wordcount: formatter: code quality improvements

- Rename new formatting function: transform() -> to_string()
- Optimise separator selection
- Other quality improvements

autoload/airline/extensions/wordcount/formatters/default.vim

@@ -6,33 +6,30 @@ scriptencoding utf-8
 let s:fmt = get(g:, 'airline#extensions#wordcount#formatter#default#fmt', '%s words')
 let s:fmt_short = get(g:, 'airline#extensions#wordcount#formatter#default#fmt_short', s:fmt == '%s words' ? '%sW' : s:fmt)
 
-function! airline#extensions#wordcount#formatters#default#transform(text)
-  if empty(a:text)
+if match(get(v:, 'lang', ''), '\v\cC|en') > -1
+  let s:decimal_group = ','
+elseif match(get(v:, 'lang', ''), '\v\cde|dk|fr|pt') > -1
+  let s:decimal_group = '.'
+else
+  let s:decimal_group = ''
+endif
+
+function! airline#extensions#wordcount#formatters#default#to_string(wordcount)
+  if empty(a:wordcount)
     return
   endif
 
-  let result = g:airline_symbols.space . g:airline_right_alt_sep . g:airline_symbols.space
   if winwidth(0) >= 80
-    let separator = s:get_decimal_group()
-    if a:text > 999 && !empty(separator)
+    if a:wordcount > 999
       " Format number according to locale, e.g. German: 1.245 or English: 1,245
-      let text = substitute(a:text, '\d\@<=\(\(\d\{3\}\)\+\)$', separator.'&', 'g')
+      let wordcount = substitute(a:wordcount, '\d\@<=\(\(\d\{3\}\)\+\)$', s:decimal_group.'&', 'g')
     else
-      let text = a:text
+      let wordcount = a:wordcount
     endif
-    let result = printf(s:fmt, a:text). result
+    let str = printf(s:fmt, wordcount)
   else
-    let result = printf(s:fmt_short, a:text). result
+    let str = printf(s:fmt_short, a:wordcount)
   endif
-  return result
-endfunction
-
-function! s:get_decimal_group()
-  if match(get(v:, 'lang', ''), '\v\cC|en') > -1
-    return ','
-  elseif match(get(v:, 'lang', ''), '\v\cde|dk|fr|pt') > -1
-    return '.'
-  endif
-  return ''
+  return str . g:airline_symbols.space . g:airline_right_alt_sep . g:airline_symbols.space
 endfunction