let s:winid = 0
let s:preview_bufnr = 0
let s:nomodeline = (v:version > 703 || (v:version == 703 && has('patch442'))) ? '<nomodeline>' : ''

function! gitgutter#hunk#set_hunks(bufnr, hunks) abort
  call gitgutter#utility#setbufvar(a:bufnr, 'hunks', a:hunks)
  call s:reset_summary(a:bufnr)
endfunction

function! gitgutter#hunk#hunks(bufnr) abort
  return gitgutter#utility#getbufvar(a:bufnr, 'hunks', [])
endfunction

function! gitgutter#hunk#reset(bufnr) abort
  call gitgutter#utility#setbufvar(a:bufnr, 'hunks', [])
  call s:reset_summary(a:bufnr)
endfunction


function! gitgutter#hunk#summary(bufnr) abort
  return gitgutter#utility#getbufvar(a:bufnr, 'summary', [0,0,0])
endfunction

function! s:reset_summary(bufnr) abort
  call gitgutter#utility#setbufvar(a:bufnr, 'summary', [0,0,0])
endfunction

function! gitgutter#hunk#increment_lines_added(bufnr, count) abort
  let summary = gitgutter#hunk#summary(a:bufnr)
  let summary[0] += a:count
  call gitgutter#utility#setbufvar(a:bufnr, 'summary', summary)
endfunction

function! gitgutter#hunk#increment_lines_modified(bufnr, count) abort
  let summary = gitgutter#hunk#summary(a:bufnr)
  let summary[1] += a:count
  call gitgutter#utility#setbufvar(a:bufnr, 'summary', summary)
endfunction

function! gitgutter#hunk#increment_lines_removed(bufnr, count) abort
  let summary = gitgutter#hunk#summary(a:bufnr)
  let summary[2] += a:count
  call gitgutter#utility#setbufvar(a:bufnr, 'summary', summary)
endfunction


function! gitgutter#hunk#next_hunk(count) abort
  let bufnr = bufnr('')
  if !gitgutter#utility#is_active(bufnr) | return | endif

  let hunks = gitgutter#hunk#hunks(bufnr)
  if empty(hunks)
    call gitgutter#utility#warn('No hunks in file')
    return
  endif

  let current_line = line('.')
  let hunk_count = 0
  for hunk in hunks
    if hunk[2] > current_line
      let hunk_count += 1
      if hunk_count == a:count
        execute 'normal!' hunk[2] . 'Gzv'
        if g:gitgutter_show_msg_on_hunk_jumping
          redraw | echo printf('Hunk %d of %d', index(hunks, hunk) + 1, len(hunks))
        endif
        if gitgutter#hunk#is_preview_window_open()
          call gitgutter#hunk#preview()
        endif
        return
      endif
    endif
  endfor
  call gitgutter#utility#warn('No more hunks')
endfunction

function! gitgutter#hunk#prev_hunk(count) abort
  let bufnr = bufnr('')
  if !gitgutter#utility#is_active(bufnr) | return | endif

  let hunks = gitgutter#hunk#hunks(bufnr)
  if empty(hunks)
    call gitgutter#utility#warn('No hunks in file')
    return
  endif

  let current_line = line('.')
  let hunk_count = 0
  for hunk in reverse(copy(hunks))
    if hunk[2] < current_line
      let hunk_count += 1
      if hunk_count == a:count
        let target = hunk[2] == 0 ? 1 : hunk[2]
        execute 'normal!' target . 'Gzv'
        if g:gitgutter_show_msg_on_hunk_jumping
          redraw | echo printf('Hunk %d of %d', index(hunks, hunk) + 1, len(hunks))
        endif
        if gitgutter#hunk#is_preview_window_open()
          call gitgutter#hunk#preview()
        endif
        return
      endif
    endif
  endfor
  call gitgutter#utility#warn('No previous hunks')
endfunction

