| 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 | Edge Cases: |
| 28 | - Invalid URL |
| 29 | - Malformed payload |
| 30 | """ |
| 31 | # Edge Case: Invalid URL |
| 32 | if url != "/users": |
| 33 | return json.dumps({"error": "Invalid URL"}) |
| 34 | |
| 35 | # Edge Case: Malformed payload |
| 36 | if payload is not None: |
| 37 | try: |
| 38 | payload_data = json.loads(payload) |
| 39 | except json.JSONDecodeError: |
| 40 | return json.dumps({"error": "Invalid payload"}) |
| 41 | |
| 42 | # Edge Case: Missing 'users' key in payload |
| 43 | if "users" not in payload_data: |
| 44 | return json.dumps({"error": "Missing 'users' key in payload"}) |
| 45 | |
| 46 | # Filter users based on payload |
| 47 | user_names = payload_data["users"] |
| 48 | users = [user for user in self.database["users"] if user["name"] in user_names] |
| 49 | users.sort(key=lambda x: x["name"]) |
| 50 | return json.dumps({"users": users}) |
| 51 | else: |
| 52 | # Return all users sorted by name |
| 53 | users = sorted(self.database["users"], key=lambda x: x["name"]) |
| 54 | return json.dumps({"users": users}) |
| 55 | |
| 56 | # Handled Edge Cases: Invalid URL, Malformed payload, Missing 'users' key in payload |
| 57 | |
| 8 | 58 | def post(self, url: str, payload: str | None = None) -> str: |
| 9 | | pass |
| 59 | """ |
| 60 | Handle POST requests to the API. |
| 61 | |
| 62 | Args: |
| 63 | url: The endpoint URL. |
| 64 | payload: JSON payload. |
| 65 | |
| 66 | Returns: |
| 67 | A JSON string response. |
| 68 | |
| 69 | Edge Cases: |
| 70 | - Invalid URL |
| 71 | - Missing payload |
| 72 | - Malformed payload |
| 73 | - User already exists (for /add) |
| 74 | - Non-existent users (for /iou) |
| 75 | - Lender and borrower are the same |
| 76 | """ |
| 77 | # Edge Case: Missing payload |
| 78 | if payload is None: |
| 79 | return json.dumps({"error": "Missing payload"}) |
| 80 | |
| 81 | # Edge Case: Malformed payload |
| 82 | try: |
| 83 | payload_data = json.loads(payload) |
| 84 | except json.JSONDecodeError: |
| 85 | return json.dumps({"error": "Invalid payload"}) |
| 86 | |
| 87 | if url == "/add": |
| 88 | # Edge Case: Missing 'user' key in payload |
| 89 | if "user" not in payload_data: |
| 90 | return json.dumps({"error": "Missing 'user' key in payload"}) |
| 91 | |
| 92 | user_name = payload_data["user"] |
| 93 | |
| 94 | # Edge Case: User already exists |
| 95 | for user in self.database["users"]: |
| 96 | if user["name"] == user_name: |
| 97 | return json.dumps({"error": "User already exists"}) |
| 98 | |
| 99 | new_user = { |
| 100 | "name": user_name, |
| 101 | "owes": {}, |
| 102 | "owed_by": {}, |
| 103 | "balance": 0.0 |
| 104 | } |
| 105 | self.database["users"].append(new_user) |
| 106 | return json.dumps(new_user) |
| 107 | |
| 108 | elif url == "/iou": |
| 109 | # Edge Case: Missing required keys in payload |
| 110 | required_keys = ["lender", "borrower", "amount"] |
| 111 | for key in required_keys: |
| 112 | if key not in payload_data: |
| 113 | return json.dumps({"error": f"Missing '{key}' key in payload"}) |
| 114 | |
| 115 | lender_name = payload_data["lender"] |
| 116 | borrower_name = payload_data["borrower"] |
| 117 | amount = payload_data["amount"] |
| 118 | |
| 119 | # Edge Case: Lender and borrower are the same |
| 120 | if lender_name == borrower_name: |
| 121 | return json.dumps({"error": "Lender and borrower cannot be the same"}) |
| 122 | |
| 123 | # Edge Case: Non-existent users |
| 124 | lender = None |
| 125 | borrower = None |
| 126 | for user in self.database["users"]: |
| 127 | if user["name"] == lender_name: |
| 128 | lender = user |
| 129 | if user["name"] == borrower_name: |
| 130 | borrower = user |
| 131 | |
| 132 | if lender is None or borrower is None: |
| 133 | return json.dumps({"error": "User does not exist"}) |
| 134 | |
| 135 | # Update debts - netting out existing debts |
| 136 | # If lender already owes borrower, reduce that amount first |
| 137 | if borrower_name in lender["owes"]: |
| 138 | existing_debt = lender["owes"][borrower_name] |
| 139 | if existing_debt > amount: |
| 140 | # Lender still owes borrower, just reduce the amount |
| 141 | lender["owes"][borrower_name] = existing_debt - amount |
| 142 | # Update borrower's owed_by to reflect the reduced amount |
| 143 | borrower["owed_by"][lender_name] = existing_debt - amount |
| 144 | elif existing_debt == amount: |
| 145 | # Debts cancel out |
| 146 | del lender["owes"][borrower_name] |
| 147 | del borrower["owed_by"][lender_name] |
| 148 | else: |
| 149 | # New debt direction: borrower owes lender |
| 150 | del lender["owes"][borrower_name] |
| 151 | del borrower["owed_by"][lender_name] |
| 152 | new_debt = amount - existing_debt |
| 153 | lender["owed_by"][borrower_name] = new_debt |
| 154 | borrower["owes"][lender_name] = new_debt |
| 155 | elif lender_name in borrower["owes"]: |
| 156 | # Borrower already owes lender, increase that amount |
| 157 | existing_debt = borrower["owes"][lender_name] |
| 158 | borrower["owes"][lender_name] = existing_debt + amount |
| 159 | lender["owed_by"][lender_name] = existing_debt + amount |
| 160 | else: |
| 161 | # No existing debt, create new debt |
| 162 | lender["owed_by"][borrower_name] = amount |
| 163 | borrower["owes"][lender_name] = amount |
| 164 | |
| 165 | # Recalculate balances |
| 166 | lender_total_owed = sum(lender["owed_by"].values()) |
| 167 | lender_total_owes = sum(lender["owes"].values()) |
| 168 | lender["balance"] = lender_total_owed - lender_total_owes |
| 169 | |
| 170 | borrower_total_owed = sum(borrower["owed_by"].values()) |
| 171 | borrower_total_owes = sum(borrower["owes"].values()) |
| 172 | borrower["balance"] = borrower_total_owed - borrower_total_owes |
| 173 | |
| 174 | # Return updated users sorted by name |
| 175 | updated_users = sorted([lender, borrower], key=lambda x: x["name"]) |
| 176 | return json.dumps({"users": updated_users}) |
| 177 | else: |
| 178 | # Edge Case: Invalid URL |
| 179 | return json.dumps({"error": "Invalid URL"}) |
| 180 | |
| 181 | # Handled Edge Cases: Invalid URL, Missing payload, Malformed payload, User already exists (for /add), |
| 182 | # Non-existent users (for /iou), Lender and borrower are the same, Missing required keys in payload |