/*!@file
  \brief   lexical analyzer implementation for APC
  \details this lexer scans a root directory given from the command line
           for subdirectories and files structured for the APC grammar.
  \author  Jordan Lavatai
  \date    Aug 2016
  ----------------------------------------------------------------------------*/
//stdc
#include <stdio.h>
#include <string.h>
#include <errno.h>
//posix
#include <unistd.h>
#include <stdlib.h>
//bison
#include "fileparser.tab.h"
#define TOKEN_BUF_SIZE 1024
#define DIRP_STACK_SIZE 512

int lexer_init(void);
int lexer(void);

static
int lexer_scan(void);

static
int  token_buf[TOKEN_BUF_SIZE], *tbp, *tbx;
static
DIR* dirp_stack[DIRP_STACK_SIZE], *dsp;

/* Initialize pointers */
int
lexer_init()
{ tbp = tbx = token_buf;
  dsp = dirp_stack;
  return 0;
}

/* Returns a token identifier and sets yylval */
int
lexer()
{ if (lexer_scan() == 0)
    return 0;
  yylval = *tbp++;
  return *tbp++;
}

/* Scanner
   Scans a filename from its alphabetically ordered list of file elements
   and tokenizes the result.  If the file list is empty, then the stack of
   directory elements will be popped and processed as they are encountered.

   Returns the number of tokens generated.
*/
#define MAX_ENTITIES 256
static
int lexer_scan()
{ static struct dirent* entity;
  static struct dirent* files[MAX_ENTITIES];
  static struct dirent* dirs = files + MAX_ENTITIES - 1;
  static int            num_files = 0;
  static int            num_dirs = 0;

  //sort out files and directories, grow directories from bottom up
  while ((entity = readdir(dirp)) != NULL)
    { switch (entity->d_type)
        { case DT_LNK:
          case DT_REG:
            files[num_files++] = entity;
            break;
          case DT_DIR:
            *(dirs - num_dirs++) = entity;
            break;
          case DT_UNKNOWN:
          default:
            printf("Ignoring unknown file: %s\n", entity->d_name);
            break;
        }
    }
  if (errno)
    perror("readdir");
  qsort(&files[0], num_files, sizeof struct dirent*, qalpha);
  num_ents = scandirat(dirfd, ".", &namelist, scanfilter, scancompar);
  if (num_ents < 0)
    { perror("scandirat");
      return -1;
    }
  //process files

  //recurse into directories

}