" Returns the hunk the cursor is currently in or an empty list if the cursor
" isn't in a hunk.
function! s:current_hunk() abort
  let bufnr = bufnr('')
  let current_hunk = []

  for hunk in gitgutter#hunk#hunks(bufnr)
    if gitgutter#hunk#cursor_in_hunk(hunk)
      let current_hunk = hunk
      break
    endif
  endfor

  return current_hunk
endfunction

" Returns truthy if the cursor is in two hunks (which can only happen if the
" cursor is on the first line and lines above have been deleted and lines
" immediately below have been deleted) or falsey otherwise.
function! s:cursor_in_two_hunks()
  let hunks = gitgutter#hunk#hunks(bufnr(''))

  if line('.') == 1 && len(hunks) > 1 && hunks[0][2:3] == [0, 0] && hunks[1][2:3] == [1, 0]
    return 1
  endif

  return 0
endfunction

" A line can be in 0 or 1 hunks, with the following exception: when the first
" line(s) of a file has been deleted, and the new second line (and
" optionally below) has been deleted, the new first line is in two hunks.
function! gitgutter#hunk#cursor_in_hunk(hunk) abort
  let current_line = line('.')

  if current_line == 1 && a:hunk[2] == 0
    return 1
  endif

  if current_line >= a:hunk[2] && current_line < a:hunk[2] + (a:hunk[3] == 0 ? 1 : a:hunk[3])
    return 1
  endif

  return 0
endfunction


function! gitgutter#hunk#in_hunk(lnum)
  " Hunks are sorted in the order they appear in the buffer.
  for hunk in gitgutter#hunk#hunks(bufnr(''))
    " if in a hunk on first line of buffer
    if a:lnum == 1 && hunk[2] == 0
      return 1
    endif

    " if in a hunk generally
    if a:lnum >= hunk[2] && a:lnum < hunk[2] + (hunk[3] == 0 ? 1 : hunk[3])
      return 1
    endif

    " if hunk starts after the given line
    if a:lnum < hunk[2]
      return 0
    endif
  endfor

  return 0
endfunction


function! gitgutter#hunk#text_object(inner) abort
  let hunk = s:current_hunk()

  if empty(hunk)
    return
  endif

  let [first_line, last_line] = [hunk[2], hunk[2] + hunk[3] - 1]

  if ! a:inner
    let lnum = last_line
    let eof = line('$')
    while lnum < eof && empty(getline(lnum + 1))
      let lnum +=1
    endwhile
    let last_line = lnum
  endif

  execute 'normal! 'first_line.'GV'.last_line.'G'
endfunction


function! gitgutter#hunk#stage(...) abort
  if !s:in_hunk_preview_window() && !gitgutter#utility#has_repo_path(bufnr('')) | return | endif

  if a:0 && (a:1 != 1 || a:2 != line('$'))
    call s:hunk_op(function('s:stage'), a:1, a:2)
  else
    call s:hunk_op(function('s:stage'))
  endif
  silent! call repeat#set("\<Plug>(GitGutterStageHunk)", -1)
endfunction

function! gitgutter#hunk#undo() abort
  if !gitgutter#utility#has_repo_path(bufnr('')) | return | endif

  call s:hunk_op(function('s:undo'))
  silent! call repeat#set("\<Plug>(GitGutterUndoHunk)", -1)
endfunction

function! gitgutter#hunk#preview() abort
  if !gitgutter#utility#has_repo_path(bufnr('')) | return | endif

  call s:hunk_op(function('s:preview'))
  silent! call repeat#set("\<Plug>(GitGutterPreviewHunk)", -1)
endfunction


function! s:hunk_op(op, ...)
  let bufnr = bufnr('')

  if s:in_hunk_preview_window()
    if string(a:op) =~ '_stage'
      " combine hunk-body in preview window with updated hunk-header
      let hunk_body = getline(1, '$')

