| 1 | import json |
| 2 | from typing import Dict, List, Optional, Any |
| 3 | |
| 1 | 4 | class RestAPI: |
| 5 | """ |
| 6 | A RESTful API for tracking IOUs between users. |
| 7 | |
| 8 | This class manages user accounts and IOU transactions in memory. |
| 9 | It supports creating users, creating IOUs between users, and retrieving user information. |
| 10 | """ |
| 11 | |
| 2 | 12 | def __init__(self, database: dict | None = None): |
| 3 | | pass |
| 4 | | |
| 13 | """ |
| 14 | Initialize the RestAPI with an optional database. |
| 15 | |
| 16 | Args: |
| 17 | database: Optional initial database with users data |
| 18 | """ |
| 19 | if database and 'users' in database: |
| 20 | # Initialize users from database |
| 21 | self.users = {} |
| 22 | for user_data in database['users']: |
| 23 | self.users[user_data['name']] = { |
| 24 | 'name': user_data['name'], |
| 25 | 'owes': user_data.get('owes', {}), |
| 26 | 'owed_by': user_data.get('owed_by', {}), |
| 27 | 'balance': user_data.get('balance', 0.0) |
| 28 | } |
| 29 | else: |
| 30 | self.users = {} |
| 31 | |
| 5 | 32 | def get(self, url: str, payload: str | None = None) -> str: |
| 6 | | pass |
| 7 | | |
| 33 | """ |
| 34 | Handle GET requests to the API. |
| 35 | |
| 36 | Args: |
| 37 | url: The endpoint URL |
| 38 | payload: Optional JSON payload |
| 39 | |
| 40 | Returns: |
| 41 | JSON response string |
| 42 | """ |
| 43 | # Edge Case: Invalid URL |
| 44 | if url != '/users': |
| 45 | return json.dumps({"error": "Invalid URL"}) |
| 46 | |
| 47 | # Edge Case: No users in system |
| 48 | if not self.users: |
| 49 | return json.dumps({"users": []}) |
| 50 | |
| 51 | if payload: |
| 52 | try: |
| 53 | data = json.loads(payload) |
| 54 | except json.JSONDecodeError: |
| 55 | # Edge Case: Invalid JSON payload |
| 56 | return json.dumps({"error": "Invalid JSON payload"}) |
| 57 | |
| 58 | # Edge Case: Missing 'users' key in payload |
| 59 | if 'users' not in data: |
| 60 | return json.dumps({"error": "Missing 'users' key in payload"}) |
| 61 | |
| 62 | requested_users = data['users'] |
| 63 | |
| 64 | # Edge Case: Empty users list in payload |
| 65 | if not requested_users: |
| 66 | return json.dumps({"users": []}) |
| 67 | |
| 68 | result = [] |
| 69 | for username in requested_users: |
| 70 | # Edge Case: Requested user does not exist |
| 71 | if username in self.users: |
| 72 | result.append(self._get_user_info(username)) |
| 73 | |
| 74 | # Sort by name |
| 75 | result.sort(key=lambda x: x['name']) |
| 76 | return json.dumps({"users": result}) |
| 77 | else: |
| 78 | # Return all users |
| 79 | result = [self._get_user_info(username) for username in self.users] |
| 80 | result.sort(key=lambda x: x['name']) |
| 81 | return json.dumps({"users": result}) |
| 82 | |
| 8 | 83 | def post(self, url: str, payload: str | None = None) -> str: |
| 9 | | pass |
| 84 | """ |
| 85 | Handle POST requests to the API. |
| 86 | |
| 87 | Args: |
| 88 | url: The endpoint URL ('/add' or '/iou') |
| 89 | payload: JSON payload with request data |
| 90 | |
| 91 | Returns: |
| 92 | JSON response string |
| 93 | """ |
| 94 | # Edge Case: Missing payload |
| 95 | if not payload: |
| 96 | return json.dumps({"error": "Missing payload"}) |
| 97 | |
| 98 | try: |
| 99 | data = json.loads(payload) |
| 100 | except json.JSONDecodeError: |
| 101 | # Edge Case: Invalid JSON payload |
| 102 | return json.dumps({"error": "Invalid JSON payload"}) |
| 103 | |
| 104 | if url == '/add': |
| 105 | # Edge Case: Missing 'user' key |
| 106 | if 'user' not in data: |
| 107 | return json.dumps({"error": "Missing 'user' key"}) |
