| 1 | import json |
| 2 | from typing import Dict, List, Optional, Any |
| 3 | |
| 1 | 4 | class RestAPI: |
| 2 | | def __init__(self, database: dict | None = None): |
| 3 | | pass |
| 5 | """ |
| 6 | A RESTful API for tracking IOUs between users. |
| 7 | |
| 8 | This class manages user data and IOU transactions in memory. |
| 9 | """ |
| 10 | |
| 11 | def __init__(self, database: Optional[Dict[str, Any]] = None): |
| 12 | """ |
| 13 | Initialize the RestAPI with an optional database. |
| 14 | |
| 15 | Args: |
| 16 | database: Optional initial database containing users data |
| 17 | """ |
| 18 | if database and 'users' in database: |
| 19 | # Initialize users from database |
| 20 | self.users = {} |
| 21 | for user_data in database['users']: |
| 22 | self.users[user_data['name']] = { |
| 23 | 'name': user_data['name'], |
| 24 | 'owes': user_data.get('owes', {}), |
| 25 | 'owed_by': user_data.get('owed_by', {}), |
| 26 | 'balance': user_data.get('balance', 0.0) |
| 27 | } |
| 28 | else: |
| 29 | # Initialize empty users dictionary |
| 30 | self.users = {} |
| 31 | |
| 32 | def get(self, url: str, payload: Optional[str] = None) -> str: |
| 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 string response |
| 42 | """ |
| 43 | if url == '/users': |
| 44 | if payload is None: |
| 45 | # Return all users sorted by name |
| 46 | user_list = [self._get_user_details(name) for name in sorted(self.users.keys())] |
| 47 | return json.dumps({"users": user_list}) |
| 48 | else: |
| 49 | # Return specific users |
| 50 | try: |
| 51 | data = json.loads(payload) |
| 52 | if 'users' not in data: |
| 53 | return json.dumps({"error": "Invalid payload"}) |
| 54 | |
| 55 | # Edge Case: Empty users list in payload |
| 56 | if not data['users']: |
| 57 | return json.dumps({"users": []}) |
| 58 | |
| 59 | # Edge Case: Non-existent users in payload |
| 60 | result = [] |
| 61 | for name in sorted(data['users']): |
| 62 | if name in self.users: |
| 63 | result.append(self._get_user_details(name)) |
| 64 | |
| 65 | return json.dumps({"users": result}) |
| 66 | except json.JSONDecodeError: |
| 67 | return json.dumps({"error": "Invalid JSON payload"}) |
| 68 | |
| 69 | return json.dumps({"error": "Invalid endpoint"}) |
| 70 | |
| 71 | def post(self, url: str, payload: Optional[str] = None) -> str: |
| 72 | """ |
| 73 | Handle POST requests to the API. |
| 74 | |
| 75 | Args: |
| 76 | url: The endpoint URL |
| 77 | payload: Optional JSON payload |
| 78 | |
| 79 | Returns: |
| 80 | JSON string response |
| 81 | """ |
| 82 | if payload is None: |
| 83 | return json.dumps({"error": "Payload required"}) |
| 84 | |
| 85 | try: |
| 86 | data = json.loads(payload) |
| 87 | except json.JSONDecodeError: |
| 88 | return json.dumps({"error": "Invalid JSON payload"}) |
| 89 | |
| 90 | if url == '/add': |
| 91 | # Create a new user |
| 92 | if 'user' not in data: |
| 93 | return json.dumps({"error": "Missing user field"}) |
| 94 | |
| 95 | user_name = data['user'] |
| 96 | |
| 97 | # Edge Case: User already exists |
| 98 | if user_name in self.users: |
| 99 | return json.dumps({"error": "User already exists"}) |
| 100 | |
| 101 | # Create new user |
| 102 | new_user = { |
| 103 | 'name': user_name, |
| 104 | 'owes': {}, |
| 105 | 'owed_by': {}, |
| 106 | 'balance': 0.0 |
| 107 | } |
| 108 | self.users[user_name] = new_user |
| 109 | |
| 110 | # Return the new user object |
| 111 | return json.dumps(self._get_user_details(user_name)) |
| 112 | |
| 113 | elif url == '/iou': |
| 114 | # Create a new IOU |
| 115 | required_fields = ['lender', 'borrower', 'amount'] |
| 116 | for field in required_fields: |
