| 1 | import json |
| 2 | |
| 1 | 3 | class RestAPI: |
| 2 | 4 | def __init__(self, database: dict | None = None): |
| 3 | | pass |
| 4 | | |
| 5 | # Edge Case: Handle None database by initializing empty structure |
| 6 | if database is None: |
| 7 | self.database = {"users": []} |
| 8 | else: |
| 9 | self.database = database |
| 10 | |
| 5 | 11 | def get(self, url: str, payload: str | None = None) -> str: |
| 6 | | pass |
| 7 | | |
| 12 | # Edge Case: Handle invalid URL |
| 13 | if url != "/users": |
| 14 | return json.dumps({"error": "Invalid URL"}) |
| 15 | |
| 16 | # Edge Case: Handle invalid payload format |
| 17 | if payload is not None: |
| 18 | try: |
| 19 | payload_data = json.loads(payload) |
| 20 | except json.JSONDecodeError: |
| 21 | return json.dumps({"error": "Invalid payload format"}) |
| 22 | |
| 23 | # Edge Case: Handle missing 'users' key in payload |
| 24 | if "users" not in payload_data: |
| 25 | return json.dumps({"error": "Missing 'users' key in payload"}) |
| 26 | |
| 27 | # Edge Case: Handle non-list 'users' value |
| 28 | if not isinstance(payload_data["users"], list): |
| 29 | return json.dumps({"error": "'users' must be a list"}) |
| 30 | |
| 31 | # Edge Case: Filter users that exist in database |
| 32 | requested_users = payload_data["users"] |
| 33 | users = [user for user in self.database["users"] if user["name"] in requested_users] |
| 34 | else: |
| 35 | # Edge Case: Return all users when no payload provided |
| 36 | users = self.database["users"] |
| 37 | |
| 38 | # Sort users by name |
| 39 | users.sort(key=lambda x: x["name"]) |
| 40 | return json.dumps({"users": users}) |
| 41 | |
| 8 | 42 | def post(self, url: str, payload: str | None = None) -> str: |
| 9 | | pass |
| 43 | # Edge Case: Handle invalid payload format |
| 44 | if payload is None: |
| 45 | return json.dumps({"error": "Payload required"}) |
| 46 | |
| 47 | try: |
| 48 | payload_data = json.loads(payload) |
| 49 | except json.JSONDecodeError: |
| 50 | return json.dumps({"error": "Invalid payload format"}) |
| 51 | |
| 52 | if url == "/add": |
| 53 | # Edge Case: Handle missing 'user' key |
| 54 | if "user" not in payload_data: |
| 55 | return json.dumps({"error": "Missing 'user' key"}) |
| 56 | |
| 57 | # Edge Case: Handle non-string user name |
| 58 | if not isinstance(payload_data["user"], str): |
| 59 | return json.dumps({"error": "User name must be a string"}) |
| 60 | |
| 61 | # Edge Case: Handle duplicate user |
| 62 | for user in self.database["users"]: |
| 63 | if user["name"] == payload_data["user"]: |
| 64 | return json.dumps({"error": "User already exists"}) |
| 65 | |
| 66 | # Create new user |
| 67 | new_user = { |
| 68 | "name": payload_data["user"], |
| 69 | "owes": {}, |
| 70 | "owed_by": {}, |
| 71 | "balance": 0.0 |
| 72 | } |
| 73 | self.database["users"].append(new_user) |
| 74 | return json.dumps(new_user) |
| 75 | |
| 76 | elif url == "/iou": |
| 77 | # Edge Case: Handle missing required keys |
| 78 | required_keys = ["lender", "borrower", "amount"] |
| 79 | for key in required_keys: |
| 80 | if key not in payload_data: |
| 81 | return json.dumps({"error": f"Missing '{key}' key"}) |
| 82 | |
| 83 | # Edge Case: Handle incorrect data types |
| 84 | if not isinstance(payload_data["lender"], str) or not isinstance(payload_data["borrower"], str): |
| 85 | return json.dumps({"error": "Lender and borrower must be strings"}) |
| 86 | |
| 87 | # Edge Case: Handle negative amount |
| 88 | if not isinstance(payload_data["amount"], (int, float)) or payload_data["amount"] < 0: |
| 89 | return json.dumps({"error": "Amount must be a non-negative number"}) |
| 90 | |
| 91 | lender_name = payload_data["lender"] |
| 92 | borrower_name = payload_data["borrower"] |
| 93 | amount = float(payload_data["amount"]) |
| 94 | |
| 95 | # Find lender and borrower in database |
| 96 | lender = None |
| 97 | borrower = None |
