"
" strip_trailing_whitespace.vim: User-defined key mapping to strip trailing
" whitespace in the whole document.
"
" Author: Tom Ryder <tom@sanctum.geek.nz>
" License: Same as Vim itself
"
if exists('g:loaded_strip_trailing_whitespace') || &compatible
  finish
endif
let g:loaded_strip_trailing_whitespace = 1

" Define function for stripping whitespace
function! s:StripTrailingWhitespace()

  " Line number of last line that had non-whitespace characters on it
  let l:cutoff = 0

  " Tracking lines trimmed between non-whitespace lines and then totalling
  let l:trimmed_buffer = 0
  let l:trimmed = 0

  " Line number of the file's last line
  let l:last = line('$')

  " Iterate over the lines
  let l:li = 1
  while l:li <= l:last

    " Get the line text
    let l:line = getline(l:li)

    " If the current line contains trailing whitespace, substitute it out
    if l:line =~# '\s\+$'
      call setline(l:li, substitute(l:line, '\s\+$', '', ''))
      let l:trimmed_buffer = l:trimmed_buffer + 1
    endif

    " If this line has any non-whitespace characters on it, update our cutoff
    " point using its index, and push the trimmed lines we've counted since
    " the last non-whitespace line onto the trimmed total
    if l:line =~# '\S'
      let l:cutoff = l:li
      let l:trimmed = l:trimmed + l:trimmed_buffer
      let l:trimmed_buffer = 0
    endif

    " Increment the line counter for the next iteration
    let l:li = l:li + 1

  endwhile

  " If the last non-whitespace line was before the last line proper, we can
  " delete all lines after it
  let l:deleted = 0
  if l:cutoff < l:last

    " Get the current line and column so we can return to it
    " (Yes I know about winsaveview() and winrestview(); I want this to work
    " even on very old versions of Vim if possible)
    let l:cursor_line = line('.')
    let l:cursor_col = col('.')

    " Delete the rest of the lines, which will move the cursor
    silent execute l:cutoff + 1 . ',$ delete _'

    " Return the cursor to the saved position (Vim 6.0 fallback)
    if exists('*cursor')
      call cursor(l:cursor_line, l:cursor_col)
    else
      execute 'normal! '
            \ . l:cursor_line . 'G'
            \ . l:cursor_col . '|'
    endif

    " Record the number of lines deleted
    let l:deleted = l:last - l:cutoff

  endif

  " Print what we did
  echomsg l:trimmed . ' trimmed, ' . l:deleted . ' deleted'

  " Return the number of affected lines
  return l:trimmed + l:deleted

endfunction

" Create mapping proxy to the function just defined
noremap <silent>
      \ <Plug>StripTrailingWhitespace
      \ :<C-U>call <SID>StripTrailingWhitespace()<CR>