| 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. |
| 10 | """ |
| 11 | # Edge Case: Handle None database by initializing empty users list |
| 12 | self.database = database if database is not None else {"users": []} |
| 13 | |
| 5 | 14 | def get(self, url: str, payload: str | None = None) -> str: |
| 6 | | pass |
| 7 | | |
| 15 | """ |
| 16 | Handle GET requests to the API. |
| 17 | |
| 18 | Args: |
| 19 | url: The endpoint URL. |
| 20 | payload: Optional JSON payload. |
| 21 | |
| 22 | Returns: |
| 23 | JSON string response. |
| 24 | |
| 25 | Raises: |
| 26 | ValueError: If URL is not recognized. |
| 27 | """ |
| 28 | # Edge Case: Handle /users endpoint |
| 29 | if url == "/users": |
| 30 | # Edge Case: Handle payload with specific users |
| 31 | if payload is not None: |
| 32 | data = json.loads(payload) |
| 33 | if "users" in data: |
| 34 | # Filter users and sort by name |
| 35 | users = [user for user in self.database["users"] if user["name"] in data["users"]] |
| 36 | users.sort(key=lambda x: x["name"]) |
| 37 | return json.dumps({"users": users}) |
| 38 | # Edge Case: Handle request for all users |
| 39 | users = sorted(self.database["users"], key=lambda x: x["name"]) |
| 40 | return json.dumps({"users": users}) |
| 41 | # Edge Case: Handle unknown URL |
| 42 | else: |
| 43 | raise ValueError(f"Unknown URL: {url}") |
| 44 | # Handled Edge Cases: /users endpoint, payload with specific users, request for all users, unknown URL |
| 45 | |
| 8 | 46 | def post(self, url: str, payload: str | None = None) -> str: |
| 9 | | pass |
| 47 | """ |
| 48 | Handle POST requests to the API. |
| 49 | |
| 50 | Args: |
| 51 | url: The endpoint URL. |
| 52 | payload: JSON payload. |
| 53 | |
| 54 | Returns: |
| 55 | JSON string response. |
| 56 | |
| 57 | Raises: |
| 58 | ValueError: If URL is not recognized or if there are issues with the payload. |
| 59 | """ |
| 60 | # Edge Case: Handle missing payload |
| 61 | if payload is None: |
| 62 | raise ValueError("Payload is required") |
| 63 | |
| 64 | data = json.loads(payload) |
| 65 | |
| 66 | # Edge Case: Handle /add endpoint |
| 67 | if url == "/add": |
| 68 | # Edge Case: Handle missing user field |
| 69 | if "user" not in data: |
| 70 | raise ValueError("User field is required") |
| 71 | |
| 72 | user_name = data["user"] |
| 73 | |
| 74 | # Edge Case: Handle duplicate user |
| 75 | for user in self.database["users"]: |
| 76 | if user["name"] == user_name: |
| 77 | raise ValueError(f"User {user_name} already exists") |
| 78 | |
| 79 | # Create new user |
| 80 | new_user = { |
| 81 | "name": user_name, |
| 82 | "owes": {}, |
| 83 | "owed_by": {}, |
| 84 | "balance": 0.0 |
| 85 | } |
| 86 | |
| 87 | self.database["users"].append(new_user) |
| 88 | return json.dumps(new_user) |
| 89 | |
| 90 | # Edge Case: Handle /iou endpoint |
| 91 | elif url == "/iou": |
| 92 | # Edge Case: Handle missing required fields |
| 93 | required_fields = ["lender", "borrower", "amount"] |
| 94 | for field in required_fields: |
| 95 | if field not in data: |
| 96 | raise ValueError(f"Missing field: {field}") |
| 97 | |
| 98 | lender_name = data["lender"] |
| 99 | borrower_name = data["borrower"] |
| 100 | amount = data["amount"] |
| 101 | |
| 102 | # Edge Case: Handle negative amount |
| 103 | if amount < 0: |
| 104 | raise ValueError("Amount must be non-negative") |
| 105 | |
| 106 | # Edge Case: Handle same lender and borrower |
| 107 | if lender_name == borrower_name: |
| 108 | raise ValueError("Lender and borrower cannot be the same") |