      let [removed, added] = [0, 0]
      for line in hunk_body
        if line[0] == '-'
          let removed += 1
        elseif line[0] == '+'
          let added += 1
        endif
      endfor

      let hunk_header = b:hunk_header
      " from count
      let hunk_header[4] = substitute(hunk_header[4], '\(-\d\+\)\(,\d\+\)\?', '\=submatch(1).",".removed', '')
      " to count
      let hunk_header[4] = substitute(hunk_header[4], '\(+\d\+\)\(,\d\+\)\?', '\=submatch(1).",".added', '')

      let hunk_diff = join(hunk_header + hunk_body, "\n")."\n"

      if &previewwindow
        call s:goto_original_window()
      endif
      call gitgutter#hunk#close_hunk_preview_window()
      call s:stage(hunk_diff)
    endif

    return
  endif

  if gitgutter#utility#is_active(bufnr)
    " Get a (synchronous) diff.
    let [async, g:gitgutter_async] = [g:gitgutter_async, 0]
    let diff = gitgutter#diff#run_diff(bufnr, g:gitgutter_diff_relative_to, 1)
    let g:gitgutter_async = async

    call gitgutter#hunk#set_hunks(bufnr, gitgutter#diff#parse_diff(diff))
    call gitgutter#diff#process_hunks(bufnr, gitgutter#hunk#hunks(bufnr))  " so the hunk summary is updated

    if empty(s:current_hunk())
      call gitgutter#utility#warn('Cursor is not in a hunk')
    elseif s:cursor_in_two_hunks()
      let choice = input('Choose hunk: upper or lower (u/l)? ')
      " Clear input
      normal! :<ESC>
      if choice =~ 'u'
        call a:op(gitgutter#diff#hunk_diff(bufnr, diff, 0))
      elseif choice =~ 'l'
        call a:op(gitgutter#diff#hunk_diff(bufnr, diff, 1))
      else
        call gitgutter#utility#warn('Did not recognise your choice')
      endif
    else
      let hunk_diff = gitgutter#diff#hunk_diff(bufnr, diff)

      if a:0
        let hunk_first_line = s:current_hunk()[2]
        let hunk_diff = s:part_of_diff(hunk_diff, a:1-hunk_first_line, a:2-hunk_first_line)
      endif

      call a:op(hunk_diff)
    endif
  endif
endfunction


function! s:stage(hunk_diff)
  let bufnr = bufnr('')

  if gitgutter#utility#clean_smudge_filter_applies(bufnr)
    let choice = input('File uses clean/smudge filter. Stage entire file (y/n)? ')
    normal! :<ESC>
    if choice =~ 'y'
      " We are about to add the file to the index so write the buffer to
      " ensure the file on disk matches it (the buffer).
      write
      let path = gitgutter#utility#repo_path(bufnr, 1)
      " Add file to index.
      let cmd = gitgutter#utility#cd_cmd(bufnr,
            \ gitgutter#git().' add '.
            \ gitgutter#utility#shellescape(gitgutter#utility#filename(bufnr)))
      let [_, error_code] = gitgutter#utility#system(cmd)
    else
      return
    endif

  else
    let diff = s:adjust_header(bufnr, a:hunk_diff)
    " Apply patch to index.
    let [_, error_code] = gitgutter#utility#system(
          \ gitgutter#utility#cd_cmd(bufnr, gitgutter#git().' apply --cached --unidiff-zero - '),
          \ diff)
  endif

  if error_code
    call gitgutter#utility#warn('Patch does not apply')
  else
    if exists('#User#GitGutterStage')
      execute 'doautocmd' s:nomodeline 'User GitGutterStage'
    endif
  endif

