feat(chat): complete channels

bundle/vim-chat/autoload/chat/gitter.vim

@@ -119,6 +119,11 @@ function! s:gitter_fetch_exit(id, data, event) abort
   endfor
 endfunction
 
+let s:channels = ['SpaceVim']
+function! chat#gitter#get_channels() abort
+  return s:channels
+endfunction
+
 function! chat#gitter#send(msg) abort
   call s:JOB.start(printf(g:gitter_send_command, substitute(a:msg, '"', '\\\"', 'g')))
 endfunction

bundle/vim-chat/autoload/chat/windows.vim

@@ -253,6 +253,16 @@ function! s:complete(base,num) abort
     if len(rsl) > 0
       return matchstr(a:base, '^/set_protocol\s*') . rsl[a:num % len(rsl)]
     endif
+  elseif a:base =~# '^/set_channel\s*\w*$' && !empty(s:protocol)
+    let channels = []
+    try
+      let channels = chat#{s:protocol}#get_channels()
+    catch
+    endtry
+    let rsl = filter(copy(channels), "v:val =~# matchstr(a:base, '\w*$') .'[^\ .]*'")
+    if len(rsl) > 0
+      return matchstr(a:base, '^/set_channel\s*') . rsl[a:num % len(rsl)]
+    endif
   endif
 
   return a:base