| 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 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 with users data |
| 17 | """ |
| 18 | if database is None: |
| 19 | self.database = {"users": []} |
| 20 | else: |
| 21 | self.database = database |
| 22 | |
| 23 | def get(self, url: str, payload: Optional[str] = None) -> str: |
| 24 | """ |
| 25 | Handle GET requests to the API. |
| 26 | |
| 27 | Args: |
| 28 | url: The endpoint URL |
| 29 | payload: Optional JSON payload |
| 30 | |
| 31 | Returns: |
| 32 | JSON response string |
| 33 | """ |
| 34 | if url == "/users": |
| 35 | if payload is None: |
| 36 | # Return all users sorted by name |
| 37 | users = self._get_all_users() |
| 38 | return json.dumps({"users": users}) |
| 39 | else: |
| 40 | # Return specific users |
| 41 | data = json.loads(payload) |
| 42 | user_names = data.get("users", []) |
| 43 | users = self._get_users_by_names(user_names) |
| 44 | return json.dumps({"users": users}) |
| 45 | |
| 46 | # Edge Case: Invalid URL |
| 47 | return json.dumps({"error": "Invalid URL"}) |
| 48 | |
| 49 | def post(self, url: str, payload: Optional[str] = None) -> str: |
| 50 | """ |
| 51 | Handle POST requests to the API. |
| 52 | |
| 53 | Args: |
| 54 | url: The endpoint URL |
| 55 | payload: Optional JSON payload |
| 56 | |
| 57 | Returns: |
| 58 | JSON response string |
| 59 | """ |
| 60 | if payload is None: |
| 61 | # Edge Case: Missing payload |
| 62 | return json.dumps({"error": "Payload required"}) |
| 63 | |
| 64 | try: |
| 65 | data = json.loads(payload) |
| 66 | except json.JSONDecodeError: |
| 67 | # Edge Case: Invalid JSON payload |
| 68 | return json.dumps({"error": "Invalid JSON payload"}) |
| 69 | |
| 70 | if url == "/add": |
| 71 | user_name = data.get("user") |
| 72 | if not user_name: |
| 73 | # Edge Case: Missing user name |
| 74 | return json.dumps({"error": "User name required"}) |
| 75 | |
| 76 | # Edge Case: User already exists |
| 77 | if self._user_exists(user_name): |
| 78 | user = next(user for user in self.database["users"] if user["name"] == user_name) |
| 79 | return json.dumps(user) |
| 80 | |
| 81 | user = self._create_user(user_name) |
| 82 | self.database["users"].append(user) |
| 83 | return json.dumps(user) |
| 84 | |
| 85 | elif url == "/iou": |
| 86 | lender_name = data.get("lender") |
| 87 | borrower_name = data.get("borrower") |
| 88 | amount = data.get("amount") |
| 89 | |
| 90 | # Edge Case: Missing required fields |
| 91 | if not lender_name or not borrower_name or amount is None: |
| 92 | return json.dumps({"error": "Lender, borrower, and amount required"}) |
| 93 | |
| 94 | # Edge Case: Invalid amount type |
| 95 | if not isinstance(amount, (int, float)): |
| 96 | return json.dumps({"error": "Amount must be a number"}) |
| 97 | |
| 98 | # Edge Case: Negative amount |
| 99 | if amount < 0: |
| 100 | return json.dumps({"error": "Amount must be positive"}) |
| 101 | |
| 102 | # Edge Case: Lender or borrower does not exist |
| 103 | if not self._user_exists(lender_name) or not self._user_exists(borrower_name): |
| 104 | return json.dumps({"error": "Both users must exist"}) |
| 105 | |
| 106 | # Edge Case: Lender and borrower are the same |
| 107 | if lender_name == borrower_name: |
| 108 | return json.dumps({"error": "Lender and borrower cannot be the same"}) |
| 109 | |
| 110 | self._update_iou(lender_name, borrower_name, amount) |
| 111 | users = self._get_users_by_names([lender_name, borrower_name]) |
| 112 | return json.dumps({"users": users}) |
| 113 | |
| 114 | # Edge Case: Invalid URL |
| 115 | return json.dumps({"error": "Invalid URL"}) |
| 116 | |
| 117 | def _get_all_users(self) -> List[Dict]: |
| 118 | """ |
| 119 | Get all users sorted by name. |
| 120 | |
| 121 | Returns: |
| 122 | List of user objects sorted by name |
| 123 | """ |
| 124 | return sorted(self.database["users"], key=lambda u: u["name"]) |
| 125 | |
| 126 | def _get_users_by_names(self, names: List[str]) -> List[Dict]: |
| 127 | """ |
| 128 | Get users by their names, sorted by name. |
| 129 | |
| 130 | Args: |
| 131 | names: List of user names |
| 132 | |
| 133 | Returns: |
| 134 | List of user objects sorted by name |
| 135 | """ |
| 136 | users = [user for user in self.database["users"] if user["name"] in names] |
| 137 | return sorted(users, key=lambda u: u["name"]) |
| 138 | |
| 139 | def _user_exists(self, name: str) -> bool: |
| 140 | """ |
| 141 | Check if a user exists. |
| 142 | |
| 143 | Args: |
| 144 | name: User name to check |
| 145 | |
| 146 | Returns: |
| 147 | True if user exists, False otherwise |
| 148 | """ |
