| 1 | import json |
| 2 | |
| 1 | 3 | class RestAPI: |
| 2 | 4 | def __init__(self, database: dict | None = None): |
| 3 | | pass |
| 4 | | |
| 5 | """ |
| 6 | Initialize the REST API with an optional database. |
| 7 | |
| 8 | Args: |
| 9 | database: A dictionary containing initial user data. |
| 10 | """ |
| 11 | if database is None: |
| 12 | self.database = {"users": []} |
| 13 | else: |
| 14 | self.database = database |
| 15 | |
| 5 | 16 | def get(self, url: str, payload: str | None = None) -> str: |
| 6 | | pass |
| 7 | | |
| 17 | """ |
| 18 | Handle GET requests to the API. |
| 19 | |
| 20 | Args: |
| 21 | url: The endpoint URL. |
| 22 | payload: Optional JSON payload. |
| 23 | |
| 24 | Returns: |
| 25 | A JSON string response. |
| 26 | |
| 27 | Raises: |
| 28 | ValueError: If the URL is not recognized. |
| 29 | """ |
| 30 | if url == "/users": |
| 31 | if payload is None: |
| 32 | # Return all users |
| 33 | users = [self._create_user_object(user) for user in self.database["users"]] |
| 34 | # Sort by name |
| 35 | users.sort(key=lambda u: u["name"]) |
| 36 | return json.dumps({"users": users}) |
| 37 | else: |
| 38 | # Return specific users |
| 39 | data = json.loads(payload) |
| 40 | user_names = data.get("users", []) |
| 41 | |
| 42 | # Edge Case: Empty user list in payload |
| 43 | if not user_names: |
| 44 | return json.dumps({"users": []}) |
| 45 | |
| 46 | # Edge Case: Non-existent users in payload |
| 47 | result_users = [] |
| 48 | for name in user_names: |
| 49 | user = self._find_user(name) |
| 50 | if user is not None: |
| 51 | result_users.append(self._create_user_object(user)) |
| 52 | |
| 53 | # Sort by name |
| 54 | result_users.sort(key=lambda u: u["name"]) |
| 55 | return json.dumps({"users": result_users}) |
| 56 | else: |
| 57 | raise ValueError(f"Unknown URL: {url}") |
| 58 | |
| 59 | # Handled Edge Cases: Empty user list in payload, Non-existent users in payload |
| 60 | |
| 8 | 61 | def post(self, url: str, payload: str | None = None) -> str: |
| 9 | | pass |
| 62 | """ |
| 63 | Handle POST requests to the API. |
| 64 | |
| 65 | Args: |
| 66 | url: The endpoint URL. |
| 67 | payload: JSON payload. |
| 68 | |
| 69 | Returns: |
| 70 | A JSON string response. |
| 71 | |
| 72 | Raises: |
| 73 | ValueError: If the URL is not recognized or if required data is missing. |
| 74 | """ |
| 75 | if url == "/add": |
| 76 | if payload is None: |
| 77 | raise ValueError("Payload required for /add") |
| 78 | |
| 79 | data = json.loads(payload) |
| 80 | name = data.get("user") |
| 81 | |
| 82 | # Edge Case: Missing user name in payload |
| 83 | if name is None: |
| 84 | raise ValueError("User name is required") |
| 85 | |
| 86 | # Edge Case: User already exists - return existing user |
| 87 | if self._find_user(name) is not None: |
| 88 | existing_user = self._find_user(name) |
| 89 | return json.dumps(self._create_user_object(existing_user)) |
| 90 | |
| 91 | new_user = { |
| 92 | "name": name, |
| 93 | "owes": {}, |
| 94 | "owed_by": {}, |
| 95 | "balance": 0.0 |
| 96 | } |
| 97 | |
| 98 | self.database["users"].append(new_user) |
| 99 | return json.dumps(self._create_user_object(new_user)) |
| 100 | |
| 101 | elif url == "/iou": |
| 102 | if payload is None: |
| 103 | raise ValueError("Payload required for /iou") |
| 104 | |
| 105 | data = json.loads(payload) |
| 106 | lender_name = data.get("lender") |
| 107 | borrower_name = data.get("borrower") |
| 108 | amount = data.get("amount") |
| 109 | |
| 110 | # Edge Case: Missing required fields in payload |
| 111 | if lender_name is None or borrower_name is None or amount is None: |
| 112 | raise ValueError("Lender, borrower, and amount are required") |
| 113 | |
| 114 | # Edge Case: Lender and borrower are the same person |
| 115 | if lender_name == borrower_name: |
| 116 | raise ValueError("Lender and borrower cannot be the same person") |
| 117 | |
| 118 | lender = self._find_user(lender_name) |
| 119 | borrower = self._find_user(borrower_name) |
| 120 | |
| 121 | # Edge Case: Auto-create users if they don't exist |
| 122 | if lender is None: |
| 123 | lender = { |
| 124 | "name": lender_name, |
| 125 | "owes": {}, |
| 126 | "owed_by": {}, |
| 127 | "balance": 0.0 |
| 128 | } |
| 129 | self.database["users"].append(lender) |
| 130 | |
| 131 | if borrower is None: |
| 132 | borrower = { |
| 133 | "name": borrower_name, |
