# L-16 MCS 260 Wed 17 Feb 2010 : a library
#
# We demonstrate the use of files with a simple model
# of a library.

from bkform import *

def show_menu():
   "shows the menu and prompts for a choice"
   print "Welcome to our library!  Choose:"
   print "  0. leave the program"
   print "  1. show all books in the collection"
   print "  2. add a new book to the collection"
   print "  3. check out a book of the library"
   print "  4. return a book to the library"
   c = raw_input("Type 0, 1, 2, 3, or 4 : ");
   return c

def number_of_books():
   "returns the number of books in the collection"
   file = open('books','r')
   collection = file.readlines()
   N = len(collection)
   file.close()
   return N

def show_books():
   "shows the books currently in the collection"
   file = open('books','r')
   collection = file.readlines()
   for book in collection:
      s = ' ' + str(get_key(book))
      s += ' ' + get_title(book)
      if get_status(book):
         print s + ' available'
      else:
         print s + ' checked out'
   file.close()

def add_book():
   "adds a book to the collection"
   N = number_of_books()
   title = raw_input('Give title : ')
   s = pack(N+1,1,title)
   file = open('books','a')
   file.write(s)
   file.close()

def checkout():
   "checks out a book"
   show_books()
   k = input('give book number : ')
   file = open('books','r')
   collection = file.readlines()
   file.close()
   file = open('books','w')
   for book in collection:
      if get_key(book) == k:
         if not get_status(book): 
            print get_title(book) + ' is unavailable'
            file.write(book)
         else:
            file.write(pack(k,0,get_title(book)))
      else:
         file.write(book)
   file.close()

def checkin():
   "return a book to the library"
   k = input('give book number : ')
   file = open('books','r')
   collection = file.readlines()
   file.close()
   file = open('books','w')
   for book in collection:
      if get_key(book) == k:
         d = pack(k,1,get_title(book))
         file.write(d)
      else:
         file.write(book)
   file.close()

def main():
   while True:
      choice = show_menu()
      if choice == '0': break
      if choice == '1': show_books()
      if choice == '2': add_book()
      if choice == '3': checkout()
      if choice == '4': checkin()

main()