#!/usr/bin/env python3
"""Simple JSON validator - validates JSON files and reports errors."""

import sys
import json

def validate_json(filepath):
    """Validate a JSON file. Returns (is_valid, error_message)."""
    try:
        with open(filepath, 'r') as f:
            json.load(f)
        return True, None
    except FileNotFoundError:
        return False, f"File not found: {filepath}"
    except json.JSONDecodeError as e:
        return False, f"Invalid JSON: {e}"
    except Exception as e:
        return False, f"Error: {e}"

if __name__ == "__main__":
    if len(sys.argv) != 2:
        print(f"Usage: {sys.argv[0]} <json-file>", file=sys.stderr)
        sys.exit(1)
    
    is_valid, error = validate_json(sys.argv[1])
    if is_valid:
        print("VALID")
        sys.exit(0)
    else:
        print(error, file=sys.stderr)
        sys.exit(1)