| 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 | # Edge Case: Handle None database by initializing empty users list |
| 12 | self.database = database if database is not None else {"users": []} |
| 13 | |
| 5 | 14 | def get(self, url: str, payload: str | None = None) -> str: |
| 6 | | pass |
| 7 | | |
| 15 | """ |
| 16 | Handle GET requests to the API. |
| 17 | |
| 18 | Args: |
| 19 | url: The endpoint URL. |
| 20 | payload: Optional JSON payload. |
| 21 | |
| 22 | Returns: |
| 23 | JSON string response. |
| 24 | """ |
| 25 | # Edge Case: Handle /users endpoint |
| 26 | if url == "/users": |
| 27 | # Edge Case: Handle payload with specific users |
| 28 | if payload is not None: |
| 29 | data = json.loads(payload) |
| 30 | if "users" in data: |
| 31 | # Edge Case: Filter users by provided list and sort by name |
| 32 | users_list = [user for user in self.database["users"] if user["name"] in data["users"]] |
| 33 | users_list.sort(key=lambda x: x["name"]) |
| 34 | return json.dumps({"users": users_list}) |
| 35 | # Edge Case: Return all users sorted by name when no payload or no users specified |
| 36 | all_users = sorted(self.database["users"], key=lambda x: x["name"]) |
| 37 | return json.dumps({"users": all_users}) |
| 38 | # Edge Case: Return empty response for unknown endpoints |
| 39 | return json.dumps({}) |
| 40 | |
| 8 | 41 | def post(self, url: str, payload: str | None = None) -> str: |
| 9 | | pass |
| 42 | """ |
| 43 | Handle POST requests to the API. |
| 44 | |
| 45 | Args: |
| 46 | url: The endpoint URL. |
| 47 | payload: JSON payload. |
| 48 | |
| 49 | Returns: |
| 50 | JSON string response. |
| 51 | """ |
| 52 | # Edge Case: Handle None payload |
| 53 | if payload is None: |
| 54 | return json.dumps({}) |
| 55 | |
| 56 | data = json.loads(payload) |
| 57 | |
| 58 | # Edge Case: Handle /add endpoint for creating new users |
| 59 | if url == "/add": |
| 60 | # Edge Case: Check if user field exists in payload |
| 61 | if "user" not in data: |
| 62 | return json.dumps({}) |
| 63 | |
| 64 | user_name = data["user"] |
| 65 | |
| 66 | # Edge Case: Check if user already exists |
| 67 | for user in self.database["users"]: |
| 68 | if user["name"] == user_name: |
| 69 | return json.dumps({}) |
| 70 | |
| 71 | # Edge Case: Create new user with default values |
| 72 | new_user = { |
| 73 | "name": user_name, |
| 74 | "owes": {}, |
| 75 | "owed_by": {}, |
| 76 | "balance": 0.0 |
| 77 | } |
| 78 | self.database["users"].append(new_user) |
| 79 | return json.dumps(new_user) |
| 80 | |
| 81 | # Edge Case: Handle /iou endpoint for creating IOUs |
| 82 | elif url == "/iou": |
| 83 | # Edge Case: Validate required fields in payload |
| 84 | if "lender" not in data or "borrower" not in data or "amount" not in data: |
| 85 | return json.dumps({}) |
| 86 | |
| 87 | lender_name = data["lender"] |
| 88 | borrower_name = data["borrower"] |
| 89 | amount = data["amount"] |
| 90 | |
| 91 | # Edge Case: Validate amount is a positive number |
| 92 | if not isinstance(amount, (int, float)) or amount < 0: |
| 93 | return json.dumps({}) |
| 94 | |
| 95 | # Edge Case: Validate lender and borrower are different |
| 96 | if lender_name == borrower_name: |
| 97 | return json.dumps({}) |
| 98 | |
| 99 | lender = None |
| 100 | borrower = None |
| 101 | |
| 102 | # Edge Case: Find lender and borrower in database |
| 103 | for user in self.database["users"]: |
| 104 | if user["name"] == lender_name: |
| 105 | lender = user |
| 106 | elif user["name"] == borrower_name: |
| 107 | borrower = user |
| 108 | |
| 109 | # Edge Case: Validate both lender and borrower exist |
| 110 | if lender is None or borrower is None: |
| 111 | return json.dumps({}) |
| 112 | |
| 113 | # Handle debt netting logic |
