#!/usr/bin/env bash
# creates a writeable docker instance

# exit if a command fails
set -o errexit

# exit if required variables are not set
set -o nounset

# return the exit status of the final command before a failure
set -o pipefail

# check for dependencies
script_commands="gotty tmux"
missing_counter=0
for needed_command in ${script_commands}; do
  if ! hash "${needed_command}" >/dev/null 2>&1; then
    printf "Command not found in PATH: %s\n" "${needed_command}" >&2
    ((missing_counter++))
  fi
done
if ((missing_counter > 0)); then
  printf "Minimum %d commands are missing in PATH, aborting.\n" "${missing_counter}" >&2
  exit 1
fi

# make sure exactly one argument was passed
if [ "$#" -eq 2 ]; then
  distro="$1"
  command="$2"
else
  echo -e "\nUsage: $0 <docker image> <command>\n"
  exit 1
fi

## configure gotty
# listen port
listen_port="${listen_port:-"1337"}"

# web login credentials
gotty_user="${gotty_user:-"admin"}"
gotty_pass="${gotty_pass:-"fnord"}"

# tab name
gotty_title="${gotty_title:-"Try Me!"}"

## configure docker
# cores
cpu_limit="${cpu_limit:-"1"}"

# memory
mem_limit="${mem_limit:-"128m"}"

# memory+swap
swap_limit="${swap_limit:-"256m"}"

# hostname
host_name="${host_name:-"tryme"}"

# kill any existing tmux session, and start a new one
tmux has-session -t tryme && tmux kill-session -t tryme && echo "Killed old tmux session..." >/dev/null 2>&1
tmux -2 new-session -d -s tryme
echo "Created new tmux session..."

# expose an ephemeral container via gotty
tmux rename-window -t tryme:0 'GoTTY'
tmux select-window -t tryme:0
tmux send-keys "gotty --title-format "${gotty_title}" --credential "${gotty_user}":"${gotty_pass}" --port "${listen_port}" -w -- docker run --interactive --tty --rm --hostname="${host_name}" --cpus="${cpu_limit}" --memory="${mem_limit}" -- "${distro}" "${command}"" C-m
echo "Launched GoTTY..."

# attach to the new tmux session
tmux -2 attach-session -t tryme