Import Order Checking and Validation

class ImportOrderChecker:
    """Main checker class for import order validation."""
    
    visitor_class = ImportVisitor  # AST visitor class to use
    options = None  # Configuration options
    
    def __init__(self, filename, tree):
        """
        Initialize checker with file and AST.
        
        Args:
            filename: Path to file being checked  
            tree: Parsed AST or None to load from file
        """
    
    def load_file(self):
        """
        Load and parse file if not already loaded.
        
        Handles stdin input and regular files, parsing AST if needed.
        """
    
    def check_order(self):
        """
        Check import order and yield errors.
        
        Yields:
            Error objects for each import order violation found
        """
    
    def error_is_ignored(self, error):
        """
        Check if error is ignored via # noqa comment.
        
        Args:
            error: Error to check
            
        Returns:
            True if error should be ignored
        """
    
    def error(self, error):
        """
        Process error for output (override in subclasses).
        
        Args:
            error: Error to process
            
        Returns:
            Processed error object
        """

def parse_comma_separated_list(value):
    """
    Parse comma-separated configuration values.
    
    Args:
        value: Comma-separated string (e.g., "name1, name2, name3")
    
    Returns:
        Set of stripped, non-empty items
        
    Example:
        parse_comma_separated_list("app1, app2 , app3") -> {"app1", "app2", "app3"}
    """

DEFAULT_IMPORT_ORDER_STYLE = "cryptography"

NOQA_INLINE_REGEXP = re.compile(
    r"# noqa(?:: (?P<codes>([A-Z][0-9]+(?:[,\s]+)?)+))?",
    re.IGNORECASE,
)
COMMA_SEPARATED_LIST_RE = re.compile(r"[,\s]")
BLANK_LINE_RE = re.compile(r"\s*\n")

from flake8_import_order.checker import ImportOrderChecker
from flake8_import_order.styles import lookup_entry_point
import ast

# Python code to check
code = '''
import sys
import os
from myapp import utils
import json
'''

# Set up checker
tree = ast.parse(code)
checker = ImportOrderChecker('example.py', tree)
checker.options = {
    'application_import_names': ['myapp'],
    'application_package_names': [],
    'import_order_style': lookup_entry_point('cryptography')
}

# Check for violations
for error in checker.check_order():
    print(f"Line {error.lineno}: {error.code} - {error.message}")

from flake8_import_order.checker import ImportOrderChecker
from flake8_import_order.styles import lookup_entry_point

# Check a Python file
checker = ImportOrderChecker('mymodule.py', None)  # Will load from file
checker.options = {
    'application_import_names': ['myapp', 'myproject'],
    'application_package_names': ['mycompany'],
    'import_order_style': lookup_entry_point('google')
}

# Check for violations
violations = list(checker.check_order())
print(f"Found {len(violations)} import order violations")

from flake8_import_order.checker import parse_comma_separated_list

# Parse configuration values
app_names = parse_comma_separated_list("myapp, tests, utils")
print(app_names)  # {'myapp', 'tests', 'utils'}

# Handle empty values
empty_names = parse_comma_separated_list("")
print(empty_names)  # set()

from flake8_import_order.checker import ImportOrderChecker

class CustomChecker(ImportOrderChecker):
    """Custom checker with specialized error handling."""
    
    def error(self, error):
        """Custom error formatting."""
        return {
            'line': error.lineno,
            'code': error.code,
            'message': error.message,
            'severity': 'warning' if error.code.startswith('I2') else 'error'
        }
    
    def check_with_context(self):
        """Check with additional context."""
        errors = []
        for error in self.check_order():
            processed_error = self.error(error)
            errors.append(processed_error)
        return errors

import json
import os  # noqa: I100  - Ignore wrong order
from myapp import utils  # noqa  - Ignore all errors on this line