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

  // Copied from
  // https://stackoverflow.com/questions/35103745/read-a-string-as-an-input-using-scanf
  void flush() {
    int c;
    while ((c = getchar()) != '\n' & amp; & amp; c != EOF);
  }

typedef struct {
  char username[15];
  char password[15];
}
User;

typedef struct {
  int id; // must be unique
  char title[50];
  char author[50]; // if more than two, separate using ,(COMMA)
  char ISBN[50];
  char category[50];
  char publication[50];
  char description[255];
  int taken;
}
Book;

int main() {
  char option, admin_option, username[15], password[15], edit_option;
  int first_time, c, i, j, id, found;
  FILE * f;
  User user;
  Book book;

  f = fopen("librarian.check", "r");
  if (f == NULL) {
    fclose(f);
    f = fopen("librarian.check", "w");
    fputc(1, f);
    fclose(f);
  } else {
    fclose(f);
  }

  f = fopen("id.check", "r");
  if (f == NULL) {
    fclose(f);
    f = fopen("id.check", "w");
    fputc(0, f);
    fclose(f);
  } else {
    fclose(f);
  }

  printf("Log in as \n");
  printf("1:  Librarian\n");
  printf("2: Student\n");
  printf("3: Exit\n");
  printf("Enter your choice: ");
  scanf("%c", & amp; option);
  switch (option) {
  case '1':
    f = fopen("librarian.check", "r");
    if (f == NULL) {
      printf("Couldn't read file\n");
      exit(0);
    } else {
      first_time = fgetc(f);
      if (first_time == 1) {
        fclose(f);
        flush();
        printf("Provide username and password to setup\n");
        printf("Username (14 characters max): ");
        fgets(user.username, 15, stdin);
        printf("Password (14 characters max): ");
        fgets(user.password, 15, stdin);

        // write this credential to file
        f = fopen("credential.bin", "wb");
        if (f == NULL) {
          printf("Someting went wrong!!\n");
          exit(0);
        }
        fwrite( & amp; user, sizeof(User), 1, f);
        fclose(f);
        printf("Exit and login again to continue\n");
        f = fopen("librarian.check", "w");
        fputc(0, f);
        fclose(f);
      } else {
        fclose(f);
        flush();
        printf("Provide credential to login\n");
        printf("Username: ");
        fgets(username, 15, stdin);
        printf("Password: ");
        fgets(password, 15, stdin);

        // read the credential from file
        f = fopen("credential.bin", "rb");
        if (f == NULL) {
          printf("Someting went wrong!!\n");
          exit(0);
        }
        fread( & amp; user, sizeof(User), 1, f);
        if (strcmp(username, user.username) != 0 || strcmp(password, user.password) != 0) {
          printf("Username or password invalid\n");
          exit(0);
        }
        printf("Login Successful!!\n");
        printf("1: Add Book\n");
        printf("2: Search Book\n");
        printf("3: Edit Book\n");
        printf("4: Delete Book\n");
        printf("4: Moderate Student Request\n");
        printf("Enter your choice: ");
        scanf("%c", & amp; admin_option);
        switch (admin_option) {
        case '1':
          flush();
          printf("Provide the following information\n");
          printf("Title: ");
          fgets(book.title, 50, stdin);
          printf("Author: ");
          fgets(book.author, 50, stdin);
          printf("ISBN: ");
          fgets(book.ISBN, 50, stdin);
          printf("Category: ");
          fgets(book.category, 50, stdin);
          printf("Publication: ");
          fgets(book.publication, 50, stdin);
          printf("Description: ");
          fgets(book.description, 50, stdin);
          book.taken = 0;

          // increment ID
          f = fopen("id.check", "r");
          if (f == NULL) {
            printf("Someting went wrong\n");
            exit(1);
          }

          id = fgetc(f);
          fclose(f);
          book.id = id;

          // save the record
          f = fopen("book.record", "a");
          fwrite( & amp; book, sizeof(Book), 1, f);
          fclose(f);

          id++;
          f = fopen("id.check", "w");
          fputc(id, f);
          fclose(f);

          printf("Book insertion Successful!!\n");
          break;
        case '2':
          printf("Enter the book id to search: ");
          scanf("%d", & amp; id);