| 114 | # If lender already owes borrower, reduce that debt first |
| 115 | if borrower_name in lender["owes"]: |
| 116 | existing_debt = lender["owes"][borrower_name] |
| 117 | if existing_debt > amount: |
| 118 | # Lender still owes borrower after this transaction |
| 119 | lender["owes"][borrower_name] = existing_debt - amount |
| 120 | borrower["owed_by"][lender_name] = existing_debt - amount |
| 121 | # Remove any conflicting entries |
| 122 | if borrower_name in lender["owed_by"]: |
| 123 | del lender["owed_by"][borrower_name] |
| 124 | if lender_name in borrower["owes"]: |
| 125 | del borrower["owes"][lender_name] |
| 126 | elif existing_debt == amount: |
| 127 | # Debts exactly cancel out - remove all debt relationships |
| 128 | del lender["owes"][borrower_name] |
| 129 | if lender_name in borrower["owed_by"]: |
| 130 | del borrower["owed_by"][lender_name] |
| 131 | # Remove any conflicting entries |
| 132 | if borrower_name in lender["owed_by"]: |
| 133 | del lender["owed_by"][borrower_name] |
| 134 | if lender_name in borrower["owes"]: |
| 135 | del borrower["owes"][lender_name] |
| 136 | else: |
| 137 | # Borrower now owes lender (net amount) |
| 138 | del lender["owes"][borrower_name] |
| 139 | if lender_name in borrower["owed_by"]: |
| 140 | del borrower["owed_by"][lender_name] |
| 141 | lender["owed_by"][borrower_name] = amount - existing_debt |
| 142 | borrower["owes"][lender_name] = amount - existing_debt |
| 143 | # Remove any conflicting entries |
| 144 | if lender_name in borrower["owed_by"]: |
| 145 | del borrower["owed_by"][lender_name] |
| 146 | if borrower_name in lender["owes"]: |
| 147 | del lender["owes"][borrower_name] |
| 148 | else: |
| 149 | # Normal case: lender doesn't already owe borrower |
| 150 | # Update lender's owed_by |
| 151 | if borrower_name in lender["owed_by"]: |
| 152 | lender["owed_by"][borrower_name] += amount |
| 153 | else: |
| 154 | lender["owed_by"][borrower_name] = amount |
| 155 | |
| 156 | # Update borrower's owes |
| 157 | if lender_name in borrower["owes"]: |
| 158 | borrower["owes"][lender_name] += amount |
| 159 | else: |
| 160 | borrower["owes"][lender_name] = amount |
| 161 | |
| 162 | # Recalculate balances |
| 163 | lender_total_owed = sum(lender["owed_by"].values()) |
| 164 | lender_total_owes = sum(lender["owes"].values()) |
| 165 | lender["balance"] = lender_total_owed - lender_total_owes |
| 166 | |
| 167 | borrower_total_owed = sum(borrower["owed_by"].values()) |
| 168 | borrower_total_owes = sum(borrower["owes"].values()) |
| 169 | borrower["balance"] = borrower_total_owed - borrower_total_owes |
| 170 | |
| 171 | # Edge Case: Return updated user objects sorted by name |
| 172 | result_users = sorted([lender, borrower], key=lambda x: x["name"]) |
| 173 | return json.dumps({"users": result_users}) |
| 174 | |
| 175 | # Edge Case: Return empty response for unknown endpoints |
| 176 | return json.dumps({}) |
| 177 | |
| 178 | # Handled Edge Cases: None database, /users endpoint, payload with specific users, |
| 179 | # all users when no payload, unknown endpoints, None payload in POST, /add endpoint, |
| 180 | # missing user field, duplicate user, /iou endpoint, missing required fields, |
| 181 | # invalid amount, lender equals borrower, lender/borrower not found, |
| 182 | # updating existing debts, recalculating balances, unknown POST endpoints |
| 183 | |
| 184 | # Handled Edge Cases: None database, /users endpoint with and without payload, |
| 185 | # filtering and sorting users, unknown endpoints, None payload in POST, |
| 186 | # /add endpoint with missing user field and duplicate user, |
| 187 | # /iou endpoint with missing fields, invalid amount, same lender/borrower, |
| 188 | # non-existent users, updating debts, recalculating balances, unknown POST endpoints |