#!/usr/bin/env python
import pickle
import uuid
import hashlib
from os import path
import rehash

def sign_up():
    username = input("Enter the desired username:")
    password = input("Enter the desired password:")
    salt = uuid.uuid4().hex
    hashcode = rehash.sha256(salt.encode() + password.encode())
    if path.isfile('database1.pickle'):
            with open('database1.pickle', 'rb') as f:
                ret=pickle.load(f)
            if(username in ret):
                return 0
            ret[username] = {'SALT' : salt ,
                      'HASHCODE' : hashcode
                     }
    else:
        with open('database1.pickle','wb') as f:
            ret={username : { 'SALT' : salt ,
                              'HASHCODE' : hashcode

            }

            }
            pickle.dump(ret,f,protocol=pickle.HIGHEST_PROTOCOL)
            return 1

    with open('database1.pickle','wb') as f:
        pickle.dump(ret, f, protocol=pickle.HIGHEST_PROTOCOL)
    return 1


def sign_in(username):
    with open('database1.pickle', 'rb') as f:
         b = pickle.load(f)
    password = input("Enter your password:")

    salt = b[username]['SALT']
    check = rehash.sha256(salt.encode() + password.encode())
    return b[username]['HASHCODE'].hexdigest() == check.hexdigest()


def change_password(username):
    new_password=input("Enter the new password:")
    new_salt = uuid.uuid4().hex
    new_hashcode = rehash.sha256(new_salt.encode() + new_password.encode())
    with open('database1.pickle','rb') as f:
        ret = pickle.load(f)

    ret[username]['SALT'] = new_salt
    ret[username]['HASHCODE'] = new_hashcode
    with open('database1.pickle','wb') as f:
        pickle.dump(ret,f,protocol=pickle.HIGHEST_PROTOCOL)



# In[12]:


# Main Function
print("*************Hello and Welcome To UNIX Password System***********")
x ='1'
while(x=='1'):
    choice = input("Enter 1 for new user signup or 2 for returning users")
    if choice == '1' :
        ret = sign_up()
        if ret==1:
            print("User added")
        else :
            print("Username already taken")
    elif choice == '2' :
        username = input("Hi User! Please enter your username")
        ret = sign_in(username)
        if ret > 0 :
            username = print("Welcome",username)
            choice = input("1 Change Password" + "\n" + "2. Any other key to exit")
            if choice == '1':
                change_password(username)
                print("Password reset successful")
            else:
                print("See you around")
        else :
            print("Wrong password")
    else:
        print("Invalid Selection")
    x=input("press 1 for continuing usage or press any key")

print("Thank you")