| 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 initialize 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 |
| 33 | result = {"users": []} |
| 34 | for user in self.database["users"]: |
| 35 | user_copy = user.copy() |
| 36 | user_copy["balance"] = round(user_copy["balance"], 2) |
| 37 | result["users"].append(user_copy) |
| 38 | # Sort by name |
| 39 | result["users"].sort(key=lambda x: x["name"]) |
| 40 | return json.dumps(result) |
| 41 | else: |
| 42 | # Return specific users |
| 43 | data = json.loads(payload) |
| 44 | user_names = data.get("users", []) |
| 45 | |
| 46 | # Edge Case: Empty user list in payload - return all users |
| 47 | if not user_names: |
| 48 | result = {"users": []} |
| 49 | for user in self.database["users"]: |
| 50 | user_copy = user.copy() |
| 51 | user_copy["balance"] = round(user_copy["balance"], 2) |
| 52 | result["users"].append(user_copy) |
| 53 | # Sort by name |
| 54 | result["users"].sort(key=lambda x: x["name"]) |
| 55 | return json.dumps(result) |
| 56 | |
| 57 | result_users = [] |
| 58 | for user in self.database["users"]: |
| 59 | if user["name"] in user_names: |
| 60 | user_copy = user.copy() |
| 61 | user_copy["balance"] = round(user_copy["balance"], 2) |
| 62 | result_users.append(user_copy) |
| 63 | |
| 64 | # Sort by name |
| 65 | result_users.sort(key=lambda x: x["name"]) |
| 66 | return json.dumps({"users": result_users}) |
| 67 | else: |
| 68 | # Edge Case: Invalid URL |
| 69 | raise ValueError(f"Invalid URL: {url}") |
| 70 | |
| 71 | # Handled Edge Cases: Empty user list in payload, Invalid URL |
| 72 | |
| 8 | 73 | def post(self, url: str, payload: str | None = None) -> str: |
| 9 | | pass |
| 74 | """ |
| 75 | Handle POST requests to the API. |
| 76 | |
| 77 | Args: |
| 78 | url: The endpoint URL. |
| 79 | payload: JSON payload. |
| 80 | |
| 81 | Returns: |
| 82 | A JSON string response. |
| 83 | |
| 84 | Raises: |
| 85 | ValueError: If the URL is not recognized or if there are issues with the payload. |
| 86 | """ |
| 87 | if url == "/add": |
| 88 | if payload is None: |
| 89 | # Edge Case: Missing payload |
| 90 | raise ValueError("Payload required for /add") |
| 91 | |
| 92 | data = json.loads(payload) |
| 93 | user_name = data.get("user") |
| 94 | |
| 95 | # Edge Case: Missing user name in payload |
| 96 | if not user_name: |
| 97 | raise ValueError("User name required") |
| 98 | |
| 99 | # Check if user already exists |
| 100 | for user in self.database["users"]: |
| 101 | if user["name"] == user_name: |
| 102 | # Edge Case: User already exists - return existing user |
| 103 | result_user = user.copy() |
| 104 | result_user["balance"] = round(result_user["balance"], 2) |
| 105 | return json.dumps(result_user) |
| 106 | |
| 107 | # Create new user |
| 108 | new_user = { |
| 109 | "name": user_name, |
| 110 | "owes": {}, |
| 111 | "owed_by": {}, |
| 112 | "balance": 0.0 |
| 113 | } |
| 114 | self.database["users"].append(new_user) |
| 115 | |
| 116 | # Return the new user with rounded balance |
| 117 | result_user = new_user.copy() |
| 118 | result_user["balance"] = round(result_user["balance"], 2) |
| 119 | return json.dumps(result_user) |
| 120 | |
| 121 | elif url == "/iou": |
| 122 | if payload is None: |
| 123 | # Edge Case: Missing payload |
| 124 | raise ValueError("Payload required for /iou") |
| 125 | |
| 126 | data = json.loads(payload) |
| 127 | lender_name = data.get("lender") |
| 128 | borrower_name = data.get("borrower") |
| 129 | amount = data.get("amount") |
| 130 | |
| 131 | # Edge Case: Missing required fields |
| 132 | if not lender_name or not borrower_name or amount is None: |
| 133 | raise ValueError("Lender, borrower, and amount are required") |
| 134 | |
| 135 | # Edge Case: Lender and borrower are the same |
| 136 | if lender_name == borrower_name: |
| 137 | raise ValueError("Lender and borrower cannot be the same") |
| 138 | |
