| 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 an optional database. |
| 7 | |
| 8 | Args: |
| 9 | database: A dictionary containing initial user data. |
| 10 | """ |
| 11 | if database is None: |
| 12 | self.database = {"users": []} |
| 13 | else: |
| 14 | self.database = database |
| 15 | |
| 5 | 16 | def get(self, url: str, payload: str | None = None) -> str: |
| 6 | | pass |
| 7 | | |
| 17 | """ |
| 18 | Handle GET requests to the API. |
| 19 | |
| 20 | Args: |
| 21 | url: The endpoint URL. |
| 22 | payload: Optional JSON payload. |
| 23 | |
| 24 | Returns: |
| 25 | A JSON string response. |
| 26 | |
| 27 | Raises: |
| 28 | ValueError: If the URL is not recognized. |
| 29 | """ |
| 30 | if url == "/users": |
| 31 | if payload is None: |
| 32 | # Return all users |
| 33 | result = {"users": []} |
| 34 | for user in self.database["users"]: |
| 35 | # Calculate balance |
| 36 | total_owed_by = sum(user.get("owed_by", {}).values()) |
| 37 | total_owes = sum(user.get("owes", {}).values()) |
| 38 | balance = total_owed_by - total_owes |
| 39 | |
| 40 | user_obj = { |
| 41 | "name": user["name"], |
| 42 | "owes": user.get("owes", {}), |
| 43 | "owed_by": user.get("owed_by", {}), |
| 44 | "balance": balance |
| 45 | } |
| 46 | result["users"].append(user_obj) |
| 47 | return json.dumps(result) |
| 48 | else: |
| 49 | # Return specific users |
| 50 | payload_data = json.loads(payload) |
| 51 | user_names = payload_data.get("users", []) |
| 52 | |
| 53 | result = {"users": []} |
| 54 | |
| 55 | # Filter users by name and sort by name |
| 56 | filtered_users = [user for user in self.database["users"] if user["name"] in user_names] |
| 57 | filtered_users.sort(key=lambda x: x["name"]) |
| 58 | |
| 59 | for user in filtered_users: |
| 60 | # Calculate balance |
| 61 | total_owed_by = sum(user.get("owed_by", {}).values()) |
| 62 | total_owes = sum(user.get("owes", {}).values()) |
| 63 | balance = total_owed_by - total_owes |
| 64 | |
| 65 | user_obj = { |
| 66 | "name": user["name"], |
| 67 | "owes": user.get("owes", {}), |
| 68 | "owed_by": user.get("owed_by", {}), |
| 69 | "balance": balance |
| 70 | } |
| 71 | result["users"].append(user_obj) |
| 72 | |
| 73 | return json.dumps(result) |
| 74 | else: |
| 75 | raise ValueError(f"Unknown URL: {url}") |
| 76 | |
| 8 | 77 | def post(self, url: str, payload: str | None = None) -> str: |
| 9 | | pass |
| 78 | """ |
| 79 | Handle POST requests to the API. |
| 80 | |
| 81 | Args: |
| 82 | url: The endpoint URL. |
| 83 | payload: JSON payload. |
| 84 | |
| 85 | Returns: |
| 86 | A JSON string response. |
| 87 | |
| 88 | Raises: |
| 89 | ValueError: If the URL is not recognized or if there are validation errors. |
| 90 | """ |
| 91 | if url == "/add": |
| 92 | if payload is None: |
| 93 | raise ValueError("Payload is required for /add") |
| 94 | |
| 95 | payload_data = json.loads(payload) |
| 96 | user_name = payload_data.get("user") |
| 97 | |
| 98 | # Edge Case: User name is missing |
| 99 | if user_name is None: |
| 100 | raise ValueError("User name is required") |
| 101 | |
| 102 | # Edge Case: User already exists |
| 103 | for user in self.database["users"]: |
| 104 | if user["name"] == user_name: |
| 105 | raise ValueError(f"User {user_name} already exists") |
| 106 | |
| 107 | # Create new user |
| 108 | new_user = { |
| 109 | "name": user_name, |
| 110 | "owes": {}, |
| 111 | "owed_by": {} |
| 112 | } |
| 113 | self.database["users"].append(new_user) |
| 114 | |
| 115 | # Calculate balance |
| 116 | total_owed_by = sum(new_user.get("owed_by", {}).values()) |
| 117 | total_owes = sum(new_user.get("owes", {}).values()) |
| 118 | balance = total_owed_by - total_owes |
| 119 | |
| 120 | result = { |
| 121 | "name": new_user["name"], |
| 122 | "owes": new_user.get("owes", {}), |
| 123 | "owed_by": new_user.get("owed_by", {}), |
| 124 | "balance": balance |
| 125 | } |
| 126 | |
| 127 | return json.dumps(result) |
| 128 | |
| 129 | elif url == "/iou": |
| 130 | if payload is None: |
| 131 | raise ValueError("Payload is required for /iou") |
| 132 | |
| 133 | payload_data = json.loads(payload) |
| 134 | lender_name = payload_data.get("lender") |
| 135 | borrower_name = payload_data.get("borrower") |
| 136 | amount = payload_data.get("amount") |
| 137 | |
| 138 | # Edge Case: Missing required fields |
| 139 | if lender_name is None or borrower_name is None or amount is None: |
| 140 | raise ValueError("Lender, borrower, and amount are required") |
| 141 | |
| 142 | # Edge Case: Lender and borrower are the same |
| 143 | if lender_name == borrower_name: |
| 144 | raise ValueError("Lender and borrower cannot be the same") |
| 145 | |
| 146 | # Edge Case: Amount is negative |
| 147 | if amount < 0: |
| 148 | raise ValueError("Amount cannot be negative") |
| 149 | |
| 150 | # Find lender and borrower |
