/* Aplwc - A Programming Language With Constraints
 *
 * 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 <stdio.h>
#include <string.h>
#include <aplwc.h>
#include "aplwc_internal.h"

static void scan(struct aplwc_eval_context *);
static struct aplwc_token *emit(struct aplwc_eval_context *, enum aplwc_token_tag, size_t);
static bool at_end(struct aplwc_eval_context *);
static void skip_whitespace(struct aplwc_eval_context *);
static char peek(struct aplwc_eval_context *, size_t);
static void consume(struct aplwc_eval_context *, size_t);
static void give_up(struct aplwc_eval_context *);
static bool scan_syscmd(struct aplwc_eval_context *);

void
aplwc_scan_line(struct aplwc_eval_context *context, const char *line)
{
	size_t linelen = strlen(line);

	if(context->text){
		size_t textlen = strlen(context->text);
		context->text = context->aplwc->realloc(context->text, textlen + linelen + 2);
		context->text[textlen] = '\n';
		memcpy(context->text+textlen+1, line, linelen + 1);
	}else{
		context->text = context->aplwc->alloc(linelen+1);
		memcpy(context->text, line, linelen + 1);
	}

	if(context->tokens){
		for(size_t i = 0; i < context->n_tokens; i++)
			context->aplwc->free(context->tokens[i]);
		context->aplwc->free(context->tokens);
	}
	scan(context);
}

static void
scan(struct aplwc_eval_context *context)
{
	context->n_tokens = 0;
	context->tokens = NULL;
	context->offset = 0;
	context->length = strlen(context->text);

	while(!at_end(context)){
		bool scanned = false;
		
		skip_whitespace(context);
		if(at_end(context))
			continue;

		if(context->n_tokens == 0)
			scanned |= scan_syscmd(context);
		
		if(!scanned)
			give_up(context);
	}
}

static struct aplwc_token *
emit(struct aplwc_eval_context *context, enum aplwc_token_tag tag, size_t length)
{
	struct aplwc_token *tok = context->aplwc->alloc(sizeof(*tok));
	context->n_tokens++;
	context->tokens = context->aplwc->realloc(context->tokens, sizeof(*context->tokens) * context->n_tokens);
	context->tokens[context->n_tokens-1] = tok;

	memset(tok, 0, sizeof(*tok));
	tok->tag = tag;
	tok->offset_start = context->offset;
	tok->offset_end = tok->offset_start + length - 1;

	consume(context, length);
	
	return tok;
}

static bool
at_end(struct aplwc_eval_context *context)
{
	return context->offset == context->length;
}

static void
skip_whitespace(struct aplwc_eval_context *context)
{
	for(;;){
		char c = peek(context, 0);
		if((c == ' ') || (c == '\t'))
			consume(context, 1);
		else
			break;
	}
}

static char
peek(struct aplwc_eval_context *context, size_t offset)
{
	size_t index = context->offset + offset;
	if(index < context->length)
		return context->text[index];
	else
		return 0;
}

static void
consume(struct aplwc_eval_context *context, size_t n)
{
	context->offset += n;
}

static void
give_up(struct aplwc_eval_context *context)
{
	emit(context, APLWC_TOKEN_ERROR, context->length - context->offset);
}

static bool
scan_syscmd(struct aplwc_eval_context *context)
{
	if(peek(context, 0) != ')')
		return false;

	size_t len;
	
	/* Scan the syscmd itself */
	for(len = 1; !((peek(context, len) == 0) || (peek(context, len) == ' ')); len++);
	emit(context, APLWC_TOKEN_SYSCMD, len);

	/* Skip the leading whitespace */
	skip_whitespace(context);

	/* Take the rest of the line as arguments */
	for(len = 0; !((peek(context, len) == 0) || (peek(context, len) == '\n')); len++)
		printf("arglen = %zu\n", len);
	if(len > 0)
		emit(context, APLWC_TOKEN_SYSCMD_ARGS, len);

	return true;
}