pair

#!/usr/bin/env bash
# Usage: pair [<github-user>] [-t <tmux-session>]
#
# Copy the command to clipboard which grants another person access to the tmux
# session on your machine. The resulting command is in format:
#
#   ssh -t <USER>@<HOST> 'tmux attach -t <SESSION>'
#
# When given a GitHub username, it will adopt SSH keys from their GitHub
# account and add them to your `~/.ssh/authorized_keys`.

# Requirements:
# - tmux
# - ssh server
# - "github-auth" gem

set -e

tmux_session=""
github_user=""

while [ -n "$1" ]; do
  case "$1" in
  '-h' | '--help' )
    sed -ne '/^#/!q;s/.\{1,2\}//;1d;p' < "$0"
    exit 0
    ;;
  '-t'* )
    tmux_session="${1:2}"
    if [ -z "$tmux_session" ]; then
      tmux_session="$2"
      shift 2
    else
      shift 1
    fi
    ;;
  * )
    github_user="$1"
    shift 1
  esac
done

ssh_port=22

if ! nc -zv localhost $ssh_port >/dev/null 2>&1; then
  echo "Error: it seems that sshd is not running on the port $ssh_port" >&2
  if [ "$(uname -s)" = "Darwin" ]; then
    echo "Tip: System Preferences -> Sharing -> enable 'Remote Login'" >&2
  fi
  exit 1
fi

host="$(curl -fsS icanhazip.com)"
tmux="$(which tmux)"

if [ -n "$github_user" ]; then
  gh-auth add --users "$github_user"
fi

if [ -z "$tmux_session" ]; then
  tmux_session="$(tmux display -p '#{session_name}')"
fi

echo ssh -t ${USER}@${host} "'${tmux} at -t ${tmux_session}'" | tee >(pbcopy)