| 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 an optional database. |
| 7 | |
| 8 | Args: |
| 9 | database: A dictionary containing initial user data. |
| 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 | A JSON string response. |
| 26 | """ |
| 27 | if url == "/users": |
| 28 | if payload is None: |
| 29 | # Return all users sorted by name |
| 30 | users = sorted(self.database["users"], key=lambda x: x["name"]) |
| 31 | return json.dumps({"users": users}) |
| 32 | else: |
| 33 | # Edge Case: Handle invalid JSON payload |
| 34 | try: |
| 35 | data = json.loads(payload) |
| 36 | except json.JSONDecodeError: |
| 37 | return json.dumps({"error": "Invalid JSON payload"}) |
| 38 | |
| 39 | # Edge Case: Handle missing 'users' key in payload |
| 40 | if "users" not in data: |
| 41 | return json.dumps({"error": "Missing 'users' key in payload"}) |
| 42 | |
| 43 | # Filter users based on the provided list |
| 44 | requested_users = data["users"] |
| 45 | filtered_users = [user for user in self.database["users"] if user["name"] in requested_users] |
| 46 | # Sort by name |
| 47 | filtered_users.sort(key=lambda x: x["name"]) |
| 48 | return json.dumps({"users": filtered_users}) |
| 49 | |
| 50 | # Edge Case: Handle unknown URL |
| 51 | return json.dumps({"error": "Unknown endpoint"}) |
| 52 | |
| 8 | 53 | def post(self, url: str, payload: str | None = None) -> str: |
| 9 | | pass |
| 54 | """ |
| 55 | Handle POST requests to the API. |
| 56 | |
| 57 | Args: |
| 58 | url: The endpoint URL. |
| 59 | payload: JSON payload. |
| 60 | |
| 61 | Returns: |
| 62 | A JSON string response. |
| 63 | """ |
| 64 | # Edge Case: Handle missing payload |
| 65 | if payload is None: |
| 66 | return json.dumps({"error": "Payload required"}) |
| 67 | |
| 68 | # Edge Case: Handle invalid JSON payload |
| 69 | try: |
| 70 | data = json.loads(payload) |
| 71 | except json.JSONDecodeError: |
| 72 | return json.dumps({"error": "Invalid JSON payload"}) |
| 73 | |
| 74 | if url == "/add": |
| 75 | # Edge Case: Handle missing 'user' key |
| 76 | if "user" not in data: |
| 77 | return json.dumps({"error": "Missing 'user' key"}) |
| 78 | |
| 79 | user_name = data["user"] |
| 80 | |
| 81 | # Edge Case: Handle duplicate user |
| 82 | for user in self.database["users"]: |
| 83 | if user["name"] == user_name: |
| 84 | return json.dumps({"error": "User already exists"}) |
| 85 | |
| 86 | # Create new user |
| 87 | new_user = { |
| 88 | "name": user_name, |
| 89 | "owes": {}, |
| 90 | "owed_by": {}, |
| 91 | "balance": 0.0 |
| 92 | } |
| 93 | self.database["users"].append(new_user) |
| 94 | return json.dumps(new_user) |
| 95 | |
| 96 | elif url == "/iou": |
| 97 | # Edge Case: Handle missing required keys |
| 98 | required_keys = ["lender", "borrower", "amount"] |
| 99 | for key in required_keys: |
| 100 | if key not in data: |
| 101 | return json.dumps({"error": f"Missing '{key}' key"}) |
| 102 | |
| 103 | lender_name = data["lender"] |
| 104 | borrower_name = data["borrower"] |
| 105 | amount = data["amount"] |
| 106 | |
| 107 | # Edge Case: Handle non-numeric amount |
| 108 | if not isinstance(amount, (int, float)): |
| 109 | return json.dumps({"error": "Amount must be a number"}) |
| 110 | |
| 111 | # Edge Case: Handle negative amount |
| 112 | if amount < 0: |
| 113 | return json.dumps({"error": "Amount must be positive"}) |
| 114 | |
| 115 | # Edge Case: Handle lender and borrower being the same person |
| 116 | if lender_name == borrower_name: |
| 117 | return json.dumps({"error": "Lender and borrower cannot be the same"}) |
| 118 | |
| 119 | # Find lender and borrower |
| 120 | lender = None |
| 121 | borrower = None |
| 122 | for user in self.database["users"]: |
