main commit

backend/Dockerfile

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+FROM python:3.12
+WORKDIR /usr/src/app
+COPY requirements.txt .
+RUN pip install --no-cache-dir -r requirements.txt
+COPY . .
+CMD ["gunicorn", "-w", "4", "-b", "0.0.0.0:5000", "app:app"]

backend/app.py

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+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)
+    

backend/db/Dockerfile

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+FROM mongo:latest

backend/requirements.txt

@@ -0,0 +1,5 @@
+Flask
+flask_restful
+pymongo
+bcrypt
+gunicorn

docker-compose.yml

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+services:
+  web:
+    build:
+      context: .
+      dockerfile: nginx/Dockerfile
+    ports:
+      - "80:80"
+    volumes:
+      - ./nginx/nginx.conf:/etc/nginx/nginx.conf:ro
+    command: [nginx-debug, '-g', 'daemon off;']
+  db:
+    build:
+      context: ./backend/db
+    ports:
+      - "27017:27017"
+  backend:
+    build:
+      context: ./backend

frontend/index.html

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+<!DOCTYPE html>
+<html lang="en">
+
+<head>
+    <meta charset="UTF-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <title>Bank API</title>
+    <style>
+        body {
+            font-family: monospace;
+            max-width: 600px;
+            margin: 40px auto;
+            padding: 0 20px;
+        }
+
+        h1 {
+            font-size: 18px;
+        }
+
+        h2 {
+            font-size: 14px;
+            margin-top: 24px;
+            border-bottom: 1px solid #ccc;
+            padding-bottom: 4px;
+        }
+
+        input,
+        button {
+            font-family: monospace;
+            font-size: 13px;
+            padding: 4px 8px;
+            margin: 2px 0;
+        }
+
+        button {
+            cursor: pointer;
+        }
+
+        .result {
+            background: #f0f0f0;
+            padding: 8px;
+            margin-top: 8px;
+            white-space: pre-wrap;
+            font-size: 13px;
+            min-height: 20px;
+        }
+    </style>
+</head>
+
+<body>
+    <h1>Bank API</h1>
+
+    <h2>Register</h2>
+    <input id="reg-user" placeholder="username">
+    <input id="reg-pass" placeholder="password" type="password">
+    <button
+        onclick="api('/api/register', {username: v('reg-user'), password: v('reg-pass')}, 'reg-res')">Register</button>
+    <div class="result" id="reg-res"></div>
+
+    <h2>Add Money</h2>
+    <input id="add-user" placeholder="username">
+    <input id="add-pass" placeholder="password" type="password">
+    <input id="add-amount" placeholder="amount" type="number">
+    <button
+        onclick="api('/api/add', {username: v('add-user'), password: v('add-pass'), amount: n('add-amount')}, 'add-res')">Add</button>
+    <div class="result" id="add-res"></div>
+
+    <h2>Transfer</h2>
+    <input id="tr-user" placeholder="username">
+    <input id="tr-pass" placeholder="password" type="password">
+    <input id="tr-to" placeholder="to">
+    <input id="tr-amount" placeholder="amount" type="number">
+    <button
+        onclick="api('/api/transfer', {username: v('tr-user'), password: v('tr-pass'), to: v('tr-to'), amount: n('tr-amount')}, 'tr-res')">Transfer</button>
+    <div class="result" id="tr-res"></div>
+
+    <h2>Balance</h2>
+    <input id="bal-user" placeholder="username">
+    <input id="bal-pass" placeholder="password" type="password">
+    <button onclick="api('/api/balance', {username: v('bal-user'), password: v('bal-pass')}, 'bal-res')">Check</button>
+    <div class="result" id="bal-res"></div>
+
+    <h2>Take Loan</h2>
+    <input id="loan-user" placeholder="username">
+    <input id="loan-pass" placeholder="password" type="password">
+    <input id="loan-amount" placeholder="amount" type="number">
+    <button
+        onclick="api('/api/take_loan', {username: v('loan-user'), password: v('loan-pass'), amount: n('loan-amount')}, 'loan-res')">Take
+        Loan</button>
+    <div class="result" id="loan-res"></div>
+
+    <h2>Pay Loan</h2>
+    <input id="pay-user" placeholder="username">
+    <input id="pay-pass" placeholder="password" type="password">
+    <input id="pay-amount" placeholder="amount" type="number">
+    <button
+        onclick="api('/api/pay_loan', {username: v('pay-user'), password: v('pay-pass'), amount: n('pay-amount')}, 'pay-res')">Pay
+        Loan</button>
+    <div class="result" id="pay-res"></div>
+
+    <script>
+        function v(id) { return document.getElementById(id).value; }
+        function n(id) { return Number(document.getElementById(id).value); }
+        async function api(url, body, resId) {
+            const el = document.getElementById(resId);
+            el.textContent = 'Loading...';
+            try {
+                const res = await fetch(url, {
+                    method: 'POST',
+                    headers: { 'Content-Type': 'application/json' },
+                    body: JSON.stringify(body)
+                });
+                const data = await res.json();
+                el.textContent = JSON.stringify(data, null, 2);
+            } catch (e) {
+                el.textContent = 'Error: ' + e.message;
+            }
+        }
+    </script>
+</body>
+
+</html>

nginx/Dockerfile

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+FROM nginx:latest
+COPY ./frontend/index.html /var/www/html/index.html

nginx/nginx.conf

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+events {
+    worker_connections 1024;
+}
+http {
+    upstream backend {
+    server backend:5000;
+}
+server {
+    listen       80 default_server;
+    listen  [::]:80;
+    server_name  backend;
+
+    location /api/ {
+        proxy_pass http://backend/;
+        proxy_set_header Host $host;
+        proxy_set_header X-Real-IP $remote_addr;
+        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+        proxy_set_header X-Forwarded-Proto $scheme;
+    }
+        location / {
+            root   /var/www/html;
+            index  index.html;
+        }
+}
+}