| 1 | import json |
| 2 | from typing import Dict, List, Any |
| 3 | |
| 1 | 4 | class RestAPI: |
| 2 | 5 | def __init__(self, database: dict | None = None): |
| 3 | | pass |
| 6 | if database is None: |
| 7 | self.database = {"users": []} |
| 8 | else: |
| 9 | self.database = database |
| 4 | 10 | |
| 5 | 11 | def get(self, url: str, payload: str | None = None) -> str: |
| 6 | | pass |
| 12 | if url == "/users": |
| 13 | if payload is None: |
| 14 | # Return all users sorted by name |
| 15 | users = sorted(self.database["users"], key=lambda x: x["name"]) |
| 16 | return json.dumps({"users": users}) |
| 17 | else: |
| 18 | try: |
| 19 | data = json.loads(payload) |
| 20 | if "users" not in data: |
| 21 | return json.dumps({"error": "Invalid payload"}) |
| 22 | |
| 23 | # Edge Case: Empty user list in GET request |
| 24 | if not data["users"]: |
| 25 | return json.dumps({"users": []}) |
| 26 | |
| 27 | # Filter users by the provided list |
| 28 | filtered_users = [user for user in self.database["users"] if user["name"] in data["users"]] |
| 29 | # Sort by name |
| 30 | filtered_users.sort(key=lambda x: x["name"]) |
| 31 | return json.dumps({"users": filtered_users}) |
| 32 | except json.JSONDecodeError: |
| 33 | return json.dumps({"error": "Invalid JSON payload"}) |
| 34 | else: |
| 35 | return json.dumps({"error": "Invalid URL"}) |
| 7 | 36 | |
| 8 | 37 | def post(self, url: str, payload: str | None = None) -> str: |
| 9 | | pass |
| 38 | if payload is None: |
| 39 | return json.dumps({"error": "Payload required"}) |
| 40 | |
| 41 | try: |
| 42 | data = json.loads(payload) |
| 43 | except json.JSONDecodeError: |
| 44 | return json.dumps({"error": "Invalid JSON payload"}) |
| 45 | |
| 46 | if url == "/add": |
| 47 | # Edge Case: Missing required fields in POST requests |
| 48 | if "user" not in data: |
| 49 | return json.dumps({"error": "Missing user field"}) |
| 50 | |
| 51 | user_name = data["user"] |
| 52 | |
| 53 | # Edge Case: Invalid user names in requests |
| 54 | if not isinstance(user_name, str) or not user_name: |
| 55 | return json.dumps({"error": "Invalid user name"}) |
| 56 | |
| 57 | # Edge Case: Duplicate user creation |
| 58 | for user in self.database["users"]: |
| 59 | if user["name"] == user_name: |
| 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 | # Edge Case: Missing required fields in POST requests |
| 73 | required_fields = ["lender", "borrower", "amount"] |
| 74 | for field in required_fields: |
| 75 | if field not in data: |
| 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: Invalid user names in requests |
| 83 | if not isinstance(lender_name, str) or not lender_name or not isinstance(borrower_name, str) or not borrower_name: |
| 84 | return json.dumps({"error": "Invalid user names"}) |
| 85 | |
| 86 | # Edge Case: Negative or zero amount values |
| 87 | if not isinstance(amount, (int, float)) or amount <= 0: |
| 88 | return json.dumps({"error": "Invalid amount"}) |
| 89 | |
| 90 | # Edge Case: Self-borrowing (user lending to themselves) |
| 91 | if lender_name == borrower_name: |
| 92 | return json.dumps({"error": "Cannot create IOU between same user"}) |
| 93 | |
| 94 | lender = None |
| 95 | borrower = None |
| 96 | |
| 97 | # Find lender and borrower |
| 98 | for user in self.database["users"]: |
| 99 | if user["name"] == lender_name: |
| 100 | lender = user |
| 101 | if user["name"] == borrower_name: |
| 102 | borrower = user |
| 103 | |
| 104 | # Edge Case: Non-existent users in IOU requests |
| 105 | if lender is None or borrower is None: |
| 106 | return json.dumps({"error": "User not found"}) |
| 107 | |
| 108 | # Update lender's owed_by and borrower's owes |
| 109 | # If borrower already owes lender, reduce that amount first |
| 110 | if borrower_name in lender["owed_by"]: |
| 111 | lender["owed_by"][borrower_name] += amount |
| 112 | else: |
| 113 | lender["owed_by"][borrower_name] = amount |
| 114 | |
| 115 | if lender_name in borrower["owes"]: |
| 116 | borrower["owes"][lender_name] += amount |
| 117 | else: |
| 118 | borrower["owes"][lender_name] = amount |
| 119 | |
| 120 | # Recalculate balances |
| 121 | lender_total_owed = sum(lender["owed_by"].values()) |
| 122 | lender_total_owes = sum(lender["owes"].values()) |
| 123 | lender["balance"] = lender_total_owed - lender_total_owes |
| 124 | |
| 125 | borrower_total_owed = sum(borrower["owed_by"].values()) |
| 126 | borrower_total_owes = sum(borrower["owes"].values()) |
| 127 | borrower["balance"] = borrower_total_owed - borrower_total_owes |
| 128 | |
| 129 | # Return updated users sorted by name |
| 130 | updated_users = [lender, borrower] |
| 131 | updated_users.sort(key=lambda x: x["name"]) |
| 132 | return json.dumps({"users": updated_users}) |
| 133 | else: |
| 134 | return json.dumps({"error": "Invalid URL"}) |
| 135 | |
| 136 | def _get_user(self, name: str) -> Dict | None: |
| 137 | for user in self.database["users"]: |
| 138 | if user["name"] == name: |
| 139 | return user |
| 140 | return None |
| 141 | |
| 142 | def _calculate_balance(self, user: Dict) -> float: |
| 143 | total_owed_by = sum(user["owed_by"].values()) |
| 144 | total_owes = sum(user["owes"].values()) |
| 145 | return total_owed_by - total_owes |
| 146 | |
| 147 | # Handled Edge Cases: Duplicate user creation, Invalid user names in requests, Negative or zero amount values, Self-borrowing (user lending to themselves), Non-existent users in IOU requests, Missing required fields in POST requests, Invalid JSON payload format, Empty user list in GET request |