/* (C) Copyright 2008 Nick Mudge <mudgen@gmail.com>
 * This code can be freely copied and modified.
 */
#include <ctype.h>
#include "parser.h"

extern char *input;
Token *token;

static char *next_input = NULL;
static Token *la(void);

void peek(void) {
	char *beginning;
	if(input != next_input && next_input != NULL)
		return;
	beginning = input;
	token = la();	
	next_input = input;
	input = beginning;
}
void next(void) {
	input = next_input;
}

Token *la(void) {	
	Token *token;
	if ((token = malloc(sizeof(Token))) == NULL) {
		memory_error();
	}
	while(isspace(*input)) input++;
	if(*input == '\0') {
		token->id = END_OF_TOKENS;
		return token;
	}		
	if(isdigit(*input)) {
		token->id = NUM;
		token->value = atoi(input);
		while(isdigit(*input)) input++;
		return token;
	}
	else if(*input == '+' || *input == '-' || *input == '*' || *input == '/' || *input == '(' || *input == ')') {
		token->id = *input;
		input++;
		return token;
	}
	token->id = ERROR_CHAR;
	return token;
}