| 1 | | class RestAPI: |
| 2 | | def __init__(self, database: dict | None = None): |
| 3 | | pass |
| 1 | import json |
| 2 | import sqlite3 |
| 3 | from typing import Dict, List, Optional |
| 4 | 4 | |
| 5 | | def get(self, url: str, payload: str | None = None) -> str: |
| 6 | | pass |
| 5 | class RestAPI: |
| 6 | """ |
| 7 | A RESTful API for tracking IOUs between users. |
| 8 | |
| 9 | This class provides methods to handle GET and POST requests for managing users |
| 10 | and their IOUs (I Owe You) using an SQLite database for persistence. |
| 11 | """ |
| 12 | |
| 13 | def __init__(self, database: Optional[Dict] = None): |
| 14 | """ |
| 15 | Initialize the RestAPI with an optional initial database. |
| 16 | |
| 17 | Args: |
| 18 | database: Optional dictionary containing initial user data. |
| 19 | """ |
| 20 | # Create an in-memory SQLite database |
| 21 | self.conn = sqlite3.connect(':memory:', check_same_thread=False) |
| 22 | self.conn.row_factory = sqlite3.Row # Enable column access by name |
| 23 | self.cursor = self.conn.cursor() |
| 24 | |
| 25 | # Create tables |
| 26 | self.cursor.execute(''' |
| 27 | CREATE TABLE users ( |
| 28 | name TEXT PRIMARY KEY |
| 29 | ) |
| 30 | ''') |
| 31 | |
| 32 | self.cursor.execute(''' |
| 33 | CREATE TABLE ious ( |
| 34 | id INTEGER PRIMARY KEY AUTOINCREMENT, |
| 35 | lender TEXT, |
| 36 | borrower TEXT, |
| 37 | amount REAL, |
| 38 | FOREIGN KEY(lender) REFERENCES users(name), |
| 39 | FOREIGN KEY(borrower) REFERENCES users(name) |
| 40 | ) |
| 41 | ''') |
| 42 | |
| 43 | self.conn.commit() |
| 44 | |
| 45 | # Load initial data if provided |
| 46 | if database and 'users' in database: |
| 47 | for user_data in database['users']: |
| 48 | self._add_user(user_data['name']) |
| 49 | |
| 50 | # Add owed amounts |
| 51 | if 'owed_by' in user_data: |
| 52 | for borrower, amount in user_data['owed_by'].items(): |
| 53 | self._add_user(borrower) |
| 54 | self.cursor.execute( |
| 55 | 'INSERT INTO ious (lender, borrower, amount) VALUES (?, ?, ?)', |
| 56 | (user_data['name'], borrower, amount) |
| 57 | ) |
| 58 | |
| 59 | # Add owed amounts (from other perspective) |
| 60 | if 'owes' in user_data: |
| 61 | for lender, amount in user_data['owes'].items(): |
| 62 | self._add_user(lender) |
| 63 | self.cursor.execute( |
| 64 | 'INSERT INTO ious (lender, borrower, amount) VALUES (?, ?, ?)', |
| 65 | (lender, user_data['name'], amount) |
| 66 | ) |
| 67 | |
| 68 | self.conn.commit() |
| 69 | |
| 70 | def _add_user(self, name: str) -> None: |
| 71 | """ |
| 72 | Add a user to the database if they don't already exist. |
| 73 | |
| 74 | Args: |
| 75 | name: The name of the user to add. |
| 76 | """ |
| 77 | # Edge Case: Prevent duplicate user creation |
| 78 | self.cursor.execute('INSERT OR IGNORE INTO users (name) VALUES (?)', (name,)) |
| 79 | self.conn.commit() |
| 80 | |
| 81 | def _get_user(self, name: str) -> Optional[Dict]: |
| 82 | """ |
| 83 | Get a user's information. |
| 84 | |
| 85 | Args: |
| 86 | name: The name of the user to retrieve. |
| 87 | |
| 88 | Returns: |
| 89 | A dictionary representing the user, or None if not found. |
| 90 | """ |
| 91 | # Edge Case: Check if user exists |
