" gs will propegate a change made to a <cword> over a text object. This is done
" by the plugin taking note of the word under the cursor before a text change is
" made and what the word was changed to after the text was changed, and gs will
" create a substitute command based on that and apply it to a text object.
"
" This is extremely useful and ergonomic for renaming variables, types or
" otherwise in a text body.

noremap  <silent> gs :set operatorfunc=<SID>do_subst_enter<cr>g@
xnoremap <silent> gs :call <SID>v_do_subst_enter()<cr>

" gS is like gs, except it:
"
"  * doesn't feed a newline at the end
"  * doesn't wrap the string to substitue in word boundaries.
noremap  <silent> gS :set operatorfunc=<SID>do_subst_no_enter<cr>g@
xnoremap <silent> gS :call <SID>v_do_subst_no_enter()<cr>

" Hotkey for replacing the most recently searched matches.
noremap <C-s> <esc>:<C-u>%s//

let s:current_word_1 = ''
let s:current_word = ''

let s:old_word = ''
let s:new_word = ''

function! s:save_cur_word() abort
  let s:current_word_1 = s:current_word
  let s:current_word = expand("<cword>")
endfunction

function! s:save_new_word_from_insert() abort
  let l:new_word = expand("<cword>")

  " Don't replace the last useful substitution with foo -> foo.
  if l:new_word ==# s:current_word
    return
  endif

  " InsertLeave happens before CursorMoved.
  let s:old_word = s:current_word
  let s:new_word = l:new_word
endfunction

function! s:save_new_word() abort
  " For a normal-mode change CursorMoved fires first, so current_word now
  " describes the post-change cursor position. current_word_1 is therefore
  " the word from immediately before the change.
  let s:old_word = s:current_word_1
  let s:new_word = expand("<cword>")
endfunction

augroup FieldMarshalSubstitute
  au!
  autocmd CursorMoved * call s:save_cur_word()
  autocmd TextChanged * call s:save_new_word()
  autocmd InsertLeave * call s:save_new_word_from_insert()
augroup END

function! s:do_subst_enter(...) abort
  call s:do_subst_priv("'[", "']", v:true)
endfunction

function! s:do_subst_no_enter(...) abort
  call s:do_subst_priv("'[", "']", v:false)
endfunction

function! s:v_do_subst_enter(...) abort
  call s:do_subst_priv("'<", "'>", v:true)

endfunction

function! s:v_do_subst_no_enter(...) abort
  call s:do_subst_priv("'<", "'>", v:false)
endfunction

function! s:do_subst_priv(m0, m1, do_enter) abort

  let [_, lnum0, _, _] = getpos(a:m0)
  let [_, lnum1, _, _] = getpos(a:m1)

  " Need to call feedkeys() because @. may contain special characters like
  " backspace.
  call feedkeys(
        \ printf(
        \ ":%s %d,%d s/\\V%s%s%s/%s/g%s",
        \ a:do_enter ? "silent!" : "",
        \ lnum0,
        \ lnum1,
        \ a:do_enter ? "\\<" : "",
        \ escape(s:old_word, '/\'),
        \ a:do_enter ? "\\>" : "",
        \ escape(s:new_word, '/\'),
        \ a:do_enter ? "\n" : ""))
endfunction