| 1 | import json |
| 2 | from typing import Dict, List, Optional |
| 3 | |
| 1 | 4 | class RestAPI: |
| 2 | 5 | def __init__(self, database: dict | None = None): |
| 3 | | pass |
| 4 | | |
| 6 | """ |
| 7 | Initialize the REST API with an optional database. |
| 8 | |
| 9 | Args: |
| 10 | database: A dictionary containing initial user data. |
| 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 response as a string. |
| 27 | """ |
| 28 | if url == "/users": |
| 29 | if payload is None: |
| 30 | # Return all users |
| 31 | return json.dumps({"users": sorted(self.database["users"], key=lambda x: x["name"])}) |
| 32 | else: |
| 33 | # Return specific users |
| 34 | data = json.loads(payload) |
| 35 | users_list = data.get("users", []) |
| 36 | |
| 37 | # Edge Case: Empty users list in payload |
| 38 | if not users_list: |
| 39 | return json.dumps({"users": []}) |
| 40 | |
| 41 | # Filter users |
| 42 | result_users = [user for user in self.database["users"] if user["name"] in users_list] |
| 43 | result_users.sort(key=lambda x: x["name"]) |
| 44 | |
| 45 | # Edge Case: User not found |
| 46 | if len(result_users) != len(users_list): |
| 47 | # Some users were not found, but we still return what we have |
| 48 | pass |
| 49 | |
| 50 | return json.dumps({"users": result_users}) |
| 51 | |
| 52 | # Edge Case: Invalid URL |
| 53 | return json.dumps({"error": "Invalid URL"}) |
| 54 | |
| 8 | 55 | def post(self, url: str, payload: str | None = None) -> str: |
| 9 | | pass |
| 56 | """ |
| 57 | Handle POST requests to the API. |
| 58 | |
| 59 | Args: |
| 60 | url: The endpoint URL. |
| 61 | payload: JSON payload. |
| 62 | |
| 63 | Returns: |
| 64 | JSON response as a string. |
| 65 | """ |
| 66 | if payload is None: |
| 67 | # Edge Case: Missing payload |
| 68 | return json.dumps({"error": "Payload required"}) |
| 69 | |
| 70 | try: |
| 71 | data = json.loads(payload) |
| 72 | except json.JSONDecodeError: |
| 73 | # Edge Case: Invalid JSON payload |
| 74 | return json.dumps({"error": "Invalid JSON payload"}) |
| 75 | |
| 76 | if url == "/add": |
| 77 | user_name = data.get("user") |
| 78 | |
| 79 | # Edge Case: Missing user name |
| 80 | if not user_name: |
| 81 | return json.dumps({"error": "User name required"}) |
| 82 | |
| 83 | # Edge Case: User already exists |
| 84 | for user in self.database["users"]: |
| 85 | if user["name"] == user_name: |
| 86 | return json.dumps({"error": "User already exists"}) |
| 87 | |
| 88 | # Create new user |
| 89 | new_user = { |
| 90 | "name": user_name, |
| 91 | "owes": {}, |
| 92 | "owed_by": {}, |
| 93 | "balance": 0.0 |
| 94 | } |
| 95 | self.database["users"].append(new_user) |
| 96 | return json.dumps(new_user) |
| 97 | |
| 98 | elif url == "/iou": |
| 99 | lender_name = data.get("lender") |
| 100 | borrower_name = data.get("borrower") |
| 101 | amount = data.get("amount") |
| 102 | |
| 103 | # Edge Case: Missing required fields |
| 104 | if not lender_name or not borrower_name or amount is None: |
| 105 | return json.dumps({"error": "Lender, borrower, and amount are required"}) |
| 106 | |
| 107 | # Edge Case: Invalid amount type |
| 108 | if not isinstance(amount, (int, float)): |
| 109 | return json.dumps({"error": "Amount must be a number"}) |
| 110 | |
| 111 | # Edge Case: Negative amount |
| 112 | if amount < 0: |
