| 1 | import json |
| 2 | from typing import Dict, List, Optional, Any |
| 3 | |
| 1 | 4 | class RestAPI: |
| 2 | 5 | def __init__(self, database: dict | None = None): |
| 3 | | pass |
| 4 | | |
| 6 | """ |
| 7 | Initialize the REST API with a database of users. |
| 8 | |
| 9 | Args: |
| 10 | database: A dictionary containing user data with IOUs |
| 11 | """ |
| 12 | if database is None: |
| 13 | self.database = {"users": []} |
| 14 | else: |
| 15 | self.database = database |
| 16 | |
| 5 | 17 | def get(self, url: str, payload: str | None = None) -> str: |
| 6 | | pass |
| 7 | | |
| 18 | """ |
| 19 | Handle GET requests to the API. |
| 20 | |
| 21 | Args: |
| 22 | url: The endpoint URL |
| 23 | payload: Optional JSON payload |
| 24 | |
| 25 | Returns: |
| 26 | JSON string response |
| 27 | """ |
| 28 | if url == "/users": |
| 29 | if payload is None: |
| 30 | # Return all users sorted by name |
| 31 | users = sorted(self.database["users"], key=lambda x: x["name"]) |
| 32 | return json.dumps({"users": users}) |
| 33 | else: |
| 34 | # Return specific users |
| 35 | data = json.loads(payload) |
| 36 | user_names = data.get("users", []) |
| 37 | |
| 38 | # Edge Case: Empty users list in payload |
| 39 | if not user_names: |
| 40 | return json.dumps({"users": []}) |
| 41 | |
| 42 | # Filter users by name |
| 43 | filtered_users = [user for user in self.database["users"] if user["name"] in user_names] |
| 44 | # Sort by name |
| 45 | filtered_users.sort(key=lambda x: x["name"]) |
| 46 | return json.dumps({"users": filtered_users}) |
| 47 | |
| 48 | # Edge Case: Invalid URL |
| 49 | return json.dumps({"error": "Invalid URL"}) |
| 50 | |
| 8 | 51 | def post(self, url: str, payload: str | None = None) -> str: |
| 9 | | pass |
| 52 | """ |
| 53 | Handle POST requests to the API. |
| 54 | |
| 55 | Args: |
| 56 | url: The endpoint URL |
| 57 | payload: JSON payload |
| 58 | |
| 59 | Returns: |
| 60 | JSON string response |
| 61 | """ |
| 62 | if payload is None: |
| 63 | # Edge Case: Missing payload |
| 64 | return json.dumps({"error": "Payload required"}) |
| 65 | |
| 66 | try: |
| 67 | data = json.loads(payload) |
| 68 | except json.JSONDecodeError: |
| 69 | # Edge Case: Invalid JSON payload |
| 70 | return json.dumps({"error": "Invalid JSON payload"}) |
| 71 | |
| 72 | if url == "/add": |
| 73 | user_name = data.get("user") |
| 74 | |
| 75 | # Edge Case: Missing user name |
| 76 | if not user_name: |
| 77 | return json.dumps({"error": "User name required"}) |
| 78 | |
| 79 | # Edge Case: User already exists |
| 80 | for user in self.database["users"]: |
| 81 | if user["name"] == user_name: |
| 82 | return json.dumps({"error": "User already exists"}) |
| 83 | |
| 84 | # Create new user |
| 85 | new_user = { |
| 86 | "name": user_name, |
| 87 | "owes": {}, |
| 88 | "owed_by": {}, |
| 89 | "balance": 0.0 |
| 90 | } |
| 91 | |
| 92 | self.database["users"].append(new_user) |
| 93 | return json.dumps(new_user) |
| 94 | |
| 95 | elif url == "/iou": |
| 96 | lender_name = data.get("lender") |
| 97 | borrower_name = data.get("borrower") |
| 98 | amount = data.get("amount") |
| 99 | |
| 100 | # Edge Case: Missing required fields |
| 101 | if not lender_name or not borrower_name or amount is None: |
| 102 | return json.dumps({"error": "Lender, borrower, and amount required"}) |
| 103 | |
| 104 | # Edge Case: Invalid amount type |
| 105 | if not isinstance(amount, (int, float)): |
| 106 | return json.dumps({"error": "Amount must be a number"}) |
| 107 | |
| 108 | # Edge Case: Negative amount |
| 109 | if amount < 0: |
| 110 | return json.dumps({"error": "Amount must be positive"}) |
| 111 | |
| 112 | # Edge Case: Lender and borrower are the same |
| 113 | if lender_name == borrower_name: |
| 114 | return json.dumps({"error": "Lender and borrower cannot be the same"}) |
| 115 | |
| 116 | # Find lender and borrower |
| 117 | lender = None |
| 118 | borrower = None |
| 119 | |
| 120 | for user in self.database["users"]: |
| 121 | if user["name"] == lender_name: |
| 122 | lender = user |
| 123 | elif user["name"] == borrower_name: |
| 124 | borrower = user |
| 125 | |
| 126 | # Edge Case: Lender not found |
| 127 | if lender is None: |
| 128 | return json.dumps({"error": "Lender not found"}) |
| 129 | |
| 130 | # Edge Case: Borrower not found |
| 131 | if borrower is None: |
| 132 | return json.dumps({"error": "Borrower not found"}) |
| 133 | |
| 134 | # Update IOUs with proper debt handling |
| 135 | # Handle the case where lender already owes borrower |
| 136 | if borrower_name in lender["owes"]: |
| 137 | # Lender already owes borrower - add to existing debt |
| 138 | lender["owes"][borrower_name] += amount |
| 139 | borrower["owed_by"][lender_name] += amount |
| 140 | # Handle the case where borrower already owes lender |
| 141 | elif borrower_name in lender["owed_by"]: |
| 142 | # Borrower already owes lender - add to existing credit |
| 143 | lender["owed_by"][borrower_name] += amount |
| 144 | borrower["owes"][lender_name] += amount |
| 145 | else: |
| 146 | # No existing relationship between lender and borrower |
| 147 | # Update lender's owed_by |
| 148 | lender["owed_by"][borrower_name] = amount |
| 149 | # Update borrower's owes |
| 150 | borrower["owes"][lender_name] = amount |
| 151 | |
| 152 | # Recalculate balances |
| 153 | lender_total_owed = sum(lender["owed_by"].values()) |
| 154 | lender_total_owes = sum(lender["owes"].values()) |
| 155 | lender["balance"] = lender_total_owed - lender_total_owes |
| 156 | |
| 157 | borrower_total_owed = sum(borrower["owed_by"].values()) |
| 158 | borrower_total_owes = sum(borrower["owes"].values()) |
| 159 | borrower["balance"] = borrower_total_owed - borrower_total_owes |
| 160 | |
| 161 | # Return updated users sorted by name |
| 162 | updated_users = [lender, borrower] |
| 163 | updated_users.sort(key=lambda x: x["name"]) |
| 164 | return json.dumps({"users": updated_users}) |
| 165 | |
| 166 | # Edge Case: Invalid URL |
| 167 | return json.dumps({"error": "Invalid URL"}) |
| 168 | |
| 169 | # Handled Edge Cases: Invalid URL, Missing payload, Invalid JSON payload |
| 170 | # Handled Edge Cases: Missing user name, User already exists |
| 171 | # Handled Edge Cases: Missing required fields, Invalid amount type, Negative amount, Lender and borrower are the same |
| 172 | # Handled Edge Cases: Lender not found, Borrower not found |