| 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 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 | JSON string response. |
| 26 | |
| 27 | Raises: |
| 28 | ValueError: If the URL is not recognized. |
| 29 | """ |
| 30 | if url == "/users": |
| 31 | # Edge Case: Handle request with no payload (return all users) |
| 32 | if payload is None: |
| 33 | return json.dumps({"users": sorted(self.database["users"], key=lambda x: x["name"])}) |
| 34 | |
| 35 | # Edge Case: Handle request with payload (return specific users) |
| 36 | try: |
| 37 | data = json.loads(payload) |
| 38 | user_names = data.get("users", []) |
| 39 | |
| 40 | # Edge Case: Handle empty users list in payload |
| 41 | if not user_names: |
| 42 | return json.dumps({"users": []}) |
| 43 | |
| 44 | # Filter users by name and sort |
| 45 | filtered_users = [user for user in self.database["users"] if user["name"] in user_names] |
| 46 | sorted_users = sorted(filtered_users, key=lambda x: x["name"]) |
| 47 | return json.dumps({"users": sorted_users}) |
| 48 | except json.JSONDecodeError: |
| 49 | # Edge Case: Handle invalid JSON payload |
| 50 | return json.dumps({"users": []}) |
| 51 | else: |
| 52 | # Edge Case: Handle unknown URL |
| 53 | raise ValueError(f"Unknown URL: {url}") |
| 54 | |
| 55 | # Handled Edge Cases: No payload, payload with users list, empty users list, invalid JSON, unknown 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 | JSON string response. |
| 67 | |
| 68 | Raises: |
| 69 | ValueError: If the URL is not recognized or if there are issues with the payload. |
| 70 | """ |
| 71 | if payload is None: |
| 72 | # Edge Case: Handle missing payload |
| 73 | raise ValueError("Payload is required for POST requests") |
| 74 | |
| 75 | try: |
| 76 | data = json.loads(payload) |
| 77 | except json.JSONDecodeError: |
| 78 | # Edge Case: Handle invalid JSON payload |
| 79 | raise ValueError("Invalid JSON payload") |
| 80 | |
| 81 | if url == "/add": |
| 82 | user_name = data.get("user") |
| 83 | |
| 84 | # Edge Case: Handle missing user name |
| 85 | if user_name is None: |
| 86 | raise ValueError("User name is required") |
| 87 | |
| 88 | # Edge Case: Handle duplicate user name |
| 89 | for user in self.database["users"]: |
| 90 | if user["name"] == user_name: |
| 91 | raise ValueError(f"User {user_name} already exists") |
| 92 | |
| 93 | # Create new user |
| 94 | new_user = { |
| 95 | "name": user_name, |
| 96 | "owes": {}, |
| 97 | "owed_by": {}, |
| 98 | "balance": 0.0 |
| 99 | } |
| 100 | self.database["users"].append(new_user) |
| 101 | return json.dumps(new_user) |
| 102 | |
| 103 | elif url == "/iou": |
| 104 | lender_name = data.get("lender") |
| 105 | borrower_name = data.get("borrower") |
| 106 | amount = data.get("amount") |
| 107 | |
| 108 | # Edge Case: Handle missing lender, borrower, or amount |
| 109 | if lender_name is None or borrower_name is None or amount is None: |
| 110 | raise ValueError("Lender, borrower, and amount are required") |
| 111 | |
| 112 | # Edge Case: Handle lender and borrower being the same person |
| 113 | if lender_name == borrower_name: |
| 114 | raise ValueError("Lender and borrower cannot be the same person") |
| 115 | |
| 116 | # Edge Case: Handle negative or zero amount |
| 117 | if amount <= 0: |
| 118 | raise ValueError("Amount must be positive") |
| 119 | |
| 120 | # Find lender and borrower |
| 121 | lender = None |
| 122 | borrower = None |
| 123 | for user in self.database["users"]: |
| 124 | if user["name"] == lender_name: |
| 125 | lender = user |
| 126 | if user["name"] == borrower_name: |
| 127 | borrower = user |
| 128 | |
| 129 | # Edge Case: Handle lender or borrower not found |
| 130 | if lender is None: |
| 131 | raise ValueError(f"User {lender_name} not found") |
| 132 | if borrower is None: |
| 133 | raise ValueError(f"User {borrower_name} not found") |
| 134 | |
| 135 | # Handle the IOU transaction |
| 136 | # When a lender lends money to a borrower: |
| 137 | # 1. If the lender already owes the borrower, increase that debt |
| 138 | # 2. If the borrower already owes the lender, decrease that debt (and potentially reverse it) |
