#!/usr/bin/env bash

set -euo pipefail

# NOTE: Neither WAYLAND_DISPLAY nor DISPLAY may be exported when starting
# KWin.  KWin uses their presence (even as empty strings) to select the
# nested Wayland or X11 backend instead of the bare-metal DRM/KMS backend.
# Clients (the greeter UI, KDE session apps) receive WAYLAND_DISPLAY from
# redbear-session-launch instead.
unset DISPLAY
unset WAYLAND_DISPLAY
export XDG_SESSION_TYPE=wayland
export LIBSEAT_BACKEND=seatd
export SEATD_SOCK=/run/seatd.sock
export QT_PLUGIN_PATH="${QT_PLUGIN_PATH:-/usr/plugins}"
export QT_QPA_PLATFORM_PLUGIN_PATH="${QT_QPA_PLATFORM_PLUGIN_PATH:-/usr/plugins/platforms}"
export QML2_IMPORT_PATH="${QML2_IMPORT_PATH:-/usr/qml}"
export QT_WAYLAND_SHELL_INTEGRATION="${QT_WAYLAND_SHELL_INTEGRATION:-xdg-shell}"
export XCURSOR_THEME="${XCURSOR_THEME:-Pop}"
export XKB_CONFIG_ROOT="${XKB_CONFIG_ROOT:-/usr/share/X11/xkb}"
export KWIN_COMPOSE="${KWIN_COMPOSE:-O2}"
export QT_DEBUG_PLUGINS=1
export QT_LOGGING_RULES="${QT_LOGGING_RULES:-*.debug=true}"
export MESA_LOADER_DRIVER_OVERRIDE="${MESA_LOADER_DRIVER_OVERRIDE:-virtio_gpu}"

if [ -z "${XDG_RUNTIME_DIR:-}" ]; then
    export XDG_RUNTIME_DIR="/tmp/run/redbear-greeter"
fi

mkdir -p "$XDG_RUNTIME_DIR"

drm_scheme_ready() {
    # Check if /scheme/drm/card0 can be opened. On Redox, stat and test -e
    # are unreliable for scheme paths. Opening the scheme path with redir
    # succeeds if the scheme daemon has registered the device, fails otherwise.
    # Do NOT read from it (head -c 1) — DRM scheme fds are request/response,
    # not streaming, so a read would block waiting for a request response.
    ( exec 3<"/scheme/drm/card0" && exec 3>&- ) >/dev/null 2>&1
}

wait_for_drm_scheme() {
    local wait_seconds="${REDBEAR_DRM_WAIT_SECONDS:-10}"
    local attempts=0

    if drm_scheme_ready; then
        return 0
    fi

    echo "redbear-greeter-compositor: waiting up to ${wait_seconds}s for DRM device(s): /scheme/drm:/scheme/drm/card0" >&2

    attempts=$((wait_seconds * 2))

    while [ "$attempts" -gt 0 ]; do
        if drm_scheme_ready; then
            return 0
        fi

        sleep 0.5
        attempts=$((attempts - 1))
    done

    drm_scheme_ready
}

# Prefer kwin_wayland (real KWin compositor). Fall back to redbear-compositor only if
# KWin is not installed (e.g. text-only target accidentally includes greeter).
COMPOSITOR=""
if command -v kwin_wayland >/dev/null 2>&1; then
    COMPOSITOR="kwin_wayland"
elif command -v /usr/bin/kwin_wayland >/dev/null 2>&1; then
    COMPOSITOR="/usr/bin/kwin_wayland"
elif command -v redbear-compositor >/dev/null 2>&1; then
    COMPOSITOR="redbear-compositor"
    echo "redbear-greeter-compositor: kwin_wayland not found, falling back to redbear-compositor" >&2
else
    echo "redbear-greeter-compositor: no compositor found (need kwin_wayland or redbear-compositor)" >&2
    exit 1
fi

# pcid-spawner is intentionally async in Red Bear OS, so service ordering only guarantees that
# spawning has started. Wait for the DRM scheme to appear.
if wait_for_drm_scheme; then
    export KWIN_DRM_DEVICES="${KWIN_DRM_DEVICES:-/scheme/drm/card0}"
    echo "redbear-greeter-compositor: using DRM compositor backend (KWIN_DRM_DEVICES=${KWIN_DRM_DEVICES})" >&2

    # NOTE: QDBusConnection::sessionBus() blocks on Redox when attempting Unix socket
    # connect(), even when dbus-daemon is running. All KWin sessionBus() calls in the
    # startup path have been bypassed in the KWin source. We do NOT set
    # DBUS_SESSION_BUS_ADDRESS so that remaining sessionBus() calls with env-var guards
    # skip gracefully. If a future change re-enables D-Bus session bus, the Qt/Redox
    # Unix socket connect() issue must be resolved first.

    echo "redbear-greeter-compositor: env DBUS_SESSION_BUS_ADDRESS=${DBUS_SESSION_BUS_ADDRESS:-unset} DBUS_SYSTEM_BUS_ADDRESS=${DBUS_SYSTEM_BUS_ADDRESS:-unset}" >&2
    echo "redbear-greeter-compositor: launching $COMPOSITOR" >&2
    unset QT_QPA_PLATFORM
    "$COMPOSITOR"
    EXIT_CODE=$?
    echo "redbear-greeter-compositor: compositor exited with code $EXIT_CODE" >&2
    exit $EXIT_CODE
fi

# No DRM at all — fall back to virtual backend.
unset KWIN_DRM_DEVICES
echo "redbear-greeter-compositor: no DRM device found, using virtual compositor backend" >&2
"$COMPOSITOR"
exit $?