| 1 | import json |
| 2 | |
| 1 | 3 | class RestAPI: |
| 2 | 4 | def __init__(self, database: dict | None = None): |
| 3 | | pass |
| 4 | | |
| 5 | """ |
| 6 | Initialize the REST API with a database. |
| 7 | |
| 8 | Args: |
| 9 | database: A dictionary containing user data with keys 'users'. |
| 10 | """ |
| 11 | self.database = database if database else {"users": []} |
| 12 | |
| 5 | 13 | def get(self, url: str, payload: str | None = None) -> str: |
| 6 | | pass |
| 7 | | |
| 14 | """ |
| 15 | Handle GET requests to the API. |
| 16 | |
| 17 | Args: |
| 18 | url: The endpoint URL. |
| 19 | payload: Optional JSON payload. |
| 20 | |
| 21 | Returns: |
| 22 | A JSON string response. |
| 23 | """ |
| 24 | if url == "/users": |
| 25 | if payload is None: |
| 26 | # Return all users sorted by name |
| 27 | users = self._get_all_users() |
| 28 | return json.dumps({"users": users}) |
| 29 | else: |
| 30 | # Return specific users sorted by name |
| 31 | data = json.loads(payload) |
| 32 | user_names = data.get("users", []) |
| 33 | |
| 34 | # Edge Case: Empty user list in payload |
| 35 | if not user_names: |
| 36 | return json.dumps({"users": []}) |
| 37 | |
| 38 | users = self._get_users_by_names(user_names) |
| 39 | return json.dumps({"users": users}) |
| 40 | |
| 41 | # Edge Case: Invalid URL |
| 42 | return json.dumps({"error": "Invalid URL"}) |
| 43 | |
| 8 | 44 | def post(self, url: str, payload: str | None = None) -> str: |
| 9 | | pass |
| 45 | """ |
| 46 | Handle POST requests to the API. |
| 47 | |
| 48 | Args: |
| 49 | url: The endpoint URL. |
| 50 | payload: JSON payload. |
| 51 | |
| 52 | Returns: |
| 53 | A JSON string response. |
| 54 | """ |
| 55 | if payload is None: |
| 56 | # Edge Case: Missing payload |
| 57 | return json.dumps({"error": "Payload required"}) |
| 58 | |
| 59 | data = json.loads(payload) |
| 60 | |
| 61 | if url == "/add": |
| 62 | user_name = data.get("user") |
| 63 | |
| 64 | # Edge Case: Missing user name |
| 65 | if not user_name: |
| 66 | return json.dumps({"error": "User name required"}) |
| 67 | |
| 68 | # Edge Case: User already exists |
| 69 | if self._user_exists(user_name): |
| 70 | return json.dumps({"error": "User already exists"}) |
| 71 | |
| 72 | new_user = self._create_user(user_name) |
| 73 | self.database["users"].append(new_user) |
| 74 | return json.dumps(new_user) |
| 75 | |
| 76 | elif url == "/iou": |
| 77 | lender_name = data.get("lender") |
| 78 | borrower_name = data.get("borrower") |
| 79 | amount = data.get("amount") |
| 80 | |
| 81 | # Edge Case: Missing required fields |
| 82 | if not lender_name or not borrower_name or amount is None: |
| 83 | return json.dumps({"error": "Lender, borrower, and amount required"}) |
| 84 | |
| 85 | # Edge Case: Lender and borrower are the same |
| 86 | if lender_name == borrower_name: |
| 87 | return json.dumps({"error": "Lender and borrower cannot be the same"}) |
| 88 | |
| 89 | # Edge Case: Negative amount |
| 90 | if amount < 0: |
| 91 | return json.dumps({"error": "Amount must be non-negative"}) |
| 92 | |
| 93 | # Edge Case: User does not exist |
| 94 | if not self._user_exists(lender_name) or not self._user_exists(borrower_name): |
| 95 | return json.dumps({"error": "Both users must exist"}) |
| 96 | |
| 97 | # Update IOUs |
| 98 | self._update_iou(lender_name, borrower_name, amount) |
| 99 | |
| 100 | # Return updated users |
| 101 | users = self._get_users_by_names([lender_name, borrower_name]) |
| 102 | return json.dumps({"users": users}) |
| 103 | |
| 104 | # Edge Case: Invalid URL |
| 105 | return json.dumps({"error": "Invalid URL"}) |
| 106 | |
| 107 | def _get_all_users(self) -> list: |
| 108 | """ |
| 109 | Get all users sorted by name. |
| 110 | |
| 111 | Returns: |
| 112 | A list of user objects sorted by name. |
| 113 | """ |
| 114 | users = [self._format_user(user) for user in self.database["users"]] |
