| 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 an optional database. |
| 7 | |
| 8 | Args: |
| 9 | database: A dictionary containing initial user data. |
| 10 | """ |
| 11 | if database is None: |
| 12 | self.database = {"users": []} |
| 13 | else: |
| 14 | self.database = database |
| 15 | |
| 5 | 16 | def get(self, url: str, payload: str | None = None) -> str: |
| 6 | | pass |
| 7 | | |
| 17 | """ |
| 18 | Handle GET requests to the API. |
| 19 | |
| 20 | Args: |
| 21 | url: The endpoint URL. |
| 22 | payload: Optional JSON payload. |
| 23 | |
| 24 | Returns: |
| 25 | A JSON string response. |
| 26 | |
| 27 | Raises: |
| 28 | ValueError: If the URL is not recognized. |
| 29 | """ |
| 30 | if url == "/users": |
| 31 | if payload is None: |
| 32 | # Return all users |
| 33 | return json.dumps({"users": self._get_all_users()}) |
| 34 | else: |
| 35 | # Return specific users |
| 36 | data = json.loads(payload) |
| 37 | user_names = data.get("users", []) |
| 38 | return json.dumps({"users": self._get_users_by_names(user_names)}) |
| 39 | else: |
| 40 | raise ValueError(f"Unknown URL: {url}") |
| 41 | |
| 8 | 42 | def post(self, url: str, payload: str | None = None) -> str: |
| 9 | | pass |
| 43 | """ |
| 44 | Handle POST requests to the API. |
| 45 | |
| 46 | Args: |
| 47 | url: The endpoint URL. |
| 48 | payload: JSON payload. |
| 49 | |
| 50 | Returns: |
| 51 | A JSON string response. |
| 52 | |
| 53 | Raises: |
| 54 | ValueError: If the URL is not recognized or if required data is missing. |
| 55 | """ |
| 56 | if url == "/add": |
| 57 | if payload is None: |
| 58 | raise ValueError("Payload is required for /add endpoint") |
| 59 | |
| 60 | data = json.loads(payload) |
| 61 | user_name = data.get("user") |
| 62 | |
| 63 | # Edge Case: Missing user name in payload |
| 64 | if user_name is None: |
| 65 | raise ValueError("User name is required") |
| 66 | |
| 67 | # Edge Case: User already exists |
| 68 | if self._find_user(user_name) is not None: |
| 69 | raise ValueError(f"User {user_name} already exists") |
| 70 | |
| 71 | new_user = { |
| 72 | "name": user_name, |
| 73 | "owes": {}, |
| 74 | "owed_by": {}, |
| 75 | "balance": 0.0 |
| 76 | } |
| 77 | |
| 78 | self.database["users"].append(new_user) |
| 79 | |
| 80 | return json.dumps(new_user) |
| 81 | |
| 82 | elif url == "/iou": |
| 83 | if payload is None: |
| 84 | raise ValueError("Payload is required for /iou endpoint") |
| 85 | |
| 86 | data = json.loads(payload) |
| 87 | lender_name = data.get("lender") |
| 88 | borrower_name = data.get("borrower") |
| 89 | amount = data.get("amount") |
| 90 | |
| 91 | # Edge Case: Missing required fields |
| 92 | if lender_name is None or borrower_name is None or amount is None: |
| 93 | raise ValueError("Lender, borrower, and amount are required") |
| 94 | |
| 95 | # Edge Case: Lender and borrower are the same person |
| 96 | if lender_name == borrower_name: |
| 97 | raise ValueError("Lender and borrower cannot be the same person") |
| 98 | |
| 99 | # Edge Case: Negative amount |
| 100 | if amount < 0: |
| 101 | raise ValueError("Amount must be non-negative") |
| 102 | |
| 103 | lender = self._find_user(lender_name) |
| 104 | borrower = self._find_user(borrower_name) |
| 105 | |
| 106 | # Edge Case: Lender or borrower does not exist |
| 107 | if lender is None: |
| 108 | raise ValueError(f"User {lender_name} does not exist") |
| 109 | if borrower is None: |
| 110 | raise ValueError(f"User {borrower_name} does not exist") |
| 111 | |
| 112 | # Update lender's owed_by |
| 113 | if borrower_name in lender["owed_by"]: |
| 114 | lender["owed_by"][borrower_name] += amount |
| 115 | else: |
| 116 | lender["owed_by"][borrower_name] = amount |
| 117 | |
| 118 | # Update borrower's owes |
| 119 | if lender_name in borrower["owes"]: |
| 120 | borrower["owes"][lender_name] += amount |
| 121 | else: |
