| 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 the structure: |
| 11 | {"users": [{"name": str, "owes": dict, "owed_by": dict, "balance": float}]} |
| 12 | """ |
| 13 | if database is None: |
| 14 | self.database = {"users": []} |
| 15 | else: |
| 16 | self.database = database |
| 17 | |
| 5 | 18 | def get(self, url: str, payload: str | None = None) -> str: |
| 6 | | pass |
| 7 | | |
| 19 | """ |
| 20 | Handle GET requests to the API. |
| 21 | |
| 22 | Args: |
| 23 | url: The endpoint URL (e.g., "/users") |
| 24 | payload: Optional JSON string containing request parameters |
| 25 | |
| 26 | Returns: |
| 27 | JSON string response |
| 28 | """ |
| 29 | if url == "/users": |
| 30 | if payload is None: |
| 31 | # Return all users sorted by name |
| 32 | sorted_users = sorted(self.database["users"], key=lambda x: x["name"]) |
| 33 | return json.dumps({"users": sorted_users}) |
| 34 | else: |
| 35 | # Return only specified users |
| 36 | payload_data = json.loads(payload) |
| 37 | requested_users = payload_data.get("users", []) |
| 38 | |
| 39 | # Filter users that exist in the database |
| 40 | filtered_users = [user for user in self.database["users"] if user["name"] in requested_users] |
| 41 | |
| 42 | # Sort by name |
| 43 | sorted_users = sorted(filtered_users, key=lambda x: x["name"]) |
| 44 | |
| 45 | return json.dumps({"users": sorted_users}) |
| 46 | |
| 47 | # If URL is not recognized |
| 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 (e.g., "/add", "/iou") |
| 56 | payload: JSON string containing request data |
| 57 | |
| 58 | Returns: |
| 59 | JSON string response |
| 60 | """ |
| 61 | if payload is None: |
| 62 | return json.dumps({"error": "Payload required"}) |
| 63 | |
| 64 | payload_data = json.loads(payload) |
| 65 | |
| 66 | if url == "/add": |
| 67 | # Edge Case: Missing user field in payload |
| 68 | if "user" not in payload_data: |
| 69 | return json.dumps({"error": "User field required"}) |
| 70 | |
| 71 | new_user_name = payload_data["user"] |
| 72 | |
| 73 | # Edge Case: User already exists - return existing user |
| 74 | for user in self.database["users"]: |
| 75 | if user["name"] == new_user_name: |
| 76 | return json.dumps(user) |
| 77 | |
| 78 | # Create new user |
| 79 | new_user = { |
| 80 | "name": new_user_name, |
| 81 | "owes": {}, |
| 82 | "owed_by": {}, |
| 83 | "balance": 0.0 |
| 84 | } |
| 85 | |
| 86 | self.database["users"].append(new_user) |
| 87 | |
| 88 | # Return the new user object |
| 89 | return json.dumps(new_user) |
| 90 | |
| 91 | elif url == "/iou": |
| 92 | # Edge Case: Missing required fields in payload |
| 93 | required_fields = ["lender", "borrower", "amount"] |
| 94 | for field in required_fields: |
| 95 | if field not in payload_data: |
| 96 | return json.dumps({"error": f"Missing field: {field}"}) |
| 97 | |
| 98 | lender_name = payload_data["lender"] |
| 99 | borrower_name = payload_data["borrower"] |
| 100 | amount = payload_data["amount"] |
| 101 | |
| 102 | # Edge Case: Lender and borrower are the same person |
| 103 | if lender_name == borrower_name: |
| 104 | return json.dumps({"error": "Lender and borrower cannot be the same"}) |
| 105 | |
| 106 | # Edge Case: Amount is negative |
| 107 | if amount < 0: |
| 108 | return json.dumps({"error": "Amount cannot be negative"}) |
| 109 | |
| 110 | # Find lender and borrower in database |
| 111 | lender = None |
| 112 | borrower = None |
| 113 | |
| 114 | for user in self.database["users"]: |
| 115 | if user["name"] == lender_name: |
| 116 | lender = user |
| 117 | elif user["name"] == borrower_name: |
| 118 | borrower = user |
| 119 | |
| 120 | # Edge Case: Lender or borrower does not exist |
| 121 | if lender is None or borrower is None: |
| 122 | raise ValueError("Lender or borrower does not exist") |
| 123 | |
| 124 | # Update lender's owed_by and borrower's owes |
| 125 | # If borrower already owes lender, add to existing amount |
| 126 | if borrower_name in lender["owed_by"]: |
| 127 | lender["owed_by"][borrower_name] += amount |
| 128 | else: |
| 129 | lender["owed_by"][borrower_name] = amount |
| 130 | |
| 131 | if lender_name in borrower["owes"]: |
| 132 | borrower["owes"][lender_name] += amount |
| 133 | else: |
| 134 | borrower["owes"][lender_name] = amount |
| 135 | |
| 136 | # Update balances |
| 137 | lender["balance"] += amount |
| 138 | borrower["balance"] -= amount |
| 139 | |
| 140 | # Return updated user objects sorted by name |
| 141 | updated_users = sorted([lender, borrower], key=lambda x: x["name"]) |
| 142 | return json.dumps({"users": updated_users}) |
| 143 | |
| 144 | # If URL is not recognized |
| 145 | return json.dumps({"error": "Invalid URL"}) |
| 146 | |
| 147 | # Handled Edge Cases: Missing user field, user already exists, missing required fields, |
| 148 | # lender and borrower are the same, negative amount, lender or borrower does not exist |
| 149 | |
| 150 | # Handled Edge Cases: Missing users in payload, invalid URL |