| 113 | return json.dumps({"error": "Amount must be positive"}) |
| 114 | |
| 115 | # Edge Case: Lender and borrower are the same |
| 116 | if lender_name == borrower_name: |
| 117 | return json.dumps({"error": "Lender and borrower cannot be the same"}) |
| 118 | |
| 119 | # Find users |
| 120 | lender = None |
| 121 | borrower = None |
| 122 | for user in self.database["users"]: |
| 123 | if user["name"] == lender_name: |
| 124 | lender = user |
| 125 | elif user["name"] == borrower_name: |
| 126 | borrower = user |
| 127 | |
| 128 | # Edge Case: User not found |
| 129 | if lender is None or borrower is None: |
| 130 | return json.dumps({"error": "User not found"}) |
| 131 | |
| 132 | # Handle debt offsetting logic |
| 133 | # If lender owes borrower money, reduce that debt first |
| 134 | if borrower_name in lender["owes"]: |
| 135 | existing_debt = lender["owes"][borrower_name] |
| 136 | if amount > existing_debt: |
| 137 | # Remove the existing debt and add the remaining to owed_by |
| 138 | del lender["owes"][borrower_name] |
| 139 | del borrower["owed_by"][lender_name] |
| 140 | lender["owed_by"][borrower_name] = amount - existing_debt |
| 141 | borrower["owes"][lender_name] = amount - existing_debt |
| 142 | elif amount == existing_debt: |
| 143 | # Exact match, remove both entries |
| 144 | del lender["owes"][borrower_name] |
| 145 | del borrower["owed_by"][lender_name] |
| 146 | else: |
| 147 | # Reduce the existing debt |
| 148 | lender["owes"][borrower_name] -= amount |
| 149 | del borrower["owed_by"][lender_name] |
| 150 | else: |
| 151 | # No existing debt from lender to borrower, add to owed_by |
| 152 | if borrower_name in lender["owed_by"]: |
| 153 | lender["owed_by"][borrower_name] += amount |
| 154 | else: |
| 155 | lender["owed_by"][borrower_name] = amount |
| 156 | |
| 157 | if lender_name in borrower["owes"]: |
| 158 | borrower["owes"][lender_name] += amount |
| 159 | else: |
| 160 | borrower["owes"][lender_name] = amount |
| 161 | |
| 162 | # Recalculate balances |
| 163 | lender_total_owed = sum(lender["owed_by"].values()) |
| 164 | lender_total_owes = sum(lender["owes"].values()) |
| 165 | lender["balance"] = lender_total_owed - lender_total_owes |
| 166 | |
| 167 | borrower_total_owed = sum(borrower["owed_by"].values()) |
| 168 | borrower_total_owes = sum(borrower["owes"].values()) |
| 169 | borrower["balance"] = borrower_total_owed - borrower_total_owes |
| 170 | |
| 171 | # Clean up empty debt entries |
| 172 | lender["owes"] = {k: v for k, v in lender["owes"].items() if v != 0} |
| 173 | lender["owed_by"] = {k: v for k, v in lender["owed_by"].items() if v != 0} |
| 174 | borrower["owes"] = {k: v for k, v in borrower["owes"].items() if v != 0} |
| 175 | borrower["owed_by"] = {k: v for k, v in borrower["owed_by"].items() if v != 0} |
| 176 | |
| 177 | # Return updated users |
| 178 | result_users = sorted([lender, borrower], key=lambda x: x["name"]) |
| 179 | return json.dumps({"users": result_users}) |
| 180 | |
| 181 | # Edge Case: Invalid URL |
| 182 | return json.dumps({"error": "Invalid URL"}) |
| 183 | |
| 184 | # Handled Edge Cases: Invalid URL, Missing payload, Invalid JSON payload, Missing user name, |
| 185 | # User already exists, Missing required fields, Invalid amount type, Negative amount, |
| 186 | # Lender and borrower are the same, User not found, Empty users list in payload |