| 1 | | class RestAPI: |
| 2 | | def __init__(self, database: dict | None = None): |
| 3 | | pass |
| 4 | | |
| 5 | | def get(self, url: str, payload: str | None = None) -> str: |
| 6 | | pass |
| 1 | import json |
| 2 | from typing import Dict, List, Optional, Any |
| 7 | 3 | |
| 8 | | def post(self, url: str, payload: str | None = None) -> str: |
| 9 | | pass |
| 4 | class RestAPI: |
| 5 | """ |
| 6 | A RESTful API for tracking IOUs between users. |
| 7 | |
| 8 | This class manages user accounts and IOUs in memory, providing endpoints |
| 9 | to add users, create IOUs, and retrieve user information. |
| 10 | """ |
| 11 | |
| 12 | def __init__(self, database: Optional[Dict[str, Any]] = None): |
| 13 | """ |
| 14 | Initialize the REST API with an optional initial database. |
| 15 | |
| 16 | Args: |
| 17 | database: Optional initial database dictionary with 'users' key |
| 18 | """ |
| 19 | # Edge Case: Handle None database by initializing empty users list |
| 20 | self.users = {} |
| 21 | if database and 'users' in database: |
| 22 | for user_data in database['users']: |
| 23 | self.users[user_data['name']] = user_data |
| 24 | |
| 25 | def _calculate_balance(self, user_data: Dict[str, Any]) -> float: |
| 26 | """ |
| 27 | Calculate the balance for a user based on what they owe and are owed. |
| 28 | |
| 29 | Args: |
| 30 | user_data: Dictionary containing user information |
| 31 | |
| 32 | Returns: |
| 33 | float: The calculated balance |
| 34 | """ |
| 35 | total_owed_by_others = sum(user_data.get('owed_by', {}).values()) |
| 36 | total_owed_to_others = sum(user_data.get('owes', {}).values()) |
| 37 | return round(total_owed_by_others - total_owed_to_others, 2) |
| 38 | |
| 39 | def _get_user(self, name: str) -> Optional[Dict[str, Any]]: |
| 40 | """ |
| 41 | Get a user by name, returning a copy with calculated balance. |
| 42 | |
| 43 | Args: |
| 44 | name: Name of the user to retrieve |
| 45 | |
| 46 | Returns: |
| 47 | Dictionary with user data or None if user doesn't exist |
| 48 | """ |
| 49 | # Edge Case: Return None for non-existent users |
| 50 | if name not in self.users: |
| 51 | return None |
| 52 | |
| 53 | user = self.users[name].copy() |
| 54 | user['balance'] = self._calculate_balance(user) |
| 55 | return user |
| 56 | |
| 57 | def get(self, url: str, payload: Optional[str] = None) -> str: |
| 58 | """ |
| 59 | Handle GET requests to the API. |
| 60 | |
| 61 | Args: |
| 62 | url: The endpoint URL |
| 63 | payload: Optional JSON payload |
| 64 | |
| 65 | Returns: |
| 66 | JSON string response |
| 67 | """ |
| 68 | # Edge Case: Handle /users endpoint |
| 69 | if url == '/users': |
| 70 | # Edge Case: Handle payload with specific users list |
| 71 | if payload: |
| 72 | try: |
| 73 | data = json.loads(payload) |
| 74 | if 'users' in data: |
| 75 | # Edge Case: Return only requested users, sorted by name |
| 76 | result_users = [] |
| 77 | for name in sorted(data['users']): |
| 78 | user = self._get_user(name) |
| 79 | # Edge Case: Skip non-existent users in the list |
| 80 | if user: |
| 81 | result_users.append(user) |
| 82 | return json.dumps({'users': result_users}) |
| 83 | except json.JSONDecodeError: |
| 84 | # Edge Case: Handle invalid JSON payload |
| 85 | pass |
| 86 | else: |
| 87 | # Edge Case: Return all users sorted by name |
| 88 | all_users = [self._get_user(name) for name in sorted(self.users.keys())] |
| 89 | return json.dumps({'users': all_users}) |
| 90 | |
| 91 | # Edge Case: Handle unknown endpoints |
| 92 | return json.dumps({}) |
| 93 | |
| 94 | def post(self, url: str, payload: Optional[str] = None) -> str: |
| 95 | """ |
| 96 | Handle POST requests to the API. |
| 97 | |
| 98 | Args: |
| 99 | url: The endpoint URL |
| 100 | payload: Optional JSON payload |
| 101 | |
| 102 | Returns: |
| 103 | JSON string response |
| 104 | """ |
| 105 | # Edge Case: Handle invalid JSON payload |
| 106 | if not payload: |
| 107 | return json.dumps({}) |
| 108 | |
| 109 | try: |
| 110 | data = json.loads(payload) |
| 111 | except json.JSONDecodeError: |
| 112 | return json.dumps({}) |
| 113 | |
