| 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 data and IOU transactions in memory. |
| 9 | It supports creating users, creating IOUs, 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 | # Initialize empty users dictionary |
| 31 | self.users = {} |
| 32 | |
| 5 | 33 | def get(self, url: str, payload: str | None = None) -> str: |
| 6 | | pass |
| 7 | | |
| 34 | """ |
| 35 | Handle GET requests to the API. |
| 36 | |
| 37 | Args: |
| 38 | url: The endpoint URL |
| 39 | payload: Optional JSON payload |
| 40 | |
| 41 | Returns: |
| 42 | JSON string response |
| 43 | """ |
| 44 | if url == '/users': |
| 45 | # Edge Case: Handle request with no payload (list all users) |
| 46 | if payload is None: |
| 47 | user_list = [self._get_user_details(name) for name in sorted(self.users.keys())] |
| 48 | return json.dumps({"users": user_list}) |
| 49 | |
| 50 | # Edge Case: Handle request with payload (list specific users) |
| 51 | try: |
| 52 | data = json.loads(payload) |
| 53 | if 'users' in data: |
| 54 | # Filter users by provided names |
| 55 | user_list = [] |
| 56 | for name in sorted(data['users']): |
| 57 | if name in self.users: |
| 58 | user_list.append(self._get_user_details(name)) |
| 59 | return json.dumps({"users": user_list}) |
| 60 | else: |
| 61 | # Edge Case: Malformed payload (missing 'users' key) |
| 62 | return json.dumps({"users": []}) |
| 63 | except json.JSONDecodeError: |
| 64 | # Edge Case: Invalid JSON payload |
| 65 | return json.dumps({"users": []}) |
| 66 | |
| 67 | # Edge Case: Unknown endpoint |
| 68 | return json.dumps({"error": "Not found"}) |
| 69 | |
| 8 | 70 | def post(self, url: str, payload: str | None = None) -> str: |
| 9 | | pass |
| 71 | """ |
| 72 | Handle POST requests to the API. |
| 73 | |
| 74 | Args: |
| 75 | url: The endpoint URL |
| 76 | payload: JSON payload |
| 77 | |
| 78 | Returns: |
| 79 | JSON string response |
| 80 | """ |
| 81 | if payload is None: |
| 82 | # Edge Case: Missing payload |
| 83 | return json.dumps({"error": "Payload required"}) |
| 84 | |
| 85 | try: |
| 86 | data = json.loads(payload) |
| 87 | except json.JSONDecodeError: |
| 88 | # Edge Case: Invalid JSON payload |
| 89 | return json.dumps({"error": "Invalid JSON"}) |
| 90 | |
| 91 | if url == '/add': |
| 92 | # Edge Case: Missing 'user' in payload |
| 93 | if 'user' not in data: |
| 94 | return json.dumps({"error": "Missing user"}) |
| 95 | |
| 96 | user_name = data['user'] |
| 97 | |
| 98 | # Edge Case: User already exists |
| 99 | if user_name in self.users: |
| 100 | return json.dumps({"error": "User already exists"}) |
| 101 | |
| 102 | # Create new user |
| 103 | self.users[user_name] = { |
| 104 | 'name': user_name, |
| 105 | 'owes': {}, |
| 106 | 'owed_by': {}, |
| 107 | 'balance': 0.0 |
| 108 | } |
| 109 | |
| 110 | return json.dumps(self._get_user_details(user_name)) |
| 111 | |
| 112 | elif url == '/iou': |
| 113 | # Edge Case: Missing required fields |
| 114 | if not all(key in data for key in ['lender', 'borrower', 'amount']): |
| 115 | return json.dumps({"error": "Missing required fields"}) |
| 116 | |
| 117 | lender_name = data['lender'] |
| 118 | borrower_name = data['borrower'] |
| 119 | amount = data['amount'] |
| 120 | |
| 121 | # Edge Case: Invalid amount type or negative amount |
| 122 | if not isinstance(amount, (int, float)) or amount < 0: |
| 123 | return json.dumps({"error": "Invalid amount"}) |
| 124 | |