| 115 | return sorted(users, key=lambda x: x["name"]) |
| 116 | |
| 117 | def _get_users_by_names(self, names: list) -> list: |
| 118 | """ |
| 119 | Get specific users by their names, sorted by name. |
| 120 | |
| 121 | Args: |
| 122 | names: A list of user names. |
| 123 | |
| 124 | Returns: |
| 125 | A list of user objects sorted by name. |
| 126 | """ |
| 127 | users = [] |
| 128 | for user in self.database["users"]: |
| 129 | if user["name"] in names: |
| 130 | users.append(self._format_user(user)) |
| 131 | return sorted(users, key=lambda x: x["name"]) |
| 132 | |
| 133 | def _user_exists(self, name: str) -> bool: |
| 134 | """ |
| 135 | Check if a user exists in the database. |
| 136 | |
| 137 | Args: |
| 138 | name: The name of the user. |
| 139 | |
| 140 | Returns: |
| 141 | True if the user exists, False otherwise. |
| 142 | """ |
| 143 | return any(user["name"] == name for user in self.database["users"]) |
| 144 | |
| 145 | def _create_user(self, name: str) -> dict: |
| 146 | """ |
| 147 | Create a new user object. |
| 148 | |
| 149 | Args: |
| 150 | name: The name of the user. |
| 151 | |
| 152 | Returns: |
| 153 | A new user object. |
| 154 | """ |
| 155 | return { |
| 156 | "name": name, |
| 157 | "owes": {}, |
| 158 | "owed_by": {}, |
| 159 | "balance": 0.0 |
| 160 | } |
| 161 | |
| 162 | def _format_user(self, user: dict) -> dict: |
| 163 | """ |
| 164 | Format a user object, calculating the balance. |
| 165 | |
| 166 | Args: |
| 167 | user: The user object. |
| 168 | |
| 169 | Returns: |
| 170 | A formatted user object with calculated balance. |
| 171 | """ |
| 172 | owes_total = sum(user.get("owes", {}).values()) |
| 173 | owed_by_total = sum(user.get("owed_by", {}).values()) |
| 174 | balance = round(owed_by_total - owes_total, 2) |
| 175 | |
| 176 | # Ensure balance is properly formatted |
| 177 | return { |
| 178 | "name": user["name"], |
| 179 | "owes": user.get("owes", {}), |
| 180 | "owed_by": user.get("owed_by", {}), |
| 181 | "balance": balance |
| 182 | } |
| 183 | |
| 184 | def _update_iou(self, lender_name: str, borrower_name: str, amount: float) -> None: |
| 185 | """ |
| 186 | Update the IOU records between lender and borrower. |
| 187 | |
| 188 | Args: |
| 189 | lender_name: The name of the lender. |
| 190 | borrower_name: The name of the borrower. |
| 191 | amount: The amount of the IOU. |
| 192 | """ |
| 193 | lender = next(user for user in self.database["users"] if user["name"] == lender_name) |
| 194 | borrower = next(user for user in self.database["users"] if user["name"] == borrower_name) |
| 195 | |
| 196 | # Update lender's owed_by |
| 197 | if "owed_by" not in lender: |
| 198 | lender["owed_by"] = {} |
| 199 | if borrower_name in lender["owed_by"]: |
| 200 | lender["owed_by"][borrower_name] += amount |
| 201 | else: |
| 202 | lender["owed_by"][borrower_name] = amount |
| 203 | |
| 204 | # Update borrower's owes |
| 205 | if "owes" not in borrower: |
| 206 | borrower["owes"] = {} |
| 207 | if lender_name in borrower["owes"]: |
| 208 | borrower["owes"][lender_name] += amount |
| 209 | else: |
| 210 | borrower["owes"][lender_name] = amount |
| 211 | |
| 212 | # Edge Case: Handle zero balances by removing entries |
| 213 | if lender["owed_by"][borrower_name] == 0: |
| 214 | del lender["owed_by"][borrower_name] |
| 215 | if not lender["owed_by"]: |
| 216 | del lender["owed_by"] |
| 217 | |
| 218 | if borrower["owes"][lender_name] == 0: |
| 219 | del borrower["owes"][lender_name] |
| 220 | if not borrower["owes"]: |
| 221 | del borrower["owes"] |
| 222 | |
| 223 | # Handled Edge Cases: Invalid URL, Missing payload, Missing user name, User already exists, |
| 224 | # Missing required fields, Lender and borrower are the same, Negative amount, User does not exist, |
| 225 | # Empty user list in payload, Zero balances |