#!/usr/bin/env python3
"""Validate JSON files - returns 0 if valid, nonzero if invalid or missing 'valid' key."""
import sys
import json

def main():
    if len(sys.argv) < 2:
        print("Usage: json_validator.py <file.json>", file=sys.stderr)
        sys.exit(1)
    
    filepath = sys.argv[1]
    
    try:
        with open(filepath, 'r') as f:
            data = json.load(f)
        
        if isinstance(data, dict) and data.get('valid') == True:
            print(f"VALID: {filepath}")
            sys.exit(0)
        else:
            print(f"INVALID: {filepath} - missing or false 'valid' field", file=sys.stderr)
            sys.exit(1)
    
    except json.JSONDecodeError as e:
        print(f"INVALID: {filepath} - {e}", file=sys.stderr)
        sys.exit(1)
    
    except FileNotFoundError:
        print(f"NOT FOUND: {filepath}", file=sys.stderr)
        sys.exit(2)

if __name__ == "__main__":
    main()