| 1 | import json |
| 2 | |
| 1 | 3 | class RestAPI: |
| 2 | 4 | def __init__(self, database: dict | None = None): |
| 3 | | pass |
| 4 | | |
| 5 | # Initialize the database with provided data or empty dict |
| 6 | self.database = database if database is not None else {"users": []} |
| 7 | |
| 5 | 8 | def get(self, url: str, payload: str | None = None) -> str: |
| 6 | | pass |
| 7 | | |
| 9 | # Handle GET requests to /users endpoint |
| 10 | if url == "/users": |
| 11 | # Edge Case: Handle when no payload is provided - return all users |
| 12 | if payload is None: |
| 13 | # Create a copy of users to avoid modifying original data |
| 14 | users_copy = [] |
| 15 | for user in self.database["users"]: |
| 16 | users_copy.append(self._create_user_response(user)) |
| 17 | return json.dumps({"users": users_copy}) |
| 18 | |
| 19 | # Edge Case: Handle when payload is provided but not valid JSON |
| 20 | try: |
| 21 | data = json.loads(payload) |
| 22 | except json.JSONDecodeError: |
| 23 | return json.dumps({"error": "Invalid JSON payload"}) |
| 24 | |
| 25 | # Edge Case: Handle when 'users' key is missing from payload |
| 26 | if "users" not in data: |
| 27 | return json.dumps({"error": "Missing 'users' key in payload"}) |
| 28 | |
| 29 | # Edge Case: Handle when 'users' is not a list |
| 30 | if not isinstance(data["users"], list): |
| 31 | return json.dumps({"error": "'users' must be a list"}) |
| 32 | |
| 33 | # Filter users based on the requested names |
| 34 | requested_names = data["users"] |
| 35 | filtered_users = [] |
| 36 | |
| 37 | # Edge Case: Handle when requested user doesn't exist |
| 38 | for name in requested_names: |
| 39 | user = self._find_user(name) |
| 40 | if user is not None: |
| 41 | filtered_users.append(self._create_user_response(user)) |
| 42 | |
| 43 | # Sort users by name |
| 44 | filtered_users.sort(key=lambda u: u["name"]) |
| 45 | return json.dumps({"users": filtered_users}) |
| 46 | |
| 47 | # Edge Case: Handle unknown endpoints |
| 48 | return json.dumps({"error": "Endpoint not found"}) |
| 49 | |
| 8 | 50 | def post(self, url: str, payload: str | None = None) -> str: |
| 9 | | pass |
| 51 | # Handle POST requests to /add and /iou endpoints |
| 52 | if payload is None: |
| 53 | return json.dumps({"error": "Payload required"}) |
| 54 | |
| 55 | # Edge Case: Handle when payload is not valid JSON |
| 56 | try: |
| 57 | data = json.loads(payload) |
| 58 | except json.JSONDecodeError: |
| 59 | return json.dumps({"error": "Invalid JSON payload"}) |
| 60 | |
| 61 | if url == "/add": |
| 62 | # Edge Case: Handle when 'user' key is missing |
| 63 | if "user" not in data: |
| 64 | return json.dumps({"error": "Missing 'user' key"}) |
| 65 | |
| 66 | user_name = data["user"] |
| 67 | |
| 68 | # Edge Case: Handle when user already exists |
| 69 | if self._find_user(user_name) is not None: |
| 70 | return json.dumps({"error": "User already exists"}) |
| 71 | |
| 72 | # Create new user |
| 73 | new_user = { |
| 74 | "name": user_name, |
| 75 | "owes": {}, |
| 76 | "owed_by": {}, |
| 77 | "balance": 0.0 |
| 78 | } |
| 79 | |
| 80 | self.database["users"].append(new_user) |
| 81 | return json.dumps(self._create_user_response(new_user)) |
| 82 | |
| 83 | elif url == "/iou": |
| 84 | # Edge Case: Handle missing required keys |
| 85 | required_keys = ["lender", "borrower", "amount"] |
