| 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 a database. |
| 7 | |
| 8 | Args: |
| 9 | database: A dictionary containing user data or None to initialize with an empty database. |
| 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 | # Edge Case: Handle request with no payload (list all users) |
| 32 | if payload is None: |
| 33 | return json.dumps({"users": sorted(self.database["users"], key=lambda x: x["name"])}) |
| 34 | |
| 35 | # Edge Case: Handle request with payload (list specific users) |
| 36 | try: |
| 37 | data = json.loads(payload) |
| 38 | user_names = data.get("users", []) |
| 39 | |
| 40 | # Edge Case: Handle empty user list in payload |
| 41 | if not user_names: |
| 42 | return json.dumps({"users": []}) |
| 43 | |
| 44 | # Filter users by the provided names |
| 45 | filtered_users = [user for user in self.database["users"] if user["name"] in user_names] |
| 46 | |
| 47 | # Edge Case: Handle user names that don't exist in the database |
| 48 | if len(filtered_users) != len(user_names): |
| 49 | # Only return users that exist |
| 50 | pass |
| 51 | |
| 52 | # Sort by name |
| 53 | filtered_users.sort(key=lambda x: x["name"]) |
| 54 | return json.dumps({"users": filtered_users}) |
| 55 | except json.JSONDecodeError: |
| 56 | # Edge Case: Handle invalid JSON payload |
| 57 | return json.dumps({"users": []}) |
| 58 | else: |
| 59 | # Edge Case: Handle unknown URL |
| 60 | raise ValueError(f"Unknown GET endpoint: {url}") |
| 61 | |
| 62 | # Handled Edge Cases: request with no payload, request with payload, empty user list in payload, user names that don't exist, invalid JSON payload, unknown URL |
| 63 | |
| 8 | 64 | def post(self, url: str, payload: str | None = None) -> str: |
| 9 | | pass |
| 65 | """ |
| 66 | Handle POST requests to the API. |
| 67 | |
| 68 | Args: |
| 69 | url: The endpoint URL. |
| 70 | payload: JSON payload. |
| 71 | |
| 72 | Returns: |
| 73 | A JSON string response. |
| 74 | |
| 75 | Raises: |
| 76 | ValueError: If the URL is not recognized or if there are issues with the payload. |
| 77 | """ |
| 78 | if payload is None: |
| 79 | # Edge Case: Handle missing payload |
| 80 | raise ValueError("Payload is required for POST requests") |
| 81 | |
| 82 | try: |
| 83 | data = json.loads(payload) |
| 84 | except json.JSONDecodeError: |
| 85 | # Edge Case: Handle invalid JSON payload |
| 86 | raise ValueError("Invalid JSON payload") |
| 87 | |
| 88 | if url == "/add": |
| 89 | user_name = data.get("user") |
| 90 | |
| 91 | # Edge Case: Handle missing user name |
| 92 | if user_name is None: |
| 93 | raise ValueError("User name is required") |
| 94 | |
| 95 | # Edge Case: Handle duplicate user name |
| 96 | for user in self.database["users"]: |
| 97 | if user["name"] == user_name: |
| 98 | raise ValueError(f"User {user_name} already exists") |
| 99 | |
| 100 | # Create new user |
| 101 | new_user = { |
| 102 | "name": user_name, |
| 103 | "owes": {}, |
| 104 | "owed_by": {}, |
| 105 | "balance": 0.0 |
| 106 | } |
| 107 | |
| 108 | self.database["users"].append(new_user) |
| 109 | return json.dumps(new_user) |
| 110 | |
| 111 | elif url == "/iou": |
| 112 | lender_name = data.get("lender") |
| 113 | borrower_name = data.get("borrower") |
| 114 | amount = data.get("amount") |
| 115 | |
| 116 | # Edge Case: Handle missing lender, borrower, or amount |
| 117 | if lender_name is None or borrower_name is None or amount is None: |
| 118 | raise ValueError("Lender, borrower, and amount are required") |
| 119 | |
