| 1 | import json |
| 2 | |
| 1 | 3 | class RestAPI: |
| 2 | 4 | def __init__(self, database=None): |
| 3 | | pass |
| 5 | if database is None: |
| 6 | self.database = {"users": []} |
| 7 | else: |
| 8 | self.database = database |
| 4 | 9 | |
| 5 | 10 | def get(self, url, payload=None): |
| 6 | | pass |
| 11 | if url == "/users": |
| 12 | if payload is None: |
| 13 | # Return all users |
| 14 | return json.dumps({"users": self._get_all_users_with_balance()}) |
| 15 | else: |
| 16 | # Return specific users |
| 17 | data = json.loads(payload) |
| 18 | users_list = data.get("users", []) |
| 19 | result_users = [] |
| 20 | for user_name in users_list: |
| 21 | user = self._get_user(user_name) |
| 22 | if user: |
| 23 | result_users.append(self._calculate_user_balance(user)) |
| 24 | # Sort by name |
| 25 | result_users.sort(key=lambda x: x["name"]) |
| 26 | return json.dumps({"users": result_users}) |
| 27 | return json.dumps({}) |
| 7 | 28 | |
| 8 | 29 | def post(self, url, payload=None): |
| 9 | | pass |
| 30 | if payload is None: |
| 31 | return json.dumps({}) |
| 32 | |
| 33 | data = json.loads(payload) |
| 34 | |
| 35 | if url == "/add": |
| 36 | user_name = data.get("user") |
| 37 | # Edge Case: Missing user field in payload |
| 38 | if user_name is None: |
| 39 | return json.dumps({}) |
| 40 | |
| 41 | # Edge Case: User already exists |
| 42 | if self._get_user(user_name): |
| 43 | return json.dumps({}) |
| 44 | |
| 45 | new_user = { |
| 46 | "name": user_name, |
| 47 | "owes": {}, |
| 48 | "owed_by": {} |
| 49 | } |
| 50 | self.database["users"].append(new_user) |
| 51 | return json.dumps(self._calculate_user_balance(new_user)) |
| 52 | |
| 53 | elif url == "/iou": |
| 54 | lender_name = data.get("lender") |
| 55 | borrower_name = data.get("borrower") |
| 56 | amount = data.get("amount") |
| 57 | |
| 58 | # Edge Case: Missing required fields |
| 59 | if lender_name is None or borrower_name is None or amount is None: |
| 60 | return json.dumps({}) |
| 61 | |
| 62 | # Edge Case: Invalid amount (negative or zero) |
| 63 | if amount <= 0: |
| 64 | return json.dumps({}) |
| 65 | |
| 66 | # Edge Case: Lender and borrower are the same person |
| 67 | if lender_name == borrower_name: |
| 68 | return json.dumps({}) |
| 69 | |
| 70 | lender = self._get_user(lender_name) |
| 71 | borrower = self._get_user(borrower_name) |
| 72 | |
| 73 | # Edge Case: Non-existent users |
| 74 | if lender is None or borrower is None: |
| 75 | return json.dumps({}) |
| 76 | |
| 77 | # Update lender's owed_by and borrower's owes |
| 78 | # For lender |
| 79 | if borrower_name in lender["owed_by"]: |
| 80 | lender["owed_by"][borrower_name] += amount |
| 81 | else: |
| 82 | lender["owed_by"][borrower_name] = amount |
| 83 | |
| 84 | # For borrower |
| 85 | if lender_name in borrower["owes"]: |
| 86 | borrower["owes"][lender_name] += amount |
| 87 | else: |
| 88 | borrower["owes"][lender_name] = amount |
| 89 | |
| 90 | # Handle offsetting debts |
| 91 | self._offset_debts(lender, borrower_name) |
| 92 | self._offset_debts(borrower, lender_name) |
| 93 | |
| 94 | # Return updated users |
| 95 | updated_lender = self._calculate_user_balance(lender) |
| 96 | updated_borrower = self._calculate_user_balance(borrower) |
| 97 | |
| 98 | result = [updated_lender, updated_borrower] |
| 99 | result.sort(key=lambda x: x["name"]) |
| 100 | return json.dumps({"users": result}) |
| 101 | |
| 102 | return json.dumps({}) |
| 103 | |
| 104 | def _get_user(self, name): |
| 105 | for user in self.database["users"]: |
| 106 | if user["name"] == name: |
| 107 | return user |
| 108 | return None |
| 109 | |
| 110 | def _calculate_user_balance(self, user): |
| 111 | total_owed_by = sum(user["owed_by"].values()) |
| 112 | total_owes = sum(user["owes"].values()) |
| 113 | balance = round(total_owed_by - total_owes, 2) |
| 114 | # Handle floating point precision issues |
| 115 | if balance == -0.0: |
| 116 | balance = 0.0 |
| 117 | return { |
| 118 | "name": user["name"], |
| 119 | "owes": user["owes"], |
| 120 | "owed_by": user["owed_by"], |
| 121 | "balance": balance |
| 122 | } |
| 123 | |
| 124 | def _get_all_users_with_balance(self): |
| 125 | users_with_balance = [] |
| 126 | for user in self.database["users"]: |
| 127 | users_with_balance.append(self._calculate_user_balance(user)) |
| 128 | users_with_balance.sort(key=lambda x: x["name"]) |
| 129 | return users_with_balance |
| 130 | |
| 131 | def _offset_debts(self, user, other_user_name): |
| 132 | owes_amount = user["owes"].get(other_user_name, 0) |
| 133 | owed_by_amount = user["owed_by"].get(other_user_name, 0) |
| 134 | |
| 135 | if owes_amount > 0 and owed_by_amount > 0: |
| 136 | if owes_amount > owed_by_amount: |
| 137 | user["owes"][other_user_name] = round(owes_amount - owed_by_amount, 2) |
| 138 | # Edge Case: Remove zero balances |
| 139 | if user["owes"][other_user_name] == 0: |
| 140 | del user["owes"][other_user_name] |
| 141 | del user["owed_by"][other_user_name] |
| 142 | elif owed_by_amount > owes_amount: |
| 143 | user["owed_by"][other_user_name] = round(owed_by_amount - owes_amount, 2) |
| 144 | # Edge Case: Remove zero balances |
| 145 | if user["owed_by"][other_user_name] == 0: |
| 146 | del user["owed_by"][other_user_name] |
| 147 | del user["owes"][other_user_name] |
| 148 | else: # amounts are equal |
| 149 | del user["owes"][other_user_name] |
| 150 | del user["owed_by"][other_user_name] |
| 151 | |
| 152 | # Handled Edge Cases: Missing user field, duplicate user creation, non-existent users in IOU requests, |
| 153 | # invalid amount values (negative/zero), self-borrowing, missing required fields, empty payload, |
| 154 | # floating point precision issues, removal of zero balances |