| 1 | import json |
| 2 | from typing import Dict, List, Optional, Any |
| 3 | |
| 1 | 4 | class RestAPI: |
| 5 | """ |
| 6 | A RESTful API for tracking IOUs between users. |
| 7 | |
| 8 | This class manages user accounts and IOU transactions, allowing creation of users, |
| 9 | recording of debts, and retrieval of user balance information. |
| 10 | """ |
| 2 | 11 | def __init__(self, database: dict | None = None): |
| 3 | | pass |
| 4 | | |
| 12 | """ |
| 13 | Initialize the REST API with an optional database. |
| 14 | |
| 15 | Args: |
| 16 | database: Optional initial database with users data |
| 17 | """ |
| 18 | if database and 'users' in database: |
| 19 | # Create users dictionary with name as key for faster access |
| 20 | self.users = {user['name']: user for user in database['users']} |
| 21 | # Ensure all users have the required fields |
| 22 | for user in self.users.values(): |
| 23 | if 'owes' not in user: |
| 24 | user['owes'] = {} |
| 25 | if 'owed_by' not in user: |
| 26 | user['owed_by'] = {} |
| 27 | if 'balance' not in user: |
| 28 | user['balance'] = 0.0 |
| 29 | else: |
| 30 | self.users = {} |
| 31 | |
| 5 | 32 | def get(self, url: str, payload: str | None = None) -> str: |
| 6 | | pass |
| 7 | | |
| 33 | """ |
| 34 | Handle GET requests to the API. |
| 35 | |
| 36 | Args: |
| 37 | url: The endpoint URL |
| 38 | payload: Optional JSON payload |
| 39 | |
| 40 | Returns: |
| 41 | JSON string response |
| 42 | """ |
| 43 | if url == '/users': |
| 44 | # Edge Case: Handle request with no payload (list all users) |
| 45 | if payload is None: |
| 46 | users_list = list(self.users.values()) |
| 47 | users_list.sort(key=lambda x: x['name']) |
| 48 | return json.dumps({"users": users_list}) |
| 49 | |
| 50 | # Edge Case: Handle request with payload (list specific users) |
| 51 | try: |
| 52 | data = json.loads(payload) |
| 53 | if 'users' not in data: |
| 54 | return json.dumps({"error": "Invalid payload format"}) |
| 55 | |
| 56 | # Edge Case: Handle empty users list |
| 57 | if not data['users']: |
| 58 | return json.dumps({"users": []}) |
| 59 | |
| 60 | result_users = [] |
| 61 | for name in data['users']: |
| 62 | # Edge Case: Handle request for non-existent user |
| 63 | if name in self.users: |
| 64 | result_users.append(self.users[name]) |
| 65 | else: |
| 66 | # Create user if they don't exist |
| 67 | new_user = { |
| 68 | "name": name, |
| 69 | "owes": {}, |
| 70 | "owed_by": {}, |
| 71 | "balance": 0.0 |
| 72 | } |
| 73 | self.users[name] = new_user |
| 74 | result_users.append(new_user) |
| 75 | |
| 76 | result_users.sort(key=lambda x: x['name']) |
| 77 | return json.dumps({"users": result_users}) |
| 78 | except json.JSONDecodeError: |
| 79 | return json.dumps({"error": "Invalid JSON payload"}) |
| 80 | |
| 81 | return json.dumps({"error": "Invalid endpoint"}) |
| 82 | |
| 8 | 83 | def post(self, url: str, payload: str | None = None) -> str: |
| 9 | | pass |
| 84 | """ |
| 85 | Handle POST requests to the API. |
| 86 | |
| 87 | Args: |
| 88 | url: The endpoint URL |
| 89 | payload: JSON payload with request data |
| 90 | |
| 91 | Returns: |
| 92 | JSON string response |
| 93 | """ |
| 94 | if payload is None: |
| 95 | return json.dumps({"error": "Payload required"}) |
| 96 | |
| 97 | try: |
| 98 | data = json.loads(payload) |
| 99 | except json.JSONDecodeError: |
| 100 | return json.dumps({"error": "Invalid JSON payload"}) |
| 101 | |
| 102 | if url == '/add': |
| 103 | # Edge Case: Handle missing user field |
| 104 | if 'user' not in data: |
| 105 | return json.dumps({"error": "Missing user field"}) |
| 106 | |
| 107 | name = data['user'] |
| 108 | |
| 109 | # Edge Case: Handle attempt to create duplicate user |
| 110 | if name in self.users: |
| 111 | return json.dumps({"error": "User already exists"}) |
| 112 | |
| 113 | new_user = { |
| 114 | "name": name, |
| 115 | "owes": {}, |
| 116 | "owed_by": {}, |
