process_utils.py

"""Resolve external tools explicitly and limit FFmpeg to media files."""

import os

from constants import FFMPEG_INPUT_FORMATS


def resolve_executable(command):
    """Return an absolute executable path without implicit working-directory search.

    An explicit path is a user selection. Bare names are searched only in
    absolute PATH entries outside the working directory. On Windows, accept
    native .exe files only: .bat/.cmd arguments otherwise pass through cmd.exe
    even with subprocess's default shell=False.
    """
    if not command:
        return None
    command = os.fspath(command)
    if os.name == "nt":
        extension = os.path.splitext(command)[1].lower()
        if not extension:
            command += ".exe"
        elif extension != ".exe":
            return None

    if os.path.dirname(command):
        candidates = [os.path.abspath(command)]
    else:
        current_dir = os.path.normcase(os.path.realpath(os.getcwd()))
        candidates = []
        for directory in os.environ.get("PATH", "").split(os.pathsep):
            directory = directory.strip('"')
            if not os.path.isabs(directory):
                continue
            directory = os.path.realpath(directory)
            if os.path.normcase(directory) == current_dir:
                continue
            candidates.append(os.path.join(directory, command))

    for candidate in candidates:
        candidate = os.path.realpath(candidate)
        if os.name == "nt" and os.path.splitext(candidate)[1].lower() != ".exe":
            continue
        if os.path.isfile(candidate) and os.access(candidate, os.X_OK):
            return candidate
    return None


def require_executable(command):
    resolved = resolve_executable(command)
    if resolved is None:
        raise FileNotFoundError(f"Executable not found in a trusted PATH directory: {command}")
    return resolved


def local_media_input_args(filepath):
    """Build input arguments shared by probing, CUDA testing and conversion.

    Absolute paths cannot become options or protocol URLs. Playlists and script
    demuxers are deliberately excluded; this is not an OS-level decoder sandbox.
    """
    filepath = os.path.abspath(filepath)
    if not os.path.isfile(filepath):
        raise FileNotFoundError(filepath)
    return [
        "-protocol_whitelist", "file",
        "-format_whitelist", FFMPEG_INPUT_FORMATS,
        "-i", filepath,
    ]