| 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 start 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 | if payload is None: |
| 32 | # Return all users sorted by name |
| 33 | users = sorted(self.database["users"], key=lambda x: x["name"]) |
| 34 | return json.dumps({"users": users}) |
| 35 | else: |
| 36 | # Return only specified users |
| 37 | data = json.loads(payload) |
| 38 | user_names = data.get("users", []) |
| 39 | |
| 40 | # Edge Case: Empty user list in payload |
| 41 | if not user_names: |
| 42 | return json.dumps({"users": []}) |
| 43 | |
| 44 | # Filter users by name |
| 45 | filtered_users = [user for user in self.database["users"] if user["name"] in user_names] |
| 46 | |
| 47 | # Edge Case: Non-existent users in payload |
| 48 | # Only return users that exist in the database |
| 49 | |
| 50 | # Sort by name |
| 51 | filtered_users.sort(key=lambda x: x["name"]) |
| 52 | return json.dumps({"users": filtered_users}) |
| 53 | else: |
| 54 | # Edge Case: Invalid URL |
| 55 | raise ValueError(f"Invalid URL: {url}") |
| 56 | |
| 8 | 57 | def post(self, url: str, payload: str | None = None) -> str: |
| 9 | | pass |
| 58 | """ |
| 59 | Handle POST requests to the API. |
| 60 | |
| 61 | Args: |
| 62 | url: The endpoint URL. |
| 63 | payload: JSON payload. |
| 64 | |
| 65 | Returns: |
| 66 | A JSON string response. |
| 67 | |
| 68 | Raises: |
| 69 | ValueError: If the URL is not recognized or if there are validation errors. |
| 70 | """ |
| 71 | if url == "/add": |
| 72 | if payload is None: |
| 73 | # Edge Case: Missing payload |
| 74 | raise ValueError("Payload required for /add endpoint") |
| 75 | |
| 76 | data = json.loads(payload) |
| 77 | user_name = data.get("user") |
| 78 | |
| 79 | # Edge Case: Missing user name in payload |
| 80 | if not user_name: |
| 81 | raise ValueError("User name is required") |
| 82 | |
| 83 | # Edge Case: User already exists |
| 84 | for user in self.database["users"]: |
| 85 | if user["name"] == user_name: |
| 86 | return json.dumps(user) |
| 87 | |
| 88 | # Create new user |
| 89 | new_user = { |
| 90 | "name": user_name, |
| 91 | "owes": {}, |
| 92 | "owed_by": {}, |
| 93 | "balance": 0.0 |
| 94 | } |
| 95 | |
| 96 | self.database["users"].append(new_user) |
| 97 | return json.dumps(new_user) |
| 98 | |
| 99 | elif url == "/iou": |
| 100 | if payload is None: |
| 101 | # Edge Case: Missing payload |
| 102 | raise ValueError("Payload required for /iou endpoint") |
| 103 | |
| 104 | data = json.loads(payload) |
| 105 | lender_name = data.get("lender") |
| 106 | borrower_name = data.get("borrower") |
| 107 | amount = data.get("amount") |
| 108 | |
| 109 | # Edge Case: Missing required fields |
| 110 | if not lender_name or not borrower_name or amount is None: |
| 111 | raise ValueError("Lender, borrower, and amount are required") |
| 112 | |
| 113 | # Edge Case: Lender and borrower are the same person |
| 114 | if lender_name == borrower_name: |
| 115 | raise ValueError("Lender and borrower cannot be the same person") |
| 116 | |
| 117 | # Edge Case: Negative amount |
| 118 | if amount < 0: |
| 119 | raise ValueError("Amount must be non-negative") |
| 120 | |
| 121 | # Find lender and borrower |
| 122 | lender = None |
| 123 | borrower = None |
| 124 | |
| 125 | for user in self.database["users"]: |
| 126 | if user["name"] == lender_name: |
| 127 | lender = user |
| 128 | elif user["name"] == borrower_name: |
| 129 | borrower = user |
| 130 | |
| 131 | # Edge Case: Lender or borrower does not exist |
| 132 | if lender is None: |
| 133 | raise ValueError(f"User {lender_name} does not exist") |
| 134 | if borrower is None: |
| 135 | raise ValueError(f"User {borrower_name} does not exist") |
| 136 | |
| 137 | # Handle the IOU transaction with proper netting |
| 138 | # Get existing debts |
| 139 | borrower_owes_lender = borrower["owes"].get(lender_name, 0) # How much borrower owes lender |
| 140 | lender_owes_borrower = lender["owes"].get(borrower_name, 0) # How much lender owes borrower |
| 141 | |
| 142 | # Calculate net change in what borrower owes lender |
| 143 | # Positive means borrower owes more to lender |
| 144 | # Negative means lender owes more to borrower |
| 145 | net_change = amount - lender_owes_borrower + borrower_owes_lender |
| 146 | |
| 147 | # Update the relationships based on the net amount |
| 148 | if net_change > 0: |
| 149 | # Borrower owes lender money |
| 150 | borrower["owes"][lender_name] = net_change |
| 151 | lender["owed_by"][borrower_name] = net_change |
| 152 | # Remove reverse relationships |
| 153 | if lender_name in borrower["owed_by"]: |
| 154 | del borrower["owed_by"][lender_name] |
| 155 | if borrower_name in lender["owes"]: |
| 156 | del lender["owes"][borrower_name] |
| 157 | elif net_change < 0: |
| 158 | # Lender owes borrower money |
| 159 | lender["owes"][borrower_name] = -net_change |
| 160 | borrower["owed_by"][lender_name] = -net_change |
| 161 | # Remove reverse relationships |
| 162 | if lender_name in borrower["owes"]: |
| 163 | del borrower["owes"][lender_name] |
| 164 | if borrower_name in lender["owed_by"]: |
| 165 | del lender["owed_by"][borrower_name] |
| 166 | else: |
| 167 | # Debts cancel out exactly |
| 168 | if lender_name in borrower["owes"]: |
| 169 | del borrower["owes"][lender_name] |
| 170 | if lender_name in borrower["owed_by"]: |
| 171 | del borrower["owed_by"][lender_name] |
| 172 | if borrower_name in lender["owes"]: |
| 173 | del lender["owes"][borrower_name] |
| 174 | if borrower_name in lender["owed_by"]: |
| 175 | del lender["owed_by"][borrower_name] |
| 176 | |
| 177 | # Recalculate balances for both users |
| 178 | lender_total_owed = sum(lender["owed_by"].values()) |
| 179 | lender_total_owes = sum(lender["owes"].values()) |
| 180 | lender["balance"] = lender_total_owed - lender_total_owes |
| 181 | |
| 182 | borrower_total_owed = sum(borrower["owed_by"].values()) |
| 183 | borrower_total_owes = sum(borrower["owes"].values()) |
| 184 | borrower["balance"] = borrower_total_owed - borrower_total_owes |
| 185 | |
| 186 | # Return updated users sorted by name |
| 187 | updated_users = [lender, borrower] |
| 188 | updated_users.sort(key=lambda x: x["name"]) |
| 189 | return json.dumps({"users": updated_users}) |
| 190 | |
| 191 | else: |
| 192 | # Edge Case: Invalid URL |
| 193 | raise ValueError(f"Invalid URL: {url}") |
| 194 | |
| 195 | # Handled Edge Cases: Invalid URL, Missing payload, Missing user name, User already exists |
| 196 | # Handled Edge Cases: Missing required fields, Lender and borrower are the same, Negative amount, |
| 197 | # Lender or borrower does not exist, Empty user list in payload, Non-existent users in payload |