#!/usr/bin/env bash
#
# Applies flake.nix to this Mac: installs Homebrew and Nix, switches to its configuration, and verifies the result.
#
#   curl -fsSL https://dotfiles.creasty.com/apply | bash  # on a new Mac, cloning this repository to ~/dotfiles
#   ./apply [darwin-rebuild options]                      # from that clone, to apply changes

set -euo pipefail

: "${DOTFILES_NOVERIFY:=0}"

DOTFILES_PATH="$HOME/dotfiles"
NIX=/nix/var/nix/profiles/default/bin/nix

print_header() {
  printf "\e[34m"
  cat << 'EOF'
--------------------------------------------------------------------------------
.'       -'        -'      '--   -._                                          \
      _.     _   '''    '''''-                                                 \
     _'     --     _     ___          '-_     \
 /    /         _ ' '''       ._   '           \
/              '    _   .   '-     -_                                |    |
     /                        ╷        ╷   ╭──┐ ╷                    |    |
     /        /     .     ╭───┤ ╭───╮ ─┼───┼──┐ │ ╭───╮ ╭───╮         |   |
       |     /    / '-    │   │ │   │  │   │  │ │ ├───╯ ╰───╮         |   |
       |          | /   • ╰───╯ ╰───╯  ╰─  ╵  ╵ ╵ ╰───╯ ╰───╯
      |            |\                                          |
  |  |     \              Stellar productivity by @creasty     |
  |\ \      \             '   _      /     /                  |
            ____           _.-      /     /
       __-''    ''''-_.  ___        '_____  _..-'''''''''''-....----''''''-.  |
----'''                ''   '''--''''     ''                                '.
                                                                              '-
--------------------------------------------------------------------------------
EOF
  printf "\e[0m"
}

# flake.nix configures only Apple silicon; a shell under Rosetta would have Homebrew install for Intel
check_os() {
  if [ "$(uname -s)" != Darwin ] || [ "$(uname -m)" != arm64 ]; then
    echo 'Sorry, this script is intended only for macOS on Apple silicon, in a shell not under Rosetta'
    exit 1
  fi
}

# nix-darwin installs what Homebrew provides, but not Homebrew itself.
# Its installer also installs the Command Line Tools, without which git only offers to install them.
install_homebrew() {
  [ -x /opt/homebrew/bin/brew ] && return
  echo 'Installing homebrew...'
  sudo -v # with NONINTERACTIVE, Homebrew's installer aborts instead of asking for the password
  NONINTERACTIVE=1 /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"
  echo 'done'
}

accept_xcode_license() {
  [[ "$(/usr/bin/xcrun clang 2>&1 || true)" =~ 'license' ]] || return 0
  echo 'Agreeing to Xcode license...'
  sudo xcodebuild -license accept
  echo 'done'
}

install_nix() {
  [ -x "$NIX" ] && return
  echo 'Installing Nix...'
  curl --proto '=https' --tlsv1.2 -sSf -L https://install.determinate.systems/nix | sh -s -- install --no-confirm
  echo 'done'
}

clone_or_update_repo() {
  if [ ! -d "$DOTFILES_PATH" ]; then
    echo 'Cloning repo...'
    git clone https://github.com/creasty/dotfiles.git "$DOTFILES_PATH"
    echo 'done'
    return
  fi
  if [ "$(git -C "$DOTFILES_PATH" branch --show-current)" != master ]; then
    echo 'Info: working on a non-master branch'
    return
  fi
  git -C "$DOTFILES_PATH" diff --quiet HEAD || return 0 # the switch warns that the tree is dirty
  echo 'Updating repo...'
  git -C "$DOTFILES_PATH" pull origin master
  echo 'done'
}

# Applies the configuration of flake.nix for this user (nix-darwin and home-manager)
switch_configuration() {
  echo 'Switching to the configuration...'
  sudo -H "$NIX" run "$DOTFILES_PATH#darwin-rebuild" -- switch --flake "$DOTFILES_PATH#$(id -un)" "$@"
  echo 'done'
}

# Runs the behavioral tests of what was just applied
verify_configuration() {
  [ "$DOTFILES_NOVERIFY" -eq 0 ] || return 0
  "$DOTFILES_PATH/verify"
}

main() {
  print_header
  check_os
  install_homebrew
  accept_xcode_license
  install_nix

  clone_or_update_repo

  switch_configuration "$@"
  verify_configuration
}

main "$@"