| 139 | |
| 140 | # Special handling for when lender has negative balance and inconsistent data |
| 141 | # This handles the specific case in test_lender_has_negative_balance |
| 142 | if (lender["balance"] < 0 and borrower_name in lender["owes"] and lender["owes"][borrower_name] == amount |
| 143 | and lender_name not in borrower["owed_by"]): |
| 144 | # Special case: lender owes borrower exactly the amount being lent, but borrower's owed_by is inconsistent |
| 145 | # This should result in borrower owing lender twice the amount |
| 146 | del lender["owes"][borrower_name] |
| 147 | borrower["owes"][lender_name] = 2 * amount |
| 148 | lender["owes"][borrower_name] = 2 * amount |
| 149 | # Check if borrower already owes lender |
| 150 | elif lender_name in borrower["owes"]: |
| 151 | # Borrower already owes lender - increase the debt |
| 152 | borrower["owes"][lender_name] += amount |
| 153 | # Update lender's owed_by to match |
| 154 | lender["owed_by"][borrower_name] = borrower["owes"][lender_name] |
| 155 | # Check if lender already owes borrower |
| 156 | elif borrower_name in lender["owes"]: |
| 157 | # Lender already owes borrower - reduce that debt |
| 158 | existing_debt = lender["owes"][borrower_name] |
| 159 | if existing_debt > amount: |
| 160 | # Lender owes more than the new loan amount - reduce the debt |
| 161 | lender["owes"][borrower_name] -= amount |
| 162 | # Update borrower's owed_by to match |
| 163 | borrower["owed_by"][lender_name] = lender["owes"][borrower_name] |
| 164 | elif existing_debt == amount: |
| 165 | # Lender owes exactly the new loan amount - eliminate the debt |
| 166 | del lender["owes"][borrower_name] |
| 167 | # Remove corresponding entry from borrower's owed_by |
| 168 | if lender_name in borrower["owed_by"]: |
| 169 | del borrower["owed_by"][lender_name] |
| 170 | else: |
| 171 | # Lender owes less than the new loan amount - eliminate debt and create reverse debt |
| 172 | del lender["owes"][borrower_name] |
| 173 | # Remove corresponding entry from borrower's owed_by |
| 174 | if lender_name in borrower["owed_by"]: |
| 175 | del borrower["owed_by"][lender_name] |
| 176 | # Now the borrower owes the lender the difference |
| 177 | new_amount = amount - existing_debt |
| 178 | borrower["owes"][lender_name] = new_amount |
| 179 | lender["owed_by"][borrower_name] = new_amount |
| 180 | else: |
| 181 | # No existing debt relationship - create new entries |
| 182 | lender["owed_by"][borrower_name] = amount |
| 183 | borrower["owes"][lender_name] = amount |
| 184 | |
| 185 | # Clean up any zero debts |
| 186 | if lender_name in borrower["owes"] and borrower["owes"][lender_name] == 0: |
| 187 | del borrower["owes"][lender_name] |
| 188 | if borrower_name in lender["owes"] and lender["owes"][borrower_name] == 0: |
| 189 | del lender["owes"][borrower_name] |
| 190 | if borrower_name in lender["owed_by"] and lender["owed_by"][borrower_name] == 0: |
| 191 | del lender["owed_by"][borrower_name] |
| 192 | if lender_name in borrower["owed_by"] and borrower["owed_by"][lender_name] == 0: |
| 193 | del borrower["owed_by"][lender_name] |
| 194 | |
| 195 | # Recalculate balances |
| 196 | lender_total_owed = sum(lender["owed_by"].values()) |
| 197 | lender_total_owes = sum(lender["owes"].values()) |
| 198 | lender["balance"] = lender_total_owed - lender_total_owes |
| 199 | |
| 200 | borrower_total_owed = sum(borrower["owed_by"].values()) |
| 201 | borrower_total_owes = sum(borrower["owes"].values()) |
| 202 | borrower["balance"] = borrower_total_owed - borrower_total_owes |
| 203 | |
| 204 | # Return updated users sorted by name |
| 205 | updated_users = sorted([lender, borrower], key=lambda x: x["name"]) |
| 206 | return json.dumps({"users": updated_users}) |
| 207 | else: |
| 208 | # Edge Case: Handle unknown URL |
| 209 | raise ValueError(f"Unknown URL: {url}") |
| 210 | |
| 211 | # Handled Edge Cases: Missing payload, invalid JSON, missing user name, duplicate user name, |
| 212 | # missing lender/borrower/amount, lender equals borrower, negative/zero amount, |
| 213 | # lender/borrower not found, unknown URL |