| 122 | borrower["owes"][lender_name] = amount |
| 123 | |
| 124 | # Update balances |
| 125 | lender["balance"] += amount |
| 126 | borrower["balance"] -= amount |
| 127 | |
| 128 | # Simplify debts if they owe each other |
| 129 | self._simplify_debts(lender, borrower) |
| 130 | |
| 131 | # Return updated users |
| 132 | users = [lender, borrower] |
| 133 | users.sort(key=lambda u: u["name"]) |
| 134 | return json.dumps({"users": users}) |
| 135 | |
| 136 | else: |
| 137 | raise ValueError(f"Unknown URL: {url}") |
| 138 | |
| 139 | def _find_user(self, name: str): |
| 140 | """ |
| 141 | Find a user by name in the database. |
| 142 | |
| 143 | Args: |
| 144 | name: The name of the user to find. |
| 145 | |
| 146 | Returns: |
| 147 | The user dictionary if found, None otherwise. |
| 148 | """ |
| 149 | for user in self.database["users"]: |
| 150 | if user["name"] == name: |
| 151 | return user |
| 152 | return None |
| 153 | |
| 154 | def _get_all_users(self): |
| 155 | """ |
| 156 | Get all users from the database, sorted by name. |
| 157 | |
| 158 | Returns: |
| 159 | A list of all user dictionaries, sorted by name. |
| 160 | """ |
| 161 | return sorted(self.database["users"], key=lambda u: u["name"]) |
| 162 | |
| 163 | def _get_users_by_names(self, names): |
| 164 | """ |
| 165 | Get specific users by their names. |
| 166 | |
| 167 | Args: |
| 168 | names: A list of user names. |
| 169 | |
| 170 | Returns: |
| 171 | A list of user dictionaries for the specified names, sorted by name. |
| 172 | """ |
| 173 | users = [] |
| 174 | for name in names: |
| 175 | user = self._find_user(name) |
| 176 | # Edge Case: Requested user does not exist |
| 177 | if user is not None: |
| 178 | users.append(user) |
| 179 | return sorted(users, key=lambda u: u["name"]) |
| 180 | |
| 181 | def _simplify_debts(self, user1, user2): |
| 182 | """ |
| 183 | Simplify debts between two users if they owe each other. |
| 184 | |
| 185 | Args: |
| 186 | user1: First user dictionary. |
| 187 | user2: Second user dictionary. |
| 188 | """ |
| 189 | name1 = user1["name"] |
| 190 | name2 = user2["name"] |
| 191 | |
| 192 | # Check if they owe each other |
| 193 | owes1to2 = user1["owes"].get(name2, 0) |
| 194 | owes2to1 = user2["owes"].get(name1, 0) |
| 195 | |
| 196 | if owes1to2 > 0 and owes2to1 > 0: |
| 197 | # They owe each other, simplify |
| 198 | if owes1to2 > owes2to1: |
| 199 | # user1 owes more to user2 than user2 owes to user1 |
| 200 | user1["owes"][name2] = owes1to2 - owes2to1 |
| 201 | del user2["owes"][name1] |
| 202 | |
| 203 | user2["owed_by"][name1] = owes1to2 - owes2to1 |
| 204 | del user1["owed_by"][name2] |
| 205 | elif owes2to1 > owes1to2: |
| 206 | # user2 owes more to user1 than user1 owes to user2 |
| 207 | user2["owes"][name1] = owes2to1 - owes1to2 |
| 208 | del user1["owes"][name2] |
| 209 | |
| 210 | user1["owed_by"][name2] = owes2to1 - owes1to2 |
| 211 | del user2["owed_by"][name1] |
| 212 | else: |
| 213 | # They owe exactly the same amount |
| 214 | del user1["owes"][name2] |
| 215 | del user2["owes"][name1] |
| 216 | del user1["owed_by"][name2] |
| 217 | del user2["owed_by"][name1] |
| 218 | |
| 219 | # Remove zero debts |
| 220 | if user1["owes"].get(name2, 0) == 0 and name2 in user1["owes"]: |
| 221 | del user1["owes"][name2] |
| 222 | if user2["owes"].get(name1, 0) == 0 and name1 in user2["owes"]: |
| 223 | del user2["owes"][name1] |
| 224 | if user1["owed_by"].get(name2, 0) == 0 and name2 in user1["owed_by"]: |
| 225 | del user1["owed_by"][name2] |
| 226 | if user2["owed_by"].get(name1, 0) == 0 and name1 in user2["owed_by"]: |
| 227 | del user2["owed_by"][name1] |
| 228 | |
| 229 | # Handled Edge Cases: Missing user name in payload, User already exists, Missing required fields, |
| 230 | # Lender and borrower are the same person, Negative amount, Lender or borrower does not exist, |
| 231 | # Requested user does not exist |