#!/usr/bin/env python3
"""Python syntax checker - verifies .py files for syntax errors."""

import ast
import sys
from pathlib import Path


def check_python_syntax(filepath: str) -> tuple[bool, str]:
    """Check if a Python file has valid syntax.
    
    Returns:
        tuple: (is_valid, error_message)
    """
    try:
        with open(filepath, 'r', encoding='utf-8') as f:
            source = f.read()
        ast.parse(source, filename=filepath)
        return True, ""
    except SyntaxError as e:
        return False, f"{filepath}:{e.lineno}:{e.offset}: {e.msg}"
    except Exception as e:
        return False, f"{filepath}: {type(e).__name__}: {e}"


def check_dir(directory: str, recursive: bool = False) -> dict:
    """Check all Python files in a directory.
    
    Returns:
        dict: {valid_count, invalid_count, errors: [...]}
    """
    results = {"valid_count": 0, "invalid_count": 0, "errors": []}
    path = Path(directory)
    
    if recursive:
        files = path.rglob("*.py")
    else:
        files = path.glob("*.py")
    
    for f in files:
        is_valid, error = check_python_syntax(str(f))
        if is_valid:
            results["valid_count"] += 1
        else:
            results["invalid_count"] += 1
            results["errors"].append(error)
    
    return results


if __name__ == "__main__":
    if len(sys.argv) < 2:
        print("Usage: python python_syntax_checker.py <directory|file> [--recursive]")
        sys.exit(1)
    
    target = sys.argv[1]
    recursive = "--recursive" in sys.argv
    
    if Path(target).is_file():
        valid, error = check_python_syntax(target)
        if valid:
            print(f"OK: {target}")
            sys.exit(0)
        else:
            print(f"SYNTAX ERROR: {error}")
            sys.exit(1)
    else:
        results = check_dir(target, recursive)
        print(f"Valid: {results['valid_count']}, Invalid: {results['invalid_count']}")
        for err in results['errors']:
            print(f"  {err}")
        sys.exit(0 if results['invalid_count'] == 0 else 1)