| 125 | # Edge Case: Lender or borrower does not exist |
| 126 | if lender_name not in self.users or borrower_name not in self.users: |
| 127 | return json.dumps({"error": "User does not exist"}) |
| 128 | |
| 129 | # Edge Case: Lender and borrower are the same person |
| 130 | if lender_name == borrower_name: |
| 131 | return json.dumps({"error": "Cannot create IOU between same user"}) |
| 132 | |
| 133 | # Update IOUs |
| 134 | # Update lender's owed_by |
| 135 | if borrower_name in self.users[lender_name]['owed_by']: |
| 136 | self.users[lender_name]['owed_by'][borrower_name] += amount |
| 137 | else: |
| 138 | self.users[lender_name]['owed_by'][borrower_name] = amount |
| 139 | |
| 140 | # Update borrower's owes |
| 141 | if lender_name in self.users[borrower_name]['owes']: |
| 142 | self.users[borrower_name]['owes'][lender_name] += amount |
| 143 | else: |
| 144 | self.users[borrower_name]['owes'][lender_name] = amount |
| 145 | |
| 146 | # Recalculate balances |
| 147 | self._recalculate_balance(lender_name) |
| 148 | self._recalculate_balance(borrower_name) |
| 149 | |
| 150 | # Return updated user information |
| 151 | users = [ |
| 152 | self._get_user_details(lender_name), |
| 153 | self._get_user_details(borrower_name) |
| 154 | ] |
| 155 | users.sort(key=lambda u: u['name']) |
| 156 | |
| 157 | return json.dumps({"users": users}) |
| 158 | |
| 159 | # Edge Case: Unknown endpoint |
| 160 | return json.dumps({"error": "Not found"}) |
| 161 | |
| 162 | def _get_user_details(self, name: str) -> Dict[str, Any]: |
| 163 | """ |
| 164 | Get a user's details with calculated balance. |
| 165 | |
| 166 | Args: |
| 167 | name: The user's name |
| 168 | |
| 169 | Returns: |
| 170 | Dictionary with user details |
| 171 | """ |
| 172 | user = self.users[name].copy() |
| 173 | # Ensure balance is calculated correctly |
| 174 | user['balance'] = self._calculate_balance(name) |
| 175 | return user |
| 176 | |
| 177 | def _calculate_balance(self, name: str) -> float: |
| 178 | """ |
| 179 | Calculate a user's balance. |
| 180 | |
| 181 | Args: |
| 182 | name: The user's name |
| 183 | |
| 184 | Returns: |
| 185 | The user's balance |
| 186 | """ |
| 187 | user = self.users[name] |
| 188 | total_owed_by = sum(user['owed_by'].values()) |
| 189 | total_owes = sum(user['owes'].values()) |
| 190 | return round(total_owed_by - total_owes, 2) |
| 191 | |
| 192 | def _recalculate_balance(self, name: str) -> None: |
| 193 | """ |
| 194 | Recalculate and update a user's balance. |
| 195 | |
| 196 | Args: |
| 197 | name: The user's name |
| 198 | """ |
| 199 | self.users[name]['balance'] = self._calculate_balance(name) |
| 200 | |
| 201 | # Handled Edge Cases: |
| 202 | # - GET /users with no payload (list all users) |
| 203 | # - GET /users with payload (list specific users) |
| 204 | # - GET /users with malformed payload (missing 'users' key) |
| 205 | # - GET /users with invalid JSON payload |
| 206 | # - GET with unknown endpoint |
| 207 | # - POST with missing payload |
| 208 | # - POST with invalid JSON payload |
| 209 | # - POST /add with missing 'user' in payload |
| 210 | # - POST /add with existing user |
| 211 | # - POST /iou with missing required fields |
| 212 | # - POST /iou with invalid amount type or negative amount |
| 213 | # - POST /iou with non-existent lender or borrower |
| 214 | # - POST /iou with same lender and borrower |
| 215 | # - POST with unknown endpoint |