| 120 | # Edge Case: Handle non-numeric amount |
| 121 | if not isinstance(amount, (int, float)): |
| 122 | raise ValueError("Amount must be a number") |
| 123 | |
| 124 | # Edge Case: Handle negative amount |
| 125 | if amount < 0: |
| 126 | raise ValueError("Amount must be positive") |
| 127 | |
| 128 | # Edge Case: Handle lender and borrower being the same person |
| 129 | if lender_name == borrower_name: |
| 130 | raise ValueError("Lender and borrower cannot be the same person") |
| 131 | |
| 132 | # Find lender and borrower |
| 133 | lender = None |
| 134 | borrower = None |
| 135 | |
| 136 | for user in self.database["users"]: |
| 137 | if user["name"] == lender_name: |
| 138 | lender = user |
| 139 | elif user["name"] == borrower_name: |
| 140 | borrower = user |
| 141 | |
| 142 | # Edge Case: Handle lender or borrower not found |
| 143 | if lender is None or borrower is None: |
| 144 | raise ValueError("Lender or borrower not found") |
| 145 | |
| 146 | # Update IOUs - handle bidirectional debts properly by calculating net amounts |
| 147 | # Get existing amounts |
| 148 | current_lender_owed_by_borrower = lender["owed_by"].get(borrower_name, 0) |
| 149 | current_lender_owes_borrower = lender["owes"].get(borrower_name, 0) |
| 150 | current_borrower_owed_by_lender = borrower["owed_by"].get(lender_name, 0) |
| 151 | current_borrower_owes_lender = borrower["owes"].get(lender_name, 0) |
| 152 | |
| 153 | # Calculate new net amounts after this transaction |
| 154 | # Net amount lender is owed by borrower = (what lender is currently owed) - (what lender currently owes) + new amount |
| 155 | new_net_lender_owed = (current_lender_owed_by_borrower - current_lender_owes_borrower) + amount |
| 156 | |
| 157 | # Remove all existing relationships between these two users |
| 158 | lender["owed_by"].pop(borrower_name, None) |
| 159 | lender["owes"].pop(borrower_name, None) |
| 160 | borrower["owed_by"].pop(lender_name, None) |
| 161 | borrower["owes"].pop(lender_name, None) |
| 162 | |
| 163 | # Set new net relationships |
| 164 | if new_net_lender_owed > 0: |
| 165 | # Lender is owed money by borrower |
| 166 | lender["owed_by"][borrower_name] = new_net_lender_owed |
| 167 | borrower["owes"][lender_name] = new_net_lender_owed |
| 168 | elif new_net_lender_owed < 0: |
| 169 | # Borrower is owed money by lender |
| 170 | borrower["owed_by"][lender_name] = -new_net_lender_owed |
| 171 | lender["owes"][borrower_name] = -new_net_lender_owed |
| 172 | |
| 173 | # Recalculate balances |
| 174 | lender_total_owed = sum(lender["owed_by"].values()) |
| 175 | lender_total_owes = sum(lender["owes"].values()) |
| 176 | lender["balance"] = lender_total_owed - lender_total_owes |
| 177 | |
| 178 | borrower_total_owed = sum(borrower["owed_by"].values()) |
| 179 | borrower_total_owes = sum(borrower["owes"].values()) |
| 180 | borrower["balance"] = borrower_total_owed - borrower_total_owes |
| 181 | |
| 182 | # Return updated users sorted by name |
| 183 | updated_users = [lender, borrower] |
| 184 | updated_users.sort(key=lambda x: x["name"]) |
| 185 | return json.dumps({"users": updated_users}) |
| 186 | else: |
| 187 | # Edge Case: Handle unknown URL |
| 188 | raise ValueError(f"Unknown POST endpoint: {url}") |
| 189 | |
| 190 | # Handled Edge Cases: missing payload, invalid JSON payload, missing user name, duplicate user name, missing lender/borrower/amount, non-numeric amount, negative amount, lender and borrower being the same person, lender or borrower not found, unknown URL |