  " Refresh gitgutter's view of buffer.
  call gitgutter#process_buffer(bufnr, 1)
endfunction


function! s:undo(hunk_diff)
  " Apply reverse patch to buffer.
  let hunk  = gitgutter#diff#parse_hunk(split(a:hunk_diff, '\n')[4])
  let lines = map(split(a:hunk_diff, '\r\?\n')[5:], 'v:val[1:]')
  let lnum  = hunk[2]
  let added_only   = hunk[1] == 0 && hunk[3]  > 0
  let removed_only = hunk[1]  > 0 && hunk[3] == 0

  if removed_only
    call append(lnum, lines)
  elseif added_only
    execute lnum .','. (lnum+len(lines)-1) .'d _'
  else
    call append(lnum-1, lines[0:hunk[1]])
    execute (lnum+hunk[1]) .','. (lnum+hunk[1]+hunk[3]) .'d _'
  endif

  " Refresh gitgutter's view of buffer.
  call gitgutter#process_buffer(bufnr(''), 1)
endfunction


function! s:preview(hunk_diff)
  let lines = split(a:hunk_diff, '\r\?\n')
  let header = lines[0:4]
  let body = lines[5:]

  call s:open_hunk_preview_window()
  call s:populate_hunk_preview_window(header, body)
  call s:enable_staging_from_hunk_preview_window()
  if &previewwindow
    call s:goto_original_window()
  endif
endfunction


" Returns a new hunk diff using the specified lines from the given one.
" Assumes all lines are additions.
" a:first, a:last - 0-based indexes into the body of the hunk.
function! s:part_of_diff(hunk_diff, first, last)
  let diff_lines = split(a:hunk_diff, '\n', 1)

  " adjust 'to' line count in header
  let diff_lines[4] = substitute(diff_lines[4], '\(+\d\+\)\(,\d\+\)\?', '\=submatch(1).",".(a:last-a:first+1)', '')

  return join(diff_lines[0:4] + diff_lines[5+a:first:5+a:last], "\n")."\n"
endfunction


function! s:adjust_header(bufnr, hunk_diff)
  let filepath = gitgutter#utility#repo_path(a:bufnr, 0)
  return s:adjust_hunk_summary(s:fix_file_references(filepath, a:hunk_diff))
endfunction


" Replaces references to temp files with the actual file.
function! s:fix_file_references(filepath, hunk_diff)
  let lines = split(a:hunk_diff, '\n')

  let left_prefix  = matchstr(lines[2], '[abciow12]').'/'
  let right_prefix = matchstr(lines[3], '[abciow12]').'/'
  let quote        = lines[0][11] == '"' ? '"' : ''

  let left_file  = quote.left_prefix.a:filepath.quote
  let right_file = quote.right_prefix.a:filepath.quote

  let lines[0] = 'diff --git '.left_file.' '.right_file
  let lines[2] = '--- '.left_file
  let lines[3] = '+++ '.right_file

  return join(lines, "\n")."\n"
endfunction


function! s:adjust_hunk_summary(hunk_diff) abort
  let line_adjustment = s:line_adjustment_for_current_hunk()
  let diff = split(a:hunk_diff, '\n', 1)
  let diff[4] = substitute(diff[4], '+\zs\(\d\+\)', '\=submatch(1)+line_adjustment', '')
  return join(diff, "\n")
endfunction


" Returns the number of lines the current hunk is offset from where it would
" be if any changes above it in the file didn't exist.
function! s:line_adjustment_for_current_hunk() abort
  let bufnr = bufnr('')
  let adj = 0
  for hunk in gitgutter#hunk#hunks(bufnr)
    if gitgutter#hunk#cursor_in_hunk(hunk)
      break
    else
      let adj += hunk[1] - hunk[3]
    endif
  endfor
  return adj
endfunction


function! s:in_hunk_preview_window()
  if g:gitgutter_preview_win_floating
    return win_id2win(s:winid) == winnr()
  else
    return &previewwindow
  endif
endfunction


