| 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. |
| 10 | """ |
| 11 | self.database = database if database is not None 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 | Edge Cases: |
| 25 | - Invalid URL |
| 26 | - Malformed payload |
| 27 | """ |
| 28 | # Edge Case: Invalid URL |
| 29 | if url != "/users": |
| 30 | return json.dumps({"error": "Invalid URL"}) |
| 31 | |
| 32 | # Edge Case: Malformed payload |
| 33 | if payload is not None: |
| 34 | try: |
| 35 | payload_data = json.loads(payload) |
| 36 | except json.JSONDecodeError: |
| 37 | return json.dumps({"error": "Invalid payload"}) |
| 38 | else: |
| 39 | payload_data = None |
| 40 | |
| 41 | users = self.database["users"] |
| 42 | |
| 43 | if payload_data and "users" in payload_data: |
| 44 | # Filter users based on payload |
| 45 | specified_users = payload_data["users"] |
| 46 | filtered_users = [user for user in users if user["name"] in specified_users] |
| 47 | # Sort by name |
| 48 | result_users = sorted(filtered_users, key=lambda x: x["name"]) |
| 49 | else: |
| 50 | # Return all users sorted by name |
| 51 | result_users = sorted(users, key=lambda x: x["name"]) |
| 52 | |
| 53 | return json.dumps({"users": result_users}) |
| 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 | A JSON string response. |
| 65 | |
| 66 | Edge Cases: |
| 67 | - Invalid URL |
| 68 | - Missing or malformed payload |
| 69 | - User already exists (for /add) |
| 70 | - Non-existent users (for /iou) |
| 71 | - Lender and borrower are the same |
| 72 | """ |
| 73 | # Edge Case: Missing payload |
| 74 | if payload is None: |
| 75 | return json.dumps({"error": "Missing payload"}) |
| 76 | |
| 77 | # Edge Case: Malformed payload |
| 78 | try: |
| 79 | payload_data = json.loads(payload) |
| 80 | except json.JSONDecodeError: |
| 81 | return json.dumps({"error": "Invalid payload"}) |
| 82 | |
| 83 | # Edge Case: Invalid URL |
| 84 | if url == "/add": |
| 85 | return self._add_user(payload_data) |
| 86 | elif url == "/iou": |
| 87 | return self._create_iou(payload_data) |
| 88 | else: |
| 89 | return json.dumps({"error": "Invalid URL"}) |
| 90 | |
| 91 | def _add_user(self, payload_data: dict) -> str: |
| 92 | """ |
| 93 | Add a new user to the database. |
| 94 | |
| 95 | Args: |
| 96 | payload_data: Dictionary containing user information. |
| 97 | |
| 98 | Returns: |
| 99 | A JSON string response with the new user object. |
| 100 | |
| 101 | Edge Cases: |
| 102 | - Missing 'user' field |
| 103 | - User already exists |
| 104 | """ |
| 105 | # Edge Case: Missing 'user' field |
| 106 | if "user" not in payload_data: |
| 107 | return json.dumps({"error": "Missing user field"}) |
| 108 | |
| 109 | user_name = payload_data["user"] |
| 110 | |
| 111 | # Edge Case: User already exists |
| 112 | for user in self.database["users"]: |
| 113 | if user["name"] == user_name: |
| 114 | return json.dumps(user) # Return existing user instead of error |
| 115 | |
| 116 | new_user = { |
| 117 | "name": user_name, |
| 118 | "owes": {}, |
| 119 | "owed_by": {}, |
| 120 | "balance": 0.0 |
| 121 | } |
| 122 | |
| 123 | self.database["users"] = sorted(self.database["users"] + [new_user], key=lambda x: x["name"]) |
| 124 | |
| 125 | return json.dumps(new_user) |
| 126 | |
| 127 | def _create_iou(self, payload_data: dict) -> str: |
| 128 | """ |
| 129 | Create an IOU between two users. |
| 130 | |
| 131 | Args: |
| 132 | payload_data: Dictionary containing lender, borrower, and amount. |
| 133 | |
| 134 | Returns: |
| 135 | A JSON string response with updated user objects. |
| 136 | |
| 137 | Edge Cases: |
| 138 | - Missing required fields (lender, borrower, amount) |
| 139 | - Lender and borrower are the same |
| 140 | - Non-existent users |
| 141 | """ |
| 142 | # Edge Case: Missing required fields |
| 143 | required_fields = ["lender", "borrower", "amount"] |
| 144 | for field in required_fields: |
| 145 | if field not in payload_data: |
| 146 | return json.dumps({"error": f"Missing {field} field"}) |
| 147 | |
| 148 | lender_name = payload_data["lender"] |
| 149 | borrower_name = payload_data["borrower"] |
| 150 | amount = payload_data["amount"] |
| 151 | |
| 152 | # Edge Case: Lender and borrower are the same |
| 153 | if lender_name == borrower_name: |
| 154 | return json.dumps({"error": "Lender and borrower cannot be the same"}) |
| 155 | |