| 134 | "owes": {}, |
| 135 | "owed_by": {}, |
| 136 | "balance": 0.0 |
| 137 | } |
| 138 | self.database["users"].append(borrower) |
| 139 | |
| 140 | # Handle zero amount IOUs - don't create entries |
| 141 | if amount == 0.0: |
| 142 | lender_obj = self._create_user_object(lender) |
| 143 | borrower_obj = self._create_user_object(borrower) |
| 144 | users = sorted([lender_obj, borrower_obj], key=lambda u: u["name"]) |
| 145 | return json.dumps({"users": users}) |
| 146 | |
| 147 | # Update lender's owed_by and borrower's owes |
| 148 | # Handle netting of debts properly |
| 149 | if borrower_name in lender["owed_by"]: |
| 150 | lender["owed_by"][borrower_name] += amount |
| 151 | else: |
| 152 | lender["owed_by"][borrower_name] = amount |
| 153 | |
| 154 | if lender_name in borrower["owes"]: |
| 155 | borrower["owes"][lender_name] += amount |
| 156 | else: |
| 157 | borrower["owes"][lender_name] = amount |
| 158 | |
| 159 | # Net the debts if both sides have entries |
| 160 | self._net_debts(lender, borrower) |
| 161 | |
| 162 | # Update balances |
| 163 | lender["balance"] += amount |
| 164 | borrower["balance"] -= amount |
| 165 | |
| 166 | # Create response |
| 167 | lender_obj = self._create_user_object(lender) |
| 168 | borrower_obj = self._create_user_object(borrower) |
| 169 | |
| 170 | # Sort by name |
| 171 | users = sorted([lender_obj, borrower_obj], key=lambda u: u["name"]) |
| 172 | return json.dumps({"users": users}) |
| 173 | |
| 174 | else: |
| 175 | raise ValueError(f"Unknown URL: {url}") |
| 176 | |
| 177 | # Handled Edge Cases: Missing user name in payload, User already exists, Missing required fields in payload, |
| 178 | # Lender and borrower are the same person, Lender or borrower does not exist |
| 179 | |
| 180 | def _find_user(self, name: str): |
| 181 | """ |
| 182 | Find a user by name in the database. |
| 183 | |
| 184 | Args: |
| 185 | name: The name of the user to find. |
| 186 | |
| 187 | Returns: |
| 188 | The user dictionary if found, None otherwise. |
| 189 | """ |
| 190 | for user in self.database["users"]: |
| 191 | if user["name"] == name: |
| 192 | return user |
| 193 | return None |
| 194 | |
| 195 | def _create_user_object(self, user): |
| 196 | """ |
| 197 | Create a user object for API responses. |
| 198 | |
| 199 | Args: |
| 200 | user: The user dictionary from the database. |
| 201 | |
| 202 | Returns: |
| 203 | A dictionary representing the user object. |
| 204 | """ |
| 205 | # Ensure balance is a float |
| 206 | balance = float(user["balance"]) |
| 207 | |
| 208 | return { |
| 209 | "name": user["name"], |
| 210 | "owes": user["owes"], |
| 211 | "owed_by": user["owed_by"], |
| 212 | "balance": balance |
| 213 | } |
| 214 | |
| 215 | def _net_debts(self, user1, user2): |
| 216 | """ |
| 217 | Net debts between two users to eliminate redundant entries. |
| 218 | |
| 219 | Args: |
| 220 | user1: First user dictionary. |
| 221 | user2: Second user dictionary. |
| 222 | """ |
| 223 | name1 = user1["name"] |
| 224 | name2 = user2["name"] |
| 225 | |
| 226 | # Get amounts owed between users |
| 227 | user1_owes_user2 = user1["owes"].get(name2, 0.0) |
| 228 | user2_owes_user1 = user2["owes"].get(name1, 0.0) |
| 229 | user1_owed_by_user2 = user1["owed_by"].get(name2, 0.0) |
| 230 | user2_owed_by_user1 = user2["owed_by"].get(name1, 0.0) |
| 231 | |
| 232 | # Net the debts |
| 233 | net_user1_owes = user1_owes_user2 - user2_owes_user1 |
| 234 | net_user2_owes = user2_owes_user1 - user1_owes_user2 |
| 235 | |
| 236 | # Update user1's records |
| 237 | if net_user1_owes > 0: |
| 238 | user1["owes"][name2] = net_user1_owes |
| 239 | user1["owed_by"].pop(name2, None) |
| 240 | elif net_user1_owes < 0: |
| 241 | user1["owed_by"][name2] = -net_user1_owes |
| 242 | user1["owes"].pop(name2, None) |
| 243 | else: |
| 244 | user1["owes"].pop(name2, None) |
| 245 | user1["owed_by"].pop(name2, None) |
| 246 | |
| 247 | # Update user2's records |
| 248 | if net_user2_owes > 0: |
| 249 | user2["owes"][name1] = net_user2_owes |
| 250 | user2["owed_by"].pop(name1, None) |
| 251 | elif net_user2_owes < 0: |
| 252 | user2["owed_by"][name1] = -net_user2_owes |
| 253 | user2["owes"].pop(name1, None) |
| 254 | else: |
| 255 | user2["owes"].pop(name1, None) |
| 256 | user2["owed_by"].pop(name1, None) |
| 257 | |
| 258 | # Handled Edge Cases: None in this helper function |