| 92 | self.cursor.execute('SELECT name FROM users WHERE name = ?', (name,)) |
| 93 | if not self.cursor.fetchone(): |
| 94 | return None |
| 95 | |
| 96 | # Calculate amounts owed by this user |
| 97 | self.cursor.execute( |
| 98 | 'SELECT borrower, SUM(amount) as total FROM ious WHERE lender = ? GROUP BY borrower', |
| 99 | (name,) |
| 100 | ) |
| 101 | owed_by = {row['borrower']: row['total'] for row in self.cursor.fetchall()} |
| 102 | |
| 103 | # Calculate amounts this user owes |
| 104 | self.cursor.execute( |
| 105 | 'SELECT lender, SUM(amount) as total FROM ious WHERE borrower = ? GROUP BY lender', |
| 106 | (name,) |
| 107 | ) |
| 108 | owes = {row['lender']: row['total'] for row in self.cursor.fetchall()} |
| 109 | |
| 110 | # Calculate balance |
| 111 | total_owed_by = sum(owed_by.values()) |
| 112 | total_owes = sum(owes.values()) |
| 113 | balance = round(total_owed_by - total_owes, 2) |
| 114 | |
| 115 | return { |
| 116 | 'name': name, |
| 117 | 'owes': owes, |
| 118 | 'owed_by': owed_by, |
| 119 | 'balance': balance |
| 120 | } |
| 121 | |
| 122 | def get(self, url: str, payload: Optional[str] = None) -> str: |
| 123 | """ |
| 124 | Handle GET requests. |
| 125 | |
| 126 | Args: |
| 127 | url: The endpoint URL. |
| 128 | payload: Optional JSON payload. |
| 129 | |
| 130 | Returns: |
| 131 | A JSON string response. |
| 132 | |
| 133 | Raises: |
| 134 | ValueError: If the URL is not recognized. |
| 135 | """ |
| 136 | if url == '/users': |
| 137 | # Edge Case: Handle invalid JSON payload |
| 138 | try: |
| 139 | data = json.loads(payload) if payload else {} |
| 140 | except json.JSONDecodeError: |
| 141 | return json.dumps({'error': 'Invalid JSON payload'}) |
| 142 | |
| 143 | # Get all users |
| 144 | self.cursor.execute('SELECT name FROM users ORDER BY name') |
| 145 | all_users = [row['name'] for row in self.cursor.fetchall()] |
| 146 | |
| 147 | # Filter by specified users if provided |
| 148 | if 'users' in data and data['users']: |
| 149 | # Edge Case: Filter only existing users |
| 150 | specified_users = set(data['users']) |
| 151 | user_list = [user for user in all_users if user in specified_users] |
| 152 | else: |
| 153 | user_list = all_users |
| 154 | |
| 155 | # Get user details |
| 156 | users = [self._get_user(name) for name in user_list] |
| 157 | # Edge Case: Remove None values for non-existent users |
| 158 | users = [user for user in users if user is not None] |
| 159 | |
| 160 | return json.dumps({'users': users}) |
| 161 | |
| 162 | # Edge Case: Handle unrecognized URLs |
| 163 | return json.dumps({'error': 'Invalid URL'}) |
| 164 | |
| 165 | def post(self, url: str, payload: Optional[str] = None) -> str: |
| 166 | """ |
| 167 | Handle POST requests. |
| 168 | |
| 169 | Args: |
| 170 | url: The endpoint URL. |
| 171 | payload: Optional JSON payload. |
| 172 | |
| 173 | Returns: |
| 174 | A JSON string response. |
| 175 | |
| 176 | Raises: |
| 177 | ValueError: If the URL is not recognized or payload is invalid. |
| 178 | """ |
| 179 | # Edge Case: Handle missing payload |
| 180 | if not payload: |
| 181 | return json.dumps({'error': 'Missing payload'}) |
| 182 | |
| 183 | # Edge Case: Handle invalid JSON payload |
| 184 | try: |
| 185 | data = json.loads(payload) |
