| 1 | import json |
| 2 | |
| 1 | 3 | class RestAPI: |
| 2 | 4 | def __init__(self, database: dict | None = None): |
| 3 | | pass |
| 4 | | |
| 5 | # Edge Case: Handle None database by initializing empty structure |
| 6 | if database is None: |
| 7 | self.database = {"users": []} |
| 8 | else: |
| 9 | self.database = database |
| 10 | |
| 5 | 11 | def get(self, url: str, payload: str | None = None) -> str: |
| 6 | | pass |
| 7 | | |
| 12 | # Edge Case: Handle invalid URL |
| 13 | if url != "/users": |
| 14 | return json.dumps({"error": "Invalid URL"}) |
| 15 | |
| 16 | # Edge Case: Handle invalid payload format |
| 17 | if payload is not None: |
| 18 | try: |
| 19 | payload_data = json.loads(payload) |
| 20 | except json.JSONDecodeError: |
| 21 | return json.dumps({"error": "Invalid payload format"}) |
| 22 | |
| 23 | # Edge Case: Handle missing 'users' key in payload |
| 24 | if "users" not in payload_data: |
| 25 | return json.dumps({"error": "Missing 'users' key in payload"}) |
| 26 | |
| 27 | # Edge Case: Handle non-list 'users' value in payload |
| 28 | if not isinstance(payload_data["users"], list): |
| 29 | return json.dumps({"error": "'users' must be a list"}) |
| 30 | |
| 31 | # Filter users based on payload |
| 32 | users_list = [] |
| 33 | for user_name in payload_data["users"]: |
| 34 | user = self._get_user_by_name(user_name) |
| 35 | # Edge Case: Handle user not found |
| 36 | if user is not None: |
| 37 | users_list.append(user) |
| 38 | |
| 39 | # Sort users by name |
| 40 | users_list.sort(key=lambda x: x["name"]) |
| 41 | return json.dumps({"users": users_list}) |
| 42 | else: |
| 43 | # Return all users sorted by name |
| 44 | users_list = self.database["users"].copy() |
| 45 | users_list.sort(key=lambda x: x["name"]) |
| 46 | return json.dumps({"users": users_list}) |
| 47 | |
| 8 | 48 | def post(self, url: str, payload: str | None = None) -> str: |
| 9 | | pass |
| 49 | # Edge Case: Handle invalid URL |
| 50 | if url not in ["/add", "/iou"]: |
| 51 | return json.dumps({"error": "Invalid URL"}) |
| 52 | |
| 53 | # Edge Case: Handle missing payload |
| 54 | if payload is None: |
| 55 | return json.dumps({"error": "Missing payload"}) |
| 56 | |
| 57 | # Edge Case: Handle invalid payload format |
| 58 | try: |
| 59 | payload_data = json.loads(payload) |
| 60 | except json.JSONDecodeError: |
| 61 | return json.dumps({"error": "Invalid payload format"}) |
| 62 | |
| 63 | if url == "/add": |
| 64 | # Edge Case: Handle missing 'user' key in payload |
| 65 | if "user" not in payload_data: |
| 66 | return json.dumps({"error": "Missing 'user' key in payload"}) |
| 67 | |
| 68 | user_name = payload_data["user"] |
| 69 | |
| 70 | # Edge Case: Handle non-string user name |
| 71 | if not isinstance(user_name, str): |
| 72 | return json.dumps({"error": "User name must be a string"}) |
| 73 | |
| 74 | # Edge Case: Handle duplicate user - return existing user |
| 75 | existing_user = self._get_user_by_name(user_name) |
| 76 | if existing_user is not None: |
| 77 | return json.dumps(existing_user) |
| 78 | |
| 79 | # Create new user |
| 80 | new_user = { |
| 81 | "name": user_name, |
| 82 | "owes": {}, |
| 83 | "owed_by": {}, |
| 84 | "balance": 0.0 |
| 85 | } |
| 86 | self.database["users"].append(new_user) |
| 87 | return json.dumps(new_user) |
| 88 | |
| 89 | elif url == "/iou": |
| 90 | # Edge Case: Handle missing required keys in payload |
| 91 | required_keys = ["lender", "borrower", "amount"] |
| 92 | for key in required_keys: |
| 93 | if key not in payload_data: |
| 94 | return json.dumps({"error": f"Missing '{key}' key in payload"}) |
| 95 | |
| 96 | lender_name = payload_data["lender"] |
| 97 | borrower_name = payload_data["borrower"] |
| 98 | amount = payload_data["amount"] |
| 99 | |
| 100 | # Edge Case: Handle non-string lender or borrower |
| 101 | if not isinstance(lender_name, str) or not isinstance(borrower_name, str): |
| 102 | return json.dumps({"error": "Lender and borrower must be strings"}) |
| 103 | |
| 104 | # Edge Case: Handle non-numeric amount |
| 105 | if not isinstance(amount, (int, float)): |
| 106 | return json.dumps({"error": "Amount must be a number"}) |
| 107 | |
| 108 | # Edge Case: Handle negative amount - treat as positive (or handle gracefully) |
| 109 | # For this implementation, we'll allow negative amounts to be processed |
| 110 | |
| 111 | # Edge Case: Handle same lender and borrower |
| 112 | if lender_name == borrower_name: |
| 113 | return json.dumps({"error": "Lender and borrower cannot be the same"}) |
| 114 | |
| 115 | lender = self._get_user_by_name(lender_name) |
| 116 | borrower = self._get_user_by_name(borrower_name) |
| 117 | |
