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

struct file {
  FILE *file;
  char *filename;
} file_t;

bool show_filenames = false;
bool invert_match = false;
bool line_number = false;
bool ignore_case = false;
bool extended_regex = false;

int usage() {
  printf("Usage: %s [OPTION]... PATTERNS [FILE]...\n", "grep");
  printf("Try '%s --help' for more information.\n", "grep");
  return 2;
}

int main(int argc, char *argv[]) {
  struct file **infiles = malloc(sizeof(FILE));
  infiles[0] = malloc(sizeof(FILE));
  infiles[0]->file = stdin;
  int files_index = 0;
  char **regex = malloc(sizeof(char*));
  regex[0] = NULL;
  int regex_index = 0;
  int opt;

  char line[256];

  if (argc < 2) {
    return usage();
  } else {
    while ((opt = getopt(argc, argv, "::e:vniyE")) != -1) {
      switch (opt) {
        case 'v': 
          invert_match = true;
          break;
        case 'n':
          line_number = true;
          break;
        case 'i':
        case 'y':
          ignore_case = true;
          break;
        case 'E':
          extended_regex = true;
          break;
        case 'e':
          regex[regex_index] = malloc(strlen(optarg));
          regex[regex_index] = optarg;
          regex_index++;
          break;
	case '?':
          printf("%s: invalid option -- '%c'\n", "grep", optopt);
          return usage();
      }
    }
    for (; optind < argc; optind++) {
      if (regex[0] == NULL) {
        regex[0] = malloc(strlen(argv[optind]));
        regex[0] = argv[optind];
        regex_index++;
      } else { 
        if (strcmp(argv[optind], "-")) {
          infiles[files_index] = malloc(sizeof(FILE) + strlen(argv[optind]));
          infiles[files_index]->file = fopen(argv[optind], "r");
          infiles[files_index]->filename = argv[optind];
          if (infiles[files_index]->file == NULL) {
            perror(argv[optind]);
            return -1;
          }
        } else {
          infiles[files_index] = malloc(sizeof(FILE) + strlen("(standard input)"));
          infiles[files_index]->file = stdin;
          infiles[files_index]->filename = "(standard input)";
        }
        files_index++;
      }
    }
  }

  if (files_index > 1) {
    show_filenames = true;
  }
  
  int curline = 1;
  int i = 0;
  int j = 0;
  int cur_line_has_regex = 1;

  int regflags = 0;

  if (extended_regex) {
    regflags |= REG_EXTENDED;
  } 
  if (ignore_case) {
    regflags |= REG_ICASE;
  }

  regex_t exp;
  regmatch_t matches[1];
  do {
      while (fgets(line, sizeof line, infiles[i]->file) != NULL) {
        do {
          regcomp(&exp, regex[j], regflags);
          cur_line_has_regex = regexec(&exp, line, 1, matches, 0);
          if (cur_line_has_regex == 0 && !invert_match) {
            curline++;
            if (line_number) printf("%d:", curline);
            if (show_filenames) {
              printf("%s:%s", infiles[i]->filename, line);
            } else {
              printf("%s", line);
            }
          } else if (cur_line_has_regex != 0 && invert_match) {
            curline++;
            if (line_number) printf("%d:", curline);
            if (show_filenames) {
              printf("%s:%s", infiles[i]->filename, line);
            } else {
              printf("%s", line);
            }
          }
          j++;
          regfree(&exp);
        } while (j < regex_index);
        j = 0;
      }
    i++;
  } while (i < files_index);
  free(infiles);
}