/*
 * include/lexer.h
 *
 * HUSH lexical analysis module
 * CISC 301 -- Operating Systems, Project 2
 *
 * Copyright (C) 2025  Douglas B. Rumbaugh <dbrumbaugh@harrisburgu.edu>
 *
 * Distributed under the Modified BSD License
 *
 */
#ifndef H_HUSH_LEXER
#define H_HUSH_LEXER

#include <ctype.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "config.h"

enum token_type {
  TKN_COMMAND,
  TKN_OUT_REDIR,
  TKN_IN_REDIR,
  TKN_PIPE,
  TKN_FILENAME,
  TKN_ARG,
  TKN_INVALID,
  TKN_VARKEY,
  TKN_VARVAL
};

typedef struct token {
  char *text;
  enum token_type type;
  struct token *next;
} token;

/*
 * Accepts a null-terminate string representing
 * a full command and returns the pointer to the
 * head of a list of parsed tokens. The provided
 * string must have been trimmed to remove all
 * leading and trailing whitespace characters.
 *
 * The tokens contain pointers into the provided
 * command string, and so the parsed command is
 * only valid so long as the provided string has
 * not been altered.
 *
 * This function's behavior is undefined if the
 * input string is *not* null-terminated, or if
 * it has leading or trailing whitespace.
 */

token *parse_command(char *cmdstr);

/*
 * Accepts the pointer to the head of a list
 * of parsed tokens and validates that the
 * tokens are syntactically valid. If the
 * sequence is valid, NULL will be returned.
 * If the sequence is invalid, a pointer to
 * the first invalid token will be returned.
 */
token *validate_command(token *cmd);

/*
 * Removes all leading and trailing whitespace from
 * the provided string, and returns a pointer to the
 * beginning of the trimmed string. Necessary as the
 * first stage of parsing.
 */
char *trim(char *str);

void print_parsed_command(FILE *file, token *cmd);

void destroy_tokens(token *tokens);

#endif