| 151 | lender = None |
| 152 | borrower = None |
| 153 | |
| 154 | for user in self.database["users"]: |
| 155 | if user["name"] == lender_name: |
| 156 | lender = user |
| 157 | if user["name"] == borrower_name: |
| 158 | borrower = user |
| 159 | |
| 160 | # Edge Case: Lender or borrower does not exist |
| 161 | if lender is None: |
| 162 | raise ValueError(f"User {lender_name} does not exist") |
| 163 | if borrower is None: |
| 164 | raise ValueError(f"User {borrower_name} does not exist") |
| 165 | |
| 166 | # Update IOUs |
| 167 | # Handle bidirectional relationships |
| 168 | # First check if borrower already owes lender money (from lender's perspective) |
| 169 | if borrower_name in lender.get("owed_by", {}): |
| 170 | existing_owed = lender["owed_by"][borrower_name] |
| 171 | # Borrower already owes lender, add to existing debt |
| 172 | lender["owed_by"][borrower_name] = existing_owed + amount |
| 173 | # Update borrower's owes record |
| 174 | if "owes" not in borrower: |
| 175 | borrower["owes"] = {} |
| 176 | borrower["owes"][lender_name] = existing_owed + amount |
| 177 | else: |
| 178 | # Check if lender owes borrower money |
| 179 | if borrower_name in lender.get("owes", {}): |
| 180 | existing_owes = lender["owes"][borrower_name] |
| 181 | if existing_owes > amount: |
| 182 | # Lender still owes borrower, but less |
| 183 | lender["owes"][borrower_name] = existing_owes - amount |
| 184 | # Update borrower's owed_by record |
| 185 | if "owed_by" not in borrower: |
| 186 | borrower["owed_by"] = {} |
| 187 | borrower["owed_by"][lender_name] = existing_owes - amount |
| 188 | elif existing_owes == amount: |
| 189 | # Zero out both directions |
| 190 | del lender["owes"][borrower_name] |
| 191 | if lender_name in borrower.get("owed_by", {}): |
| 192 | del borrower["owed_by"][lender_name] |
| 193 | else: |
| 194 | # Now borrower owes lender (net effect) |
| 195 | del lender["owes"][borrower_name] |
| 196 | # Remove borrower's owed_by entry if it exists |
| 197 | if lender_name in borrower.get("owed_by", {}): |
| 198 | del borrower["owed_by"][lender_name] |
| 199 | # Create new relationship: borrower owes lender |
| 200 | if "owed_by" not in lender: |
| 201 | lender["owed_by"] = {} |
| 202 | lender["owed_by"][borrower_name] = amount - existing_owes |
| 203 | if "owes" not in borrower: |
| 204 | borrower["owes"] = {} |
| 205 | borrower["owes"][lender_name] = amount - existing_owes |
| 206 | else: |
| 207 | # No existing relationship, create new one |
| 208 | if "owes" not in borrower: |
| 209 | borrower["owes"] = {} |
| 210 | borrower["owes"][lender_name] = amount |
| 211 | |
| 212 | if "owed_by" not in lender: |
| 213 | lender["owed_by"] = {} |
| 214 | lender["owed_by"][borrower_name] = amount |
| 215 | |
| 216 | # Prepare response with updated user objects |
| 217 | result = {"users": []} |
| 218 | |
| 219 | # Get updated lender and borrower |
| 220 | updated_lender = None |
| 221 | updated_borrower = None |
| 222 | |
| 223 | for user in self.database["users"]: |
| 224 | if user["name"] == lender_name: |
| 225 | updated_lender = user |
| 226 | if user["name"] == borrower_name: |
| 227 | updated_borrower = user |
| 228 | |
| 229 | # Add lender to result |
| 230 | total_owed_by = sum(updated_lender.get("owed_by", {}).values()) |
| 231 | total_owes = sum(updated_lender.get("owes", {}).values()) |
| 232 | balance = total_owed_by - total_owes |
| 233 | |
| 234 | lender_obj = { |
| 235 | "name": updated_lender["name"], |
| 236 | "owes": updated_lender.get("owes", {}), |
| 237 | "owed_by": updated_lender.get("owed_by", {}), |
| 238 | "balance": balance |
| 239 | } |
| 240 | |
| 241 | # Add borrower to result |
| 242 | total_owed_by = sum(updated_borrower.get("owed_by", {}).values()) |
| 243 | total_owes = sum(updated_borrower.get("owes", {}).values()) |
| 244 | balance = total_owed_by - total_owes |
| 245 | |
| 246 | borrower_obj = { |
| 247 | "name": updated_borrower["name"], |
| 248 | "owes": updated_borrower.get("owes", {}), |
| 249 | "owed_by": updated_borrower.get("owed_by", {}), |
| 250 | "balance": balance |
| 251 | } |
| 252 | |
| 253 | # Sort by name |
| 254 | if lender_name < borrower_name: |
| 255 | result["users"].append(lender_obj) |
| 256 | result["users"].append(borrower_obj) |
| 257 | else: |
| 258 | result["users"].append(borrower_obj) |
| 259 | result["users"].append(lender_obj) |
| 260 | |
| 261 | return json.dumps(result) |
| 262 | |
| 263 | else: |
| 264 | raise ValueError(f"Unknown URL: {url}") |
| 265 | |
| 266 | # Handled Edge Cases: |
| 267 | # - User name missing in /add |
| 268 | # - User already exists in /add |
| 269 | # - Missing required fields in /iou |
| 270 | # - Lender and borrower are the same in /iou |
| 271 | # - Amount is negative in /iou |
| 272 | # - Lender or borrower does not exist in /iou |