| 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 an optional database. |
| 8 | |
| 9 | Args: |
| 10 | database: Optional initial database dictionary |
| 11 | """ |
| 12 | if database is None: |
| 13 | self.database = {"users": []} |
| 14 | else: |
| 15 | self.database = database |
| 16 | |
| 17 | def get_user_by_name(self, name: str) -> Optional[Dict]: |
| 18 | """ |
| 19 | Find a user by their name in the database. |
| 20 | |
| 21 | Args: |
| 22 | name: Name of the user to find |
| 23 | |
| 24 | Returns: |
| 25 | User dictionary if found, None otherwise |
| 26 | """ |
| 27 | for user in self.database["users"]: |
| 28 | if user["name"] == name: |
| 29 | return user |
| 30 | return None |
| 31 | |
| 32 | def calculate_balance(self, user: Dict) -> float: |
| 33 | """ |
| 34 | Calculate the balance for a user based on what they owe and are owed. |
| 35 | |
| 36 | Args: |
| 37 | user: User dictionary |
| 38 | |
| 39 | Returns: |
| 40 | Calculated balance |
| 41 | """ |
| 42 | total_owed_by = sum(user["owed_by"].values()) |
| 43 | total_owes = sum(user["owes"].values()) |
| 44 | return round(total_owed_by - total_owes, 2) |
| 45 | |
| 46 | def update_user_balances(self) -> None: |
| 47 | """Update balance for all users in the database.""" |
| 48 | for user in self.database["users"]: |
| 49 | user["balance"] = self.calculate_balance(user) |
| 50 | |
| 5 | 51 | def get(self, url: str, payload: str | None = None) -> str: |
| 6 | | pass |
| 7 | | |
| 52 | """ |
| 53 | Handle GET requests to the API. |
| 54 | |
| 55 | Args: |
| 56 | url: Request URL |
| 57 | payload: Optional JSON payload |
| 58 | |
| 59 | Returns: |
| 60 | JSON response string |
| 61 | """ |
| 62 | # Edge Case: Invalid URL |
| 63 | if url != "/users": |
| 64 | return json.dumps({"error": "Invalid URL"}) |
| 65 | |
| 66 | # Edge Case: Malformed payload |
| 67 | if payload is not None: |
| 68 | try: |
| 69 | payload_data = json.loads(payload) |
| 70 | except json.JSONDecodeError: |
| 71 | return json.dumps({"error": "Invalid payload"}) |
| 72 | else: |
| 73 | payload_data = None |
| 74 | |
| 75 | # Update all user balances before returning data |
| 76 | self.update_user_balances() |
| 77 | |
| 78 | # Edge Case: No users in database |
| 79 | if not self.database["users"]: |
| 80 | return json.dumps({"users": []}) |
| 81 | |
| 82 | # If no payload, return all users |
| 83 | if payload_data is None: |
| 84 | # Sort users by name |
| 85 | sorted_users = sorted(self.database["users"], key=lambda x: x["name"]) |
| 86 | return json.dumps({"users": sorted_users}) |
| 87 | |
| 88 | # Edge Case: Payload missing 'users' key |
| 89 | if "users" not in payload_data: |
| 90 | return json.dumps({"error": "Invalid payload"}) |
| 91 | |
| 92 | # Edge Case: Empty users list in payload |
| 93 | if not payload_data["users"]: |
| 94 | return json.dumps({"users": []}) |
| 95 | |
| 96 | # Filter users based on payload |
| 97 | requested_users = [] |
| 98 | for username in payload_data["users"]: |
| 99 | user = self.get_user_by_name(username) |
| 100 | # Edge Case: Requested user does not exist |
| 101 | if user is not None: |
| 102 | requested_users.append(user) |
| 103 | |
| 104 | # Sort users by name |
| 105 | sorted_users = sorted(requested_users, key=lambda x: x["name"]) |
| 106 | return json.dumps({"users": sorted_users}) |
| 107 | |
| 8 | 108 | def post(self, url: str, payload: str | None = None) -> str: |
| 9 | | pass |
| 109 | """ |
| 110 | Handle POST requests to the API. |
| 111 | |
| 112 | Args: |
| 113 | url: Request URL |
| 114 | payload: Optional JSON payload |
| 115 | |
| 116 | Returns: |
| 117 | JSON response string |
| 118 | """ |
| 119 | # Edge Case: Invalid URL |
| 120 | if url not in ["/add", "/iou"]: |
| 121 | return json.dumps({"error": "Invalid URL"}) |
| 122 | |
| 123 | # Edge Case: Missing payload |
| 124 | if payload is None: |
| 125 | return json.dumps({"error": "Missing payload"}) |
| 126 | |
| 127 | # Edge Case: Malformed payload |
| 128 | try: |
| 129 | payload_data = json.loads(payload) |
| 130 | except json.JSONDecodeError: |
| 131 | return json.dumps({"error": "Invalid payload"}) |
| 132 | |
| 133 | if url == "/add": |
| 134 | # Edge Case: Missing 'user' in payload |
| 135 | if "user" not in payload_data: |
