"""Utility functions for path validation and security."""

import os
import re


class PathValidator:
    """Validates and sanitizes user-provided file and folder paths."""

    @staticmethod
    def _normalize_relative_path(path: str) -> str:
        if not isinstance(path, str):
            return ""
        normalized = re.sub(r"[\\/]+", "/", path).strip("/ ")
        return normalized

    @staticmethod
    def is_valid_filename(filename: str) -> bool:
        if not filename or not isinstance(filename, str):
            return False

        filename = filename.strip()
        if not filename or len(filename) > 250:
            return False

        if ".." in filename or "/" in filename or "\\" in filename:
            return False

        invalid_chars = set('<>:"/\\|?*')
        if any((char in invalid_chars or ord(char) < 32) for char in filename):
            return False

        reserved = {
            "CON",
            "PRN",
            "AUX",
            "NUL",
            "COM1",
            "COM2",
            "COM3",
            "COM4",
            "COM5",
            "COM6",
            "COM7",
            "COM8",
            "COM9",
            "LPT1",
            "LPT2",
            "LPT3",
            "LPT4",
            "LPT5",
            "LPT6",
            "LPT7",
            "LPT8",
            "LPT9",
        }
        if filename.split(".")[0].upper() in reserved:
            return False

        return True

    @staticmethod
    def is_valid_path(path: str) -> bool:
        normalized = PathValidator._normalize_relative_path(path or "")
        if normalized == "":
            return True

        parts = normalized.split("/")
        return all(PathValidator.is_valid_filename(part) for part in parts)

    @staticmethod
    def validate_folder_structure(path_parts: list[str]) -> bool:
        return all(PathValidator.is_valid_filename(part) for part in path_parts if part)


def sanitize_filename(filename: str) -> str:
    if not filename:
        return "file"

    sanitized = re.sub(r'[<>:"/\\|?*\x00-\x1F]', "_", filename)
    sanitized = sanitized.strip(". ")
    return sanitized or "file"


def format_file_size(size_bytes: int) -> str:
    if size_bytes == 0:
        return "0 B"

    size = float(size_bytes)
    for unit in ["B", "KB", "MB", "GB"]:
        if size < 1024.0:
            return f"{size:.2f} {unit}"
        size /= 1024.0
    return f"{size:.2f} TB"


def get_file_extension(filename: str) -> str:
    return os.path.splitext(filename)[1].lstrip(".").lower()