rc rc;
	size_t i;
	enum aplwc_rc (*scans[])(struct scan_state *, struct token_list *, size_t, int) = {
		identifier,
		keyword,
		number,
		text,
		comment,
		single_sym /* Must be last */
	};
	MEMPTRS(state->aplwc, 1);
	MEMPTR(0, tokens);

	skip_space(state);
	T.start = state->offset;
	rc = APLWC_INVALID_SYNTAX;
	for(i = 0; (rc == APLWC_INVALID_SYNTAX) && (i < NELEM(scans)); i++){
		rc = scans[i](state, tokens, token_index, check_only);
		switch(rc){
		case APLWC_OK:
			break;
		case APLWC_INVALID_SYNTAX:
			state->offset = tokens->tokens[token_index].start;
			break;
		default:
			goto end;
		}
	}
	T.end = state->offset;
	skip_space(state);
end:
	MEMPTRS_EXIT(state->aplwc);
	return rc;
}

#undef T

static enum aplwc_rc 
check(struct aplwc *aplwc, struct string *text, size_t *n)
{
	struct scan_state state;
	struct token_list *tokens;
	enum aplwc_rc ret;
	size_t count;

	MEMPTRS(aplwc, 2);
	MEMPTR(0, text);

	if((tokens = memory_alloc_token_list(aplwc, 1)) == NULL){
		ret = aplwc->last_error;
		goto end;
	}
	MEMPTR(1, tokens);

	init_scan_state(&state, aplwc, &text);

	for(count = 0; peek(&state); count++){
		ret = next_token(&state, tokens, 0, 1);
		if(ret != APLWC_OK)
			goto end;
	}

	*n = count;
	ret = APLWC_OK;
end:
	MEMPTRS_EXIT(aplwc);
	return ret; 
}

static enum aplwc_rc
scan(struct aplwc *aplwc, struct string *text, struct token_list *tokens)
{
	struct scan_state state;
	enum aplwc_rc ret;
	size_t count;

	MEMPTRS(aplwc, 2);
	MEMPTR(0, text);
	MEMPTR(1, tokens);

	init_scan_state(&state, aplwc, &text);

	ret = APLWC_OK;
	for(count = 0; (ret == APLWC_OK) && peek(&state); count++){
		ret = next_token(&state, tokens, count, 0);
	}

	MEMPTRS_EXIT(aplwc);
	return ret;
}

struct token_list *
scan_string(struct aplwc *aplwc, struct string *text, int oneline)
{
	enum aplwc_rc rc;
	struct token_list *tokens;
	size_t n, i;

	MEMPTRS(aplwc, 2);
	MEMPTR(0, text);

	tokens = NULL;
	if((rc = check(aplwc, text, &n)) != APLWC_OK)
		goto end;

	tokens = memory_alloc_token_list(aplwc, n);
	if(tokens == NULL){
		rc = aplwc->last_error;
		goto end;
	}
	MEMPTR(1, tokens);

	tokens->text = text;
	tokens->length = n;
	if((rc = scan(aplwc, text, tokens)) != APLWC_OK)
		goto end;

	for(i = 0; oneline && (i < n); i++){
		if(tokens->tokens[i].tag != TOKEN_TAG_NEWLINE)
			continue;

		for(i++; i < n; i++){
			if(tokens->tokens[i].tag != TOKEN_TAG_NEWLINE){
				rc = APLWC_INVALID_SYNTAX;
				tokens = NULL;
				goto end;
			}
		}
	}

end:
	aplwc->last_error = rc;
	MEMPTRS_EXIT(aplwc);
	return tokens;
}

static void
resolve_unknown(struct aplwc_module *module, struct token *t)
{
	symbol_t s;
	struct module_member *m;

	assert(t && (t->tag == TOKEN_TAG_UNKNOWN_SYM));
	if(module == NULL)
		return;

	s = t->data.symbol;

	for(m = module->members; m; m = m->link){
		if(m->name == s){
found:
			t->tag = TOKEN_TAG_IDENTIFIER;
			return;
		}
	}

	for(m = module->imports; m; m = m->link){
		if(m->name == s)
			goto found;
	}
}

enum aplwc_rc
check_tokens(struct aplwc_module *module, struct token_list *tokens)
{
	size_t i;
	enum aplwc_rc rc;

	for(i = 0, rc = APLWC_OK; (rc == APLWC_OK) && (i < tokens->length); i++){
		switch(tokens->tokens[i].tag){
		case TOKEN_TAG_UNKNOWN_SYM:
			resolve_unknown(module, &tokens->tokens[i]);
			if(tokens->tokens[i].tag == TOKEN_TAG_UNKNOWN_SYM)
				return APLWC_INVALID_SYNTAX;
			break;
		default:
			break;
		}
	}

	return rc;
}

enum aplwc_rc
keyword_init(struct aplwc *aplwc)
{
	enum keyword kw;
	const char *cstr;
	struct string *str;
	symbol_t sym;

	aplwc->last_error = APLWC_OK;
	for(kw = 0; kw < N_KWDS; kw++){
		switch(kw){
		case KW_MODULE: cstr = "module"; break;
		case KW_SYMBOL: cstr = "symbol"; break;
		case KW_EXPORT: cstr = "export"; break;
		case N_KWDS: assert(0); break;
		}

		if((str = chars_to_string(aplwc, cstr, -1)) == NULL)
			break;
		if(getsym(aplwc, str, &sym) != APLWC_OK)
			break;
		aplwc->keyword_symbols[kw] = sym;
	}

	return aplwc->last_error;
}