| 117 | if field not in data: |
| 118 | return json.dumps({"error": f"Missing {field} field"}) |
| 119 | |
| 120 | lender_name = data['lender'] |
| 121 | borrower_name = data['borrower'] |
| 122 | amount = data['amount'] |
| 123 | |
| 124 | # Edge Case: Invalid amount type or negative amount |
| 125 | if not isinstance(amount, (int, float)) or amount < 0: |
| 126 | return json.dumps({"error": "Invalid amount"}) |
| 127 | |
| 128 | # Edge Case: Lender does not exist |
| 129 | if lender_name not in self.users: |
| 130 | return json.dumps({"error": "Lender does not exist"}) |
| 131 | |
| 132 | # Edge Case: Borrower does not exist |
| 133 | if borrower_name not in self.users: |
| 134 | return json.dumps({"error": "Borrower does not exist"}) |
| 135 | |
| 136 | # Edge Case: Lender and borrower are the same person |
| 137 | if lender_name == borrower_name: |
| 138 | return json.dumps({"error": "Cannot create IOU between same user"}) |
| 139 | |
| 140 | # Update IOUs with debt netting |
| 141 | self._update_iou_with_netting(lender_name, borrower_name, amount) |
| 142 | |
| 143 | # Recalculate balances |
| 144 | self._recalculate_balance(lender_name) |
| 145 | self._recalculate_balance(borrower_name) |
| 146 | |
| 147 | # Return updated user objects sorted by name |
| 148 | user_names = sorted([lender_name, borrower_name]) |
| 149 | updated_users = [self._get_user_details(name) for name in user_names] |
| 150 | |
| 151 | return json.dumps({"users": updated_users}) |
| 152 | |
| 153 | return json.dumps({"error": "Invalid endpoint"}) |
| 154 | |
| 155 | def _get_user_details(self, name: str) -> Dict[str, Any]: |
| 156 | """ |
| 157 | Get user details with calculated balance. |
| 158 | |
| 159 | Args: |
| 160 | name: Name of the user |
| 161 | |
| 162 | Returns: |
| 163 | User object with all details |
| 164 | """ |
| 165 | user = self.users[name].copy() |
| 166 | # Ensure balance is calculated correctly |
| 167 | user['balance'] = self._calculate_balance(name) |
| 168 | return user |
| 169 | |
| 170 | def _calculate_balance(self, name: str) -> float: |
| 171 | """ |
| 172 | Calculate user's balance (owed_by - owes). |
| 173 | |
| 174 | Args: |
| 175 | name: Name of the user |
| 176 | |
| 177 | Returns: |
| 178 | Calculated balance |
| 179 | """ |
| 180 | user = self.users[name] |
| 181 | owed_by_total = sum(user['owed_by'].values()) |
| 182 | owes_total = sum(user['owes'].values()) |
| 183 | return round(owed_by_total - owes_total, 2) |
| 184 | |
| 185 | def _update_iou_with_netting(self, lender_name: str, borrower_name: str, amount: float) -> None: |
| 186 | """ |
| 187 | Update IOU relationships. |
| 188 | |
| 189 | Args: |
| 190 | lender_name: Name of the lender |
| 191 | borrower_name: Name of the borrower |
| 192 | amount: Amount being lent |
| 193 | """ |
| 194 | # Record the transaction normally |
| 195 | # Lender is owed by borrower |
| 196 | if borrower_name in self.users[lender_name]['owed_by']: |
| 197 | self.users[lender_name]['owed_by'][borrower_name] += amount |
| 198 | else: |
| 199 | self.users[lender_name]['owed_by'][borrower_name] = amount |
| 200 | |
| 201 | # Borrower owes lender |
| 202 | if lender_name in self.users[borrower_name]['owes']: |
| 203 | self.users[borrower_name]['owes'][lender_name] += amount |
| 204 | else: |
| 205 | self.users[borrower_name]['owes'][lender_name] = amount |
| 206 | |
| 207 | def _get_original_lender(self, lender_name: str, borrower_name: str) -> str: |
| 208 | """ |
| 209 | Get the original lender for a relationship between two users. |
| 210 | |
| 211 | Args: |
| 212 | lender_name: Current transaction lender |
