function! s:_vital_loaded(V) abort
  let s:Hint = a:V.import('HitAHint.Hint')
  let s:PHighlight = a:V.import('Palette.Highlight')
  let s:Buffer = a:V.import('Vim.Buffer')
  let s:Prelude = a:V.import('Prelude')
  let s:Set = a:V.import('Data.Set')
  let s:Input = a:V.import('Over.Input')
endfunction

function! s:_vital_depends() abort
  return [
  \   'HitAHint.Hint',
  \   'Palette.Highlight',
  \   'Vim.Buffer',
  \   'Prelude',
  \   'Data.Set',
  \   'Over.Input',
  \ ]
endfunction

let s:TRUE = !0
let s:FALSE = 0
let s:DIRECTION = {'forward': 0, 'backward': 1}

" Check Vim version
function! s:has_patch(major, minor, patch) abort
  let l:version = (a:major * 100 + a:minor)
  return has('patch-' . a:major . '.' . a:minor . '.' . a:patch) ||
    \ (v:version > l:version) ||
    \ (v:version == l:version && 'patch' . a:patch)
endfunction

" matchadd('Conceal', {pattern}, {priority}, -1, {'conceal': {char}}}) can
" highlight pattern and conceal target correctly even if the target is keyword
" characters.
" - http://ftp.vim.org/vim/patches/7.4/7.4.792
" - https://groups.google.com/forum/#!searchin/vim_dev/matchadd$20conceal/vim_dev/8bKa98GhHdk/VOzIBhd1m8YJ
let s:can_preserve_syntax = s:has_patch(7, 4, 792)

" s:move() moves cursor over/accross window with Hit-A-Hint feature like
" vim-easymotion
" @param {dict} config
function! s:move(pattern, ...) abort
  let o = s:new_overwin(get(a:, 1, {}))
  return o.pattern(a:pattern)
endfunction

function! s:move_f(...) abort
  echo 'Target: '
  let c = s:Input.getchar()
  return s:move(c, get(a:, 1, {}))
endfunction

function! s:move_f2() abort
  echo 'Target: '
  let c = s:Input.getchar()
  redraw
  echo 'Target: ' . c
  let c2 = s:Input.getchar()
  return s:move(s:Prelude.escape_pattern(c . c2), get(a:, 1, {}))
endfunction


let s:overwin = {
\   'config': {
\     'keys': 'asdghklqwertyuiopzxcvbnmfj;',
\     'use_upper': s:FALSE,
\     'auto_land': s:TRUE,
\     'highlight': {
\       'shade': 'HitAHintShade',
\       'target': 'HitAHintTarget',
\     },
\     'jump_first_target_keys': [],
\     'do_shade': s:TRUE,
\   }
\ }

function! s:_init_hl() abort
  highlight default HitAHintShade ctermfg=242 guifg=#777777
  highlight default HitAHintTarget ctermfg=81 guifg=#66D9EF
endfunction

call s:_init_hl()

augroup vital-hit-a-hint-motion-default-highlight
  autocmd!
  autocmd ColorScheme * call s:_init_hl()
augroup END


function! s:new_overwin(...) abort
  let o = deepcopy(s:overwin)
  call s:deepextend(o.config, get(a:, 1, {}))
  return o
endfunction

function! s:overwin.pattern(pattern) abort
  let winpos = self.select_winpos(self.gather_poses_overwin(a:pattern), self.config.keys)
  if winpos is# -1
  else
    call s:move_to_winpos(winpos)
  endif
endfunction

" @param {{winnr: [lnum, cnum]}}
function! s:move_to_winpos(winpos) abort
  let [winnr_str, pos] = a:winpos
  let winnr = str2nr(winnr_str)
  let is_win_moved = !(winnr is# winnr())
  if is_win_moved
    if exists('#WinLeave')
      doautocmd WinLeave *
    endif
    call s:move_to_win(winnr)
  else
    normal! m`
  endif
  call cursor(pos)
  if is_win_moved && exists('#WinEnter')
    doautocmd WinEnter *
  endif
endfunction

function! s:overwin.select_winpos(winnr2poses, keys) abort
  let wposes = s:winnr2poses_to_list(a:winnr2poses)
  if self.config.auto_land && len(wposes) is# 1
    return wposes[0]
  endif
  call self.set_options()
  try
    return self.choose_prompt(s:Hint.create(wposes, a:keys))
  finally
    call self.restore_options()
  endtry
endfunction

function! s:overwin.set_options() abort
  " s:move_to_win() takes long time if 'foldmethod' == 'syntax' or 'expr'
  let self.save_foldmethod = {}
  for winnr in range(1, winnr('$'))
    let self.save_foldmethod[winnr] = getwinvar(winnr, '&foldmethod')
    call setwinvar(winnr, '&foldmethod', 'manual')
  endfor
endfunction

function! s:overwin.restore_options() abort
  for winnr in range(1, winnr('$'))
    call setwinvar(winnr, '&foldmethod', self.save_foldmethod[winnr])
  endfor
endfunction

