| 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: Optional initial database dictionary containing 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 | 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 | return json.dumps({"users": self._get_all_users()}) |
| 34 | else: |
| 35 | # Return specific users |
| 36 | data = json.loads(payload) |
| 37 | user_names = data.get("users", []) |
| 38 | return json.dumps({"users": self._get_users_by_names(user_names)}) |
| 39 | else: |
| 40 | raise ValueError(f"Unknown GET URL: {url}") |
| 41 | |
| 8 | 42 | def post(self, url: str, payload: str | None = None) -> str: |
| 9 | | pass |
| 43 | """ |
| 44 | Handle POST requests to the API. |
| 45 | |
| 46 | Args: |
| 47 | url: The endpoint URL. |
| 48 | payload: JSON payload. |
| 49 | |
| 50 | Returns: |
| 51 | JSON string response. |
| 52 | |
| 53 | Raises: |
| 54 | ValueError: If the URL is not recognized or if there are validation errors. |
| 55 | """ |
| 56 | if url == "/add": |
| 57 | if payload is None: |
| 58 | raise ValueError("Payload required for /add endpoint") |
| 59 | |
| 60 | data = json.loads(payload) |
| 61 | user_name = data.get("user") |
| 62 | |
| 63 | # Edge Case: Missing user name in payload |
| 64 | if user_name is None: |
| 65 | raise ValueError("User name is required") |
| 66 | |
| 67 | # Edge Case: User already exists |
| 68 | if self._find_user(user_name) is not None: |
| 69 | raise ValueError(f"User {user_name} already exists") |
| 70 | |
| 71 | new_user = { |
| 72 | "name": user_name, |
| 73 | "owes": {}, |
| 74 | "owed_by": {}, |
| 75 | "balance": 0.0 |
| 76 | } |
| 77 | |
| 78 | self.database["users"].append(new_user) |
| 79 | |
| 80 | # Edge Case: Return the new user object |
| 81 | return json.dumps(new_user) |
| 82 | |
| 83 | elif url == "/iou": |
| 84 | if payload is None: |
| 85 | raise ValueError("Payload required for /iou endpoint") |
| 86 | |
| 87 | data = json.loads(payload) |
| 88 | lender_name = data.get("lender") |
| 89 | borrower_name = data.get("borrower") |
| 90 | amount = data.get("amount") |
| 91 | |
| 92 | # Edge Case: Missing required fields |
| 93 | if lender_name is None or borrower_name is None or amount is None: |
| 94 | raise ValueError("Lender, borrower, and amount are required") |
| 95 | |
| 96 | # Edge Case: Lender and borrower are the same person |
| 97 | if lender_name == borrower_name: |
| 98 | raise ValueError("Lender and borrower cannot be the same person") |
| 99 | |
| 100 | # Edge Case: Amount is negative |
| 101 | if amount < 0: |
| 102 | raise ValueError("Amount must be non-negative") |
| 103 | |
| 104 | lender = self._find_user(lender_name) |
| 105 | borrower = self._find_user(borrower_name) |
| 106 | |
| 107 | # Edge Case: Lender or borrower does not exist |
| 108 | if lender is None: |
| 109 | raise ValueError(f"User {lender_name} does not exist") |
| 110 | if borrower is None: |
| 111 | raise ValueError(f"User {borrower_name} does not exist") |
| 112 | |
| 113 | # Update lender's owed_by |
| 114 | if borrower_name in lender["owed_by"]: |
| 115 | lender["owed_by"][borrower_name] += amount |
| 116 | else: |
| 117 | lender["owed_by"][borrower_name] = amount |
| 118 | |
| 119 | # Update borrower's owes |
| 120 | if lender_name in borrower["owes"]: |
| 121 | borrower["owes"][lender_name] += amount |
| 122 | else: |
| 123 | borrower["owes"][lender_name] = amount |
| 124 | |
| 125 | # Recalculate balances |
| 126 | self._recalculate_balance(lender) |
| 127 | self._recalculate_balance(borrower) |
| 128 | |
| 129 | # Return updated users sorted by name |
| 130 | users = [lender, borrower] |
| 131 | users.sort(key=lambda u: u["name"]) |
| 132 | |
| 133 | return json.dumps({"users": users}) |
| 134 | |
| 135 | else: |
| 136 | raise ValueError(f"Unknown POST URL: {url}") |
| 137 | |
| 138 | def _find_user(self, name: str): |
| 139 | """ |
| 140 | Find a user by name in the database. |
| 141 | |
| 142 | Args: |
| 143 | name: The name of the user to find. |
| 144 | |
| 145 | Returns: |
| 146 | The user dictionary if found, None otherwise. |
| 147 | """ |
| 148 | for user in self.database["users"]: |
| 149 | if user["name"] == name: |
| 150 | return user |
| 151 | return None |
| 152 | |
| 153 | def _recalculate_balance(self, user): |
| 154 | """ |
| 155 | Recalculate the balance for a user based on their owes and owed_by. |
| 156 | |
| 157 | Args: |
| 158 | user: The user dictionary to update. |
| 159 | """ |
| 160 | total_owed_by = sum(user["owed_by"].values()) |
| 161 | total_owes = sum(user["owes"].values()) |
| 162 | user["balance"] = round(total_owed_by - total_owes, 2) |
| 163 | |
| 164 | def _get_all_users(self): |
| 165 | """ |
| 166 | Get all users from the database, sorted by name. |
| 167 | |
| 168 | Returns: |
| 169 | List of user dictionaries sorted by name. |
| 170 | """ |
| 171 | return sorted(self.database["users"], key=lambda u: u["name"]) |
| 172 | |
| 173 | def _get_users_by_names(self, names): |
| 174 | """ |
| 175 | Get specific users by their names. |
| 176 | |
| 177 | Args: |
| 178 | names: List of user names to retrieve. |
| 179 | |
| 180 | Returns: |
| 181 | List of user dictionaries sorted by name. |
| 182 | """ |
| 183 | users = [] |
| 184 | for name in names: |
| 185 | user = self._find_user(name) |
| 186 | # Edge Case: User not found - skip silently as per specification |
| 187 | if user is not None: |
| 188 | users.append(user) |
| 189 | return sorted(users, key=lambda u: u["name"]) |
| 190 | |
| 191 | # Handled Edge Cases: Missing user name in payload, user already exists, |
| 192 | # missing required fields, lender and borrower are the same person, |
| 193 | # amount is negative, lender or borrower does not exist, |
| 194 | # user not found when retrieving specific users |