#!/usr/bin/env bash
# from https://github.com/0atman/noboilerplate/blob/main/scripts/38-nixos.md#dont-use-nix-env
# docstring=quick edit (or ling xD) for nixos config
set -E -o pipefail
shopt -s failglob
export LC_ALL=C.UTF8

INITIAL_PWD="$(pwd)"
PROJECT="$HOME/Projects/NixOS"
GIT_PATTERN="." # "*.nix"
SELF_EDITOR="$EDITOR" # here you can overwrite which editor should be used

# switch into the project for the whole script
cd "$PROJECT" || exit 1


exit_with_new_shell() {
  # check if already in directory
  [[ "$INITIAL_PWD" = "$PROJECT" ]] && printf '>>> already in directory\n' && exit 0

  cd "$PROJECT" || exit 1

  printf '\n'
  printf '>>> opening a new \"%s\" shell\n' "$(basename "$SHELL")"
  printf '    cwd: %s\n' "$(pwd)"
  "$SHELL"
  exit 0
}


ask_for_rebuild() {
  printf ">>> Do you want to rebuild NixOS? [y/N]\n"
  printf "<<< " && read -r YESNO
  if ! [[ "${YESNO,,}" == "y" ]]; then
    exit_with_new_shell
  fi
}


rebuild() {
  printf ">>> Rebuilding NixOS\n"
  sudo nixos-rebuild switch | tee nixos-switch.log || (
    grep --color error nixos-switch.log && false)
}

autoformat() {
  printf ">>> auto formating ..."
  nix fmt . &> /dev/null
  printf " DONE!\n"
}


quick_edit() {
  "$SELF_EDITOR"

  # check if there are changes at all
  [[ -z "$(git diff -U0 "$GIT_PATTERN")" ]] && echo ">>> no changes, exiting ..." && exit_with_new_shell

  # only then do auto formating
  autoformat

  # and then show the user a diff
  git diff -U0 "$GIT_PATTERN" # as a seperate command so we get nice colors and pager

  ask_for_rebuild

  printf ">>> Add everything to git staging so nix can find it\n"
  git add "$GIT_PATTERN"

  rebuild

  gen=$(nixos-rebuild list-generations | grep current)

  printf ">>> commiting to git\n"
  git commit -am "$gen"

  exit_with_new_shell
}


update() {
  nix flake update
  ask_for_rebuild
  rebuild
}


help_msg() {
  printf -- '# only one option can be selected\n'
  printf -- '  without arguments            -> quick edit mode\n'
  printf -- '--edit                 | -e    -> only edit\n'
  printf -- '--update               | -u    -> update the system\n'
  printf -- '--autoformat           | -f    -> only autoformat\n'
  printf -- '--new-shell-in-project | -s    -> start new shell, with cwd in the project\n'
  printf -- '--help                 | -h    -> show this message\n'
}


if [[ -z "$1" ]]; then
	quick_edit
elif [[ "$1" = "--edit" || "$1" = "-e" ]]; then
  "$SELF_EDITOR"
elif [[ "$1" = "--update" || "$1" = "-u" ]]; then
  update
elif [[ "$1" = "--autoformat" || "$1" = "-f" ]]; then
  autoformat
elif [[ "$1" = "--new-shell-in-project" || "$1" = "-s" ]]; then
  exit_with_new_shell
elif [[ "$1" = "--help" || "$1" = "-h" ]]; then
  help_msg
else
  help_msg
  printf "=================\n"
	printf "didn't recognise: %s\n" "$1"
  exit 1
fi