#!/usr/bin/env bash

## Back up my files to each of my external drives.
##
## Usage: backup
##
## Dependencies: GNU coreutils, GNU grep, GNU sed, rsync

set -euo pipefail
shopt -s inherit_errexit

die() { echo -e "$(basename "$0"): $1" >&2; exit 1; }

[[ " $* " =~ ' --help ' ]] && sed -n 's/^## *//p' "$0" && exit
(( UID != 0 )) || die 'do not run as root'

sources=(
  ~/./.archive
  ~/./.bashrc
  ~/./.config/.archive
  ~/./.config/Xresources
  ~/./.config/chromium/Default/Bookmarks
  ~/./.config/chromium/Default/Custom\ Dictionary.txt
  ~/./.config/dunst
  ~/./.config/emacs/.archive
  ~/./.config/emacs/init.el
  ~/./.config/emacs/lisp
  ~/./.config/emacs/themes
  ~/./.config/fontconfig
  ~/./.config/git
  ~/./.config/gpick/README
  ~/./.config/gthumb/README
  ~/./.config/gtk-3.0
  ~/./.config/gtk-4.0
  ~/./.config/mpv
  ~/./.config/openbox
  ~/./.config/pip
  ~/./.config/procps/README
  ~/./.config/shellcheckrc
  ~/./.config/user-dirs.dirs
  ~/./.config/zathura
  ~/./.gnupg
  ~/./.ignore
  ~/./.local/share/.archive
  ~/./.local/share/password-store
  ~/./.local/share/selectcmd.dat
  ~/./.local/share/systemd/user
  ~/./.local/share/zathura
  ~/./.mozilla/firefox/j8lriz5r.4/.archive
  ~/./.mozilla/firefox/j8lriz5r.4/bookmarkbackups
  ~/./.mozilla/firefox/j8lriz5r.4/bookmarks.html
  ~/./.mozilla/firefox/j8lriz5r.4/chrome
  ~/./.mozilla/firefox/j8lriz5r.4/persdict.dat
  ~/./.mozilla/firefox/j8lriz5r.4/sessionstore-backups
  ~/./.mozilla/firefox/j8lriz5r.4/user.js
  ~/./.npmrc
  ~/./.ssh
  ~/./.xinitrc
  ~/./main
)

exclusions=(
  --exclude='*.asc' # OpenPGP keys exported for temporary use.
  --exclude='*.log'
  --exclude='*.log.*' # foo.log.2, foo.log.old, etc.
  --exclude='*.sqlite-wal' # Write-ahead log files.
  --exclude='.build/*'
  --exclude='.next/*' # Build directory for Next.js apps.
  --exclude='.wrangler/*' # Temporary files for projects that use Wrangler.
  --exclude='__pycache__/*'
  --exclude='build/*' # Build directory for Remix apps.
  --exclude='dist/*' # Build directory for Astro projects.
  --exclude='joshscalisi.com/src/dotfiles/*'
  --exclude='joshscalisi.com/src/scripts/*'
  --exclude='joshscalisi.com/vendor/*'
  --exclude='node_modules/*'
)

destinations=(
  /media/wd-25a2-2tb/backups
  /media/wd-25e2-2tb-1/backups
  /media/wd-25e2-2tb-2/backups
)

# Create backups.
for dest in "${destinations[@]}"; do
  [[ -d $dest ]] || die "destination not found: $dest"

  latest_backup=$dest/latest
  new_backup=$dest/$(date +%Y/%m/%d%H%M%S)
  rsync_opts=(-vaRHAXh --mkpath "${exclusions[@]}")

  # Enable the creation of hard links to unchanged files if there is a previous
  # backup in the destination directory.
  if [[ -d $latest_backup ]]; then
    rsync_opts+=(--link-dest="$latest_backup")
  else
    echo -e "\nPrevious backup not found: $latest_backup"
    read -rp 'Create a new full backup without hard links? ' input
    [[ $input =~ ^[Yy] ]] && break
  fi

  echo -e "\nCreating backup in $new_backup"
  rsync "${rsync_opts[@]}" "${sources[@]}" "$new_backup" |
    # Don't print blank lines, directories, or Git files.
    grep -ve '^$' -e '/$' -e '/.git/'
  ln -fns "$new_backup" "$latest_backup"
done