| 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. |
| 10 | """ |
| 11 | self.database = database if database else {"users": []} |
| 12 | |
| 5 | 13 | def get(self, url: str, payload: str | None = None) -> str: |
| 6 | | pass |
| 7 | | |
| 14 | """ |
| 15 | Handle GET requests to the API. |
| 16 | |
| 17 | Args: |
| 18 | url: The endpoint URL. |
| 19 | payload: Optional JSON payload. |
| 20 | |
| 21 | Returns: |
| 22 | A JSON string response. |
| 23 | """ |
| 24 | if url == "/users": |
| 25 | if payload: |
| 26 | data = json.loads(payload) |
| 27 | if "users" in data: |
| 28 | # Filter users based on the provided list |
| 29 | user_names = data["users"] |
| 30 | users = [user for user in self.database["users"] if user["name"] in user_names] |
| 31 | # Sort users by name |
| 32 | users.sort(key=lambda x: x["name"]) |
| 33 | return json.dumps({"users": users}) |
| 34 | else: |
| 35 | # Return all users sorted by name |
| 36 | users = sorted(self.database["users"], key=lambda x: x["name"]) |
| 37 | return json.dumps({"users": users}) |
| 38 | |
| 39 | return json.dumps({"error": "Invalid URL"}) |
| 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 | A JSON string response. |
| 51 | """ |
| 52 | if not payload: |
| 53 | return json.dumps({"error": "Payload required"}) |
| 54 | |
| 55 | data = json.loads(payload) |
| 56 | |
| 57 | if url == "/add": |
| 58 | # Edge Case: Check if user already exists |
| 59 | user_name = data.get("user") |
| 60 | if not user_name: |
| 61 | return json.dumps({"error": "User name required"}) |
| 62 | |
| 63 | for user in self.database["users"]: |
| 64 | if user["name"] == user_name: |
| 65 | return json.dumps({"error": "User already exists"}) |
| 66 | |
| 67 | # Create new user |
| 68 | new_user = { |
| 69 | "name": user_name, |
| 70 | "owes": {}, |
| 71 | "owed_by": {}, |
| 72 | "balance": 0.0 |
| 73 | } |
| 74 | self.database["users"].append(new_user) |
| 75 | return json.dumps(new_user) |
| 76 | |
| 77 | elif url == "/iou": |
| 78 | # Edge Case: Validate required fields |
| 79 | lender_name = data.get("lender") |
| 80 | borrower_name = data.get("borrower") |
| 81 | amount = data.get("amount") |
| 82 | |
| 83 | if not lender_name or not borrower_name or amount is None: |
| 84 | return json.dumps({"error": "Missing required fields"}) |
| 85 | |
| 86 | # Edge Case: Validate amount is a positive number |
| 87 | if not isinstance(amount, (int, float)) or amount < 0: |
| 88 | return json.dumps({"error": "Invalid amount"}) |
| 89 | |
| 90 | # Edge Case: Check if lender and borrower are the same person |
| 91 | if lender_name == borrower_name: |
| 92 | return json.dumps({"error": "Lender and borrower cannot be the same"}) |
| 93 | |
| 94 | # Edge Case: Check if both users exist |
| 95 | lender = None |
| 96 | borrower = None |
| 97 | for user in self.database["users"]: |
| 98 | if user["name"] == lender_name: |
| 99 | lender = user |
| 100 | elif user["name"] == borrower_name: |
| 101 | borrower = user |
| 102 | |
| 103 | if not lender or not borrower: |
| 104 | return json.dumps({"error": "Both users must exist"}) |
| 105 | |
| 106 | # Handle IOU creation with proper debt netting |
| 107 | # When lender lends amount to borrower: |
| 108 | # - borrower owes lender (borrower["owes"][lender] increases) |
| 109 | # - lender is owed by borrower (lender["owed_by"][borrower] increases) |
| 110 | |
| 111 | # Check existing debts |
| 112 | existing_borrower_owes_lender = borrower["owes"].get(lender_name, 0) # What borrower already owes lender |
| 113 | existing_lender_owes_borrower = lender["owes"].get(borrower_name, 0) # What lender already owes borrower |
| 114 | |
| 115 | # When lender lends amount to borrower, we add to what borrower owes lender |
| 116 | new_borrower_owes_lender = existing_borrower_owes_lender + amount |
| 117 | |
| 118 | # Net the debts |
| 119 | if new_borrower_owes_lender > existing_lender_owes_borrower: |
| 120 | # Borrower owes more than lender owes, so net: borrower owes lender |
| 121 | net_owed = new_borrower_owes_lender - existing_lender_owes_borrower |
| 122 | lender["owed_by"][borrower_name] = net_owed |
| 123 | lender["owes"].pop(borrower_name, None) # Remove any owes entry |
| 124 | |
| 125 | borrower["owes"][lender_name] = net_owed |
| 126 | borrower["owed_by"].pop(lender_name, None) # Remove any owed_by entry |
| 127 | elif new_borrower_owes_lender < existing_lender_owes_borrower: |
| 128 | # Lender owes more than borrower owes, so net: lender owes borrower |
| 129 | net_owed = existing_lender_owes_borrower - new_borrower_owes_lender |
| 130 | lender["owes"][borrower_name] = net_owed |
| 131 | lender["owed_by"].pop(borrower_name, None) # Remove any owed_by entry |
| 132 | |
| 133 | borrower["owed_by"][lender_name] = net_owed |
| 134 | borrower["owes"].pop(lender_name, None) # Remove any owes entry |
| 135 | else: |
| 136 | # Debts exactly cancel out |
| 137 | lender["owes"].pop(borrower_name, None) |
| 138 | lender["owed_by"].pop(borrower_name, None) |
| 139 | borrower["owes"].pop(lender_name, None) |
| 140 | borrower["owed_by"].pop(lender_name, None) |
| 141 | |
| 142 | # Clean up any zero debts |
| 143 | lender["owes"] = {k: v for k, v in lender["owes"].items() if v != 0} |
| 144 | lender["owed_by"] = {k: v for k, v in lender["owed_by"].items() if v != 0} |
| 145 | borrower["owes"] = {k: v for k, v in borrower["owes"].items() if v != 0} |
| 146 | borrower["owed_by"] = {k: v for k, v in borrower["owed_by"].items() if v != 0} |
| 147 | |
| 148 | # Recalculate balances |
| 149 | lender_total_owed = sum(lender["owed_by"].values()) |
| 150 | lender_total_owes = sum(lender["owes"].values()) |
| 151 | lender["balance"] = lender_total_owed - lender_total_owes |
| 152 | |
| 153 | borrower_total_owed = sum(borrower["owed_by"].values()) |
| 154 | borrower_total_owes = sum(borrower["owes"].values()) |
| 155 | borrower["balance"] = borrower_total_owed - borrower_total_owes |
| 156 | |
| 157 | # Return updated users sorted by name |
| 158 | users = sorted([lender, borrower], key=lambda x: x["name"]) |
| 159 | return json.dumps({"users": users}) |
| 160 | |
| 161 | return json.dumps({"error": "Invalid URL"}) |
| 162 | # Handled Edge Cases: User already exists, missing required fields, invalid amount, lender and borrower are the same, users don't exist, existing debts |
| 163 | # Handled Edge Cases: Invalid URL, missing payload |