| 109 | |
| 110 | # Find lender and borrower |
| 111 | lender = None |
| 112 | borrower = None |
| 113 | |
| 114 | for user in self.database["users"]: |
| 115 | if user["name"] == lender_name: |
| 116 | lender = user |
| 117 | elif user["name"] == borrower_name: |
| 118 | borrower = user |
| 119 | |
| 120 | # Edge Case: Handle lender not found |
| 121 | if lender is None: |
| 122 | raise ValueError(f"User {lender_name} not found") |
| 123 | |
| 124 | # Edge Case: Handle borrower not found |
| 125 | if borrower is None: |
| 126 | raise ValueError(f"User {borrower_name} not found") |
| 127 | |
| 128 | # Handle existing debts between lender and borrower |
| 129 | # When lender "lends" borrower amount, it reduces any debt the lender owes the borrower |
| 130 | # and increases any debt the borrower owes the lender |
| 131 | |
| 132 | # Get existing debts |
| 133 | lender_owes_borrower = lender["owes"].get(borrower_name, 0) |
| 134 | borrower_owes_lender = borrower["owes"].get(lender_name, 0) |
| 135 | |
| 136 | # Apply the new IOU: lender is lending amount to borrower |
| 137 | # This means the borrower now owes the lender additional amount |
| 138 | # Net out the existing debts: borrower_owes_lender + amount - lender_owes_borrower |
| 139 | net_debt_borrower_to_lender = borrower_owes_lender + amount - lender_owes_borrower |
| 140 | |
| 141 | # Clear existing relationships |
| 142 | if borrower_name in lender["owes"]: |
| 143 | del lender["owes"][borrower_name] |
| 144 | if lender_name in borrower["owes"]: |
| 145 | del borrower["owes"][lender_name] |
| 146 | if borrower_name in lender["owed_by"]: |
| 147 | del lender["owed_by"][borrower_name] |
| 148 | if lender_name in borrower["owed_by"]: |
| 149 | del borrower["owed_by"][lender_name] |
| 150 | |
| 151 | # Set new relationships based on net amounts |
| 152 | # Only one direction should have a debt relationship |
| 153 | if net_debt_borrower_to_lender > 0: |
| 154 | # Borrower owes lender |
| 155 | borrower["owes"][lender_name] = net_debt_borrower_to_lender |
| 156 | lender["owed_by"][borrower_name] = net_debt_borrower_to_lender |
| 157 | elif net_debt_borrower_to_lender < 0: |
| 158 | # Lender owes borrower |
| 159 | lender_owes_borrower = -net_debt_borrower_to_lender |
| 160 | lender["owes"][borrower_name] = lender_owes_borrower |
| 161 | borrower["owed_by"][lender_name] = lender_owes_borrower |
| 162 | # If net_debt_borrower_to_lender == 0, no relationship is set (debts cancel out) |
| 163 | |
| 164 | # Recalculate balances |
| 165 | lender_total_owed = sum(lender["owed_by"].values()) |
| 166 | lender_total_owes = sum(lender["owes"].values()) |
| 167 | lender["balance"] = lender_total_owed - lender_total_owes |
| 168 | |
| 169 | borrower_total_owed = sum(borrower["owed_by"].values()) |
| 170 | borrower_total_owes = sum(borrower["owes"].values()) |
| 171 | borrower["balance"] = borrower_total_owed - borrower_total_owes |
| 172 | |
| 173 | # Return updated users sorted by name |
| 174 | users = [lender, borrower] |
| 175 | users.sort(key=lambda x: x["name"]) |
| 176 | return json.dumps({"users": users}) |
| 177 | |
| 178 | # Edge Case: Handle unknown URL |
| 179 | else: |
| 180 | raise ValueError(f"Unknown URL: {url}") |
| 181 | # Handled Edge Cases: /add endpoint, /iou endpoint, missing payload, missing user field, duplicate user, missing required fields, negative amount, same lender and borrower, lender not found, borrower not found, unknown URL |