Accounting Entry Validator

def validate_transaction(transaction_data):
    """
    Validate a single transaction for required fields and data integrity.
    Returns(bool, list_of_errors).
    """
    errors = []
    required_fields = ["date", "amount", "account_code", "description", "type"]
    for field in required_fields:
        if field not in transaction_data or transaction_data[field] in [None, "", " "]:
            errors.append(f"Missing or empty field: {field}")
    try:
        datetime.strptime(transaction_data.get("date", ""), "%Y-%m-%d")
    except ValueError:
        errors.append("Invalid date format, expected YYYY-MM-DD")
    if not isinstance(transaction_data.get("amount"), (int, float)):
        errors.append("Amount must be numeric")
    if not str(transaction_data.get("account_code", "")).isdigit():
        errors.append("Invalid account code: must be numeric")
    return (len(errors) == 0, errors)

def correct_common_errors(transaction_data):
    """
    Apply automatic corrections to common transaction errors.
    Returns corrected transaction_data and list of applied corrections.
    """
    corrections = []
    if transaction_data.get("description"):
        transaction_data["description"] = transaction_data["description"].strip()
    if "account_code" in transaction_data and transaction_data["account_code"]:
        if isinstance(transaction_data["account_code"], int):
            transaction_data["account_code"] = str(transaction_data["account_code"]).zfill(4)
            corrections.append("Normalized account code format")
    if "amount" in transaction_data:
        try:
            transaction_data["amount"] = float(transaction_data["amount"])
        except ValueError:
            corrections.append("Amount correction failed - non-numeric")
    return transaction_data, corrections

def check_duplicate_transactions(transactions):
    """
    Check for potential duplicate transactions based on amount, account, and date.
    Returns list of(transaction, duplicate_info) for potential duplicates.
    """
    duplicates = []
    for i, t1 in enumerate(transactions):
        for j, t2 in enumerate(transactions[i + 1 :], i + 1):
            if (
                t1.get("amount") == t2.get("amount")
                and t1.get("account_code") == t2.get("account_code")
                and t1.get("date") == t2.get("date")
                and t1.get("description") == t2.get("description")
            ):
                duplicates.append((t1, {"type": "exact_duplicate", "duplicate_of": t2}))
            elif(
                t1.get("amount") == t2.get("amount")
                and t1.get("account_code") == t2.get("account_code")
                and t1.get("date") == t2.get("date")
            ):
                duplicates.append((t1, {"type": "near_duplicate", "duplicate_of": t2}))
    return duplicates

def validate_business_rules(transaction_data, business_rules=None):
    """
    Validate transaction against business rules and account code ranges.
    Returns(bool, list_of_violations).
    """
    if business_rules is None:
        business_rules = {
            "account_code_ranges": {
                "assets": (1000, 1999),
                "liabilities": (2000, 2999),
                "equity": (3000, 3999),
                "revenue": (4000, 4999),
                "expenses": (5000, 5999),
            },
            "max_amount": 1000000,
            "min_amount": 0.01,
            "prohibited_accounts": ["0000", "9999"],
        }
    violations = []
    account_code = int(transaction_data.get("account_code", 0))
    valid_range = False
    for category, (min_code, max_code) in business_rules["account_code_ranges"].items():
        if min_code <= account_code <= max_code:
            valid_range = True
            break
    if not valid_range:
        violations.append(f"Account code {account_code} is outside valid ranges")
    amount = transaction_data.get("amount", 0)
    if amount > business_rules["max_amount"]:
        violations.append(f"Amount {amount} exceeds maximum allowed {business_rules['max_amount']}")
    if amount < business_rules["min_amount"]:
        violations.append(f"Amount {amount} is below minimum allowed {business_rules['min_amount']}")
    if str(transaction_data.get("account_code")) in business_rules["prohibited_accounts"]:
        violations.append(f"Account code {transaction_data.get('account_code')} is prohibited")
    return (len(violations) == 0, violations)