| 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 structure |
| 6 | if database is None: |
| 7 | self.database = {"users": []} |
| 8 | else: |
| 9 | self.database = database |
| 10 | |
| 5 | 11 | def get(self, url: str, payload: str | None = None) -> str: |
| 6 | | pass |
| 7 | | |
| 12 | # Edge Case: Handle invalid URL |
| 13 | if url != "/users": |
| 14 | return json.dumps({"error": "Invalid URL"}) |
| 15 | |
| 16 | # Edge Case: Handle invalid payload format |
| 17 | if payload is not None: |
| 18 | try: |
| 19 | payload_data = json.loads(payload) |
| 20 | except json.JSONDecodeError: |
| 21 | return json.dumps({"error": "Invalid payload format"}) |
| 22 | |
| 23 | # Edge Case: Handle missing 'users' key in payload |
| 24 | if "users" not in payload_data: |
| 25 | return json.dumps({"error": "Missing 'users' key in payload"}) |
| 26 | |
| 27 | # Edge Case: Handle non-list 'users' value |
| 28 | if not isinstance(payload_data["users"], list): |
| 29 | return json.dumps({"error": "'users' must be a list"}) |
| 30 | |
| 31 | # Filter users based on payload |
| 32 | requested_users = payload_data["users"] |
| 33 | users = [user for user in self.database["users"] if user["name"] in requested_users] |
| 34 | # Sort by name |
| 35 | users.sort(key=lambda x: x["name"]) |
| 36 | else: |
| 37 | # Return all users if no payload |
| 38 | users = self.database["users"].copy() |
| 39 | # Sort by name |
| 40 | users.sort(key=lambda x: x["name"]) |
| 41 | |
| 42 | return json.dumps({"users": users}) |
| 43 | |
| 8 | 44 | def post(self, url: str, payload: str | None = None) -> str: |
| 9 | | pass |
| 45 | # Edge Case: Handle invalid payload format |
| 46 | if payload is None: |
| 47 | return json.dumps({"error": "Payload required"}) |
| 48 | |
| 49 | try: |
| 50 | payload_data = json.loads(payload) |
| 51 | except json.JSONDecodeError: |
| 52 | return json.dumps({"error": "Invalid payload format"}) |
| 53 | |
| 54 | if url == "/add": |
| 55 | # Edge Case: Handle missing 'user' key |
| 56 | if "user" not in payload_data: |
| 57 | return json.dumps({"error": "Missing 'user' key"}) |
| 58 | |
| 59 | new_user_name = payload_data["user"] |
| 60 | |
| 61 | # Edge Case: Handle non-string user name |
| 62 | if not isinstance(new_user_name, str): |
| 63 | return json.dumps({"error": "User name must be a string"}) |
| 64 | |
| 65 | # Edge Case: Handle duplicate user |
| 66 | for user in self.database["users"]: |
| 67 | if user["name"] == new_user_name: |
| 68 | return json.dumps({"error": "User already exists"}) |
| 69 | |
| 70 | # Create new user |
| 71 | new_user = { |
| 72 | "name": new_user_name, |
| 73 | "owes": {}, |
| 74 | "owed_by": {}, |
| 75 | "balance": 0.0 |
| 76 | } |
| 77 | |
| 78 | self.database["users"].append(new_user) |
| 79 | return json.dumps(new_user) |
| 80 | |
| 81 | elif url == "/iou": |
| 82 | # Edge Case: Handle missing required keys |
| 83 | required_keys = ["lender", "borrower", "amount"] |
| 84 | for key in required_keys: |
| 85 | if key not in payload_data: |
| 86 | return json.dumps({"error": f"Missing '{key}' key"}) |
| 87 | |
| 88 | lender_name = payload_data["lender"] |
| 89 | borrower_name = payload_data["borrower"] |
| 90 | amount = payload_data["amount"] |
| 91 | |
| 92 | # Edge Case: Handle non-string lender/borrower names |
| 93 | if not isinstance(lender_name, str) or not isinstance(borrower_name, str): |
| 94 | return json.dumps({"error": "Lender and borrower must be strings"}) |
| 95 | |
| 96 | # Edge Case: Handle non-numeric amount |
| 97 | if not isinstance(amount, (int, float)): |
| 98 | return json.dumps({"error": "Amount must be a number"}) |
| 99 | |
| 100 | # Edge Case: Handle negative amount |
| 101 | if amount < 0: |
| 102 | return json.dumps({"error": "Amount must be positive"}) |