| 136 | return json.dumps({"error": "Missing user"}) |
| 137 | |
| 138 | username = payload_data["user"] |
| 139 | |
| 140 | # Edge Case: User already exists |
| 141 | if self.get_user_by_name(username) is not None: |
| 142 | return json.dumps({"error": "User already exists"}) |
| 143 | |
| 144 | # Create new user |
| 145 | new_user = { |
| 146 | "name": username, |
| 147 | "owes": {}, |
| 148 | "owed_by": {}, |
| 149 | "balance": 0.0 |
| 150 | } |
| 151 | self.database["users"].append(new_user) |
| 152 | return json.dumps(new_user) |
| 153 | |
| 154 | elif url == "/iou": |
| 155 | # Edge Case: Missing required fields in payload |
| 156 | required_fields = ["lender", "borrower", "amount"] |
| 157 | for field in required_fields: |
| 158 | if field not in payload_data: |
| 159 | return json.dumps({"error": f"Missing {field}"}) |
| 160 | |
| 161 | lender_name = payload_data["lender"] |
| 162 | borrower_name = payload_data["borrower"] |
| 163 | amount = payload_data["amount"] |
| 164 | |
| 165 | # Edge Case: Invalid amount type |
| 166 | if not isinstance(amount, (int, float)): |
| 167 | return json.dumps({"error": "Invalid amount"}) |
| 168 | |
| 169 | # Edge Case: Negative amount |
| 170 | if amount < 0: |
| 171 | return json.dumps({"error": "Invalid amount"}) |
| 172 | |
| 173 | # Edge Case: Lender and borrower are the same |
| 174 | if lender_name == borrower_name: |
| 175 | return json.dumps({"error": "Cannot create IOU between same user"}) |
| 176 | |
| 177 | # Find users |
| 178 | lender = self.get_user_by_name(lender_name) |
| 179 | borrower = self.get_user_by_name(borrower_name) |
| 180 | |
| 181 | # Edge Case: Lender does not exist |
| 182 | if lender is None: |
| 183 | return json.dumps({"error": "Lender does not exist"}) |
| 184 | |
| 185 | # Edge Case: Borrower does not exist |
| 186 | if borrower is None: |
| 187 | return json.dumps({"error": "Borrower does not exist"}) |
| 188 | |
| 189 | # Update IOUs |
| 190 | # Update what borrower owes to lender |
| 191 | if lender_name in borrower["owes"]: |
| 192 | borrower["owes"][lender_name] += amount |
| 193 | else: |
| 194 | borrower["owes"][lender_name] = amount |
| 195 | |
| 196 | # Update what lender is owed by borrower |
| 197 | if borrower_name in lender["owed_by"]: |
| 198 | lender["owed_by"][borrower_name] += amount |
| 199 | else: |
| 200 | lender["owed_by"][borrower_name] = amount |
| 201 | |
| 202 | # Handle offsetting debts |
| 203 | # If borrower also owes money to lender in owed_by, offset them |
| 204 | if lender_name in borrower["owed_by"]: |
| 205 | owed_amount = borrower["owed_by"][lender_name] |
| 206 | owes_amount = borrower["owes"][lender_name] |
| 207 | |
| 208 | if owed_amount > owes_amount: |
| 209 | borrower["owed_by"][lender_name] = round(owed_amount - owes_amount, 2) |
| 210 | del borrower["owes"][lender_name] |
| 211 | # Update lender's records |
| 212 | del lender["owed_by"][borrower_name] |
| 213 | lender["owes"][borrower_name] = round(owed_amount - owes_amount, 2) |
| 214 | elif owes_amount > owed_amount: |
| 215 | borrower["owes"][lender_name] = round(owes_amount - owed_amount, 2) |
| 216 | del borrower["owed_by"][lender_name] |
| 217 | # Update lender's records |
| 218 | del lender["owes"][borrower_name] |
| 219 | lender["owed_by"][borrower_name] = round(owes_amount - owed_amount, 2) |
| 220 | else: # They are equal |
| 221 | del borrower["owed_by"][lender_name] |
| 222 | del borrower["owes"][lender_name] |
| 223 | del lender["owed_by"][borrower_name] |
| 224 | del lender["owes"][borrower_name] |
| 225 | |
| 226 | # Update balances |
| 227 | lender["balance"] = self.calculate_balance(lender) |
| 228 | borrower["balance"] = self.calculate_balance(borrower) |
| 229 | |
| 230 | # Return updated users sorted by name |
| 231 | updated_users = sorted([lender, borrower], key=lambda x: x["name"]) |
| 232 | return json.dumps({"users": updated_users}) |
| 233 | |
| 234 | # Handled Edge Cases: Invalid URL, Malformed payload, No users in database, Empty users list in payload, |
| 235 | # Requested user does not exist, Missing 'user' in payload, User already exists, Missing required fields in payload, |
| 236 | # Invalid amount type, Negative amount, Lender and borrower are the same, Lender does not exist, Borrower does not exist |