| 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 a database. |
| 7 | |
| 8 | Args: |
| 9 | database: A dictionary containing user data. |
| 10 | """ |
| 11 | self.database = database if database is not None else {"users": []} |
| 12 | |
| 5 | 13 | def get(self, url: str, payload: str | None = None) -> str: |
| 6 | | pass |
| 7 | | |
| 14 | """ |
| 15 | Handle GET requests to the API. |
| 16 | |
| 17 | Args: |
| 18 | url: The endpoint URL. |
| 19 | payload: Optional JSON payload. |
| 20 | |
| 21 | Returns: |
| 22 | A JSON string response. |
| 23 | """ |
| 24 | if url == "/users": |
| 25 | if payload is None: |
| 26 | # Return all users sorted by name |
| 27 | users = sorted(self.database["users"], key=lambda x: x["name"]) |
| 28 | return json.dumps({"users": users}) |
| 29 | else: |
| 30 | # Return specified users sorted by name |
| 31 | data = json.loads(payload) |
| 32 | user_names = data.get("users", []) |
| 33 | |
| 34 | # Edge Case: Empty user list in payload |
| 35 | if not user_names: |
| 36 | return json.dumps({"users": []}) |
| 37 | |
| 38 | # Filter users by name |
| 39 | users = [user for user in self.database["users"] if user["name"] in user_names] |
| 40 | users = sorted(users, key=lambda x: x["name"]) |
| 41 | |
| 42 | # Edge Case: Some requested users don't exist |
| 43 | # (We just return the ones that do exist) |
| 44 | |
| 45 | return json.dumps({"users": users}) |
| 46 | |
| 47 | # Edge Case: Invalid URL |
| 48 | return json.dumps({"error": "Invalid URL"}) |
| 49 | |
| 8 | 50 | def post(self, url: str, payload: str | None = None) -> str: |
| 9 | | pass |
| 51 | """ |
| 52 | Handle POST requests to the API. |
| 53 | |
| 54 | Args: |
| 55 | url: The endpoint URL. |
| 56 | payload: JSON payload. |
| 57 | |
| 58 | Returns: |
| 59 | A JSON string response. |
| 60 | """ |
| 61 | if payload is None: |
| 62 | # Edge Case: Missing payload |
| 63 | return json.dumps({"error": "Payload required"}) |
| 64 | |
| 65 | data = json.loads(payload) |
| 66 | |
| 67 | if url == "/add": |
| 68 | user_name = data.get("user") |
| 69 | |
| 70 | # Edge Case: Missing user name |
| 71 | if not user_name: |
| 72 | return json.dumps({"error": "User name required"}) |
| 73 | |
| 74 | # Edge Case: User already exists |
| 75 | for user in self.database["users"]: |
| 76 | if user["name"] == user_name: |
| 77 | return json.dumps({"error": "User already exists"}) |
| 78 | |
| 79 | # Create new user |
| 80 | new_user = { |
| 81 | "name": user_name, |
| 82 | "owes": {}, |
| 83 | "owed_by": {}, |
| 84 | "balance": 0.0 |
| 85 | } |
| 86 | self.database["users"].append(new_user) |
| 87 | |
| 88 | return json.dumps(new_user) |
| 89 | |
| 90 | elif url == "/iou": |
| 91 | lender_name = data.get("lender") |
| 92 | borrower_name = data.get("borrower") |
| 93 | amount = data.get("amount") |
| 94 | |
| 95 | # Edge Case: Missing required fields |
| 96 | if not lender_name or not borrower_name or amount is None: |
| 97 | return json.dumps({"error": "Lender, borrower, and amount required"}) |
| 98 | |
| 99 | # Edge Case: Lender and borrower are the same |
| 100 | if lender_name == borrower_name: |
| 101 | return json.dumps({"error": "Lender and borrower cannot be the same"}) |
| 102 | |
| 103 | # Edge Case: Negative amount |
| 104 | if amount < 0: |
| 105 | return json.dumps({"error": "Amount must be positive"}) |
| 106 | |
| 107 | # Find lender and borrower |
| 108 | lender = None |
| 109 | borrower = None |
| 110 | |
| 111 | for user in self.database["users"]: |
| 112 | if user["name"] == lender_name: |
| 113 | lender = user |
| 114 | elif user["name"] == borrower_name: |
| 115 | borrower = user |
| 116 | |
| 117 | # Edge Case: Lender or borrower doesn't exist |
| 118 | if lender is None or borrower is None: |
| 119 | return json.dumps({"error": "Lender or borrower does not exist"}) |
| 120 | |
| 121 | # Update owes/owed_by relationships |
| 122 | # Handle existing debts between lender and borrower |
| 123 | |
| 124 | # Get existing amounts |
| 125 | existing_lender_owes = lender["owes"].get(borrower_name, 0) |
| 126 | existing_lender_owed_by = lender["owed_by"].get(borrower_name, 0) |
| 127 | |
| 128 | # Calculate net amount owed from borrower to lender |
| 129 | # If lender already owes borrower, this reduces the debt |
| 130 | # If borrower already owes lender, this increases the debt |
| 131 | net_amount = amount - existing_lender_owes + existing_lender_owed_by |
| 132 | |
| 133 | # Remove old entries |
| 134 | if borrower_name in lender["owes"]: |
| 135 | del lender["owes"][borrower_name] |
| 136 | if borrower_name in lender["owed_by"]: |
| 137 | del lender["owed_by"][borrower_name] |
| 138 | if lender_name in borrower["owes"]: |
| 139 | del borrower["owes"][lender_name] |
| 140 | if lender_name in borrower["owed_by"]: |
| 141 | del borrower["owed_by"][lender_name] |
| 142 | |
| 143 | # Add new entries based on net amount |
| 144 | if net_amount > 0: |
| 145 | # Borrower owes lender (positive net amount) |
| 146 | lender["owed_by"][borrower_name] = net_amount |
| 147 | borrower["owes"][lender_name] = net_amount |
| 148 | elif net_amount < 0: |
| 149 | # Lender owes borrower (negative net amount) |
| 150 | lender["owes"][borrower_name] = -net_amount |
| 151 | borrower["owed_by"][lender_name] = -net_amount |
| 152 | # If net_amount == 0, no entries needed (debt cancelled out) |
| 153 | |
| 154 | # Recalculate balances |
| 155 | lender_total_owed = sum(lender["owed_by"].values()) |
| 156 | lender_total_owes = sum(lender["owes"].values()) |
| 157 | lender["balance"] = lender_total_owed - lender_total_owes |
| 158 | |
| 159 | borrower_total_owed = sum(borrower["owed_by"].values()) |
| 160 | borrower_total_owes = sum(borrower["owes"].values()) |
| 161 | borrower["balance"] = borrower_total_owed - borrower_total_owes |
| 162 | |
| 163 | # Return updated users sorted by name |
| 164 | users = sorted([lender, borrower], key=lambda x: x["name"]) |
| 165 | return json.dumps({"users": users}) |
| 166 | |
| 167 | # Edge Case: Invalid URL |
| 168 | return json.dumps({"error": "Invalid URL"}) |
| 169 | |
| 170 | # Handled Edge Cases: Invalid URL, Missing payload, Missing user name, User already exists, Missing required fields, Lender and borrower are the same, Negative amount, Lender or borrower doesn't exist |