| 149 | return any(user["name"] == name for user in self.database["users"]) |
| 150 | |
| 151 | def _create_user(self, name: str) -> Dict: |
| 152 | """ |
| 153 | Create a new user object. |
| 154 | |
| 155 | Args: |
| 156 | name: Name of the user |
| 157 | |
| 158 | Returns: |
| 159 | New user object |
| 160 | """ |
| 161 | return { |
| 162 | "name": name, |
| 163 | "owes": {}, |
| 164 | "owed_by": {}, |
| 165 | "balance": 0.0 |
| 166 | } |
| 167 | |
| 168 | def _update_iou(self, lender_name: str, borrower_name: str, amount: float) -> None: |
| 169 | """ |
| 170 | Update the IOU between lender and borrower. |
| 171 | |
| 172 | Args: |
| 173 | lender_name: Name of the lender |
| 174 | borrower_name: Name of the borrower |
| 175 | amount: Amount of the IOU |
| 176 | """ |
| 177 | lender = next(user for user in self.database["users"] if user["name"] == lender_name) |
| 178 | borrower = next(user for user in self.database["users"] if user["name"] == borrower_name) |
| 179 | |
| 180 | # Check if there's an existing debt in the opposite direction |
| 181 | # If borrower already owes lender money, this is additional debt in the same direction |
| 182 | if lender_name in borrower["owes"]: |
| 183 | # Simply add to existing debt |
| 184 | borrower["owes"][lender_name] += amount |
| 185 | if borrower_name in lender["owed_by"]: |
| 186 | lender["owed_by"][borrower_name] += amount |
| 187 | else: |
| 188 | lender["owed_by"][borrower_name] = amount |
| 189 | # Update balances |
| 190 | lender["balance"] += amount |
| 191 | borrower["balance"] -= amount |
| 192 | return |
| 193 | |
| 194 | # Check if there's an existing debt in the same direction (lender owes borrower) |
| 195 | # If lender already owes borrower money, reduce that debt first |
| 196 | if borrower_name in lender["owes"]: |
| 197 | existing_debt = lender["owes"][borrower_name] |
| 198 | if amount < existing_debt: |
| 199 | # New IOU is smaller than existing debt, reduce the existing debt |
| 200 | lender["owes"][borrower_name] = existing_debt - amount |
| 201 | # Borrower is still owed money, but less than before |
| 202 | if lender_name in borrower["owed_by"]: |
| 203 | borrower["owed_by"][lender_name] = existing_debt - amount |
| 204 | # Update balances |
| 205 | lender["balance"] += amount |
| 206 | borrower["balance"] -= amount |
| 207 | return |
| 208 | elif amount == existing_debt: |
| 209 | # New IOU exactly cancels existing debt |
| 210 | del lender["owes"][borrower_name] |
| 211 | if lender_name in borrower["owed_by"]: |
| 212 | del borrower["owed_by"][lender_name] |
| 213 | # Update balances |
| 214 | lender["balance"] += amount |
| 215 | borrower["balance"] -= amount |
| 216 | return |
| 217 | else: |
| 218 | # New IOU is larger than existing debt, net the difference |
| 219 | net_amount = amount - existing_debt |
| 220 | del lender["owes"][borrower_name] |
| 221 | if lender_name in borrower["owed_by"]: |
| 222 | del borrower["owed_by"][lender_name] |
| 223 | # Now the borrower owes the lender the net amount |
| 224 | borrower["owes"][lender_name] = net_amount |
| 225 | lender["owed_by"][borrower_name] = net_amount |
| 226 | # Update balances |
| 227 | lender["balance"] += amount |
| 228 | borrower["balance"] -= amount |
| 229 | return |
| 230 | |
| 231 | # No existing debt, add new debt |
| 232 | if borrower_name in lender["owed_by"]: |
| 233 | lender["owed_by"][borrower_name] += amount |
| 234 | else: |
| 235 | lender["owed_by"][borrower_name] = amount |
| 236 | |
| 237 | if lender_name in borrower["owes"]: |
| 238 | borrower["owes"][lender_name] += amount |
| 239 | else: |
| 240 | borrower["owes"][lender_name] = amount |
| 241 | |
| 242 | # Update balances |
| 243 | lender["balance"] += amount |
| 244 | borrower["balance"] -= amount |
| 245 | |
| 246 | # Clean up zero balances |
| 247 | if borrower_name in lender["owed_by"] and lender["owed_by"][borrower_name] == 0: |
| 248 | del lender["owed_by"][borrower_name] |
| 249 | if lender_name in borrower["owes"] and borrower["owes"][lender_name] == 0: |
| 250 | del borrower["owes"][lender_name] |
| 251 | if borrower_name in lender["owes"] and lender["owes"][borrower_name] == 0: |
| 252 | del lender["owes"][borrower_name] |
| 253 | if lender_name in borrower["owed_by"] and borrower["owed_by"][lender_name] == 0: |
| 254 | del borrower["owed_by"][lender_name] |
| 255 | |
| 256 | # Handled Edge Cases: Invalid URL, Missing payload, Invalid JSON payload, Missing user name, |
| 257 | # User already exists, Missing required fields, Invalid amount type, Negative amount, |
| 258 | # Lender or borrower does not exist, Lender and borrower are the same |