| 186 | except json.JSONDecodeError: |
| 187 | return json.dumps({'error': 'Invalid JSON payload'}) |
| 188 | |
| 189 | if url == '/add': |
| 190 | # Edge Case: Handle missing user field |
| 191 | if 'user' not in data: |
| 192 | return json.dumps({'error': 'Missing user field'}) |
| 193 | |
| 194 | name = data['user'] |
| 195 | |
| 196 | # Edge Case: Handle empty user name |
| 197 | if not name: |
| 198 | return json.dumps({'error': 'User name cannot be empty'}) |
| 199 | |
| 200 | # Add user |
| 201 | self._add_user(name) |
| 202 | |
| 203 | # Return user object |
| 204 | user = self._get_user(name) |
| 205 | return json.dumps(user) |
| 206 | |
| 207 | elif url == '/iou': |
| 208 | # Edge Case: Validate required fields |
| 209 | required_fields = ['lender', 'borrower', 'amount'] |
| 210 | for field in required_fields: |
| 211 | if field not in data: |
| 212 | return json.dumps({'error': f'Missing {field} field'}) |
| 213 | |
| 214 | lender = data['lender'] |
| 215 | borrower = data['borrower'] |
| 216 | amount = data['amount'] |
| 217 | |
| 218 | # Edge Case: Validate amount is a positive number |
| 219 | if not isinstance(amount, (int, float)) or amount <= 0: |
| 220 | return json.dumps({'error': 'Amount must be a positive number'}) |
| 221 | |
| 222 | # Edge Case: Validate lender and borrower are different |
| 223 | if lender == borrower: |
| 224 | return json.dumps({'error': 'Lender and borrower cannot be the same'}) |
| 225 | |
| 226 | # Add users if they don't exist |
| 227 | self._add_user(lender) |
| 228 | self._add_user(borrower) |
| 229 | |
| 230 | # Add IOU |
| 231 | self.cursor.execute( |
| 232 | 'INSERT INTO ious (lender, borrower, amount) VALUES (?, ?, ?)', |
| 233 | (lender, borrower, amount) |
| 234 | ) |
| 235 | self.conn.commit() |
| 236 | |
| 237 | # Return updated user objects |
| 238 | lender_obj = self._get_user(lender) |
| 239 | borrower_obj = self._get_user(borrower) |
| 240 | |
| 241 | # Edge Case: Handle database inconsistency |
| 242 | if not lender_obj or not borrower_obj: |
| 243 | return json.dumps({'error': 'Failed to retrieve user data'}) |
| 244 | |
| 245 | return json.dumps({'users': sorted([lender_obj, borrower_obj], key=lambda x: x['name'])}) |
| 246 | |
| 247 | # Edge Case: Handle unrecognized URLs |
| 248 | return json.dumps({'error': 'Invalid URL'}) |
| 249 | |
| 250 | def __del__(self): |
| 251 | """ |
| 252 | Close the database connection when the object is destroyed. |
| 253 | """ |
| 254 | if hasattr(self, 'conn'): |
| 255 | self.conn.close() |
| 7 | 256 | |
| 8 | | def post(self, url: str, payload: str | None = None) -> str: |
| 9 | | pass |
| 257 | # Handled Edge Cases: |
| 258 | # - Prevent duplicate user creation |
| 259 | # - Check if user exists |
| 260 | # - Handle invalid JSON payload |
| 261 | # - Filter only existing users |
| 262 | # - Remove None values for non-existent users |
| 263 | # - Handle unrecognized URLs |
| 264 | # - Handle missing payload |
| 265 | # - Handle missing user field |
| 266 | # - Handle empty user name |
| 267 | # - Validate required fields |
| 268 | # - Validate amount is a positive number |
| 269 | # - Validate lender and borrower are different |
| 270 | # - Handle database inconsistency |