/*
 * main.c - Main entry point for neogrep
 * $author:        Buckwheat of Neo-Sekai Club
 * $creation-date: 2026/02/28
 * $version:       1.0.0
 *
 */

#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <sys/mman.h>
#include <sys/stat.h>

#define NEWLINE '\n'
#define NULTERM '\0'

/* Function Declarations */

static int
err_msg(const char*);

static int
substr_check(char*, const char*, int, int, int);

/* Function Definitions */

static int
err_msg(const char* msg)
{
  printf("ERROR: %s\n", msg);
  return 1;
}

static int
substr_check(char* data, const char* substr, int start, int len, int line)
{
  int   newlen = len + 1;
  char* str    = (char*)malloc(sizeof(char) * newlen);
  
  if (!str)
    return -1;

  for (int index = 0; index < newlen; index++)
    if (index == len)
      str[index] = NULTERM;
    else
      str[index] = data[index + start];

  if (strstr(str, substr))
    printf("\033[1;31mLine %d: \033[4;32m%s\033[0m", line, str);

  free(str);
        
  return 0;
}

int
main(int argc, char** argv)
{
  if (argc > 3 || argc < 3)
    return err_msg("Insufficient arg count\nUsage: ng <file> <string>");

  struct stat file_info;
  char*       file_map;

  int         char_count = 0;
  int         file_size  = 0;
  int         line_count = 0;
  int         src_file   = -1;
  const char* substr     = argv[2];
  const char* src_name   = argv[1];

  src_file = open(src_name, O_RDONLY, 0);
  if (src_file == -1)
    return err_msg("Could not open input file");

  fstat(src_file, &file_info);
  file_size = file_info.st_size;

  file_map = (char*)mmap(NULL, file_size, PROT_READ,
      MAP_SHARED, src_file, 0);
  
  if (file_map == MAP_FAILED)
  {
    close(src_file);
    return err_msg("mmap failed");
  }

  for (int index = 0; index < file_size; index++)
  {
    char current = file_map[index];

    if (current == NEWLINE)
    {
      line_count++;
      char_count = substr_check(file_map, substr,
          index - char_count, char_count + 1, line_count);
    }
    
    else
      char_count++;

    if (char_count == -1)
      return err_msg("Failed to malloc");
  }

  if (munmap(file_map, file_size) == -1)
    return err_msg("munmap failed");
        
  return 0;
}