#!/bin/bash

# from: https://gist.github.com/RichardBronosky/56d8f614fab2bacdd8b048fb58d0c0c7

LINUX_copy() {
  cat | xclip -selection clipboard
}

LINUX_paste() {
  xclip -selection clipboard -o
}

WSL_copy() {
  cat | /mnt/c/Windows/System32/clip.exe
}

WSL_paste() {
  /mnt/c/Windows/System32/WindowsPowerShell/v1.0/powershell.exe Get-Clipboard | sed 's/\r//'
}

CYGWIN_copy() {
  cat >/dev/clipboard
}

CYGWIN_paste() {
  cat /dev/clipboard
}

MAC_copy() {
  cat | pbcopy
}

MAC_paste() {
  pbpaste
}

stdin_is_a_pipe() {
  [[ -p /dev/stdin ]]
}

stdin_is_a_tty() {
  [[ -t 0 ]]
}

stdin_is_pipe_like() {
  stdin_is_a_pipe || ! stdin_is_a_tty
}

stdout_is_pipe_like() {
  ! stdout_is_a_tty # meaning # it must be a pipe or redirection
}

stdout_is_a_tty() {
  [[ -t 1 ]]
}

requested_open_ended() {
  [[ ${args[0]:-} == "-" ]]
}

requested_test_suite() {
  [[ ${args[0]:-} == "--test" ]]
}

enable_tee_like_chaining() {
  # see `man tee`
  if stdout_is_pipe_like; then
    ${os}_paste
  elif requested_open_ended; then
    ${os}_paste
    echo
  fi
}

prevent_prompt_from_being_on_the_same_line() {
  if stdout_is_a_tty; then # we don't have to be strict about not altering the output
    echo
  fi
}

detect_os() {
  if [[ -f /proc/version ]] && grep -iq Microsoft /proc/version; then
    printf WSL
  else
    case "$(uname -s)" in
    Linux*) printf LINUX ;;
    Darwin*) printf MAC ;;
    CYGWIN*) printf CYGWIN ;;
    esac
  fi
}

test_suite() {
  # setup
  printf '1234' | ${BASH_SOURCE[0]}

  printf "\n1. output to TTY\n"
  ${BASH_SOURCE[0]}
  printf "1234 should be above.\n"

  printf "\n2. output to pipe\n"
  ${BASH_SOURCE[0]} | cat
  echo
  printf "1234 should be above.\n"

  printf "\n3. input from pipe and output to pipe\n"
  printf '1234' | ${BASH_SOURCE[0]} | cat
  echo
  printf "1234 should be above.\n"
}

function debug() {
  stdin_is_a_pipe && echo "stdin_is_a_pipe: 1" >>/tmp/ono || echo "stdin_is_a_pipe: 0" >>/tmp/ono
  stdin_is_a_tty && echo "stdin_is_a_tty: 1" >>/tmp/ono || echo "stdin_is_a_tty: 0" >>/tmp/ono
  stdin_is_pipe_like && echo "stdin_is_pipe_like: 1" >>/tmp/ono || echo "stdin_is_pipe_like: 0" >>/tmp/ono
  stdout_is_pipe_like && echo "stdout_is_pipe_like: 1" >>/tmp/ono || echo "stdout_is_pipe_like: 0" >>/tmp/ono
  stdout_is_a_tty && echo "stdout_is_a_tty: 1" >>/tmp/ono || echo "stdout_is_a_tty: 0" >>/tmp/ono
  echo >>/tmp/ono
}

main() {
  os="$(detect_os)"
  if stdin_is_pipe_like; then
    "${os}_copy"
    enable_tee_like_chaining
  else # stdin is not pipe-like
    "${os}_paste"
    prevent_prompt_from_being_on_the_same_line
  fi
}

args=("$@")
if requested_test_suite; then
  export DEBUG=1
  test_suite
else
  [[ ${DEBUG:-} == 1 ]] && debug
  main
fi