| 98 | for user in self.database["users"]: |
| 99 | if user["name"] == lender_name: |
| 100 | lender = user |
| 101 | elif user["name"] == borrower_name: |
| 102 | borrower = user |
| 103 | |
| 104 | # Edge Case: Handle lender and borrower being the same person |
| 105 | if lender_name == borrower_name: |
| 106 | # Return the user unchanged (no-op) |
| 107 | return json.dumps({"users": [lender]}) |
| 108 | |
| 109 | # Edge Case: Handle lender or borrower not existing |
| 110 | if lender is None or borrower is None: |
| 111 | return json.dumps({"error": "Lender or borrower does not exist"}) |
| 112 | |
| 113 | # Handle netting of reciprocal debts |
| 114 | # Check if there are existing debts in both directions |
| 115 | lender_owes_borrower = lender["owes"].get(borrower_name, 0.0) |
| 116 | borrower_owes_lender = borrower["owes"].get(lender_name, 0.0) |
| 117 | |
| 118 | # Calculate net debt: positive means lender is owed, negative means borrower is owed |
| 119 | # If lender already owes borrower, that reduces what lender is owed |
| 120 | # If borrower already owes lender, that increases what lender is owed |
| 121 | net_debt = amount - lender_owes_borrower + borrower_owes_lender |
| 122 | |
| 123 | # Clear existing debts |
| 124 | if borrower_name in lender["owes"]: |
| 125 | del lender["owes"][borrower_name] |
| 126 | if lender_name in borrower["owes"]: |
| 127 | del borrower["owes"][lender_name] |
| 128 | if borrower_name in lender["owed_by"]: |
| 129 | del lender["owed_by"][borrower_name] |
| 130 | if lender_name in borrower["owed_by"]: |
| 131 | del borrower["owed_by"][lender_name] |
| 132 | |
| 133 | # Set up new net debt |
| 134 | if net_debt > 0: |
| 135 | # Lender is owed money |
| 136 | lender["owed_by"][borrower_name] = net_debt |
| 137 | borrower["owes"][lender_name] = net_debt |
| 138 | elif net_debt < 0: |
| 139 | # Borrower is owed money (negative debt means lender owes) |
| 140 | lender["owes"][borrower_name] = -net_debt |
| 141 | borrower["owed_by"][lender_name] = -net_debt |
| 142 | # If net_debt == 0, no debts are created (both are cleared) |
| 143 | |
| 144 | # Recalculate balances |
| 145 | lender_total_owed = sum(lender["owed_by"].values()) |
| 146 | lender_total_owes = sum(lender["owes"].values()) |
| 147 | lender["balance"] = lender_total_owed - lender_total_owes |
| 148 | |
| 149 | borrower_total_owed = sum(borrower["owed_by"].values()) |
| 150 | borrower_total_owes = sum(borrower["owes"].values()) |
| 151 | borrower["balance"] = borrower_total_owed - borrower_total_owes |
| 152 | |
| 153 | # Return updated users sorted by name |
| 154 | updated_users = [lender, borrower] |
| 155 | updated_users.sort(key=lambda x: x["name"]) |
| 156 | return json.dumps({"users": updated_users}) |
| 157 | |
| 158 | # Recalculate balances |
| 159 | lender_total_owed = sum(lender["owed_by"].values()) |
| 160 | lender_total_owes = sum(lender["owes"].values()) |
| 161 | lender["balance"] = lender_total_owed - lender_total_owes |
| 162 | |
| 163 | borrower_total_owed = sum(borrower["owed_by"].values()) |
| 164 | borrower_total_owes = sum(borrower["owes"].values()) |
| 165 | borrower["balance"] = borrower_total_owed - borrower_total_owes |
| 166 | |
| 167 | # Return updated users sorted by name |
| 168 | updated_users = [lender, borrower] |
| 169 | updated_users.sort(key=lambda x: x["name"]) |
| 170 | return json.dumps({"users": updated_users}) |
| 171 | |
| 172 | else: |
| 173 | # Edge Case: Handle invalid URL |
| 174 | return json.dumps({"error": "Invalid URL"}) |
| 175 | |
| 176 | # Handled Edge Cases: None database, invalid URL, invalid payload format, missing 'users' key, non-list 'users' value, |
| 177 | # non-existent users in payload, missing 'user' key, non-string user name, duplicate user, |
| 178 | # missing required keys in /iou, incorrect data types, negative amount, same lender and borrower, |
| 179 | # non-existent lender or borrower |