| 1 | import json |
| 2 | from typing import Dict, List, Optional, Any |
| 3 | |
| 1 | 4 | class RestAPI: |
| 2 | 5 | def __init__(self, database: dict | None = None): |
| 3 | | pass |
| 4 | | |
| 6 | """ |
| 7 | Initialize the REST API with an optional database. |
| 8 | |
| 9 | Args: |
| 10 | database: Optional initial database dictionary containing users data |
| 11 | """ |
| 12 | if database and 'users' in database: |
| 13 | # Edge Case: Handle initial database with users |
| 14 | self.users = {user['name']: user for user in database['users']} |
| 15 | else: |
| 16 | # Edge Case: Handle empty or None database |
| 17 | self.users = {} |
| 18 | |
| 19 | def _get_user(self, name: str) -> Dict[str, Any]: |
| 20 | """ |
| 21 | Get a user object by name, creating it if it doesn't exist. |
| 22 | |
| 23 | Args: |
| 24 | name: Name of the user |
| 25 | |
| 26 | Returns: |
| 27 | User object |
| 28 | """ |
| 29 | # Edge Case: Create user if not exists |
| 30 | if name not in self.users: |
| 31 | self.users[name] = { |
| 32 | 'name': name, |
| 33 | 'owes': {}, |
| 34 | 'owed_by': {}, |
| 35 | 'balance': 0.0 |
| 36 | } |
| 37 | return self.users[name] |
| 38 | |
| 39 | def _calculate_balance(self, user: Dict[str, Any]) -> float: |
| 40 | """ |
| 41 | Calculate the balance for a user. |
| 42 | |
| 43 | Args: |
| 44 | user: User object |
| 45 | |
| 46 | Returns: |
| 47 | Calculated balance |
| 48 | """ |
| 49 | # Edge Case: Handle calculation when owes or owed_by might be missing |
| 50 | total_owed_by = sum(user.get('owed_by', {}).values()) |
| 51 | total_owes = sum(user.get('owes', {}).values()) |
| 52 | return round(total_owed_by - total_owes, 2) |
| 53 | |
| 54 | def _update_user_balances(self, user_name: str) -> None: |
| 55 | """ |
| 56 | Update the balance for a specific user. |
| 57 | |
| 58 | Args: |
| 59 | user_name: Name of the user to update |
| 60 | """ |
| 61 | user = self._get_user(user_name) |
| 62 | user['balance'] = self._calculate_balance(user) |
| 63 | |
| 5 | 64 | def get(self, url: str, payload: str | None = None) -> str: |
| 6 | | pass |
| 7 | | |
| 65 | """ |
| 66 | Handle GET requests to the API. |
| 67 | |
| 68 | Args: |
| 69 | url: Endpoint URL |
| 70 | payload: Optional JSON payload |
| 71 | |
| 72 | Returns: |
| 73 | JSON response string |
| 74 | """ |
| 75 | # Edge Case: Handle /users endpoint |
| 76 | if url == '/users': |
| 77 | if payload is None: |
| 78 | # Return all users sorted by name |
| 79 | users_list = [user for name, user in sorted(self.users.items())] |
| 80 | return json.dumps({'users': users_list}) |
| 81 | else: |
| 82 | # Return specific users sorted by name |
| 83 | payload_data = json.loads(payload) |
| 84 | user_names = payload_data.get('users', []) |
| 85 | users_list = [self.users[name] for name in sorted(user_names) if name in self.users] |
| 86 | return json.dumps({'users': users_list}) |
| 87 | |
| 88 | # Edge Case: Handle unknown endpoint |
| 89 | return json.dumps({"error": "Not found"}) |
| 90 | |
| 8 | 91 | def post(self, url: str, payload: str | None = None) -> str: |
| 9 | | pass |
| 92 | """ |
| 93 | Handle POST requests to the API. |
| 94 | |
| 95 | Args: |
| 96 | url: Endpoint URL |
| 97 | payload: JSON payload |
| 98 | |
| 99 | Returns: |
| 100 | JSON response string |
| 101 | """ |
| 102 | # Edge Case: Handle None payload |
| 103 | if payload is None: |
| 104 | return json.dumps({"error": "Payload required"}) |
| 105 | |
| 106 | payload_data = json.loads(payload) |
| 107 | |
| 108 | # Edge Case: Handle /add endpoint |
| 109 | if url == '/add': |
| 110 | user_name = payload_data.get('user') |
| 111 | # Edge Case: Handle missing user in payload |
| 112 | if not user_name: |
| 113 | return json.dumps({"error": "User name required"}) |
| 114 | # Edge Case: Handle duplicate user |
| 115 | if user_name in self.users: |
| 116 | return json.dumps({"error": "User already exists"}) |
| 117 | |
| 118 | new_user = { |
| 119 | 'name': user_name, |
| 120 | 'owes': {}, |
| 121 | 'owed_by': {}, |
| 122 | 'balance': 0.0 |
| 123 | } |
| 124 | self.users[user_name] = new_user |
| 125 | return json.dumps(new_user) |
| 126 | |
| 127 | # Edge Case: Handle /iou endpoint |
| 128 | elif url == '/iou': |
| 129 | lender_name = payload_data.get('lender') |
| 130 | borrower_name = payload_data.get('borrower') |
| 131 | amount = payload_data.get('amount') |
| 132 | |
| 133 | # Edge Case: Handle missing required fields |
| 134 | if not lender_name or not borrower_name or amount is None: |
| 135 | return json.dumps({"error": "Lender, borrower, and amount required"}) |
| 136 | |
| 137 | # Edge Case: Handle invalid amount type |
| 138 | if not isinstance(amount, (int, float)): |
| 139 | return json.dumps({"error": "Amount must be a number"}) |
| 140 | |
| 141 | # Edge Case: Handle negative amount |
| 142 | if amount < 0: |
| 143 | return json.dumps({"error": "Amount must be positive"}) |
| 144 | |
| 145 | # Edge Case: Handle same lender and borrower |
| 146 | if lender_name == borrower_name: |
| 147 | return json.dumps({"error": "Cannot create IOU between same user"}) |
| 148 | |
| 149 | # Get or create users |
| 150 | lender = self._get_user(lender_name) |
| 151 | borrower = self._get_user(borrower_name) |
| 152 | |
| 153 | # Update lender's owed_by |
| 154 | if borrower_name not in lender['owed_by']: |
| 155 | lender['owed_by'][borrower_name] = 0.0 |
| 156 | lender['owed_by'][borrower_name] = round(lender['owed_by'][borrower_name] + amount, 2) |
| 157 | |
| 158 | # Update borrower's owes |
| 159 | if lender_name not in borrower['owes']: |
| 160 | borrower['owes'][lender_name] = 0.0 |
| 161 | borrower['owes'][lender_name] = round(borrower['owes'][lender_name] + amount, 2) |
| 162 | |
| 163 | # Update balances |
| 164 | self._update_user_balances(lender_name) |
| 165 | self._update_user_balances(borrower_name) |
| 166 | |
| 167 | # Return updated users sorted by name |
| 168 | updated_users = sorted([lender, borrower], key=lambda u: u['name']) |
| 169 | return json.dumps({'users': updated_users}) |
| 170 | |
| 171 | # Edge Case: Handle unknown endpoint |
| 172 | return json.dumps({"error": "Not found"}) |
| 173 | # Handled Edge Cases: None payload, /add endpoint, /iou endpoint, missing user in payload, duplicate user, missing required fields, invalid amount type, negative amount, same lender and borrower, unknown endpoint |
| 174 | # Handled Edge Cases: Initial database with users, empty or None database, /users endpoint, unknown endpoint |