| 86 | for key in required_keys: |
| 87 | if key not in data: |
| 88 | return json.dumps({"error": f"Missing '{key}' key"}) |
| 89 | |
| 90 | lender_name = data["lender"] |
| 91 | borrower_name = data["borrower"] |
| 92 | amount = data["amount"] |
| 93 | |
| 94 | # Edge Case: Handle when amount is not a number |
| 95 | if not isinstance(amount, (int, float)): |
| 96 | return json.dumps({"error": "Amount must be a number"}) |
| 97 | |
| 98 | # Edge Case: Handle when amount is negative |
| 99 | if amount < 0: |
| 100 | return json.dumps({"error": "Amount must be positive"}) |
| 101 | |
| 102 | # Edge Case: Handle when lender or borrower doesn't exist |
| 103 | lender = self._find_user(lender_name) |
| 104 | borrower = self._find_user(borrower_name) |
| 105 | |
| 106 | if lender is None or borrower is None: |
| 107 | return json.dumps({"error": "Both lender and borrower must exist"}) |
| 108 | |
| 109 | # Edge Case: Handle when lender and borrower are the same person |
| 110 | if lender_name == borrower_name: |
| 111 | return json.dumps({"error": "Lender and borrower cannot be the same person"}) |
| 112 | |
| 113 | # Update IOU records |
| 114 | # Update lender's owed_by |
| 115 | if borrower_name in lender["owed_by"]: |
| 116 | lender["owed_by"][borrower_name] += amount |
| 117 | else: |
| 118 | lender["owed_by"][borrower_name] = amount |
| 119 | |
| 120 | # Update borrower's owes |
| 121 | if lender_name in borrower["owes"]: |
| 122 | borrower["owes"][lender_name] += amount |
| 123 | else: |
| 124 | borrower["owes"][lender_name] = amount |
| 125 | |
| 126 | # Update balances |
| 127 | lender["balance"] += amount |
| 128 | borrower["balance"] -= amount |
| 129 | |
| 130 | # Return updated user information |
| 131 | updated_users = [ |
| 132 | self._create_user_response(lender), |
| 133 | self._create_user_response(borrower) |
| 134 | ] |
| 135 | updated_users.sort(key=lambda u: u["name"]) |
| 136 | |
| 137 | return json.dumps({"users": updated_users}) |
| 138 | |
| 139 | # Edge Case: Handle unknown endpoints |
| 140 | return json.dumps({"error": "Endpoint not found"}) |
| 141 | |
| 142 | def _find_user(self, name: str): |
| 143 | # Helper method to find a user by name |
| 144 | for user in self.database["users"]: |
| 145 | if user["name"] == name: |
| 146 | return user |
| 147 | return None |
| 148 | |
| 149 | def _create_user_response(self, user: dict) -> dict: |
| 150 | # Helper method to create a user response object |
| 151 | # Calculate balance from owes and owed_by |
| 152 | total_owed = sum(user["owes"].values()) |
| 153 | total_owed_by = sum(user["owed_by"].values()) |
| 154 | balance = total_owed_by - total_owed |
| 155 | |
| 156 | return { |
| 157 | "name": user["name"], |
| 158 | "owes": user["owes"], |
| 159 | "owed_by": user["owed_by"], |
| 160 | "balance": balance |
| 161 | } |
| 162 | # Handled Edge Cases: Initialization with None database, GET /users with no payload, GET /users with invalid JSON, GET /users missing 'users' key, GET /users with non-list 'users', GET /users with non-existent user, GET unknown endpoint, POST with no payload, POST with invalid JSON, POST /add missing 'user' key, POST /add user already exists, POST /iou missing keys, POST /iou non-numeric amount, POST /iou negative amount, POST /iou non-existent user, POST /iou lender equals borrower, POST unknown endpoint |