| 123 | if user["name"] == lender_name: |
| 124 | lender = user |
| 125 | if user["name"] == borrower_name: |
| 126 | borrower = user |
| 127 | |
| 128 | # Edge Case: Handle unknown lender or borrower |
| 129 | if lender is None or borrower is None: |
| 130 | return json.dumps({"error": "Unknown user"}) |
| 131 | |
| 132 | # Update lender's owed_by and borrower's owes |
| 133 | # If borrower already owes lender, increase the amount |
| 134 | if borrower_name in lender["owed_by"]: |
| 135 | lender["owed_by"][borrower_name] += amount |
| 136 | else: |
| 137 | lender["owed_by"][borrower_name] = amount |
| 138 | |
| 139 | if lender_name in borrower["owes"]: |
| 140 | borrower["owes"][lender_name] += amount |
| 141 | else: |
| 142 | borrower["owes"][lender_name] = amount |
| 143 | |
| 144 | # Handle case where borrower previously owed money to lender |
| 145 | # This would reduce the amount in borrower's owed_by and lender's owes |
| 146 | if borrower_name in lender["owes"]: |
| 147 | if lender["owes"][borrower_name] > amount: |
| 148 | # Reduce the owes amount |
| 149 | lender["owes"][borrower_name] -= amount |
| 150 | borrower["owed_by"][lender_name] -= amount |
| 151 | # Remove entries if they become zero |
| 152 | if lender["owes"][borrower_name] == 0: |
| 153 | del lender["owes"][borrower_name] |
| 154 | if borrower["owed_by"][lender_name] == 0: |
| 155 | del borrower["owed_by"][lender_name] |
| 156 | # Remove from owed_by since debt is reduced |
| 157 | del lender["owed_by"][borrower_name] |
| 158 | del borrower["owes"][lender_name] |
| 159 | elif lender["owes"][borrower_name] == amount: |
| 160 | # Exact match, remove both entries |
| 161 | del lender["owes"][borrower_name] |
| 162 | del borrower["owed_by"][lender_name] |
| 163 | # Also remove from owed_by since debt is cleared |
| 164 | del lender["owed_by"][borrower_name] |
| 165 | del borrower["owes"][lender_name] |
| 166 | else: |
| 167 | # Amount is greater than what borrower owed to lender |
| 168 | # Remove the owes entry and add to owed_by |
| 169 | original_owes = lender["owes"][borrower_name] |
| 170 | del lender["owes"][borrower_name] |
| 171 | del borrower["owed_by"][lender_name] |
| 172 | # Adjust the owed_by amount |
| 173 | lender["owed_by"][borrower_name] = amount - original_owes |
| 174 | borrower["owes"][lender_name] = amount - original_owes |
| 175 | |
| 176 | # Recalculate balances |
| 177 | lender_balance = 0.0 |
| 178 | for owed_amount in lender["owed_by"].values(): |
| 179 | lender_balance += owed_amount |
| 180 | for owes_amount in lender["owes"].values(): |
| 181 | lender_balance -= owes_amount |
| 182 | lender["balance"] = lender_balance |
| 183 | |
| 184 | borrower_balance = 0.0 |
| 185 | for owed_amount in borrower["owed_by"].values(): |
| 186 | borrower_balance += owed_amount |
| 187 | for owes_amount in borrower["owes"].values(): |
| 188 | borrower_balance -= owes_amount |
| 189 | borrower["balance"] = borrower_balance |
| 190 | |
| 191 | # Return updated user objects sorted by name |
| 192 | updated_users = [lender, borrower] |
| 193 | updated_users.sort(key=lambda x: x["name"]) |
| 194 | return json.dumps({"users": updated_users}) |
| 195 | |
| 196 | # Edge Case: Handle unknown URL |
| 197 | return json.dumps({"error": "Unknown endpoint"}) |
| 198 | |
| 199 | # Handled Edge Cases: |
| 200 | # - Invalid JSON payload in GET and POST |
| 201 | # - Missing required keys in POST payloads |
| 202 | # - Unknown URLs in GET and POST |
| 203 | # - Missing payload in POST |
| 204 | # - Duplicate user in /add |
| 205 | # - Non-numeric or negative amount in /iou |
| 206 | # - Lender and borrower being the same in /iou |
| 207 | # - Unknown lender or borrower in /iou |