| 1 | import json |
| 2 | |
| 1 | 3 | class RestAPI: |
| 2 | 4 | def __init__(self, database: dict | None = None): |
| 3 | | pass |
| 4 | | |
| 5 | # Edge Case: Handle None database by initializing empty users list |
| 6 | self.database = database if database is not None else {"users": []} |
| 7 | # Ensure all users have required fields |
| 8 | for user in self.database["users"]: |
| 9 | if "owes" not in user: |
| 10 | user["owes"] = {} |
| 11 | if "owed_by" not in user: |
| 12 | user["owed_by"] = {} |
| 13 | if "balance" not in user: |
| 14 | user["balance"] = 0.0 |
| 15 | |
| 5 | 16 | def get(self, url: str, payload: str | None = None) -> str: |
| 6 | | pass |
| 7 | | |
| 17 | # Edge Case: Handle invalid URL |
| 18 | if url != "/users": |
| 19 | return json.dumps({"error": "Invalid URL"}) |
| 20 | |
| 21 | # Edge Case: Handle malformed payload |
| 22 | if payload is not None: |
| 23 | try: |
| 24 | payload_data = json.loads(payload) |
| 25 | except json.JSONDecodeError: |
| 26 | return json.dumps({"error": "Invalid payload"}) |
| 27 | else: |
| 28 | payload_data = None |
| 29 | |
| 30 | users = self.database["users"] |
| 31 | |
| 32 | # Calculate balances for all users |
| 33 | for user in users: |
| 34 | owed_to_user = sum(user.get("owed_by", {}).values()) |
| 35 | owed_by_user = sum(user.get("owes", {}).values()) |
| 36 | user["balance"] = round(owed_to_user - owed_by_user, 2) |
| 37 | |
| 38 | # If no payload, return all users |
| 39 | if payload_data is None: |
| 40 | # Sort users by name |
| 41 | sorted_users = sorted(users, key=lambda x: x["name"]) |
| 42 | return json.dumps({"users": sorted_users}) |
| 43 | |
| 44 | # Edge Case: Handle missing 'users' key in payload |
| 45 | if "users" not in payload_data: |
| 46 | return json.dumps({"error": "Missing users key in payload"}) |
| 47 | |
| 48 | # Filter users by the provided list |
| 49 | requested_names = payload_data["users"] |
| 50 | |
| 51 | # Edge Case: Handle non-list users value |
| 52 | if not isinstance(requested_names, list): |
| 53 | return json.dumps({"error": "Users must be a list"}) |
| 54 | |
| 55 | filtered_users = [user for user in users if user["name"] in requested_names] |
| 56 | |
| 57 | # Edge Case: Handle request for non-existent users (they're simply not included) |
| 58 | # Sort by name |
| 59 | sorted_users = sorted(filtered_users, key=lambda x: x["name"]) |
| 60 | |
| 61 | return json.dumps({"users": sorted_users}) |
| 62 | |
| 8 | 63 | def post(self, url: str, payload: str | None = None) -> str: |
| 9 | | pass |
| 64 | # Edge Case: Handle invalid URL |
| 65 | if url not in ["/add", "/iou"]: |
| 66 | return json.dumps({"error": "Invalid URL"}) |
| 67 | |
| 68 | # Edge Case: Handle missing payload |
| 69 | if payload is None: |
| 70 | return json.dumps({"error": "Payload required"}) |
| 71 | |
| 72 | # Edge Case: Handle malformed payload |
| 73 | try: |
| 74 | payload_data = json.loads(payload) |
| 75 | except json.JSONDecodeError: |
| 76 | return json.dumps({"error": "Invalid payload"}) |
| 77 | |
| 78 | users = self.database["users"] |
| 79 | |
| 80 | if url == "/add": |
| 81 | # Edge Case: Handle missing 'user' key |
| 82 | if "user" not in payload_data: |
| 83 | return json.dumps({"error": "Missing user key"}) |
| 84 | |
| 85 | new_user_name = payload_data["user"] |
| 86 | |
| 87 | # Edge Case: Handle non-string user name |
| 88 | if not isinstance(new_user_name, str): |
| 89 | return json.dumps({"error": "User name must be a string"}) |