| 118 | # Edge Case: Handle lender or borrower not found |
| 119 | if lender is None: |
| 120 | return json.dumps({"error": "Lender not found"}) |
| 121 | if borrower is None: |
| 122 | return json.dumps({"error": "Borrower not found"}) |
| 123 | |
| 124 | # Update IOUs |
| 125 | if amount != 0: |
| 126 | # Update the direct relationship |
| 127 | # When lender lends borrower amount: |
| 128 | # - borrower is owed by lender (borrower.owed_by[lender] += amount) |
| 129 | # - lender owes to borrower (lender.owes[borrower] += amount) |
| 130 | if lender_name in borrower["owed_by"]: |
| 131 | borrower["owed_by"][lender_name] += amount |
| 132 | else: |
| 133 | borrower["owed_by"][lender_name] = amount |
| 134 | |
| 135 | if borrower_name in lender["owes"]: |
| 136 | lender["owes"][borrower_name] += amount |
| 137 | else: |
| 138 | lender["owes"][borrower_name] = amount |
| 139 | |
| 140 | # Net the relationships between lender and borrower |
| 141 | # Calculate net amounts |
| 142 | lender_owed_by_borrower = lender["owed_by"].get(borrower_name, 0) |
| 143 | lender_owes_borrower = lender["owes"].get(borrower_name, 0) |
| 144 | borrower_owes_lender = borrower["owes"].get(lender_name, 0) |
| 145 | borrower_owed_by_lender = borrower["owed_by"].get(lender_name, 0) |
| 146 | |
| 147 | # Calculate net amounts (positive means first person owes second person) |
| 148 | net_lender_owes_borrower = lender_owes_borrower - lender_owed_by_borrower |
| 149 | net_borrower_owes_lender = borrower_owes_lender - borrower_owed_by_lender |
| 150 | |
| 151 | # Clear existing relationships between these two |
| 152 | if borrower_name in lender["owed_by"]: |
| 153 | del lender["owed_by"][borrower_name] |
| 154 | if lender_name in borrower["owes"]: |
| 155 | del borrower["owes"][lender_name] |
| 156 | if lender_name in lender["owes"]: |
| 157 | del lender["owes"][lender_name] |
| 158 | if borrower_name in borrower["owed_by"]: |
| 159 | del borrower["owed_by"][borrower_name] |
| 160 | |
| 161 | # Set new netted relationships |
| 162 | # If net_lender_owes_borrower > 0, lender owes borrower |
| 163 | # If net_lender_owes_borrower < 0, borrower owes lender (lender is owed by borrower) |
| 164 | if net_lender_owes_borrower > 0: |
| 165 | lender["owes"][borrower_name] = net_lender_owes_borrower |
| 166 | borrower["owed_by"][lender_name] = net_lender_owes_borrower |
| 167 | elif net_lender_owes_borrower < 0: |
| 168 | lender_owed_amount = abs(net_lender_owes_borrower) |
| 169 | lender["owed_by"][borrower_name] = lender_owed_amount |
| 170 | borrower["owes"][lender_name] = lender_owed_amount |
| 171 | |
| 172 | # Similarly for the other direction |
| 173 | if net_borrower_owes_lender > 0: |
| 174 | borrower["owes"][lender_name] = net_borrower_owes_lender |
| 175 | lender["owed_by"][borrower_name] = net_borrower_owes_lender |
| 176 | elif net_borrower_owes_lender < 0: |
| 177 | borrower_owed_amount = abs(net_borrower_owes_lender) |
| 178 | borrower["owed_by"][lender_name] = borrower_owed_amount |
| 179 | lender["owes"][borrower_name] = borrower_owed_amount |
| 180 | else: |
| 181 | # For zero amounts, remove any existing relationships in both directions |
| 182 | if borrower_name in lender["owed_by"]: |
| 183 | del lender["owed_by"][borrower_name] |
| 184 | if lender_name in borrower["owes"]: |
| 185 | del borrower["owes"][lender_name] |
| 186 | if lender_name in lender["owes"]: |
| 187 | del lender["owes"][lender_name] |
| 188 | if borrower_name in borrower["owed_by"]: |
| 189 | del borrower["owed_by"][borrower_name] |
| 190 | |
| 191 | # Recalculate balances |
| 192 | self._recalculate_balance(lender) |
| 193 | self._recalculate_balance(borrower) |
| 194 | |
| 195 | # Return updated users sorted by name |
| 196 | users_list = [lender, borrower] |
| 197 | users_list.sort(key=lambda x: x["name"]) |
| 198 | return json.dumps({"users": users_list}) |
| 199 | |
| 200 | def _get_user_by_name(self, name: str): |
| 201 | for user in self.database["users"]: |
| 202 | if user["name"] == name: |
| 203 | return user |
| 204 | return None |
| 205 | |
| 206 | def _recalculate_balance(self, user): |
| 207 | total_owed_by = sum(user["owed_by"].values()) |
| 208 | total_owes = sum(user["owes"].values()) |
| 209 | user["balance"] = round(total_owed_by - total_owes, 2) |
| 210 | |
| 211 | # Handled Edge Cases: None database, invalid URL, invalid payload format, missing 'users' key, non-list 'users' value, user not found, missing payload, missing 'user' key, non-string user name, duplicate user, missing required keys, non-string lender/borrower, non-numeric amount, negative amount, same lender/borrower, lender/borrower not found |