" Floating window: does not move cursor to floating window.
" Preview window: moves cursor to preview window.
function! s:open_hunk_preview_window()
  let source_wrap = &wrap
  let source_window = winnr()

  if g:gitgutter_preview_win_floating
    if exists('*nvim_open_win')
      call gitgutter#hunk#close_hunk_preview_window()

      let buf = nvim_create_buf(v:false, v:false)
      " Set default width and height for now.
      let s:winid = nvim_open_win(buf, v:false, g:gitgutter_floating_window_options)
      call nvim_win_set_option(s:winid, 'wrap', source_wrap ? v:true : v:false)
      call nvim_buf_set_option(buf, 'filetype',  'diff')
      call nvim_buf_set_option(buf, 'buftype',   'acwrite')
      call nvim_buf_set_option(buf, 'bufhidden', 'delete')
      call nvim_buf_set_option(buf, 'swapfile',  v:false)
      call nvim_buf_set_name(buf, 'gitgutter://hunk-preview')

      if g:gitgutter_close_preview_on_escape
        let winnr = nvim_win_get_number(s:winid)
        execute winnr.'wincmd w'
        nnoremap <buffer> <silent> <Esc> :<C-U>call gitgutter#hunk#close_hunk_preview_window()<CR>
        wincmd w
      endif

      " Assumes cursor is in original window.
      autocmd CursorMoved,TabLeave <buffer> ++once call gitgutter#hunk#close_hunk_preview_window()

      return
    endif

    if exists('*popup_create')
      if g:gitgutter_close_preview_on_escape
        let g:gitgutter_floating_window_options.filter = function('s:close_popup_on_escape')
      endif

      let s:winid = popup_create('', g:gitgutter_floating_window_options)

      call setbufvar(winbufnr(s:winid), '&filetype', 'diff')
      call setwinvar(s:winid, '&wrap', source_wrap)

      return
    endif
  endif

  if exists('&previewpopup')
    let [previewpopup, &previewpopup] = [&previewpopup, '']
  endif

  " Specifying where to open the preview window can lead to the cursor going
  " to an unexpected window when the preview window is closed (#769).
  silent! noautocmd execute g:gitgutter_preview_win_location 'pedit gitgutter://hunk-preview'
  silent! wincmd P
  setlocal statusline=%{''}
  doautocmd WinEnter
  if exists('*win_getid')
    let s:winid = win_getid()
  else
    let s:preview_bufnr = bufnr('')
  endif
  setlocal filetype=diff buftype=acwrite bufhidden=delete
  let &l:wrap = source_wrap
  let b:source_window = source_window
  " Reset some defaults in case someone else has changed them.
  setlocal noreadonly modifiable noswapfile
  if g:gitgutter_close_preview_on_escape
    " Ensure cursor goes to the expected window.
    nnoremap <buffer> <silent> <Esc> :<C-U>execute b:source_window . "wincmd w"<Bar>pclose<CR>
  endif

  if exists('&previewpopup')
    let &previewpopup=previewpopup
  endif
endfunction


function! s:close_popup_on_escape(winid, key)
  if a:key == "\<Esc>"
    call popup_close(a:winid)
    return 1
  endif
  return 0
endfunction


" Floating window: does not care where cursor is.
" Preview window: assumes cursor is in preview window.
function! s:populate_hunk_preview_window(header, body)
  if g:gitgutter_preview_win_floating
    if exists('*nvim_open_win')
      " Assumes cursor is not in previewing window.
      call nvim_buf_set_var(winbufnr(s:winid), 'hunk_header', a:header)

      let [_scrolloff, &scrolloff] = [&scrolloff, 0]

      let [width, height] = s:screen_lines(a:body)
      let height = min([height, g:gitgutter_floating_window_options.height])
      call nvim_win_set_width(s:winid, width)
      call nvim_win_set_height(s:winid, height)

      let &scrolloff=_scrolloff

      call nvim_buf_set_lines(winbufnr(s:winid), 0, -1, v:false, [])
      call nvim_buf_set_lines(winbufnr(s:winid), 0, -1, v:false, a:body)
      call nvim_buf_set_option(winbufnr(s:winid), 'modified', v:false)