| 114 | # Edge Case: Handle /add endpoint for creating new users |
| 115 | if url == '/add': |
| 116 | if 'user' in data: |
| 117 | name = data['user'] |
| 118 | # Edge Case: Prevent creating duplicate users |
| 119 | if name in self.users: |
| 120 | return json.dumps({}) |
| 121 | |
| 122 | # Edge Case: Create new user with default empty values |
| 123 | new_user = { |
| 124 | 'name': name, |
| 125 | 'owes': {}, |
| 126 | 'owed_by': {}, |
| 127 | 'balance': 0.0 |
| 128 | } |
| 129 | self.users[name] = new_user |
| 130 | return json.dumps(new_user) |
| 131 | |
| 132 | # Edge Case: Handle /iou endpoint for creating IOUs |
| 133 | elif url == '/iou': |
| 134 | required_fields = ['lender', 'borrower', 'amount'] |
| 135 | # Edge Case: Validate all required fields are present |
| 136 | if not all(field in data for field in required_fields): |
| 137 | return json.dumps({}) |
| 138 | |
| 139 | lender_name = data['lender'] |
| 140 | borrower_name = data['borrower'] |
| 141 | amount = data['amount'] |
| 142 | |
| 143 | # Edge Case: Validate lender and borrower exist |
| 144 | if lender_name not in self.users or borrower_name not in self.users: |
| 145 | return json.dumps({}) |
| 146 | |
| 147 | # Edge Case: Validate amount is a positive number |
| 148 | if not isinstance(amount, (int, float)) or amount <= 0: |
| 149 | return json.dumps({}) |
| 150 | |
| 151 | # Get references to the user objects |
| 152 | lender = self.users[lender_name] |
| 153 | borrower = self.users[borrower_name] |
| 154 | |
| 155 | # Initialize owes/owed_by dictionaries if they don't exist |
| 156 | if 'owes' not in lender: |
| 157 | lender['owes'] = {} |
| 158 | if 'owed_by' not in lender: |
| 159 | lender['owed_by'] = {} |
| 160 | if 'owes' not in borrower: |
| 161 | borrower['owes'] = {} |
| 162 | if 'owed_by' not in borrower: |
| 163 | borrower['owed_by'] = {} |
| 164 | |
| 165 | # Update what the borrower owes the lender |
| 166 | if borrower_name in lender['owed_by']: |
| 167 | lender['owed_by'][borrower_name] += amount |
| 168 | else: |
| 169 | lender['owed_by'][borrower_name] = amount |
| 170 | |
| 171 | if lender_name in borrower['owes']: |
| 172 | borrower['owes'][lender_name] += amount |
| 173 | else: |
| 174 | borrower['owes'][lender_name] = amount |
| 175 | |
| 176 | # Handle debt cancellation |
| 177 | if lender_name in lender['owes'] and borrower_name in borrower['owed_by']: |
| 178 | # If they both owe each other, cancel the debts |
| 179 | lender_owes_borrower = lender['owes'].get(borrower_name, 0) |
| 180 | borrower_owes_lender = borrower['owes'].get(lender_name, 0) |
| 181 | |
| 182 | if lender_owes_borrower > 0 and borrower_owes_lender > 0: |
| 183 | if lender_owes_borrower > borrower_owes_lender: |
| 184 | lender['owes'][borrower_name] -= borrower_owes_lender |
| 185 | del borrower['owes'][lender_name] |
| 186 | borrower['owed_by'][lender_name] = lender_owes_borrower - borrower_owes_lender |
| 187 | del lender['owed_by'][borrower_name] |
| 188 | elif borrower_owes_lender > lender_owes_borrower: |
| 189 | borrower['owes'][lender_name] -= lender_owes_borrower |
| 190 | del lender['owes'][borrower_name] |
| 191 | lender['owed_by'][borrower_name] = borrower_owes_lender - lender_owes_borrower |
| 192 | del borrower['owed_by'][lender_name] |
| 193 | else: # Equal amounts |
| 194 | del lender['owes'][borrower_name] |
| 195 | del borrower['owes'][lender_name] |
| 196 | del lender['owed_by'][borrower_name] |
| 197 | del borrower['owed_by'][lender_name] |
| 198 | |
| 199 | # Return updated user information sorted by name |
| 200 | updated_users = [ |
| 201 | self._get_user(lender_name), |
| 202 | self._get_user(borrower_name) |
| 203 | ] |
| 204 | updated_users.sort(key=lambda u: u['name']) |
| 205 | return json.dumps({'users': updated_users}) |
| 206 | |
| 207 | # Edge Case: Handle unknown endpoints |
| 208 | return json.dumps({}) |
| 209 | |
| 210 | # Handled Edge Cases: None database, non-existent users, invalid JSON payload, |
| 211 | # unknown endpoints, duplicate users, missing required fields, |
| 212 | # non-existent lender/borrower, invalid amount values, |
| 213 | # debt cancellation logic |