| 1 | import json |
| 2 | from typing import Dict, Any, List, Optional |
| 3 | |
| 1 | 4 | class RestAPI: |
| 2 | 5 | def __init__(self, database: dict | None = None): |
| 3 | | pass |
| 6 | if database is None: |
| 7 | self.database = {"users": []} |
| 8 | else: |
| 9 | self.database = database |
| 10 | |
| 11 | def _get_user(self, name: str) -> Optional[Dict[str, Any]]: |
| 12 | """Helper method to get a user by name""" |
| 13 | for user in self.database["users"]: |
| 14 | if user["name"] == name: |
| 15 | return user |
| 16 | return None |
| 17 | |
| 18 | def _create_user(self, name: str) -> Dict[str, Any]: |
| 19 | """Helper method to create a new user""" |
| 20 | user = { |
| 21 | "name": name, |
| 22 | "owes": {}, |
| 23 | "owed_by": {}, |
| 24 | "balance": 0.0 |
| 25 | } |
| 26 | self.database["users"].append(user) |
| 27 | return user |
| 28 | |
| 29 | def _calculate_balance(self, user: Dict[str, Any]) -> float: |
| 30 | """Helper method to calculate user's balance""" |
| 31 | total_owed_by_others = sum(user["owed_by"].values()) |
| 32 | total_owed_to_others = sum(user["owes"].values()) |
| 33 | return round(total_owed_by_others - total_owed_to_others, 2) |
| 34 | |
| 35 | def _update_balances(self, lender_name: str, borrower_name: str) -> None: |
| 36 | """Helper method to update balances for lender and borrower""" |
| 37 | lender = self._get_user(lender_name) |
| 38 | borrower = self._get_user(borrower_name) |
| 39 | |
| 40 | if lender: |
| 41 | lender["balance"] = self._calculate_balance(lender) |
| 42 | if borrower: |
| 43 | borrower["balance"] = self._calculate_balance(borrower) |
| 4 | 44 | |
| 5 | 45 | def get(self, url: str, payload: str | None = None) -> str: |
| 6 | | pass |
| 7 | | |
| 46 | # Edge Case: Invalid URL |
| 47 | if url != "/users": |
| 48 | return json.dumps({"error": "Invalid URL"}) |
| 49 | |
| 50 | # Edge Case: Malformed payload |
| 51 | if payload is not None: |
| 52 | try: |
| 53 | payload_data = json.loads(payload) |
| 54 | except json.JSONDecodeError: |
| 55 | return json.dumps({"error": "Invalid payload"}) |
| 56 | else: |
| 57 | payload_data = None |
| 58 | |
| 59 | users = self.database["users"] |
| 60 | |
| 61 | # If no payload, return all users |
| 62 | if payload_data is None or "users" not in payload_data: |
| 63 | # Edge Case: No users in database |
| 64 | if not users: |
| 65 | return json.dumps({"users": []}) |
| 66 | result_users = users |
| 67 | else: |
| 68 | # Edge Case: Empty users list in payload |
| 69 | if not payload_data["users"]: |
| 70 | return json.dumps({"users": []}) |
| 71 | |
| 72 | # Filter users by names in payload |
| 73 | result_users = [] |
| 74 | for user_name in payload_data["users"]: |
| 75 | user = self._get_user(user_name) |
| 76 | # Edge Case: Requested user does not exist |
| 77 | if user is not None: |
| 78 | result_users.append(user) |
| 79 | |
| 80 | # Edge Case: None of the requested users exist |
| 81 | if not result_users: |
| 82 | return json.dumps({"users": []}) |
| 83 | |
| 84 | # Sort users by name |
| 85 | result_users.sort(key=lambda x: x["name"]) |
| 86 | |
| 87 | # Create response with updated balances |
| 88 | response_users = [] |
| 89 | for user in result_users: |
| 90 | response_user = user.copy() |
| 91 | response_user["balance"] = self._calculate_balance(user) |
| 92 | response_users.append(response_user) |
| 93 | |
| 94 | return json.dumps({"users": response_users}) |
| 95 | |
| 8 | 96 | def post(self, url: str, payload: str | None = None) -> str: |
| 9 | | pass |
| 97 | # Edge Case: Malformed payload |
| 98 | if payload is None: |
| 99 | return json.dumps({"error": "Payload required"}) |
| 100 | |
| 101 | try: |
| 102 | payload_data = json.loads(payload) |
| 103 | except json.JSONDecodeError: |
| 104 | return json.dumps({"error": "Invalid payload"}) |
| 105 | |
| 106 | if url == "/add": |
| 107 | # Edge Case: Missing user field |
| 108 | if "user" not in payload_data: |
| 109 | return json.dumps({"error": "Missing user field"}) |
| 110 | |
| 111 | user_name = payload_data["user"] |
| 112 | |
| 113 | # Edge Case: User already exists |
| 114 | if self._get_user(user_name) is not None: |
| 115 | return json.dumps({"error": "User already exists"}) |
| 116 | |
| 117 | # Create new user |
| 118 | new_user = self._create_user(user_name) |
| 119 | return json.dumps(new_user) |
| 120 | |
| 121 | elif url == "/iou": |
| 122 | # Edge Case: Missing required fields |
| 123 | required_fields = ["lender", "borrower", "amount"] |
| 124 | for field in required_fields: |
| 125 | if field not in payload_data: |
