#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <string.h>

#define error "minimal_length maximal_length options custom_characters\n"

int str_to_int(char* str) {
  int output = 0;

  for (int i = 0; i < strlen(str); i++) {
    if (str[i] < '0' || str[i] > '9') {
      printf("That is not a number.\n");
      exit(1);
    }

    output *= 10;
    output += str[i] - '0';
  }

  return output;
}

void not_avaliable_options(char** argv) {
  if (strcmp(argv[3], "-c") != 0) {
    printf(error);
    exit(1);
  }
}

void invalid_args(int argc) {
  if (argc < 4 && argc > 5) {
    printf("nuhuh\n");
    exit(1);
  }
}

char* character_list(int argc, char** argv) {
  const char uppercase[] = "QWERTZUIOPASDFGHJKLYXCVBNM";
  const char lowercase[] = "qwertzuiopasdfghjklyxcvbnm";
  const char symbols[] = "/!?._-#&";
  const char numbers[] = "0123456789";

  char* output;

  if (argc == 4) {
    int final_size = 0;

    for (int i = 0; argv[3][i] != '\0'; i++) {
      switch (argv[3][i]) {
        case 'U':
          final_size += sizeof(uppercase) - 1;
          break;
        case 'l':
          final_size += sizeof(lowercase) - 1;
          break;
        case 's':
          final_size += sizeof(symbols) - 1;
          break;
        case 'n':
          final_size += sizeof(numbers) - 1;
          break;
        default:
          printf(error);
          exit(1);
      }
    }

    output = malloc(sizeof(char) * (final_size + 1));

    int last_index = 0;
    const char* current_list;
    int size;

    for (int i = 0; argv[3][i] != '\0'; i++) {
      switch (argv[3][i]) {
        case 'U':
          current_list = uppercase;
          size = sizeof(uppercase) - 1;
          break;
        case 'l':
          current_list = lowercase;
          size = sizeof(lowercase) - 1;
          break;
        case 's':
          current_list = symbols;
          size = sizeof(symbols) - 1;
          break;
        case 'n':
          current_list = numbers;
          size = sizeof(numbers) - 1;
          break;
      }

      for (int j = 0; j < size; j++) {
        output[last_index] = current_list[j];
        last_index++;
      }
    }
    output[final_size] = '\0';
  }

  else if (argc == 5) {
    int final_size = 0;

    for (int i = 0; argv[4][i] != '\0'; i++) {
      final_size++;
    }

    output = malloc(sizeof(char) * (final_size + 1));

    for (int i = 0; argv[4][i] != '\0'; i++) {
      output[i] = argv[4][i];
    }

    output[final_size] = '\0';
  }

  return output;
}

int random_len(int min_length, int max_length) {
  return rand() % (max_length - min_length + 1) + min_length;
}

char* random_str(int length, char* symbols) {
  char* str = malloc(sizeof(char) * (length + 1));

  for (int i = 0; i < length; i++) {
    int index = rand() % strlen(symbols);
    str[i] = symbols[index];
  }

  str[length] = '\0';

  return str;
}

int main(int argc, char** argv) {
  invalid_args(argc);

  if (argc == 5) {
    not_avaliable_options(argv);
  }

  srand(time(NULL));

  int min_length = str_to_int(argv[1]);
  int max_length = str_to_int(argv[2]);

  if (min_length > max_length) {
    printf("Your minimal length is longer than your maximal length.\n");
    exit(1);
  }

  int length = random_len(min_length, max_length);

  char* symbols = character_list(argc, argv);
  char* password = random_str(length, symbols);
  free(symbols);
  puts(password);
  free(password);
}