          // search in the database
          f = fopen("book.record", "rb");
          found = 0;
          i = 0;
          while (fread( & amp; book, sizeof(Book), 1, f)) {
            if (book.id == id) {
              // matched
              found = 1;
              printf("Book Found!!\n");
              printf("Title: %s", book.title);
              printf("Author: %s", book.author);
              printf("ISBN: %s", book.ISBN);
              printf("Category: %s", book.category);
              printf("Publication: %s", book.publication);
              printf("Description: %s", book.description);
              break;
            }
            i++;
          }
          if (found == 0) {
            printf("Sorry!! The book is not in the database\n");
          }
          fclose(f);
          break;
        case '3':
          printf("Enter the book id to edit: ");
          scanf("%d", & amp; id);
          f = fopen("book.record", "rb+");
          found = 0;
          while (fread( & amp; book, sizeof(Book), 1, f)) {
            if (book.id == id) {
              // matched
              found = 1;
              break;
            }
          }
          if (found == 0) {
            printf("Sorry!! The book is not in the database\n");
          } else {
            printf("What field do you want to edit:\n");
            printf("1. Title\n");
            printf("2. Author\n");
            printf("3. ISBN\n");
            printf("4. Category\n");
            printf("5. Publication\n");
            printf("6. Description\n");
            printf("Enter your choice: ");
            scanf("\n%c", & amp; edit_option);
            switch (edit_option) {
            case '1':
              flush();
              printf("Enter new title: ");
              fgets(book.title, 50, stdin);
              break;
            case '2':
              printf("Enter new author: ");
              fgets(book.author, 50, stdin);
              break;
            case '3':
              printf("Enter new ISBN: ");
              fgets(book.ISBN, 50, stdin);
              break;
            case '4':
              printf("Enter new Category: ");
              fgets(book.category, 50, stdin);
              break;
            case '5':
              printf("Enter new Publication: ");
              fgets(book.publication, 50, stdin);
              break;
              printf("Enter new Description: ");
              fgets(book.description, 255, stdin);
              break;
            default:
              printf("Enter 1 to 6\n");
              break;
            }
            fseek(f, i, SEEK_SET);
            fwrite( & amp; book, sizeof(Book), 1, f);
            fclose(f);
            printf("Book record modified in the database!!\n");
          }
          break;
        case '4':
          printf("Enter the book id to Delete: ");
          scanf("%d", & amp; id);
          f = fopen("book.record", "rb");
          found = 0;
          while (fread( & amp; book, sizeof(Book), 1, f)) {
            if (book.id == id) {
              // matched
              found = 1;
              break;
            }
          }
          fclose(f);
          if (found == 0) {
            printf("Sorry!! The book is not in the database\n");
          } else {
            // create a temporary file
            FILE * temp;
            temp = fopen("book.temp", "a");
            if (temp == NULL) {
              printf("Something went wrong\n");
              exit(1);
            }

            f = fopen("book.record", "rb");

            // copy all the items except item to delete
            // to temporary file
            while (fread( & amp; book, sizeof(Book), 1, f)) {
              if (book.id != id)
                fwrite( & amp; book, sizeof(Book), 1, temp);
            }
            fclose(f);
            fclose(temp);

            // delete original file
            remove("book.record");

            // rename the temporary file
            rename("book.temp", "book.record");
            printf("Book record deleted from the database!!\n");
          }
          break;
        default:
          printf("Enter only 1 - 4\n");
          break;
        }
      }
    }

    break;
  case '2':
    printf("Enter the book id to search: ");
    scanf("%d", & amp; id);

    // search in the database
    f = fopen("book.record", "rb");
    found = 0;
    i = 0;
    while (fread( & amp; book, sizeof(Book), 1, f)) {
      if (book.id == id) {
        // matched
        found = 1;
        printf("Book Found!!\n");
        printf("Title: %s", book.title);
        printf("Author: %s", book.author);
        printf("ISBN: %s", book.ISBN);
        printf("Category: %s", book.category);
        printf("Publication: %s", book.publication);
        printf("Description: %s", book.description);
        printf("Status: ");
        if (book.taken == 1) {
          printf("Not Available");
        } else {
          printf("Available\n");
        }
        break;
      }
      i++;
    }
    if (found == 0) {
      printf("Sorry!! The book is not in the database\n");
    }
    fclose(f);
    break;
  case '3':
    printf("Bye!!\n");
    exit(0);
  default:
    printf("Enter either 1 or 2 only\n");
    break;
  }