| 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 | JSON string response. |
| 26 | """ |
| 27 | if url == "/users": |
| 28 | if payload is None: |
| 29 | # Return all users |
| 30 | return json.dumps({"users": [self._format_user(user) for user in sorted(self.database["users"], key=lambda x: x["name"])]}) |
| 31 | else: |
| 32 | # Return specific users |
| 33 | data = json.loads(payload) |
| 34 | user_names = data.get("users", []) |
| 35 | users = [user for user in self.database["users"] if user["name"] in user_names] |
| 36 | users = sorted(users, key=lambda x: x["name"]) |
| 37 | return json.dumps({"users": [self._format_user(user) for user in users]}) |
| 38 | else: |
| 39 | return json.dumps({"error": "Not found"}) |
| 40 | |
| 8 | 41 | def post(self, url: str, payload: str | None = None) -> str: |
| 9 | | pass |
| 42 | """ |
| 43 | Handle POST requests to the API. |
| 44 | |
| 45 | Args: |
| 46 | url: The endpoint URL. |
| 47 | payload: JSON payload. |
| 48 | |
| 49 | Returns: |
| 50 | JSON string response. |
| 51 | """ |
| 52 | if payload is None: |
| 53 | return json.dumps({"error": "Payload required"}) |
| 54 | |
| 55 | data = json.loads(payload) |
| 56 | |
| 57 | if url == "/add": |
| 58 | user_name = data.get("user") |
| 59 | |
| 60 | # Edge Case: User name is missing |
| 61 | if not user_name: |
| 62 | return json.dumps({"error": "User name required"}) |
| 63 | |
| 64 | # Edge Case: User already exists - return the existing user |
| 65 | existing_user = next((user for user in self.database["users"] if user["name"] == user_name), None) |
| 66 | if existing_user: |
| 67 | return json.dumps(self._format_user(existing_user)) |
| 68 | |
| 69 | new_user = { |
| 70 | "name": user_name, |
| 71 | "owes": {}, |
| 72 | "owed_by": {}, |
| 73 | "balance": 0.0 |
| 74 | } |
| 75 | self.database["users"].append(new_user) |
| 76 | return json.dumps(self._format_user(new_user)) |
| 77 | |
| 78 | elif url == "/iou": |
| 79 | lender_name = data.get("lender") |
| 80 | borrower_name = data.get("borrower") |
| 81 | amount = data.get("amount") |
| 82 | |
| 83 | # Edge Case: Missing required fields |
| 84 | if not lender_name or not borrower_name or amount is None: |
| 85 | return json.dumps({"error": "Missing required fields"}) |
| 86 | |
| 87 | # Edge Case: Lender and borrower are the same |
| 88 | if lender_name == borrower_name: |
| 89 | return json.dumps({"error": "Cannot create IOU between same user"}) |
| 90 | |
| 91 | # Edge Case: Amount is negative |
| 92 | if amount < 0: |
| 93 | return json.dumps({"error": "Amount cannot be negative"}) |
| 94 | |
| 95 | # Create users if they don't exist |
| 96 | lender = next((user for user in self.database["users"] if user["name"] == lender_name), None) |
| 97 | borrower = next((user for user in self.database["users"] if user["name"] == borrower_name), None) |
| 98 | |
| 99 | if not lender: |
| 100 | lender = { |
| 101 | "name": lender_name, |
| 102 | "owes": {}, |
| 103 | "owed_by": {}, |
| 104 | "balance": 0.0 |
| 105 | } |
| 106 | self.database["users"].append(lender) |
| 107 | |
| 108 | if not borrower: |
| 109 | borrower = { |
| 110 | "name": borrower_name, |
| 111 | "owes": {}, |
| 112 | "owed_by": {}, |
| 113 | "balance": 0.0 |
| 114 | } |
| 115 | self.database["users"].append(borrower) |
| 116 | |
| 117 | # Update owes and owed_by relationships |
| 118 | # For lender: they are owed money by the borrower |
| 119 | if borrower_name in lender["owed_by"]: |
| 120 | lender["owed_by"][borrower_name] += amount |
| 121 | else: |
| 122 | lender["owed_by"][borrower_name] = amount |
| 123 | |
| 124 | # For borrower: they owe money to the lender |
| 125 | if lender_name in borrower["owes"]: |
| 126 | borrower["owes"][lender_name] += amount |
| 127 | else: |
| 128 | borrower["owes"][lender_name] = amount |
| 129 | |
| 130 | # Recalculate balances |
| 131 | lender["balance"] = sum(borrower_debt for borrower_debt in lender["owed_by"].values()) - \ |
| 132 | sum(lender_debt for lender_debt in lender["owes"].values()) |
| 133 | borrower["balance"] = sum(borrower_debt for borrower_debt in borrower["owed_by"].values()) - \ |
| 134 | sum(lender_debt for lender_debt in borrower["owes"].values()) |
| 135 | |
| 136 | # Return updated users |
| 137 | updated_users = sorted([lender, borrower], key=lambda x: x["name"]) |
| 138 | return json.dumps({"users": [self._format_user(user) for user in updated_users]}) |
| 139 | |
| 140 | else: |
| 141 | return json.dumps({"error": "Not found"}) |
| 142 | |
| 143 | def _format_user(self, user: dict) -> dict: |
| 144 | """ |
| 145 | Format a user object for output, ensuring balance is a float. |
| 146 | |
| 147 | Args: |
| 148 | user: The user dictionary to format. |
| 149 | |
| 150 | Returns: |
| 151 | Formatted user dictionary. |
| 152 | """ |
| 153 | # Edge Case: Ensure balance is calculated correctly |
| 154 | owes_total = sum(user["owes"].values()) |
| 155 | owed_by_total = sum(user["owed_by"].values()) |
| 156 | balance = round(owed_by_total - owes_total, 2) |
| 157 | |
| 158 | return { |
| 159 | "name": user["name"], |
| 160 | "owes": user["owes"], |
| 161 | "owed_by": user["owed_by"], |
| 162 | "balance": balance |
| 163 | } |
| 164 | |
| 165 | # Handled Edge Cases: |
| 166 | # 1. Missing user name in /add endpoint |
| 167 | # 2. User already exists in /add endpoint |
| 168 | # 3. Missing required fields in /iou endpoint |
| 169 | # 4. Lender and borrower are the same in /iou endpoint |
| 170 | # 5. Negative amount in /iou endpoint |
| 171 | # 6. Non-existent users in /iou endpoint |
| 172 | # 7. Proper handling of bidirectional relationships in IOUs |
| 173 | # 8. Correct balance calculation |
| 174 | # 9. Proper sorting of users in responses |
| 175 | # 10. Missing payload in requests |