| 156 | # Edge Case: Non-existent users |
| 157 | lender = None |
| 158 | borrower = None |
| 159 | for user in self.database["users"]: |
| 160 | if user["name"] == lender_name: |
| 161 | lender = user |
| 162 | if user["name"] == borrower_name: |
| 163 | borrower = user |
| 164 | |
| 165 | if lender is None or borrower is None: |
| 166 | return json.dumps({"error": "User does not exist"}) |
| 167 | |
| 168 | # Handle the IOU transaction by updating both users' records |
| 169 | # Check if there are existing debts that should be handled with the new IOU |
| 170 | |
| 171 | # Case 1: Lender owes borrower (opposite direction to new IOU) |
| 172 | if borrower_name in lender["owes"]: |
| 173 | # Lender owes borrower, check if this exactly cancels out |
| 174 | existing_debt = lender["owes"][borrower_name] |
| 175 | if existing_debt == amount: |
| 176 | # Exactly equal, remove both sides of the debt |
| 177 | del lender["owes"][borrower_name] |
| 178 | if lender_name in borrower["owed_by"]: |
| 179 | del borrower["owed_by"][lender_name] |
| 180 | else: |
| 181 | # Not equal, create independent debt relationship |
| 182 | # Remove existing debt |
| 183 | del lender["owes"][borrower_name] |
| 184 | if lender_name in borrower["owed_by"]: |
| 185 | del borrower["owed_by"][lender_name] |
| 186 | # Create new debt relationship |
| 187 | lender["owed_by"][borrower_name] = amount |
| 188 | borrower["owes"][lender_name] = amount |
| 189 | |
| 190 | # Case 2: Borrower owes lender (same direction as new IOU) |
| 191 | elif lender_name in borrower["owes"]: |
| 192 | # Borrower owes lender, accumulate with existing debt |
| 193 | borrower["owes"][lender_name] += amount |
| 194 | lender["owed_by"][borrower_name] = borrower["owes"][lender_name] |
| 195 | |
| 196 | # Case 3: Borrower is owed by lender (opposite direction to new IOU) |
| 197 | elif lender_name in borrower["owed_by"]: |
| 198 | # Borrower is owed by lender, check if this exactly cancels out |
| 199 | existing_debt = borrower["owed_by"][lender_name] |
| 200 | if existing_debt == amount: |
| 201 | # Exactly equal, remove both sides of the debt |
| 202 | del borrower["owed_by"][lender_name] |
| 203 | if borrower_name in lender["owed_by"]: |
| 204 | del lender["owed_by"][borrower_name] |
| 205 | else: |
| 206 | # Not equal, create independent debt relationship |
| 207 | # Remove existing debt |
| 208 | del borrower["owed_by"][lender_name] |
| 209 | if borrower_name in lender["owed_by"]: |
| 210 | del lender["owed_by"][borrower_name] |
| 211 | # Create new debt relationship |
| 212 | lender["owed_by"][borrower_name] = amount |
| 213 | borrower["owes"][lender_name] = amount |
| 214 | |
| 215 | # Case 4: No existing debt, create new debt relationship |
| 216 | else: |
| 217 | lender["owed_by"][borrower_name] = amount |
| 218 | borrower["owes"][lender_name] = amount |
| 219 | |
| 220 | # Recalculate balances for both users |
| 221 | lender_total_owed = sum(lender["owed_by"].values()) |
| 222 | lender_total_owes = sum(lender["owes"].values()) |
| 223 | lender["balance"] = lender_total_owed - lender_total_owes |
| 224 | |
| 225 | borrower_total_owed = sum(borrower["owed_by"].values()) |
| 226 | borrower_total_owes = sum(borrower["owes"].values()) |
| 227 | borrower["balance"] = borrower_total_owed - borrower_total_owes |
| 228 | |
| 229 | # Clean up empty dictionaries for both users |
| 230 | lender["owes"] = {k: v for k, v in lender["owes"].items() if v != 0} |
| 231 | lender["owed_by"] = {k: v for k, v in lender["owed_by"].items() if v != 0} |
| 232 | borrower["owes"] = {k: v for k, v in borrower["owes"].items() if v != 0} |
| 233 | borrower["owed_by"] = {k: v for k, v in borrower["owed_by"].items() if v != 0} |
| 234 | |
| 235 | # Return updated users sorted by name |
| 236 | updated_users = sorted([lender, borrower], key=lambda x: x["name"]) |
| 237 | |
| 238 | return json.dumps({"users": updated_users}) |
| 239 | |
| 240 | # Handled Edge Cases: Invalid URL, Malformed payload |
| 241 | # Handled Edge Cases: Invalid URL, Missing or malformed payload, User already exists (for /add), Non-existent users (for /iou), Lender and borrower are the same |
| 242 | # Handled Edge Cases: Missing 'user' field, User already exists |
| 243 | # Handled Edge Cases: Missing required fields (lender, borrower, amount), Lender and borrower are the same, Non-existent users |