#!/usr/bin/env bash
set -u

LOGTAG="revive-monitor-drm-watch"
CONFIG_FILE="${XDG_CONFIG_HOME:-$HOME/.config}/revive-monitor/config.env"
FIX_SCRIPT="${REVIVE_MONITOR_FIX_SCRIPT:-$HOME/.local/bin/revive-monitor-fix}"

# Defaults. Override in ~/.config/revive-monitor/config.env
DEBOUNCE_SECONDS="30"

if [[ -r "$CONFIG_FILE" ]]; then
    # shellcheck disable=SC1090
    source "$CONFIG_FILE"
fi

STATE_DIR="${XDG_RUNTIME_DIR:-/tmp}/revive-monitor"
LAST_RUN_FILE="$STATE_DIR/last-drm-hotplug-run"

mkdir -p "$STATE_DIR"

log() {
    logger -t "$LOGTAG" -- "$*"
}

get_active_wayland_session() {
    local sid
    local name
    local type
    local active
    local vt

    while read -r sid; do
        [[ -n "$sid" ]] || continue

        name="$(loginctl show-session "$sid" -p Name --value 2>/dev/null)"
        [[ "$name" == "$USER" ]] || continue

        type="$(loginctl show-session "$sid" -p Type --value 2>/dev/null)"
        [[ "$type" == "wayland" ]] || continue

        active="$(loginctl show-session "$sid" -p Active --value 2>/dev/null)"
        [[ "$active" == "yes" ]] || continue

        vt="$(loginctl show-session "$sid" -p VTNr --value 2>/dev/null)"

        if [[ "$vt" =~ ^[1-9][0-9]*$ ]]; then
            printf '%s:%s\n' "$sid" "$vt"
            return 0
        fi
    done < <(
        loginctl list-sessions --no-legend --no-pager 2>/dev/null | awk '{print $1}'
    )

    return 1
}

run_recovery() {
    local session_info
    local session_id
    local graphical_vt
    local now
    local last="0"
    local diff

    if ! session_info="$(get_active_wayland_session)"; then
        log "No active Wayland session - DRM hotplug ignored"
        return 0
    fi

    session_id="${session_info%%:*}"
    graphical_vt="${session_info##*:}"

    now="$(date +%s)"

    if [[ -r "$LAST_RUN_FILE" ]]; then
        last="$(cat "$LAST_RUN_FILE" 2>/dev/null || printf '0')"
    fi

    [[ "$last" =~ ^[0-9]+$ ]] || last="0"
    diff=$((now - last))

    if (( diff < DEBOUNCE_SECONDS )); then
        log "DRM hotplug ignored because of debounce (${diff}s)"
        return 0
    fi

    printf '%s\n' "$now" > "$LAST_RUN_FILE"

    log "DRM hotplug detected - Wayland session $session_id on VT $graphical_vt"

    "$FIX_SCRIPT" "$graphical_vt"

    log "Recovery after DRM hotplug finished"
}

if ! command -v udevadm >/dev/null 2>&1; then
    log "udevadm not found"
    exit 1
fi

if [[ ! -x "$FIX_SCRIPT" ]]; then
    log "Recovery script is not executable: $FIX_SCRIPT"
    exit 1
fi

log "Listening for DRM hotplug events"

stdbuf -oL udevadm monitor --kernel --property --subsystem-match=drm |
while IFS= read -r line; do
    case "$line" in
        HOTPLUG=1)
            run_recovery
            ;;
    esac
done