| 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 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 | A JSON string response. |
| 26 | """ |
| 27 | if url == "/users": |
| 28 | if payload is None: |
| 29 | # Return all users |
| 30 | result = {"users": []} |
| 31 | for user in self.database["users"]: |
| 32 | user_copy = user.copy() |
| 33 | user_copy["balance"] = self._calculate_balance(user) |
| 34 | result["users"].append(user_copy) |
| 35 | return json.dumps(result) |
| 36 | else: |
| 37 | # Return specific users |
| 38 | data = json.loads(payload) |
| 39 | user_names = data.get("users", []) |
| 40 | result = {"users": []} |
| 41 | |
| 42 | # Edge Case: Handle when users list is empty |
| 43 | if not user_names: |
| 44 | return json.dumps(result) |
| 45 | |
| 46 | # Get specified users |
| 47 | for user in self.database["users"]: |
| 48 | if user["name"] in user_names: |
| 49 | user_copy = user.copy() |
| 50 | user_copy["balance"] = self._calculate_balance(user) |
| 51 | result["users"].append(user_copy) |
| 52 | |
| 53 | # Sort by name |
| 54 | result["users"].sort(key=lambda x: x["name"]) |
| 55 | return json.dumps(result) |
| 56 | |
| 57 | # Edge Case: Handle unknown URL |
| 58 | return json.dumps({"error": "Not found"}) |
| 59 | |
| 8 | 60 | def post(self, url: str, payload: str | None = None) -> str: |
| 9 | | pass |
| 61 | """ |
| 62 | Handle POST requests to the API. |
| 63 | |
| 64 | Args: |
| 65 | url: The endpoint URL. |
| 66 | payload: JSON payload. |
| 67 | |
| 68 | Returns: |
| 69 | A JSON string response. |
| 70 | """ |
| 71 | if payload is None: |
| 72 | # Edge Case: Handle missing payload |
| 73 | return json.dumps({"error": "Payload required"}) |
| 74 | |
| 75 | data = json.loads(payload) |
| 76 | |
| 77 | if url == "/add": |
| 78 | user_name = data.get("user") |
| 79 | |
| 80 | # Edge Case: Handle missing user name |
| 81 | if not user_name: |
| 82 | return json.dumps({"error": "User name required"}) |
| 83 | |
| 84 | # Edge Case: Handle duplicate user |
| 85 | for user in self.database["users"]: |
| 86 | if user["name"] == user_name: |
| 87 | return json.dumps({"error": "User already exists"}) |
| 88 | |
| 89 | # Create new user |
| 90 | new_user = { |
| 91 | "name": user_name, |
| 92 | "owes": {}, |
| 93 | "owed_by": {} |
| 94 | } |
| 95 | self.database["users"].append(new_user) |
| 96 | |
| 97 | # Return user with balance |
| 98 | result_user = new_user.copy() |
| 99 | result_user["balance"] = 0.0 |
| 100 | return json.dumps(result_user) |
| 101 | |
| 102 | elif url == "/iou": |
| 103 | lender_name = data.get("lender") |
| 104 | borrower_name = data.get("borrower") |
| 105 | amount = data.get("amount") |
| 106 | |
| 107 | # Edge Case: Handle missing fields |
| 108 | if not lender_name or not borrower_name or amount is None: |
| 109 | return json.dumps({"error": "Lender, borrower, and amount required"}) |
| 110 | |
| 111 | # Edge Case: Handle invalid amount type |
| 112 | if not isinstance(amount, (int, float)): |
| 113 | return json.dumps({"error": "Amount must be a number"}) |
| 114 | |
| 115 | # Edge Case: Handle negative amount |
| 116 | if amount < 0: |
| 117 | return json.dumps({"error": "Amount must be positive"}) |
| 118 | |
| 119 | # Edge Case: Handle same lender and borrower |
| 120 | if lender_name == borrower_name: |
| 121 | return json.dumps({"error": "Cannot create IOU between same user"}) |
| 122 | |
| 123 | # Find users |
| 124 | lender = None |
| 125 | borrower = None |
| 126 | |
| 127 | for user in self.database["users"]: |
| 128 | if user["name"] == lender_name: |
| 129 | lender = user |
| 130 | elif user["name"] == borrower_name: |
| 131 | borrower = user |
| 132 | |
| 133 | # Edge Case: Handle user not found |
| 134 | if lender is None or borrower is None: |
| 135 | return json.dumps({"error": "User not found"}) |
| 136 | |
| 137 | # Handle the bidirectional nature of debts |
| 138 | # We need to properly net the amounts between lender and borrower |
| 139 | |
| 140 | # Get current amounts |
| 141 | lender_owes_borrower = lender["owes"].get(borrower_name, 0) |
| 142 | borrower_owes_lender = borrower["owes"].get(lender_name, 0) |
| 143 | |
| 144 | # Calculate net debt after IOU |
| 145 | # Positive means borrower owes lender, negative means lender owes borrower |
| 146 | net_debt = borrower_owes_lender + amount - lender_owes_borrower |
| 147 | |
| 148 | # Update lender's records |
| 149 | if borrower_name in lender["owes"]: |
| 150 | del lender["owes"][borrower_name] |
| 151 | if borrower_name in lender["owed_by"]: |
| 152 | del lender["owed_by"][borrower_name] |
| 153 | |
| 154 | # Update borrower's records |
| 155 | if lender_name in borrower["owes"]: |
| 156 | del borrower["owes"][lender_name] |
| 157 | if lender_name in borrower["owed_by"]: |
| 158 | del borrower["owed_by"][lender_name] |
| 159 | |
| 160 | # Set new amounts based on net debt |
| 161 | if net_debt > 0: |
| 162 | # Borrower owes lender |
| 163 | borrower["owes"][lender_name] = net_debt |
| 164 | lender["owed_by"][borrower_name] = net_debt |
| 165 | elif net_debt < 0: |
| 166 | # Lender owes borrower |
| 167 | lender["owes"][borrower_name] = abs(net_debt) |
| 168 | borrower["owed_by"][lender_name] = abs(net_debt) |
| 169 | |
| 170 | # Return updated users |
| 171 | result = {"users": []} |
| 172 | |
| 173 | lender_result = lender.copy() |
| 174 | lender_result["balance"] = self._calculate_balance(lender) |
| 175 | result["users"].append(lender_result) |
| 176 | |
| 177 | borrower_result = borrower.copy() |
| 178 | borrower_result["balance"] = self._calculate_balance(borrower) |
| 179 | result["users"].append(borrower_result) |
| 180 | |
| 181 | # Sort by name |
| 182 | result["users"].sort(key=lambda x: x["name"]) |
| 183 | return json.dumps(result) |
| 184 | |
| 185 | # Edge Case: Handle unknown URL |
| 186 | return json.dumps({"error": "Not found"}) |
| 187 | |
| 188 | def _calculate_balance(self, user: dict) -> float: |
| 189 | """ |
| 190 | Calculate the balance for a user. |
| 191 | |
| 192 | Args: |
| 193 | user: A user dictionary. |
| 194 | |
| 195 | Returns: |
| 196 | The calculated balance. |
| 197 | """ |
| 198 | total_owed_by = sum(user["owed_by"].values()) |
| 199 | total_owes = sum(user["owes"].values()) |
| 200 | return round(total_owed_by - total_owes, 2) |
| 201 | |
| 202 | # Handled Edge Cases: Missing payload, unknown URL, missing user name, duplicate user, missing fields, invalid amount type, negative amount, same lender and borrower, user not found, empty users list |