#!/usr/bin/env bash
# scripts/desk-autoswitch.sh — hotplug daemon: apply the matching desk profile
# when the SET OF OUTPUTS changes.
#
# niri has no dedicated hotplug event (verified on 26.04):
# - WorkspacesChanged carries every workspace's `output`, so the sorted
#   unique set of outputs changes exactly on connect/disconnect.
# - OutputConfigChanged is only an ACK that an IPC/config output change was
#   Applied (niri-ipc), NOT a hotplug signal.
#
# Usage: desk-autoswitch.sh watch
#
# Environment overrides:
#   DESK_AUTO_HOSTNAME  only run on this hostname (default: blankpad)
#   DESK_SCRIPT         path to desk.sh (default ~/.local/bin/desk.sh)
#   DESK_NIRI           niri binary (default niri)
#   DESK_DEBOUNCE_S     min seconds between applies (default 1.5)

set -euo pipefail

HOST="${DESK_AUTO_HOSTNAME:-blankpad}"
DESK="${DESK_SCRIPT:-$HOME/.local/bin/desk.sh}"
NIRI="${DESK_NIRI:-niri}"
DEBOUNCE="${DESK_DEBOUNCE_S:-1.5}"

usage() { sed -n '2,18p' "$0" | sed 's/^# \{0,1\}//'; }

outputs_from_event() { # $1 = one JSON event line
  jq -r '[.WorkspacesChanged.workspaces[]?.output // empty] | unique | join(" ")' <<<"$1" 2>/dev/null || true
}

watch_mode() {
  [ "$(hostname)" = "$HOST" ] || { echo "desk-autoswitch: not on $HOST, exiting"; exit 0; }
  echo "desk-autoswitch: initial match"
  "$DESK" match --apply || true

  local seen="" last_seen="" last=0 now
  # One JSON event per line; reconnect forever (niri restart drops the stream).
  while "$NIRI" msg --json event-stream 2>/dev/null | while IFS= read -r line; do
    case "$line" in
      *WorkspacesChanged*)
        seen="$(outputs_from_event "$line")"
        [ -n "$seen" ] || continue
        [ "$seen" = "$last_seen" ] && continue
        last_seen="$seen"
        now="$(date +%s.%N)"
        # swallow bursts inside the debounce window
        if awk -v l="$last" -v n="$now" -v d="$DEBOUNCE" 'BEGIN { exit !(n - l >= d) }'; then
          last="$now"
          echo "desk-autoswitch: outputs changed [$seen]"
          "$DESK" match --apply || true
        fi
        ;;
    esac
  done; do :; done
}

case "${1:-}" in
  watch) watch_mode ;;
  -h|--help) usage ;;
  *) usage >&2; exit 1 ;;
esac