| 117 | "balance": 0.0 |
| 118 | } |
| 119 | self.users[name] = new_user |
| 120 | return json.dumps(new_user) |
| 121 | |
| 122 | elif url == '/iou': |
| 123 | # Edge Case: Handle missing required fields |
| 124 | required_fields = ['lender', 'borrower', 'amount'] |
| 125 | for field in required_fields: |
| 126 | if field not in data: |
| 127 | return json.dumps({"error": f"Missing {field} field"}) |
| 128 | |
| 129 | lender_name = data['lender'] |
| 130 | borrower_name = data['borrower'] |
| 131 | amount = data['amount'] |
| 132 | |
| 133 | # Edge Case: Handle negative or zero amount |
| 134 | if amount <= 0: |
| 135 | return json.dumps({"error": "Amount must be positive"}) |
| 136 | |
| 137 | # Edge Case: Handle lender and borrower being the same person |
| 138 | if lender_name == borrower_name: |
| 139 | return json.dumps({"error": "Lender and borrower cannot be the same"}) |
| 140 | |
| 141 | # Edge Case: Handle non-existent lender |
| 142 | if lender_name not in self.users: |
| 143 | new_lender = { |
| 144 | "name": lender_name, |
| 145 | "owes": {}, |
| 146 | "owed_by": {}, |
| 147 | "balance": 0.0 |
| 148 | } |
| 149 | self.users[lender_name] = new_lender |
| 150 | |
| 151 | # Edge Case: Handle non-existent borrower |
| 152 | if borrower_name not in self.users: |
| 153 | new_borrower = { |
| 154 | "name": borrower_name, |
| 155 | "owes": {}, |
| 156 | "owed_by": {}, |
| 157 | "balance": 0.0 |
| 158 | } |
| 159 | self.users[borrower_name] = new_borrower |
| 160 | |
| 161 | lender = self.users[lender_name] |
| 162 | borrower = self.users[borrower_name] |
| 163 | |
| 164 | # Update lender's records |
| 165 | if borrower_name in lender['owes']: |
| 166 | lender['owes'][borrower_name] -= amount |
| 167 | # Edge Case: Remove entry if balance becomes zero or negative |
| 168 | if lender['owes'][borrower_name] <= 0: |
| 169 | amount_owed_to_borrower = abs(lender['owes'][borrower_name]) |
| 170 | del lender['owes'][borrower_name] |
| 171 | if amount_owed_to_borrower > 0: |
| 172 | lender['owed_by'][borrower_name] = amount_owed_to_borrower |
| 173 | else: |
| 174 | lender['owed_by'][borrower_name] = lender['owed_by'].get(borrower_name, 0) + amount |
| 175 | |
| 176 | # Update borrower's records |
| 177 | if lender_name in borrower['owed_by']: |
| 178 | borrower['owed_by'][lender_name] -= amount |
| 179 | # Edge Case: Remove entry if balance becomes zero or negative |
| 180 | if borrower['owed_by'][lender_name] <= 0: |
| 181 | amount_owed_to_lender = abs(borrower['owed_by'][lender_name]) |
| 182 | del borrower['owed_by'][lender_name] |
| 183 | if amount_owed_to_lender > 0: |
| 184 | borrower['owes'][lender_name] = amount_owed_to_lender |
| 185 | else: |
| 186 | borrower['owes'][lender_name] = borrower['owes'].get(lender_name, 0) + amount |
| 187 | |
| 188 | # Recalculate balances |
| 189 | lender_owes = sum(lender['owes'].values()) |
| 190 | lender_owed_by = sum(lender['owed_by'].values()) |
| 191 | lender['balance'] = lender_owed_by - lender_owes |
| 192 | |
| 193 | borrower_owes = sum(borrower['owes'].values()) |
| 194 | borrower_owed_by = sum(borrower['owed_by'].values()) |
| 195 | borrower['balance'] = borrower_owed_by - borrower_owes |
| 196 | |
| 197 | # Return updated user objects sorted by name |
| 198 | result_users = [lender, borrower] |
| 199 | result_users.sort(key=lambda x: x['name']) |
| 200 | return json.dumps({"users": result_users}) |
| 201 | |
| 202 | return json.dumps({"error": "Invalid endpoint"}) |
| 203 | |
| 204 | # Handled Edge Cases: Invalid JSON, missing payload, invalid endpoint, |
| 205 | # list all users, list specific users, empty users list, |
| 206 | # non-existent user in list, missing user field in add, |
| 207 | # duplicate user creation, missing fields in IOU, |
| 208 | # negative/zero amount, same lender/borrower, |
| 209 | # non-existent lender/borrower, balance zeroing entries |