[styler] Add universal theme filter function

Added universal theme filtering. Universal means the theme exists for
each installed package. This is a (rough) way of knowing that it can
apply to every intended application -- though of course will not work if
more packages are installed than intended to be changed with processors.

The `styler list themes` command will default to only show universal
themes. To list all themes invoke with `styler list themes all`.

Styler will cache the available themes after the first retrieval. The
first retrieval still takes a while (~8.7 seconds for me), but
subsequent retrievals are much quicker. Cache will automatically be
rebuilt whenever a new package is downloaded, or an already downloaded
package is updated.
The filter function, as it stands it quite inefficient and could use
a better algorithm.

Uses rg or grep in descending preference.

styler/.local/bin/styler

@@ -1,11 +1,26 @@
 #!/usr/bin/env bash
 
 readonly BASE_PATH="${STYLER_DATA_PATH:-${XDG_DATA_HOME:-$HOME/.local/share}/styler}"
+readonly CACHE_PATH="${STYLER_CACHE_PATH:-${XDG_CACHE_HOME:-$HOME/.cache}/styler}"
 
 readonly PACKAGE_PATH="$BASE_PATH/packages"
 readonly PROCESSOR_PATH="$BASE_PATH/processors"
 
-readonly VERSION="0.3.0"
+readonly VERSION="0.4.1"
+
+# ensures that some grep-like program is available, prefers rg
+setgrepper() {
+  if command -v rg 1>/dev/null 2>&1; then
+    GREPPER="rg"
+  elif command -v grep 1>/dev/null 2>&1; then
+    GREPPER="grep"
+  else
+    notify-send "grep missing" "styler needs grep, or preferably rg to work."
+    echo "grep missing!" "styler needs grep, or preferably rg to work."
+    exit 127
+  fi
+}
+setgrepper
 
 main() {
   local cmd=""
@@ -34,7 +49,7 @@ main() {
   esac
   shift
 
-  $cmd "$1"
+  $cmd "$@"
   ret=$((ret + $?))
   exit $ret
 }
@@ -56,6 +71,8 @@ usage() {
     "                                         Same as 'theme' option, but changes will be made permanent." \
     "" \
     "     list [processors|packages|themes]   Print out all currently installed processors, templates, or themes from selection. " \
+    "     list themes                         Will print out themes which are available for all installed packages." \
+    "     list themes all                     Will print out every single installed theme, regardless of its universal availability." \
     "" \
     "     download    [username/repository]   Download a base16 template into the package directory or download a processor16" \
     "                                         into the processor directory. Use user/repo format to automatically pull from github." \
@@ -99,7 +116,7 @@ get_processors() {
       for processor in "$package"/*; do
         [[ -e "$processor" ]] || break
         [[ -f "$processor" ]] || break
-        if grep -q -e '/theme_[[:alnum:]]\{1,\}$' <<<"$processor"; then
+        if ${GREPPER} -q -e '/theme_[[:alnum:]]\{1,\}$' <<<"$processor"; then
           printf "%s\n" "$(basename -- "$processor")"
         fi
       done
@@ -107,11 +124,103 @@ get_processors() {
   done
 }
 
