#!/usr/bin/env python3
"""
JSON Formatter Utility
Validates and pretty-prints JSON files with customizable indentation.
Supports file input or stdin piping.

Usage:
    json_formatter.py <input.json> [indent]      # format file
    echo '{}' | json_formatter.py              # format from stdin
    json_formatter.py invalid.json             # validate (exit 1 if invalid)
"""
import json
import sys
from pathlib import Path


def format_json(input_path: str = None, content: str = None, indent: int = 2) -> str:
    """
    Read JSON from file or string, validate it, and return formatted output.

    Args:
        input_path: Path to the JSON file (mutually exclusive with content)
        content: Raw JSON string content (mutually exclusive with input_path)
        indent: Number of spaces for indentation (default: 2)

    Returns:
        Formatted JSON string

    Raises:
        FileNotFoundError: If file doesn't exist
        json.JSONDecodeError: If file contains invalid JSON
    """
    if content is None:
        path = Path(input_path)
        if not path.exists():
            raise FileNotFoundError(f"File not found: {input_path}")
        with open(path, 'r', encoding='utf-8') as f:
            data = json.load(f)
    else:
        data = json.loads(content)

    # Validate by re-serializing
    json.dumps(data)  # Will raise if data contains non-serializable types

    return json.dumps(data, indent=indent, ensure_ascii=False, sort_keys=True)


def main():
    input_file = sys.argv[1] if len(sys.argv) > 1 else None
    indent = int(sys.argv[2]) if len(sys.argv) > 2 else 2

    try:
        if input_file:
            formatted = format_json(input_path=input_file, indent=indent)
        else:
            # Read from stdin
            content = sys.stdin.read()
            if not content.strip():
                print("Error: No input provided", file=sys.stderr)
                sys.exit(1)
            formatted = format_json(content=content, indent=indent)
        print(formatted)
        sys.exit(0)
    except FileNotFoundError as e:
        print(f"Error: {e}", file=sys.stderr)
        sys.exit(2)
    except json.JSONDecodeError as e:
        print(f"JSON Error: {e.msg} at line {e.lineno}, column {e.colno}", file=sys.stderr)
        sys.exit(3)
    except Exception as e:
        print(f"Unexpected error: {e}", file=sys.stderr)
        sys.exit(4)


if __name__ == "__main__":
    main()