| 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 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 sorted by name |
| 35 | data = json.loads(payload) |
| 36 | user_names = data.get("users", []) |
| 37 | |
| 38 | # Edge Case: Handle when users list is empty |
| 39 | if not user_names: |
| 40 | return json.dumps({"users": []}) |
| 41 | |
| 42 | # Filter users by provided names |
| 43 | users = [user for user in self.database["users"] if user["name"] in user_names] |
| 44 | users = sorted(users, key=lambda x: x["name"]) |
| 45 | return json.dumps({"users": users}) |
| 46 | |
| 47 | # Handled Edge Cases: Empty users list in payload |
| 48 | |
| 8 | 49 | def post(self, url: str, payload: str | None = None) -> str: |
| 9 | | pass |
| 50 | """ |
| 51 | Handle POST requests to the API. |
| 52 | |
| 53 | Args: |
| 54 | url: The endpoint URL. |
| 55 | payload: JSON payload. |
| 56 | |
| 57 | Returns: |
| 58 | JSON string response. |
| 59 | """ |
| 60 | if url == "/add": |
| 61 | if payload is None: |
| 62 | # Edge Case: No payload provided |
| 63 | return json.dumps({"error": "Payload required"}) |
| 64 | |
| 65 | data = json.loads(payload) |
| 66 | user_name = data.get("user") |
| 67 | |
| 68 | # Edge Case: User name not provided |
| 69 | if not user_name: |
| 70 | return json.dumps({"error": "User name required"}) |
| 71 | |
| 72 | # Edge Case: User already exists |
| 73 | for user in self.database["users"]: |
| 74 | if user["name"] == user_name: |
| 75 | return json.dumps({"error": "User already exists"}) |
| 76 | |
| 77 | # Create new user |
| 78 | new_user = { |
| 79 | "name": user_name, |
| 80 | "owes": {}, |
| 81 | "owed_by": {}, |
| 82 | "balance": 0.0 |
| 83 | } |
| 84 | |
| 85 | self.database["users"].append(new_user) |
| 86 | return json.dumps(new_user) |
| 87 | |
| 88 | elif url == "/iou": |
| 89 | if payload is None: |
| 90 | # Edge Case: No payload provided |
| 91 | return json.dumps({"error": "Payload required"}) |
| 92 | |
| 93 | data = json.loads(payload) |
| 94 | lender_name = data.get("lender") |
| 95 | borrower_name = data.get("borrower") |
| 96 | amount = data.get("amount") |
| 97 | |
| 98 | # Edge Case: Missing required fields |
| 99 | if not lender_name or not borrower_name or amount is None: |
| 100 | return json.dumps({"error": "Missing required fields"}) |
| 101 | |
| 102 | # Edge Case: Lender and borrower are the same person |
| 103 | if lender_name == borrower_name: |
| 104 | return json.dumps({"error": "Cannot create IOU between same user"}) |
| 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 |
| 111 | lender = None |
| 112 | borrower = None |
| 113 | |
| 114 | for user in self.database["users"]: |
| 115 | if user["name"] == lender_name: |
| 116 | lender = user |
| 117 | if 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 | return json.dumps({"error": "User does not exist"}) |
| 123 | |
| 124 | # Check if there's already a reverse IOU (lender owes borrower) |
| 125 | if borrower_name in lender["owes"]: |
| 126 | # There's already a reverse IOU, need to net the amounts |
| 127 | existing_reverse_amount = lender["owes"][borrower_name] |
| 128 | |
| 129 | if amount > existing_reverse_amount: |
| 130 | # New IOU is larger, borrower now owes lender the difference |
| 131 | net_amount = amount - existing_reverse_amount |
| 132 | |
| 133 | # Clear the reverse IOU |
| 134 | del lender["owes"][borrower_name] |
| 135 | del borrower["owed_by"][lender_name] |
| 136 | |
| 137 | # Create the new net IOU |
| 138 | lender["owed_by"][borrower_name] = net_amount |
| 139 | borrower["owes"][lender_name] = net_amount |
| 140 | |
| 141 | # Update balances: lender gains net_amount, borrower loses net_amount |
| 142 | # The existing reverse IOU was cancelled, so we only account for the net amount |
| 143 | lender["balance"] += net_amount |
| 144 | borrower["balance"] -= net_amount |
| 145 | |
| 146 | elif amount < existing_reverse_amount: |
| 147 | # Reverse IOU is larger, lender still owes borrower but less |
| 148 | net_amount = existing_reverse_amount - amount |
| 149 | |
| 150 | # Update the reverse IOU with the net amount |
| 151 | lender["owes"][borrower_name] = net_amount |
| 152 | borrower["owed_by"][lender_name] = net_amount |
| 153 | |
| 154 | # Update balances: lender loses net_amount, borrower gains net_amount |
| 155 | # The existing reverse IOU was reduced, so we account for the difference |
| 156 | lender["balance"] -= net_amount |
| 157 | borrower["balance"] += net_amount |
| 158 | |
| 159 | else: # amount == existing_reverse_amount |
| 160 | # IOUs are equal, create bidirectional IOU |
| 161 | # Clear the existing reverse IOU first |
| 162 | del lender["owes"][borrower_name] |
| 163 | del borrower["owed_by"][lender_name] |
| 164 | |
| 165 | # Create the new bidirectional IOU |
| 166 | lender["owed_by"][borrower_name] = amount |
| 167 | borrower["owes"][lender_name] = amount |
| 168 | |
| 169 | # Update balances to zero since IOUs cancel out net effect |
| 170 | lender["balance"] = 0.0 |
| 171 | borrower["balance"] = 0.0 |
| 172 | else: |
| 173 | # No reverse IOU exists, just add the new IOU |
| 174 | # Update lender's owed_by |
| 175 | if borrower_name in lender["owed_by"]: |
| 176 | lender["owed_by"][borrower_name] += amount |
| 177 | else: |
| 178 | lender["owed_by"][borrower_name] = amount |
| 179 | |
| 180 | # Update borrower's owes |
| 181 | if lender_name in borrower["owes"]: |
| 182 | borrower["owes"][lender_name] += amount |
| 183 | else: |
| 184 | borrower["owes"][lender_name] = amount |
| 185 | |
| 186 | # Update balances |
| 187 | lender["balance"] += amount |
| 188 | borrower["balance"] -= amount |
| 189 | |
| 190 | # Return updated user objects sorted by name |
| 191 | users = [lender, borrower] |
| 192 | users = sorted(users, key=lambda x: x["name"]) |
| 193 | return json.dumps({"users": users}) |
| 194 | |
| 195 | # Handled Edge Cases: No payload, missing fields, same user IOU, negative amount, user does not exist, bidirectional relationships |
| 196 | |
| 197 | # Handled Edge Cases: Initialization with None database |