      let ns_id = nvim_create_namespace('GitGutter')
      call nvim_buf_clear_namespace(winbufnr(s:winid), ns_id, 0, -1)
      for region in gitgutter#diff_highlight#process(a:body)
        let group = region[1] == '+' ? 'GitGutterAddIntraLine' : 'GitGutterDeleteIntraLine'
        call nvim_buf_add_highlight(winbufnr(s:winid), ns_id, group, region[0]-1, region[2]-1, region[3])
      endfor

      call nvim_win_set_cursor(s:winid, [1,0])
    endif

    if exists('*popup_create')
      call popup_settext(s:winid, a:body)

      for region in gitgutter#diff_highlight#process(a:body)
        let group = region[1] == '+' ? 'GitGutterAddIntraLine' : 'GitGutterDeleteIntraLine'
        call win_execute(s:winid, "call matchaddpos('".group."', [[".region[0].", ".region[2].", ".(region[3]-region[2]+1)."]])")
      endfor
    endif

  else
    let b:hunk_header = a:header

    %delete _
    call setline(1, a:body)
    setlocal nomodified

    let [_, height] = s:screen_lines(a:body)
    execute 'resize' height
    1

    call clearmatches()
    for region in gitgutter#diff_highlight#process(a:body)
      let group = region[1] == '+' ? 'GitGutterAddIntraLine' : 'GitGutterDeleteIntraLine'
      call matchaddpos(group, [[region[0], region[2], region[3]-region[2]+1]])
    endfor

    1
  endif
endfunction


" Calculates the number of columns and the number of screen lines the given
" array of lines will take up, taking account of wrapping.
function! s:screen_lines(lines)
  let [_virtualedit, &virtualedit]=[&virtualedit, 'all']
  let cursor = getcurpos()
  normal! 0g$
  let available_width = virtcol('.')
  call setpos('.', cursor)
  let &virtualedit=_virtualedit
  let width = min([max(map(copy(a:lines), 'strdisplaywidth(v:val)')), available_width])

  if exists('*reduce')
    let height = reduce(a:lines, { acc, val -> acc + strdisplaywidth(val) / width + (strdisplaywidth(val) % width == 0 ? 0 : 1) }, 0)
  else
    let height = eval(join(map(copy(a:lines), 'strdisplaywidth(v:val) / width + (strdisplaywidth(v:val) % width == 0 ? 0 : 1)'), '+'))
  endif

  return [width, height]
endfunction


function! s:enable_staging_from_hunk_preview_window()
  augroup gitgutter_hunk_preview
    autocmd!
    let bufnr = s:winid != 0 ? winbufnr(s:winid) : s:preview_bufnr
    execute 'autocmd BufWriteCmd <buffer='.bufnr.'> GitGutterStageHunk'
  augroup END
endfunction


function! s:goto_original_window()
  noautocmd execute b:source_window . "wincmd w"
  doautocmd WinEnter
endfunction


function! gitgutter#hunk#close_hunk_preview_window()
  let bufnr = s:winid != 0 ? winbufnr(s:winid) : s:preview_bufnr
  call setbufvar(bufnr, '&modified', 0)

  if g:gitgutter_preview_win_floating
    if win_id2win(s:winid) > 0
      execute win_id2win(s:winid).'wincmd c'
    endif
  else
    pclose
  endif

  let s:winid = 0
  let s:preview_bufnr = 0
endfunction


function gitgutter#hunk#is_preview_window_open()
  if g:gitgutter_preview_win_floating
    if win_id2win(s:winid) > 0
      execute win_id2win(s:winid).'wincmd c'
    endif
  else
    for i in range(1, winnr('$'))
      if getwinvar(i, '&previewwindow')
        return 1
      endif
    endfor
  endif
  return 0
endfunction