" Add/substracts a number from all the characters in a text object.
"
" [count]cx<obj>  - increment all the characters in the text object by count,
"                   except whitespace
" [count]cX<obj>  - decrement all characters in the text object by count, except
"                   whitespace
" [count]cgx<obj> - like cx, but include whitespace characters
" [count]cgX<obj> - like cX, but include whitespace characters
"
" The following convinence functions are added
"
" cxx, cXX, cgxx, cgXX to operate on lines.
"

noremap <silent> cx <cmd>call <sid>set_dir(v:count1,0)<bar>set operatorfunc=<sid>charadd<cr>g@
nnoremap <silent> cxx <cmd>call <sid>set_dir(v:count1,0)<bar>set operatorfunc=<sid>charadd<cr>g@_
noremap <silent> cX <cmd>call <sid>set_dir(-v:count1,0)<bar>set operatorfunc=<sid>charadd<cr>g@
nnoremap <silent> cXX <cmd>call <sid>set_dir(-v:count1,0)<bar>set operatorfunc=<sid>charadd<cr>g@_


noremap <silent> cgx <cmd>call <sid>set_dir(v:count1,1)<bar>set operatorfunc=<sid>charadd<cr>g@
nnoremap <silent> cgxx <cmd>call <sid>set_dir(v:count1,1)<bar>set operatorfunc=<sid>charadd<cr>g@_
noremap <silent> cgX <cmd>call <sid>set_dir(-v:count1,1)<bar>set operatorfunc=<sid>charadd<cr>g@
nnoremap <silent> cgXX <cmd>call <sid>set_dir(-v:count1,1)<bar>set operatorfunc=<sid>charadd<cr>g@_

let s:dir = 1
let s:incl = 0
function! s:set_dir(d, i) abort
  let s:dir = a:d
  let s:incl = a:i
endfunction

function! s:charadd(arg, ...) abort
  let save_a = getreg('a')
  let save_a_type = getregtype('a')

  if a:0
    echo a:1
    let vis = '`<' . a:arg . '`>'
  elseif a:arg == 'line'
    let vis = "'[V']"
  elseif a:arg == 'block'
    let vis = "`[\<C-v>`]"
  else
    let vis = "`[v`]"
  endif

  silent! exec printf("norm! %s\"ay", vis)
  let r = getreg('a', 1)
  let rtyp = getregtype('a')

  let nl = ""
  for c in r
    if s:incl || ! (c =~ '\_s')
      let n = char2nr(c)
      let nl .= nr2char(n + s:dir)
    else
      let nl .= c
    endif
  endfor

  call setreg('a', nl, rtyp)
  silent! exec printf("norm! gv\"ap`[")
  call setreg('a', save_a, save_a_type)
endfunction