zkt26/z1/backend/app.py

from flask import Flask, jsonify, request
from flask_restful import Api, Resource
from pymongo import MongoClient
import bcrypt

app = Flask(__name__)
api = Api(app)
client = MongoClient("mongodb://db:27017")
db = client.BankAPI
users = db["Users"]

def UserExist(username):
    if users.find_one({"Username": username}) is not None:
        return True
    return False

class Register(Resource):
    def post(self):
        postedData = request.get_json()
        username = postedData["username"]
        password = postedData["password"]

        if UserExist(username):
            retJson = {
                "status": 301,
                "msg": "Invalid username"
            }
            return jsonify(retJson)
        hashed_pw = bcrypt.hashpw(password.encode('utf8'), bcrypt.gensalt())

        users.insert_one({
            "Username": username,
            "Password": hashed_pw,
            "Own": 0,
            "Debt": 0
        })
        retJson = {
            "status": 200,
            "msg": "You successfully signed up for the API"
        }
        return jsonify(retJson)
    
def verifyPw(username, password):
    if not UserExist(username):
        return False
    hashed_pw = users.find_one({
        "Username": username
    })["Password"]
    if bcrypt.hashpw(password.encode('utf8'), hashed_pw) == hashed_pw:
        return True
    else:        
        return False
        
def cashWithUser(username):
    cash = users.find_one({"Username": username})["Own"]
    return cash
    
def debtWithUser(username):
    debt = users.find_one({"Username": username})["Debt"]
    return debt
    
def generateReturnDictionary(status,msg):
    retJson = {
        "status": status,
        "msg": msg
    }
    return retJson
    
def verifyCredentials(username, password):
    if not UserExist(username):
        return generateReturnDictionary(301, "Invalid username"), True
        
    correct_pw = verifyPw(username, password)
    if not correct_pw:
        return generateReturnDictionary(302, "Invalid password"), True
    return None, False
    
def updateAccount(username, balance):
    users.update_one({
        "Username": username
    }, {
        "$set": {
            "Own": balance
        }
    })

def updateDebt(username, balance):
    users.update_one({
        "Username": username
    }, {
        "$set": {
            "Debt": balance
        }
    })


class Add(Resource):
    def post(self):
        postedData = request.get_json()
        username = postedData["username"]

        password = postedData["password"]
        amount = postedData["amount"]

        retJson, error = verifyCredentials(username, password)
        if error:
            return jsonify(retJson)
        
        if amount <= 0:
            return jsonify(generateReturnDictionary(304, "The money amount entered must be positive!"))

        cash = cashWithUser(username)
        
        amount -=1
        bank_cash = cashWithUser("BANK")
        updateAccount("BANK", bank_cash + 1)
        updateAccount(username, cash + amount)

        return jsonify(generateReturnDictionary(200, "Amount added successfully to account"))



class Transfer(Resource):
    def post(self):
        postedData = request.get_json()
        username = postedData["username"]
        password = postedData["password"]
        to = postedData["to"]
        money = postedData["amount"]

        retJson, error = verifyCredentials(username, password)
        if error:
            return jsonify(retJson)
        
        cash = cashWithUser(username)
        if cash <= 0:
            return jsonify(generateReturnDictionary(304, "You`re out of money, please add or take a loan"))

        if not UserExist(to):
            return jsonify(generateReturnDictionary(301, "Receiver username is invalid"))
        
        cash_from = cashWithUser(username)
        cash_to = cashWithUser(to)
        bank_cash = cashWithUser("BANK")
        updateAccount("BANK", bank_cash + 1)
        updateAccount(to, cash_to + money - 1)
        updateAccount(username, cash_from - money)

        return jsonify(generateReturnDictionary(200, "Amount transferred successfully"))
    
class Balance(Resource):
    def post(self):
        postedData = request.get_json()
        username = postedData["username"]
        password = postedData["password"]
        retJson, error = verifyCredentials(username, password)
        if error:
            return jsonify(retJson)
        
        retJson = users.find_one({
            "Username": username
        }, { 
            "Password": 0,
            "_id": 0
        })

        return jsonify(retJson)
    
class TakeLoan(Resource):
    def post(self):
        postedData = request.get_json()

        username = postedData["username"]
        password = postedData["password"]
        money = postedData["amount"]

        retJson, error = verifyCredentials(username, password)

        if error:
            return jsonify(retJson)
        cash = cashWithUser(username)
        debt = debtWithUser(username)
        updateAccount(username, cash + money)
        updateDebt(username, debt + money)
        return jsonify(generateReturnDictionary(200, "Loan added successfully!"))
    

class PayLoan(Resource):
    def post(self):
        postedData = request.get_json()

        username = postedData["username"]
        password = postedData["password"]
        money = postedData["amount"]

        retJson, error = verifyCredentials(username, password)
        if error:
            return jsonify(retJson)
        
        cash = cashWithUser(username)
        if cash < money:
            return jsonify(generateReturnDictionary(303, "You don`t have enough money to pay the loan!"))
        
        debt = debtWithUser(username)
        updateAccount(username, cash - money)
        updateDebt(username, debt - money)

        return jsonify(generateReturnDictionary(200, "Loan paid successfully!"))


api.add_resource(Register, "/register")
api.add_resource(Add, "/add")
api.add_resource(Transfer, "/transfer")
api.add_resource(Balance, "/balance")
api.add_resource(TakeLoan, "/take_loan")
api.add_resource(PayLoan, "/pay_loan")

def init_bank_account():
    if not UserExist("BANK"):
        users.insert_one({
            "Username": "BANK",
            "Password": bcrypt.hashpw("admin".encode('utf8'), bcrypt.gensalt()),
            "Own": 0,
            "Debt": 0
        })

init_bank_account()

if __name__ == "__main__":
    app.run(host='0.0.0.0', debug=True)