add completion for 'cache' subcommand

assets/completions/bat.zsh

@@ -1,10 +1,28 @@
 #compdef bat
-# FIXME: help me with the subcommand `cache`, zsh completion is hard as hell
 
-local -a args
-local state
+local context state state_descr line
+typeset -A opt_args
 
-args=(
+(( $+functions[_cache_subcommand] )) ||
+_cache_subcommand() {
+    local -a args
+    args=(
+        '(-b --build -c --clear)'{-b,--build}'[Initialize or update the syntax/theme cache]'
+        '(-b --build -c --clear)'{-c,--clear}'[Remove the cached syntax definitions and themes]'
+        '(--source)'--source='[Use a different directory to load syntaxes and themes from]:directory:_files -/'
+        '(--target)'--target='[Use a different directory to store the cached syntax and theme set]:directory:_files -/'
+        '(--blank)'--blank'[Create completely new syntax and theme sets)]'
+        '(: -)'{-h,--help}'[Prints help information]'
+        '*: :'
+    )
+
+    _arguments -S -s $args
+}
+
+(( $+functions[_bat_main] )) ||
+_bat_main() {
+    local -a args
+    args=(
         '(-A --show-all)'{-A,--show-all}'[Show non-printable characters (space, tab, newline, ..)]'
         {-p,--plain}'[Show plain style (alias for `--style=plain`)]:When `-p` is used twice (`-pp`), it also disables automatic paging (alias for `--style=plain --paging=never`)'
         '(-l --language)'{-l+,--language=}'[Set the language for syntax highlighting]:<language>:->language'
@@ -29,11 +47,11 @@ args=(
         '(: -)'{-h,--help}'[Print this help message]'
         '(: -)'{-V,--version}'[Show version information]'
         '*: :_files'
-)
+    )
 
-_arguments -S -s $args
+    _arguments -S -s $args
 
-case "$state" in 
+    case "$state" in 
         language)
             local IFS=$'\n'
             local -a languages
@@ -53,4 +71,21 @@ case "$state" in
         style)
             _values -s , 'style' auto full plain changes header grid numbers snip
         ;;
-esac
+    esac
+}
+
+# first positional argument
+if (( ${#words} == 2 )); then
+    _values subcommand cache
+    _bat_main
+else
+    case $words[2] in
+        cache)
+            _cache_subcommand
+        ;;
+
+        *)
+            _bat_main
+        ;;
+    esac
+fi