Add experimental dunst support

Added simple support for dunst files. Since files can, similar to
alacritty, not be included in dunstrc, the processor invokes a similarly
invasive replacement method to add the base16 at the end of the config
file.

The procedure is similar to alacritty processor, the danger is also the
same -- it works directly on the config file and will worst case delete
the complete contents of this file. Since the processor is not tested
(other than manually looking that it does what it's supposed to) the
case of this happening is not negligible.

theme_dunst

@@ -0,0 +1,116 @@
+#!/usr/bin/env bash
+readonly dependency=("khamer/base16-dunst")
+readonly app="dunst"
+#
+# Alacritty does not support including other files into
+# its configuration yet. As such, this processor needs to
+# change the user's configuration file *itself*.
+#
+# This will generally not be a problem, though it can lead
+# to corrupted configurations in exceptional circumstances
+# (such as every line being preceded by the process control
+# regex, for whatever reason).
+#
+# In general, the processor looks for a specific line in the
+# following format:
+# '# Base16 [theme name] - alacritty color config'
+# from which it will delete everything until it finds a line:
+# '# Base16End [theme name] - alacritty color config'
+# So, if you don't want to lose anything -
+# Do NOT put anything important between those two lines.
+
+path="$1"
+package="$2"
+theme="$3"
+permanent="$4"
+
+dunst_conf="$HOME/.config/dunst/dunstrc"
+
+## Main Entrypoint
+#
+#  Finds the right theme template file and starts theme
+#  switching and, if necessary, permanent setting processes.
+main() {
+  dbg_msg $app "Starting Processor"
+  tfile="$path/$package/themes/base16-$theme.dunstrc"
+
+  if ! file_exists "$tfile"; then
+    dbg_msg $app "error" "Theme template $theme not found in package $package"
+    exit 1
+  fi
+
+  if [ ! -f "$dunst_conf" ]; then
+    dbg_msg $app "error" "$app config file not found. Please make sure file exists: $dunst_conf"
+  fi
+
+  if [[ "$permanent" == "true" ]]; then save; fi
+
+  dbg_msg $app "Processor Done"
+}
+
+## Theme setter
+#
+#  Takes care of permanently writing the desired
+#  base16 theme into application settings.
+save() {
+  dbg_msg $app "Saving theme"
+
+  startline="$(grep -ne '^# Base16 .*- dunst color config$' "$dunst_conf" | cut -f1 -d:)"
+  endline="$(grep -ne '^# Base16End .*- dunst color config$' "$dunst_conf" | cut -f1 -d:)"
+
+  tmpfile="$dunst_conf.tmp"
+  tmptheme="$dunst_conf.thm.tmp"
+  echo "" >"$tmpfile"
+  echo "" >"$tmptheme"
+
+  if [[ -n "$startline" && -z "$endline" ]] || [[ -z "$startline" && -n "$endline" ]] || [[ "$startline" -gt "$endline" ]]; then
+    dbg_msg $app "error" "Base 16 Pattern not correctly recognized in file: $dunst_conf. Please make sure pattern begins with # Base16 and ends with # Base16End and only exists once in the file. No changes to file made."
+    cat "$dunst_conf" >"$tmpfile" || exit 1
+
+  elif [[ -z "$startline" && -z "$endline" ]]; then
+    dbg_msg $app "warn" "No previous Base16 pattern found in file: $dunst_conf. If this is your first time running the processor, ignore this warning."
+    cat "$dunst_conf" >"$tmpfile" || exit 1
+
+  else
+    # remove old lines of any base16 theme
+    sed -e "$startline,$endline d" "$dunst_conf" >"$tmpfile" || exit 1
+
+  fi
+
+  # fix template theme name key for easier inclusion
+  echo "# Base16 $theme - dunst color config" >"$tmptheme"
+  cat "$tfile" >>"$tmptheme" || exit 1
+  echo "# Base16End $theme - dunst color config" >>"$tmptheme"
+
+  # combine both into final config file
+  # replace original file with new colorscheme-added version
+
+  cat "$tmpfile" "$tmptheme" >"$dunst_conf"
+
+  [ -f "$tmptheme" ] && rm "$tmptheme"
+  [ -f "$tmpfile" ] && rm "$tmpfile"
+
+  dbg_msg $app "Saved theme to $dunst_conf"
+
+  save_post
+}
+
+save_post() {
+  pkill dunst
+  dunst &
+}
+
+# Safe sourcing: https://stackoverflow.com/a/12694189
+DIR="${BASH_SOURCE%/*}"
+if [[ ! -d "$DIR" ]]; then DIR="$PWD"; fi
+# shellcheck source=utilities.sh
+. "$DIR/utilities.sh"
+## Dependency Checker
+#
+#  Makes sure the processor is called for the correct
+#  base16 package, or refuses to run if it is not.
+if printf '%s\n' "${dependency[@]}" | grep -q -P "^$package$"; then
+  main
+else
+  dbg_msg $app "error" "Processor does not work for package $package"
+fi