#!/usr/bin/env bash
# Attach a browser (via ttyd) to a single tmux window by linking it into a
# private temporary session. Unlike grouped sessions, link-window leaves no
# permanent group label on the source session, and each browser tab gets an
# independent view (own active window, own status setting).
# Usage: tmux-web-attach.sh <session> [window-index]
set -euo pipefail

sess="${1:-}"
win="${2:-}"

if [ -z "$sess" ]; then
  echo "missing session. open this page from the kanban Live Agents panel."
  sleep 2
  exit 1
fi

# Only accept existing session names; never interpret arbitrary input.
if ! tmux list-sessions -F '#{session_name}' 2>/dev/null | grep -Fxq -- "$sess"; then
  echo "unknown session: $sess"
  sleep 2
  exit 1
fi

# Default to the session's active window; validate the index either way.
if [ -z "$win" ]; then
  win="$(tmux display-message -p -t "$sess" '#{window_index}')"
fi
if ! tmux list-windows -t "$sess" -F '#{window_index}' | grep -Fxq -- "$win"; then
  echo "unknown window: $sess:$win"
  sleep 2
  exit 1
fi

src="$sess:$win"
tmp="web-$$-$RANDOM"

tmux new-session -d -s "$tmp" -x 220 -y 60
tmux set-option -t "$tmp" status off
# mouse on (session-scoped, local clients unaffected): wheel / touch scrolling
# from the browser enters copy-mode and scrolls history naturally, no prefix keys.
tmux set-option -t "$tmp" mouse on
# Replace the placeholder window with a link to the target window (-k kills the placeholder).
first="$(tmux display-message -p -t "$tmp" '#{window_index}')"
tmux link-window -k -s "$src" -t "$tmp:$first"

# A tmux window has a single size shared by every viewer. With the global
# "latest" policy a bigger local client cuts the browser view off, so pin this
# window to "smallest" while a web viewer is attached: the browser always sees
# the full content; a larger local client sees dotted padding instead.
tmux set-window-option -t "$src" window-size smallest

cleanup() {
  tmux set-window-option -u -t "$src" window-size 2>/dev/null || true
  tmux kill-session -t "$tmp" 2>/dev/null || true
}
trap cleanup EXIT HUP TERM INT

# destroy-unattached must be set only after attaching (it kills detached sessions instantly).
tmux attach -t "$tmp" \; set-option destroy-unattached on