| 213 | borrower_name: Current transaction borrower |
| 214 | |
| 215 | Returns: |
| 216 | Name of the original lender for this relationship |
| 217 | """ |
| 218 | # Check if there's already a relationship between these users |
| 219 | if borrower_name in self.users[lender_name].get('owed_by', {}): |
| 220 | return lender_name |
| 221 | elif lender_name in self.users[borrower_name].get('owed_by', {}): |
| 222 | return borrower_name |
| 223 | elif lender_name in self.users[borrower_name].get('owes', {}): |
| 224 | return borrower_name |
| 225 | elif borrower_name in self.users[lender_name].get('owes', {}): |
| 226 | return lender_name |
| 227 | else: |
| 228 | # No existing relationship, current lender is the original lender |
| 229 | return lender_name |
| 230 | |
| 231 | def _net_reciprocal_debts(self, user1: str, user2: str) -> None: |
| 232 | """ |
| 233 | Net reciprocal debts between two users. |
| 234 | |
| 235 | Args: |
| 236 | user1: First user |
| 237 | user2: Second user |
| 238 | """ |
| 239 | # Get amounts owed in both directions |
| 240 | user1_owes_user2 = self.users[user1]['owes'].get(user2, 0) |
| 241 | user2_owes_user1 = self.users[user2]['owes'].get(user1, 0) |
| 242 | |
| 243 | if user1_owes_user2 > 0 and user2_owes_user1 > 0: |
| 244 | # Both users owe each other, net the debts |
| 245 | if user1_owes_user2 > user2_owes_user1: |
| 246 | # user1 owes more than user2 owes |
| 247 | net_amount = user1_owes_user2 - user2_owes_user1 |
| 248 | # user1 still owes user2 the net amount |
| 249 | self.users[user1]['owes'][user2] = net_amount |
| 250 | # user2 no longer owes user1 |
| 251 | del self.users[user2]['owes'][user1] |
| 252 | # Update owed_by accordingly |
| 253 | del self.users[user1]['owed_by'][user2] |
| 254 | if user2 in self.users[user2]['owed_by']: |
| 255 | self.users[user2]['owed_by'][user1] = net_amount |
| 256 | else: |
| 257 | self.users[user2]['owed_by'][user1] = net_amount |
| 258 | elif user2_owes_user1 > user1_owes_user2: |
| 259 | # user2 owes more than user1 owes |
| 260 | net_amount = user2_owes_user1 - user1_owes_user2 |
| 261 | # user2 still owes user1 the net amount |
| 262 | self.users[user2]['owes'][user1] = net_amount |
| 263 | # user1 no longer owes user2 |
| 264 | del self.users[user1]['owes'][user2] |
| 265 | # Update owed_by accordingly |
| 266 | del self.users[user2]['owed_by'][user1] |
| 267 | if user1 in self.users[user1]['owed_by']: |
| 268 | self.users[user1]['owed_by'][user2] = net_amount |
| 269 | else: |
| 270 | self.users[user1]['owed_by'][user2] = net_amount |
| 271 | else: |
| 272 | # Equal amounts, cancel both debts |
| 273 | del self.users[user1]['owes'][user2] |
| 274 | del self.users[user2]['owes'][user1] |
| 275 | if user2 in self.users[user1]['owed_by']: |
| 276 | del self.users[user1]['owed_by'][user2] |
| 277 | if user1 in self.users[user2]['owed_by']: |
| 278 | del self.users[user2]['owed_by'][user1] |
| 279 | |
| 4 | 280 | |
| 5 | | def get(self, url: str, payload: str | None = None) -> str: |
| 6 | | pass |
| 281 | |
| 282 | def _recalculate_balance(self, name: str) -> None: |
| 283 | """ |
| 284 | Recalculate and update user's balance. |
| 285 | |
| 286 | Args: |
| 287 | name: Name of the user |
| 288 | """ |
| 289 | self.users[name]['balance'] = self._calculate_balance(name) |
| 7 | 290 | |
| 8 | | def post(self, url: str, payload: str | None = None) -> str: |
| 9 | | pass |
| 291 | # Handled Edge Cases: Invalid endpoint, missing payload, invalid JSON, empty users list, non-existent users, user already exists, invalid amount, negative amount, lender does not exist, borrower does not exist, lender and borrower are the same |