| 1 | import json |
| 2 | from typing import Dict, Any, List, Optional |
| 3 | |
| 4 | |
| 1 | 5 | class RestAPI: |
| 2 | 6 | def __init__(self, database: dict | None = None): |
| 3 | | pass |
| 7 | if database is None: |
| 8 | self.database = {"users": []} |
| 9 | else: |
| 10 | self.database = database |
| 4 | 11 | |
| 5 | 12 | def get(self, url: str, payload: str | None = None) -> str: |
| 6 | | pass |
| 13 | if url == "/users": |
| 14 | if payload is None: |
| 15 | # Return all users sorted by name |
| 16 | users = sorted(self.database["users"], key=lambda x: x["name"]) |
| 17 | return json.dumps({"users": users}) |
| 18 | else: |
| 19 | try: |
| 20 | data = json.loads(payload) |
| 21 | except json.JSONDecodeError: |
| 22 | # Edge Case: Malformed JSON payload |
| 23 | return json.dumps({"error": "Invalid JSON payload"}) |
| 24 | |
| 25 | if "users" not in data: |
| 26 | # Edge Case: Missing 'users' field in payload |
| 27 | return json.dumps({"error": "Missing 'users' field"}) |
| 28 | |
| 29 | requested_users = data["users"] |
| 30 | result = [] |
| 31 | for user_name in requested_users: |
| 32 | user = self._get_user(user_name) |
| 33 | if user: |
| 34 | result.append(user) |
| 35 | result.sort(key=lambda x: x["name"]) |
| 36 | return json.dumps({"users": result}) |
| 37 | else: |
| 38 | # Edge Case: Invalid URL for GET request |
| 39 | return json.dumps({"error": "Invalid URL"}) |
| 7 | 40 | |
| 8 | 41 | def post(self, url: str, payload: str | None = None) -> str: |
| 9 | | pass |
| 42 | if payload is None: |
| 43 | # Edge Case: Missing payload |
| 44 | return json.dumps({"error": "Missing payload"}) |
| 45 | |
| 46 | try: |
| 47 | data = json.loads(payload) |
| 48 | except json.JSONDecodeError: |
| 49 | # Edge Case: Malformed JSON payload |
| 50 | return json.dumps({"error": "Invalid JSON payload"}) |
| 51 | |
| 52 | if url == "/add": |
| 53 | if "user" not in data: |
| 54 | # Edge Case: Missing 'user' field in payload |
| 55 | return json.dumps({"error": "Missing 'user' field"}) |
| 56 | |
| 57 | user_name = data["user"] |
| 58 | if self._get_user(user_name): |
| 59 | # Edge Case: User already exists |
| 60 | return json.dumps({"error": "User already exists"}) |
| 61 | |
| 62 | new_user = { |
| 63 | "name": user_name, |
| 64 | "owes": {}, |
| 65 | "owed_by": {}, |
| 66 | "balance": 0.0 |
| 67 | } |
| 68 | self.database["users"].append(new_user) |
| 69 | return json.dumps(new_user) |
| 70 | |
| 71 | elif url == "/iou": |
| 72 | required_fields = ["lender", "borrower", "amount"] |
| 73 | for field in required_fields: |
| 74 | if field not in data: |
| 75 | # Edge Case: Missing required field in payload |
| 76 | return json.dumps({"error": f"Missing '{field}' field"}) |
| 77 | |
| 78 | lender_name = data["lender"] |
| 79 | borrower_name = data["borrower"] |
| 80 | amount = data["amount"] |
| 81 | |
| 82 | # Edge Case: Lender and borrower are the same person |
| 83 | if lender_name == borrower_name: |
| 84 | return json.dumps({"error": "Lender and borrower cannot be the same person"}) |
| 85 | |
| 86 | # Edge Case: Amount is not a positive number |
| 87 | if not isinstance(amount, (int, float)) or amount <= 0: |
| 88 | return json.dumps({"error": "Amount must be a positive number"}) |
| 89 | |
| 90 | lender = self._get_user(lender_name) |
| 91 | borrower = self._get_user(borrower_name) |
| 92 | |
| 93 | # Edge Case: Lender does not exist |
| 94 | if not lender: |
| 95 | return json.dumps({"error": "Lender does not exist"}) |
| 96 | |
| 97 | # Edge Case: Borrower does not exist |
| 98 | if not borrower: |
| 99 | return json.dumps({"error": "Borrower does not exist"}) |
| 100 | |
| 101 | # Update lender's records |
| 102 | if borrower_name in lender["owes"]: |
| 103 | lender["owes"][borrower_name] -= amount |
| 104 | if lender["owes"][borrower_name] <= 0: |
| 105 | amount_owed_to_borrower = abs(lender["owes"][borrower_name]) |
| 106 | del lender["owes"][borrower_name] |
| 107 | if amount_owed_to_borrower > 0: |
| 108 | lender["owed_by"][borrower_name] = amount_owed_to_borrower |
| 109 | else: |
| 110 | lender["owed_by"][borrower_name] = lender["owed_by"].get(borrower_name, 0) + amount |
| 111 | |
| 112 | # Update borrower's records |
| 113 | if lender_name in borrower["owed_by"]: |
| 114 | borrower["owed_by"][lender_name] -= amount |
| 115 | if borrower["owed_by"][lender_name] <= 0: |
| 116 | amount_owed_to_lender = abs(borrower["owed_by"][lender_name]) |
| 117 | del borrower["owed_by"][lender_name] |
| 118 | if amount_owed_to_lender > 0: |
| 119 | borrower["owes"][lender_name] = amount_owed_to_lender |
| 120 | else: |
| 121 | borrower["owes"][lender_name] = borrower["owes"].get(lender_name, 0) + amount |
| 122 | |
| 123 | # Recalculate balances |
| 124 | self._recalculate_balance(lender) |
| 125 | self._recalculate_balance(borrower) |
| 126 | |
| 127 | # Return updated user objects sorted by name |
| 128 | result = [lender, borrower] |
| 129 | result.sort(key=lambda x: x["name"]) |
| 130 | return json.dumps({"users": result}) |
| 131 | |
| 132 | else: |
| 133 | # Edge Case: Invalid URL for POST request |
| 134 | return json.dumps({"error": "Invalid URL"}) |
| 135 | |
| 136 | def _get_user(self, name: str) -> Optional[Dict[str, Any]]: |
| 137 | for user in self.database["users"]: |
| 138 | if user["name"] == name: |
| 139 | return user |
| 140 | return None |
| 141 | |
| 142 | def _recalculate_balance(self, user: Dict[str, Any]) -> None: |
| 143 | total_owed_by = sum(user["owed_by"].values()) |
| 144 | total_owes = sum(user["owes"].values()) |
| 145 | user["balance"] = round(total_owed_by - total_owes, 2) |