| 90 | |
| 91 | # Edge Case: Handle duplicate user |
| 92 | if any(user["name"] == new_user_name for user in users): |
| 93 | return json.dumps({"error": "User already exists"}) |
| 94 | |
| 95 | # Create new user |
| 96 | new_user = { |
| 97 | "name": new_user_name, |
| 98 | "owes": {}, |
| 99 | "owed_by": {}, |
| 100 | "balance": 0.0 |
| 101 | } |
| 102 | users.append(new_user) |
| 103 | return json.dumps(new_user) |
| 104 | |
| 105 | elif url == "/iou": |
| 106 | # Edge Case: Handle missing required keys |
| 107 | required_keys = ["lender", "borrower", "amount"] |
| 108 | for key in required_keys: |
| 109 | if key not in payload_data: |
| 110 | return json.dumps({"error": f"Missing {key} key"}) |
| 111 | |
| 112 | lender_name = payload_data["lender"] |
| 113 | borrower_name = payload_data["borrower"] |
| 114 | amount = payload_data["amount"] |
| 115 | |
| 116 | # Edge Case: Handle non-string lender/borrower |
| 117 | if not isinstance(lender_name, str) or not isinstance(borrower_name, str): |
| 118 | return json.dumps({"error": "Lender and borrower must be strings"}) |
| 119 | |
| 120 | # Edge Case: Handle non-numeric amount |
| 121 | if not isinstance(amount, (int, float)): |
| 122 | return json.dumps({"error": "Amount must be a number"}) |
| 123 | |
| 124 | # Edge Case: Handle negative amount |
| 125 | if amount < 0: |
| 126 | return json.dumps({"error": "Amount must be positive"}) |
| 127 | |
| 128 | # Find users |
| 129 | lender = next((user for user in users if user["name"] == lender_name), None) |
| 130 | borrower = next((user for user in users if user["name"] == borrower_name), None) |
| 131 | |
| 132 | # Edge Case: Handle lender equals borrower - return user unchanged |
| 133 | if lender_name == borrower_name: |
| 134 | # Recalculate balance for the user |
| 135 | owed_to_user = sum(lender.get("owed_by", {}).values()) |
| 136 | owed_by_user = sum(lender.get("owes", {}).values()) |
| 137 | lender["balance"] = round(owed_to_user - owed_by_user, 2) |
| 138 | return json.dumps({"users": [lender]}) |
| 139 | |
| 140 | # Edge Case: Handle non-existent lender or borrower |
| 141 | if lender is None or borrower is None: |
| 142 | return json.dumps({"error": "Both lender and borrower must exist"}) |
| 143 | |
| 144 | # Update IOUs |
| 145 | # Update lender's owed_by |
| 146 | if borrower_name in lender["owed_by"]: |
| 147 | lender["owed_by"][borrower_name] += amount |
| 148 | else: |
| 149 | lender["owed_by"][borrower_name] = amount |
| 150 | |
| 151 | # Update borrower's owes |
| 152 | if lender_name in borrower["owes"]: |
| 153 | borrower["owes"][lender_name] += amount |
| 154 | else: |
| 155 | borrower["owes"][lender_name] = amount |
| 156 | |
| 157 | # Recalculate balances |
| 158 | for user in [lender, borrower]: |
| 159 | owed_to_user = sum(user.get("owed_by", {}).values()) |
| 160 | owed_by_user = sum(user.get("owes", {}).values()) |
| 161 | user["balance"] = round(owed_to_user - owed_by_user, 2) |
| 162 | |
| 163 | # Return updated users, sorted by name |
| 164 | result_users = sorted([lender, borrower], key=lambda x: x["name"]) |
| 165 | return json.dumps({"users": result_users}) |
| 166 | # Handled Edge Cases: None database, invalid URLs, malformed payloads, missing keys, non-list users value, non-existent users, duplicate user, non-string user name, non-string lender/borrower, non-numeric amount, negative amount, lender equals borrower, non-existent lender or borrower |