"""Misc. Utilities"""
import os
import re
import shutil

# Define some constants
# List of banned command regex patterns (case-insensitive, word boundaries)
BANNED_COMMANDS = [
    # Dangerous recursive delete (match 'rm -rf /' or 'rm -rf /path').
    # Original pattern used a trailing \b after '/', which failed to match
    # because '/' is a non-word char. Use lookahead for end or whitespace.
    r"\brm\s+-rf\s+/?(?=$|\s)",
    r"\bshutdown\b.*\bnow\b",            # Immediate shutdown
    r"\breboot\b",                       # Reboot command
    r"\bmkfs\.(ext[234]|xfs|btrfs)\b",   # Filesystem formatting
    r"\bdd\s+if=.*\b",                   # Disk overwrite
    r"\b:(){:|:&};:\b",                  # Fork bomb
    r"\bpoweroff\b",                     # Power off system
    r"\binit\s+0\b",                     # Runlevel 0 (shutdown)
    r"\bhalt\b",                         # Halt system
    r"\bdel\s+/f\s+/q\s+/s\s+C:\\",      # Windows delete
    r"\bformat\s+[a-z]:",                # Windows format
]

# List of banned shell regex patterns (case-insensitive, word boundaries)
BANNED_SHELLS = [
    # r"\bsh\b",
    # r"\bbash\b",
    # r"\bzsh\b",
    # r"\bdash\b",
    r"\bpowershell\.exe\b",
    r"\bcmd\.exe\b",
]

# List of candidate shell paths
CANDIDATE_SHELLS = [
    "/bin/bash",
    "/bin/sh",
    "/bin/zsh",
    "/usr/bin/bash",
    "/usr/bin/sh",
    "/usr/bin/zsh",
    "/bin/dash",
    "/usr/bin/dash",
    "powershell.exe",
    "cmd.exe",
]


# List of available shells
def _find_available_shells() -> list[str]:
    """Detect available shell executables on the system. Block banned
    shells."""
    found = []
    for shell in CANDIDATE_SHELLS:
        shell_path = \
            shutil.which(shell) if not shell.startswith("/") else shell
        if shell_path and shutil.which(shell_path):
            if not any(re.search(pattern, shell_path) for pattern in BANNED_SHELLS):  # noqa
                found.append(shell_path)
        elif shell.startswith("/") and os.path.exists(shell):
            if not any(re.search(pattern, shell) for pattern in BANNED_SHELLS):  # noqa
                found.append(shell)

    # Remove duplicates while preserving order
    seen = set()
    unique_shells = []
    for s in found:
        if s not in seen:
            unique_shells.append(s)
            seen.add(s)

    return unique_shells


SHELLS = _find_available_shells()


__all__ = ["SHELLS"]