"""How the classroom launches VLC.

VLC is the DVD backend because its dvdnav module is what decodes disc
menus. Everything a user can see or press, though, belongs to the
classroom: the visible controls are classroom-dvd-session's overlay, and
VLC's own interface and keyboard are shut down here.
"""

import secrets

PLAYER = "vlc"

# Every hotkey VLC 3.0.23 defines, read out of `vlc -H --advanced` on
# Debian Trixie. All of them are unset before anything is bound, so a
# volunteer cannot land on crop, aspect ratio, subtitle tracks, audio
# tracks, deinterlacing or the volume by pressing a key at random.
#
# A future VLC that adds a hotkey would leave it bound. Regenerate with:
#   vlc -H --advanced | grep -oP '^\s+--key-\K[a-z0-9-]+'
ALL_HOTKEYS = (
    "aspect-ratio", "audio-track", "audiodelay-down", "audiodelay-up",
    "audiodevice-cycle", "chapter-next", "chapter-prev", "clear-playlist",
    "crop", "crop-bottom", "crop-left", "crop-right", "crop-top",
    "decr-scalefactor", "deinterlace", "deinterlace-mode", "disc-menu",
    "faster", "frame-next", "incr-scalefactor", "intf-boss",
    "intf-popup-menu", "intf-show", "jump-extrashort", "jump-long",
    "jump-medium", "jump-short", "leave-fullscreen", "length", "loop",
    "nav-activate", "nav-down", "nav-left", "nav-right", "nav-up", "next",
    "pause", "play", "play-bookmark1", "play-bookmark10", "play-bookmark2",
    "play-bookmark3", "play-bookmark4", "play-bookmark5", "play-bookmark6",
    "play-bookmark7", "play-bookmark8", "play-bookmark9", "play-pause",
    "position", "prev", "program-sid-next", "program-sid-prev", "quit",
    "random", "rate-faster-fine", "rate-normal", "rate-slower-fine",
    "record", "set-bookmark1", "set-bookmark10", "set-bookmark2",
    "set-bookmark3", "set-bookmark4", "set-bookmark5", "set-bookmark6",
    "set-bookmark7", "set-bookmark8", "set-bookmark9", "slower",
    "snapshot", "stop", "subdelay-down", "subdelay-up", "subpos-down",
    "subpos-up", "subsync-apply", "subsync-markaudio", "subsync-marksub",
    "subsync-reset", "subtitle-revtrack", "subtitle-text-scale-down",
    "subtitle-text-scale-normal", "subtitle-text-scale-up",
    "subtitle-toggle", "subtitle-track", "title-next", "title-prev",
    "toggle-autoscale", "toggle-fullscreen", "uncrop-bottom",
    "uncrop-left", "uncrop-right", "uncrop-top", "unzoom",
    "viewpoint-fov-in", "viewpoint-fov-out", "viewpoint-roll-anticlock",
    "viewpoint-roll-clock", "vol-down", "vol-mute", "vol-up", "wallpaper",
    "zoom", "zoom-double", "zoom-half", "zoom-original", "zoom-quarter",
)

# The only keys a classroom DVD responds to.
#
# Esc quits rather than leaving fullscreen: DVD mode is the whole screen,
# so there is nothing to leave, and leaving it used to strand people on a
# black VLC window with no way out. Volume is deliberately absent — the
# television owns volume.
CLASSROOM_HOTKEYS = {
    "play-pause": "Space",
    "quit": "Esc",
    # Disc menu navigation. Without these a menu can only be clicked.
    "nav-up": "Up",
    "nav-down": "Down",
    "nav-left": "Left",
    "nav-right": "Right",
    "nav-activate": "Enter",
}

# VLC dressed down to a playback surface. Verified against 3.0.23.
PRESENTATION = (
    # DVD mode is the whole display, and the compositor fullscreens the
    # window the
    # moment it maps so no wallpaper is ever visible around it.
    "--fullscreen",
    # No menu bar, no panels, dark rather than light grey.
    "--qt-minimal-view",
    "--qt-dark-palette",
    # No orange cone or album-art panel behind the video.
    "--no-qt-bgcone",
    # VLC's own fullscreen controller is replaced by the classroom bar.
    "--no-qt-fs-controller",
    # Nothing that behaves like a desktop application.
    "--no-qt-system-tray",
    "--no-qt-name-in-title",
    "--no-qt-video-autoresize",
    "--qt-notification=0",
    # Never offer to resume, never keep a list of the discs played here.
    "--qt-continue=0",
    "--no-qt-recentplay",
    # No first-run privacy dialog, no title banner over the video.
    "--no-qt-privacy-ask",
    "--no-video-title-show",
)


def control_password():
    """A fresh password for this session's control interface."""
    return secrets.token_urlsafe(24)


def player_command(device, port, password):
    """The full VLC command line for a DVD session.

    The HTTP control interface is how the classroom's own control bar
    reaches VLC. It triggers hotkey *actions* by name, which keeps
    working after every key has been unbound, and it listens on the
    loopback address behind a password generated for this session only.
    """
    command = [PLAYER, *PRESENTATION]

    for hotkey in ALL_HOTKEYS:
        command.append(f"--key-{hotkey}=")

    for hotkey, binding in CLASSROOM_HOTKEYS.items():
        command.append(f"--key-{hotkey}={binding}")

    command += [
        "--extraintf",
        "http",
        "--http-host",
        "127.0.0.1",
        "--http-port",
        str(port),
        "--http-password",
        password,
    ]

    # dvd:// selects dvdnav, which is what provides the disc menus.
    command.append(f"dvd://{device}")

    return command