#!/usr/bin/env python3
"""json_tool.py - Quick JSON formatter and validator for CLI.

Usage:
    echo '{"a":1}' | python3 json_tool.py
    python3 json_tool.py < file.json
    python3 json_tool.py --validate file.json  # just validate
"""
import sys, json, argparse

def main():
    parser = argparse.ArgumentParser(description='Format/validate JSON')
    parser.add_argument('file', nargs='?', help='JSON file to process')
    parser.add_argument('--validate', action='store_true', help='Only validate, no output')
    args = parser.parse_args()
    
    try:
        if args.file:
            content = open(args.file).read()
        else:
            content = sys.stdin.read()
        
        data = json.loads(content)
        
        if args.validate:
            print("VALID", file=sys.stderr)
        else:
            print(json.dumps(data, indent=2, sort_keys=True))
    except json.JSONDecodeError as e:
        print(f"INVALID: {e}", file=sys.stderr)
        sys.exit(1)
    except Exception as e:
        print(f"ERROR: {e}", file=sys.stderr)
        sys.exit(1)

if __name__ == '__main__':
    main()