| 103 | |
| 104 | # Edge Case: Handle same lender and borrower |
| 105 | if lender_name == borrower_name: |
| 106 | return json.dumps({"error": "Lender and borrower cannot be the same"}) |
| 107 | |
| 108 | # Find lender and borrower |
| 109 | lender = None |
| 110 | borrower = None |
| 111 | |
| 112 | for user in self.database["users"]: |
| 113 | if user["name"] == lender_name: |
| 114 | lender = user |
| 115 | elif user["name"] == borrower_name: |
| 116 | borrower = user |
| 117 | |
| 118 | # Create users if they don't exist |
| 119 | if lender is None: |
| 120 | lender = { |
| 121 | "name": lender_name, |
| 122 | "owes": {}, |
| 123 | "owed_by": {}, |
| 124 | "balance": 0.0 |
| 125 | } |
| 126 | self.database["users"].append(lender) |
| 127 | |
| 128 | if borrower is None: |
| 129 | borrower = { |
| 130 | "name": borrower_name, |
| 131 | "owes": {}, |
| 132 | "owed_by": {}, |
| 133 | "balance": 0.0 |
| 134 | } |
| 135 | self.database["users"].append(borrower) |
| 136 | |
| 137 | # Update owes and owed_by |
| 138 | # Update lender's owed_by |
| 139 | if borrower_name in lender["owed_by"]: |
| 140 | lender["owed_by"][borrower_name] += amount |
| 141 | else: |
| 142 | lender["owed_by"][borrower_name] = amount |
| 143 | |
| 144 | # Update borrower's owes |
| 145 | if lender_name in borrower["owes"]: |
| 146 | borrower["owes"][lender_name] += amount |
| 147 | else: |
| 148 | borrower["owes"][lender_name] = amount |
| 149 | |
| 150 | # Remove zero balances |
| 151 | # Clean up lender's owed_by |
| 152 | keys_to_remove = [k for k, v in lender["owed_by"].items() if v == 0] |
| 153 | for k in keys_to_remove: |
| 154 | del lender["owed_by"][k] |
| 155 | |
| 156 | # Clean up lender's owes |
| 157 | keys_to_remove = [k for k, v in lender["owes"].items() if v == 0] |
| 158 | for k in keys_to_remove: |
| 159 | del lender["owes"][k] |
| 160 | |
| 161 | # Clean up borrower's owed_by |
| 162 | keys_to_remove = [k for k, v in borrower["owed_by"].items() if v == 0] |
| 163 | for k in keys_to_remove: |
| 164 | del borrower["owed_by"][k] |
| 165 | |
| 166 | # Clean up borrower's owes |
| 167 | keys_to_remove = [k for k, v in borrower["owes"].items() if v == 0] |
| 168 | for k in keys_to_remove: |
| 169 | del borrower["owes"][k] |
| 170 | |
| 171 | # Recalculate balances |
| 172 | lender_total_owed = sum(lender["owed_by"].values()) |
| 173 | lender_total_owes = sum(lender["owes"].values()) |
| 174 | lender["balance"] = lender_total_owed - lender_total_owes |
| 175 | |
| 176 | borrower_total_owed = sum(borrower["owed_by"].values()) |
| 177 | borrower_total_owes = sum(borrower["owes"].values()) |
| 178 | borrower["balance"] = borrower_total_owed - borrower_total_owes |
| 179 | |
| 180 | # Return updated users sorted by name |
| 181 | updated_users = [lender, borrower] |
| 182 | updated_users.sort(key=lambda x: x["name"]) |
| 183 | |
| 184 | return json.dumps({"users": updated_users}) |
| 185 | |
| 186 | else: |
| 187 | # Edge Case: Handle invalid URL |
| 188 | return json.dumps({"error": "Invalid URL"}) |
| 189 | |
| 190 | # Helper method to recalculate all balances (not required by spec but useful) |
| 191 | def _recalculate_balances(self): |
| 192 | for user in self.database["users"]: |
| 193 | total_owed = sum(user["owed_by"].values()) |
| 194 | total_owes = sum(user["owes"].values()) |
| 195 | user["balance"] = total_owed - total_owes |
| 196 | |
| 197 | # Handled Edge Cases: None database, invalid URL, invalid payload format, missing 'users' key, non-list 'users' value, missing 'user' key, non-string user name, duplicate user, missing required keys in /iou, non-string lender/borrower names, non-numeric amount, negative amount, same lender and borrower, lender not found, borrower not found, invalid URL for POST |