| 126 | return json.dumps({"error": f"Missing {field} field"}) |
| 127 | |
| 128 | lender_name = payload_data["lender"] |
| 129 | borrower_name = payload_data["borrower"] |
| 130 | amount = payload_data["amount"] |
| 131 | |
| 132 | # Edge Case: Lender and borrower are the same person |
| 133 | if lender_name == borrower_name: |
| 134 | return json.dumps({"error": "Lender and borrower cannot be the same person"}) |
| 135 | |
| 136 | # Edge Case: Negative or zero amount |
| 137 | if amount <= 0: |
| 138 | return json.dumps({"error": "Amount must be positive"}) |
| 139 | |
| 140 | # Get or create lender |
| 141 | lender = self._get_user(lender_name) |
| 142 | if lender is None: |
| 143 | lender = self._create_user(lender_name) |
| 144 | |
| 145 | # Get or create borrower |
| 146 | borrower = self._get_user(borrower_name) |
| 147 | if borrower is None: |
| 148 | borrower = self._create_user(borrower_name) |
| 149 | |
| 150 | # Update IOUs |
| 151 | # When borrower borrows from lender: |
| 152 | # - borrower owes lender amount |
| 153 | # - lender is owed by borrower amount |
| 154 | |
| 155 | # Update what borrower owes to lender |
| 156 | borrower["owes"][lender_name] = borrower["owes"].get(lender_name, 0) + amount |
| 157 | |
| 158 | # Update what lender is owed by borrower |
| 159 | lender["owed_by"][borrower_name] = lender["owed_by"].get(borrower_name, 0) + amount |
| 160 | |
| 161 | # Net reverse relationships if they exist |
| 162 | # Check if there are reverse relationships that should be netted |
| 163 | borrower_owes_lender = borrower["owes"].get(lender_name, 0) |
| 164 | borrower_is_owed_by_lender = borrower["owed_by"].get(lender_name, 0) |
| 165 | |
| 166 | lender_owes_borrower = lender["owes"].get(borrower_name, 0) |
| 167 | lender_is_owed_by_borrower = lender["owed_by"].get(borrower_name, 0) |
| 168 | |
| 169 | # Calculate net amounts |
| 170 | net_borrower_owes = borrower_owes_lender - borrower_is_owed_by_lender |
| 171 | net_lender_owes = lender_owes_borrower - lender_is_owed_by_borrower |
| 172 | |
| 173 | # Update dictionaries based on net amounts |
| 174 | if net_borrower_owes > 0: |
| 175 | borrower["owes"][lender_name] = net_borrower_owes |
| 176 | if lender_name in borrower["owed_by"]: |
| 177 | del borrower["owed_by"][lender_name] |
| 178 | elif net_borrower_owes < 0: |
| 179 | if lender_name in borrower["owes"]: |
| 180 | del borrower["owes"][lender_name] |
| 181 | borrower["owed_by"][lender_name] = -net_borrower_owes |
| 182 | else: |
| 183 | # They owe each other nothing |
| 184 | if lender_name in borrower["owes"]: |
| 185 | del borrower["owes"][lender_name] |
| 186 | if lender_name in borrower["owed_by"]: |
| 187 | del borrower["owed_by"][lender_name] |
| 188 | |
| 189 | if net_lender_owes > 0: |
| 190 | lender["owes"][borrower_name] = net_lender_owes |
| 191 | if borrower_name in lender["owed_by"]: |
| 192 | del lender["owed_by"][borrower_name] |
| 193 | elif net_lender_owes < 0: |
| 194 | if borrower_name in lender["owes"]: |
| 195 | del lender["owes"][borrower_name] |
| 196 | lender["owed_by"][borrower_name] = -net_lender_owes |
| 197 | else: |
| 198 | # They owe each other nothing |
| 199 | if borrower_name in lender["owes"]: |
| 200 | del lender["owes"][borrower_name] |
| 201 | if borrower_name in lender["owed_by"]: |
| 202 | del lender["owed_by"][borrower_name] |
| 203 | |
| 204 | # Update balances |
| 205 | self._update_balances(lender_name, borrower_name) |
| 206 | |
| 207 | # Return updated user information |
| 208 | updated_lender = self._get_user(lender_name) |
| 209 | updated_borrower = self._get_user(borrower_name) |
| 210 | |
| 211 | result_users = [updated_lender, updated_borrower] |
| 212 | result_users.sort(key=lambda x: x["name"]) |
| 213 | |
| 214 | # Recalculate balances for response |
| 215 | response_users = [] |
| 216 | for user in result_users: |
| 217 | response_user = user.copy() |
| 218 | response_user["balance"] = self._calculate_balance(user) |
| 219 | response_users.append(response_user) |
| 220 | |
| 221 | return json.dumps({"users": response_users}) |
| 222 | else: |
| 223 | # Edge Case: Invalid URL |
| 224 | return json.dumps({"error": "Invalid URL"}) |
| 225 | |
| 226 | # Handled Edge Cases: Invalid URL, Malformed payload, Missing user field, User already exists, Missing required fields, |
| 227 | # Lender and borrower are the same person, Negative or zero amount, Lender does not exist, Borrower does not exist, |
| 228 | # Empty users list in payload, None of the requested users exist, No users in database |