# Shell script for `nix run .#lab` (see flake.nix).
{ lib, driver, nodes }:
''
  sock=nixos-router-lab
  log=$(mktemp -t nixos-router-lab.XXXXXX)
  trap 'tmux -L $sock kill-server 2>/dev/null || true; rm -f "$log"' EXIT
  tmux -L $sock kill-server 2>/dev/null || true

  # Bottom pane: the test-driver REPL. `script` keeps it on a tty while
  # logging everything it prints, which the per-VM panes below filter.
  # When the REPL exits, take the whole session down.
  repl=$(tmux -L $sock new-session -d -x 220 -y 60 -s lab -P -F '#{pane_id}' \
    "script -qfc '${driver}/bin/nixos-test-driver --interactive' '$log'; tmux -L $sock kill-server")
  tmux -L $sock set -g pane-border-status top
  tmux -L $sock select-pane -t "$repl" -T repl

  # Top row: one pane per VM, console lines only (prefixed "<name> #").
  prev="$repl"
  first=1
  remaining=${toString (builtins.length nodes - 1)}
  for node in ${lib.escapeShellArgs nodes}; do
    cmd="tail -F '$log' 2>/dev/null | grep -a --line-buffered -E \"(^|\\[[0-9;]*m)$node #\""
    if [ "$first" = 1 ]; then
      prev=$(tmux -L $sock split-window -vb -l 65% -t "$prev" -P -F '#{pane_id}' "$cmd")
      first=0
    else
      # Give the new pane its share of the pane being split, so the row ends up even.
      prev=$(tmux -L $sock split-window -h -l "$((100 * remaining / (remaining + 1)))%" -t "$prev" -P -F '#{pane_id}' "$cmd")
      remaining=$((remaining - 1))
    fi
    tmux -L $sock select-pane -t "$prev" -T "$node"
  done

  # Boot the VMs once the REPL is ready, and leave a reminder at the prompt.
  for _ in $(seq 60); do
    tmux -L $sock capture-pane -p -t "$repl" | grep -q CPython && break
    sleep 0.5
  done
  tmux -L $sock send-keys -t "$repl" 'start_all()' Enter
  tmux -L $sock send-keys -t "$repl" -l 'print("router.shell_interact() | client.succeed(\"ip a\") | test_script() | Ctrl-D quits, Ctrl-b d detaches")'
  tmux -L $sock send-keys -t "$repl" Enter
  tmux -L $sock select-pane -t "$repl"
  tmux -L $sock attach -t lab
''