| 139 | # Edge Case: Negative amount |
| 140 | if amount < 0: |
| 141 | raise ValueError("Amount must be non-negative") |
| 142 | |
| 143 | # Find lender and borrower |
| 144 | lender = None |
| 145 | borrower = None |
| 146 | for user in self.database["users"]: |
| 147 | if user["name"] == lender_name: |
| 148 | lender = user |
| 149 | elif user["name"] == borrower_name: |
| 150 | borrower = user |
| 151 | |
| 152 | # Edge Case: Lender or borrower not found |
| 153 | if lender is None: |
| 154 | raise ValueError(f"User {lender_name} not found") |
| 155 | if borrower is None: |
| 156 | raise ValueError(f"User {borrower_name} not found") |
| 157 | |
| 158 | # Update debts - handle debt reversal properly |
| 159 | # First check if there's an existing debt in the opposite direction |
| 160 | if borrower_name in lender["owes"]: |
| 161 | # Borrower already owes lender money (reverse direction) |
| 162 | new_debt = lender["owes"][borrower_name] - amount |
| 163 | if new_debt > 0: |
| 164 | # Borrower still owes money but less |
| 165 | lender["owes"][borrower_name] = new_debt |
| 166 | borrower["owed_by"][lender_name] = new_debt |
| 167 | # Update balances |
| 168 | lender["balance"] += amount |
| 169 | borrower["balance"] -= amount |
| 170 | elif new_debt < 0: |
| 171 | # Debt direction reversed - borrower now owes lender |
| 172 | del lender["owes"][borrower_name] |
| 173 | lender["owed_by"][borrower_name] = -new_debt |
| 174 | del borrower["owed_by"][lender_name] |
| 175 | borrower["owes"][lender_name] = -new_debt |
| 176 | # Update balances |
| 177 | lender["balance"] += amount |
| 178 | borrower["balance"] -= amount |
| 179 | else: |
| 180 | # Exact repayment - remove both entries |
| 181 | del lender["owes"][borrower_name] |
| 182 | del borrower["owed_by"][lender_name] |
| 183 | # Update balances |
| 184 | lender["balance"] += amount |
| 185 | borrower["balance"] -= amount |
| 186 | elif borrower_name in lender["owed_by"]: |
| 187 | # Lender is already owed money by borrower (same direction) - accumulate |
| 188 | lender["owed_by"][borrower_name] += amount |
| 189 | borrower["owes"][lender_name] += amount |
| 190 | # Update balances |
| 191 | lender["balance"] += amount |
| 192 | borrower["balance"] -= amount |
| 193 | else: |
| 194 | # No existing debt - create new debt |
| 195 | lender["owed_by"][borrower_name] = amount |
| 196 | borrower["owes"][lender_name] = amount |
| 197 | # Update balances |
| 198 | lender["balance"] += amount |
| 199 | borrower["balance"] -= amount |
| 200 | |
| 201 | # Handle zero balances by removing entries |
| 202 | if borrower_name in lender["owed_by"] and lender["owed_by"][borrower_name] == 0: |
| 203 | del lender["owed_by"][borrower_name] |
| 204 | |
| 205 | if lender_name in borrower["owes"] and borrower["owes"][lender_name] == 0: |
| 206 | del borrower["owes"][lender_name] |
| 207 | |
| 208 | if borrower_name in lender["owes"] and lender["owes"][borrower_name] == 0: |
| 209 | del lender["owes"][borrower_name] |
| 210 | |
| 211 | if lender_name in borrower["owed_by"] and borrower["owed_by"][lender_name] == 0: |
| 212 | del borrower["owed_by"][lender_name] |
| 213 | |
| 214 | # Prepare response |
| 215 | result_users = [] |
| 216 | for user in [lender, borrower]: |
| 217 | user_copy = user.copy() |
| 218 | user_copy["balance"] = round(user_copy["balance"], 2) |
| 219 | result_users.append(user_copy) |
| 220 | |
| 221 | # Sort by name |
| 222 | result_users.sort(key=lambda x: x["name"]) |
| 223 | return json.dumps({"users": result_users}) |
| 224 | |
| 225 | else: |
| 226 | # Edge Case: Invalid URL |
| 227 | raise ValueError(f"Invalid URL: {url}") |
| 228 | |
| 229 | # Handled Edge Cases: Missing payload, Missing user name in payload, User already exists, |
| 230 | # Missing required fields, Lender and borrower are the same, Negative amount, |
| 231 | # Lender or borrower not found, Invalid URL |