| 108 | |
| 109 | username = data['user'] |
| 110 | |
| 111 | # Edge Case: User already exists |
| 112 | if username in self.users: |
| 113 | return json.dumps({"error": "User already exists"}) |
| 114 | |
| 115 | # Create new user |
| 116 | self.users[username] = { |
| 117 | 'name': username, |
| 118 | 'owes': {}, |
| 119 | 'owed_by': {}, |
| 120 | 'balance': 0.0 |
| 121 | } |
| 122 | return json.dumps(self._get_user_info(username)) |
| 123 | |
| 124 | elif url == '/iou': |
| 125 | # Edge Case: Missing required keys |
| 126 | required_keys = ['lender', 'borrower', 'amount'] |
| 127 | for key in required_keys: |
| 128 | if key not in data: |
| 129 | return json.dumps({"error": f"Missing '{key}' key"}) |
| 130 | |
| 131 | lender = data['lender'] |
| 132 | borrower = data['borrower'] |
| 133 | amount = data['amount'] |
| 134 | |
| 135 | # Edge Case: Lender and borrower are the same |
| 136 | if lender == borrower: |
| 137 | return json.dumps({"error": "Lender and borrower cannot be the same"}) |
| 138 | |
| 139 | # Edge Case: Negative amount |
| 140 | if amount < 0: |
| 141 | return json.dumps({"error": "Amount cannot be negative"}) |
| 142 | |
| 143 | # Edge Case: Lender does not exist |
| 144 | if lender not in self.users: |
| 145 | return json.dumps({"error": "Lender does not exist"}) |
| 146 | |
| 147 | # Edge Case: Borrower does not exist |
| 148 | if borrower not in self.users: |
| 149 | return json.dumps({"error": "Borrower does not exist"}) |
| 150 | |
| 151 | # Update IOU relationships |
| 152 | # Update lender's owed_by |
| 153 | if borrower in self.users[lender]['owed_by']: |
| 154 | self.users[lender]['owed_by'][borrower] += amount |
| 155 | else: |
| 156 | self.users[lender]['owed_by'][borrower] = amount |
| 157 | |
| 158 | # Update borrower's owes |
| 159 | if lender in self.users[borrower]['owes']: |
| 160 | self.users[borrower]['owes'][lender] += amount |
| 161 | else: |
| 162 | self.users[borrower]['owes'][lender] = amount |
| 163 | |
| 164 | # Update balances |
| 165 | self.users[lender]['balance'] += amount |
| 166 | self.users[borrower]['balance'] -= amount |
| 167 | |
| 168 | # Return updated user info |
| 169 | result = [ |
| 170 | self._get_user_info(lender), |
| 171 | self._get_user_info(borrower) |
| 172 | ] |
| 173 | result.sort(key=lambda x: x['name']) |
| 174 | return json.dumps({"users": result}) |
| 175 | |
| 176 | else: |
| 177 | # Edge Case: Invalid URL |
| 178 | return json.dumps({"error": "Invalid URL"}) |
| 179 | |
| 180 | def _get_user_info(self, username: str) -> Dict[str, Any]: |
| 181 | """ |
| 182 | Get a user's information in the required format. |
| 183 | |
| 184 | Args: |
| 185 | username: The name of the user |
| 186 | |
| 187 | Returns: |
| 188 | Dictionary with user information |
| 189 | """ |
| 190 | user = self.users[username] |
| 191 | # Create a copy to avoid modifying the original |
| 192 | result = { |
| 193 | 'name': user['name'], |
| 194 | 'owes': {k: v for k, v in user['owes'].items() if v > 0}, |
| 195 | 'owed_by': {k: v for k, v in user['owed_by'].items() if v > 0}, |
| 196 | 'balance': round(user['balance'], 2) |
| 197 | } |
| 198 | return result |
| 199 | |
| 200 | # Handled Edge Cases: Invalid URL, No users in system, Invalid JSON payload, Missing 'users' key in payload, |
| 201 | # Empty users list in payload, Requested user does not exist, Missing payload, Missing 'user' key, |
| 202 | # User already exists, Missing required keys, Lender and borrower are the same, Negative amount, |
| 203 | # Lender does not exist, Borrower does not exist, Invalid URL |