# Imagine you are writing a software that maintains
# an inventory for the "Awesome" book store.
# The software contains five main menu options:
#
# 1. add_book(inventory, book_info)
#    - add the book's title and information
#      to the inventory dictionary if the title
#      has not been added.
#      (you decide what to do if the book has already been added;
#      for example, display an informative message)
#
# 2. update_book(inventory, book_info)
#    - update the book's information in the inventory dictionary
#      if the book title has been added.
#      (you decide what to do if the book does not exist in the inventory;
#      for example, display an informative message)
#
# 3. add_quantity(inventory, book_title, quantity)
#    - add the quantity to the specified book's title
#      (you should consider -- how to handle if the book does not exist)
#
# 4. reduce_quantity(inventory, book_title, quantity)
#    - reduce the quantity of the specified book's title
#      (you should consider -- how to handle if the book does not exist)
#
# 5. print_inventory(inventory)
#    - display the inventory in an easy to read format
#      (you decide what format is easy to read, don't simply print a dict)


def add_book(inventory, book_info):
    if book_info['title'] in inventory.keys():
        print(book_info['title'] + ' is already in the inventory, cannot add again')
    else:
        # Get title and remove it from book_info dict.
        title = book_info.pop('title')

        # Now book_info has only year, price, quantity
        # Then, add this book to the inventory where
        # key is the book's title, value is a book_info dict
        inventory[title] = book_info


def update_book(inventory, book_info):
    if book_info['title'] not in inventory.keys():
        print(book_info['title'] + ' does not exist. Cannot update')
    else:
        title = book_info.pop('title')
        inventory[title] = book_info


def add_quantity(inventory, book_title, quantity):
    if book_title not in inventory.keys():
        print(book_title + ' does not exist. Cannot add the quantity')
    else:
        book_info = inventory[book_title]
        book_info['quantity'] += quantity


def reduce_quantity(inventory, book_title, quantity):
    if book_title not in inventory.keys():
        print(book_title + ' does not exist. Cannot reduce the quantity')
    else:
        book_info = inventory[book_title]
        book_info['quantity'] -= quantity


def print_inventory(inventory):
    for title, book_info in inventory.items():
        print(title)
        for k_info, v_info in book_info.items():
            print("  ", k_info, "=", v_info)


print("==== Awesome store book inventory ==== \n")
book_inventory = {}

book1 = {'title': 'Intro to Python', 'year': 2019, 'price': 60, 'quantity': 75}
book2 = {'title': 'Python - banana', 'year': 2018, 'price': 64, 'quantity': 100}
book3 = {'title': 'Python Master', 'year': 2018, 'price': 70, 'quantity': 59}

add_book(book_inventory, book1)
# inventory should now contain
#   {'Intro to Python': {'year': 2019, 'price': 60, 'quantity': 75}
add_book(book_inventory, book2)
add_book(book_inventory, book3)

print_inventory(book_inventory)

# make sure that we cannot re-add the same book
# add_book(book_inventory, book1)
# notice: KeyError, why?
#   This is because book1 was passed by reference.
#   When the add_book function pops the title from book_info,
#   it reflects book1 and therefore the title no longer exists in book1
# To test whether re-add behaves properly,
# reassign book1
book1 = {'title': 'Intro to Python', 'year': 2020, 'price': 60, 'quantity': 75}
add_book(book_inventory, book1)
print('---- inventory after attempting to re-add the same book title ----')
print_inventory(book_inventory)


update_book(book_inventory, book1)
print('---- inventory after updating a book ----')
print_inventory(book_inventory)


book4 = {'title': 'New Python', 'year': 2022, 'price': 45, 'quantity': 50}
update_book(book_inventory, book4)
print('---- inventory after after attempting to update a non-existent book ----')
print_inventory(book_inventory)


add_quantity(book_inventory, 'Intro to Python', 20)
print('---- inventory after adding quantity ----')
print_inventory(book_inventory)


add_quantity(book_inventory, 'New Python', 20)
print('---- inventory after attempting to add quantity to a non-existent book ----')
print_inventory(book_inventory)


reduce_quantity(book_inventory, 'Intro to Python', 10)
print('---- inventory after reducing quantity ----')
print_inventory(book_inventory)


reduce_quantity(book_inventory, 'New Python', 20)
print('---- inventory after attempting to reduce quantity to a non-existent book ----')
print_inventory(book_inventory)


############
# You should consider:
# - passing by reference vs. global scope
# -