-# retrieves all installed themes from all packages, appends applications they exist for
+# retrieves all installed themes available to all packages
+# can be called with `all` argument to return themes which only exist for some packages
 get_themes() {
   local themes
   themes=$(find "$PACKAGE_PATH" -type f -name 'base16-*')
-  echo "$themes" | sed "s/.*\\/base16-//" | sed "s/\\..*//" | sort | uniq
+
+  local filtered
+  if [[ "$1" = "all" ]]; then
+    filtered="$(get_unique_themes "$themes")"
+  else
+    filtered="$(get_universal_themes "$themes")"
+  fi
+
+  echo "$filtered"
+}
+
+# filter down the list passed in to keep repeating base16 themes only once per name
+# and remove surrounding path information (and file ending)
+get_unique_themes() {
+  if _cache_invalid "$CACHED_UNIQUE_THEMES" "$PACKAGE_PATH"; then
+    notify-send "styler cache invalid" "rebuilding cache will take a moment..."
+    _cache_rebuild "$CACHED_UNIQUE_THEMES" _fetch_unique_themes "$@"
+  else
+    cat "$CACHED_UNIQUE_THEMES"
+  fi
+}
+readonly CACHED_UNIQUE_THEMES=${CACHE_PATH}/unique_themes
+
+# returns themes which are available in all installed packages
+# returns cached version or rebuilds cache
+get_universal_themes() {
+  if _cache_invalid "$CACHED_UNIVERSAL_THEMES" "$PACKAGE_PATH"; then
+    notify-send "styler cache invalid" "rebuilding cache will take a moment..."
+    _cache_rebuild "$CACHED_UNIVERSAL_THEMES" _fetch_universal_themes "$@"
+  else
+    cat "$CACHED_UNIVERSAL_THEMES"
+  fi
+}
+readonly CACHED_UNIVERSAL_THEMES=${CACHE_PATH}/universal_themes
+
+_fetch_unique_themes() {
+  echo "$1" | sed "s/.*\\/base16-//;s/\\..*//" | sort | uniq
+}
+
+# only keep themes which are available in every installed package
+_fetch_universal_themes() {
+  local themes="$1"
+  local unique
+  unique="$(get_unique_themes "$themes")"
+
+  local packages
+  packages="$(get_packages)"
+
+  local filtered
+  for t in $unique; do
+    for p in $packages; do
+      if ! echo "$themes" | ${GREPPER} -qe "^.*$p.*$t.*$" -; then
+        themes="$(echo "$themes" | sed "/$t/d")"
+        unique="$(echo "$unique" | sed "/$t/d")"
+        break
+      fi
+    done
+  done
+  echo "$unique"
+}
+
+# returns true if changes to $2 are newer than $1
+# used to pass in cache file for $1, what it is caching for $2
+_cache_invalid() {
+  cache_upd="$(_last_update "$1")"
+  live_upd="$(_last_update "$2")"
+  if [ "${live_upd%.*}" -gt "${cache_upd%.*}" ]; then
+    true
+  else
+    false
+  fi
+}
+
+# recreates target cache with output of function
+# arguments: "target_cache_file" "function_name" "arguments_for_function"
+_cache_rebuild() {
+  local target="$1"
+  shift
+  local fct="$1"
+  shift
+  local new
+  new="$($fct "$@")"
+  mkdir -p "$CACHE_PATH"
+  echo "$new" | tee "$target"
+}
+
+# returns time of last update to argument passed in
+# argument can be path to file or directory (searched recursively)
+# if argument does not exist gives 0
+_last_update() {
+  [[ ! -e "$1" ]] && echo 0 && return
+  find "$1" -type f -printf "%T@\n" | sort -n | tail -n 1
 }
 
 # temporarily switch theme, same thing as setting, only with permanence flag turned off for processors
@@ -152,7 +261,7 @@ set_theme() {
     appext=$(sed -e 's|^[A-Za-z0-9-]\{1,\}/base16-||' <<<"$pkg")
 
     # Compares application extension with existing processors and runs the appropriate processor if found
-    processor=$(find "$PROCESSOR_PATH" -type f | grep -e "theme_$appext")
+    processor=$(find "$PROCESSOR_PATH" -type f | ${GREPPER} -e "theme_$appext")
     if [[ -f "$processor" ]]; then
       "$processor" "$PACKAGE_PATH" "$pkg" "$theme" "$permanent"
     else
@@ -164,6 +273,7 @@ set_theme() {
 
 list() {
   local selected="$1"
+  shift
 
   case "$selected" in
   packages)
@@ -173,7 +283,7 @@ list() {
     get_processors
     ;;
   themes)
-    get_themes
+    get_themes "$@"
     ;;
   *)
     echo "Please select one of packages | processors | themes to list."
@@ -205,9 +315,9 @@ download() {
 
   # if package has patter name/base16-program, put it in packages; if name/process16-program put it in processors
   # if none of the above, assume it's a processor but warn the user
-  if grep -q -e '^[0-9A-Za-z-]\{1,\}/base16-[0-9A-Za-z-]\{1,\}$' <<<"$pkg"; then
+  if ${GREPPER} -q -e '^[0-9A-Za-z-]\{1,\}/base16-[0-9A-Za-z-]\{1,\}$' <<<"$pkg"; then
     git clone "$repo" "$PACKAGE_PATH/$pkg"
-  elif grep -q -e '^[0-9A-Za-z-]\{1,\}/process16-[0-9A-Za-z-]\{1,\}$' <<<"$pkg"; then
+  elif ${GREPPER} -q -e '^[0-9A-Za-z-]\{1,\}/process16-[0-9A-Za-z-]\{1,\}$' <<<"$pkg"; then
     git clone "$repo" "$PROCESSOR_PATH/$pkg"
   else
     echo "Package does not fit default naming scheme of packages/processors. Assuming it is a processor but please check manually."