" s:wpos_to_hint() returns dict whose key is position with window and whose
" value is the hints.
" @param Tree{string: ((winnr, (number,number))|Tree)} hint_dict
" @return {{winnr: {string: list<char>}}} poskey to hint for each window
" e.g.
" {
"   '1': {
"     '00168:00004': ['b', 'c', 'b'],
"     '00174:00001': ['b', 'c', 'a'],
"     '00188:00004': ['b', 'b'],
"     '00190:00001': ['b', 'a'],
"     '00191:00016': ['a', 'c'],
"     '00192:00004': ['a', 'b'],
"     '00195:00035': ['a', 'a']
"   },
"   '3': {
"     '00168:00004': ['c', 'c', 'c'],
"     '00174:00001': ['c', 'c', 'b'],
"     '00188:00004': ['c', 'c', 'a'],
"     '00190:00001': ['c', 'b'],
"     '00191:00016': ['c', 'a'],
"     '00192:00004': ['b', 'c', 'c']
"   }
" }
function! s:create_win2pos2hint(hint_dict) abort
  return s:_create_win2pos2hint({}, a:hint_dict)
endfunction

function! s:_create_win2pos2hint(dict, hint_dict, ...) abort
  let prefix = get(a:, 1, [])
  for [hint, v] in items(a:hint_dict)
    if type(v) is# type({})
      call s:_create_win2pos2hint(a:dict, v, prefix + [hint])
    else
      let [winnr, pos] = v
      let a:dict[winnr] = get(a:dict, winnr, {})
      let a:dict[winnr][s:pos2poskey(pos)] = prefix + [hint]
    endif
    unlet v
  endfor
  return a:dict
endfunction

" s:pos2poskey() convertes pos to poskey to use pos as dictionary keys and
" sort pos correctly.
" @param {(number,number)} pos
" @return string
" e.g. [1, 1] -> '00001:00001'
function! s:pos2poskey(pos) abort
  return join(map(copy(a:pos), "printf('%05d', v:val)"), ':')
endfunction

" s:poskey2pos() convertes poskey to pos.
" @param {string} poskey e.g. '00001:00001'
" @return {(number,number)}
" e.g. '00001:00001' -> [1, 1]
function! s:poskey2pos(poskey) abort
  return map(split(a:poskey, ':'), 'str2nr(v:val)')
endfunction

function! s:overwin.choose_prompt(hint_dict) abort
  if empty(a:hint_dict)
    redraw
    echo 'No target'
    return -1
  endif
  let hinter = s:Hinter.new(a:hint_dict, self.config)
  try
    call hinter.before()
    call hinter.show_hint()
    redraw
    echo 'Target key: '
    let c = s:Input.getchar()
    if self.config.use_upper
      let c = toupper(c)
    endif
  catch
    echo v:throwpoint . ':' . v:exception
    return -1
  finally
    call hinter.after()
  endtry

  " Jump to first target if target key is in config.jump_first_target_keys.
  if index(self.config.jump_first_target_keys, c) isnot# -1
    let c = split(self.config.keys, '\zs')[0]
  endif

  if has_key(a:hint_dict, c)
    let target = a:hint_dict[c]
    return type(target) is# type({}) ? self.choose_prompt(target) : target
  else
    redraw
    echo 'Invalid target: ' . c
    return -1
  endif
endfunction

" Hinter show hints accross window.
" save_lines: {{winnr: {lnum: string}}}
" w2l2c2h: winnr to lnum to col num to hints. col2hints is tuple because we
" need sorted col to hints pair.
" save_syntax: {{winnr: &syntax}}
"   {{winnr: {lnum: list<(cnum, list<char>)>}}}
let s:Hinter = {
\   'save_lines': {},
\   'w2l2c2h': {},
\   'winnrs': [],
\   'save_syntax': {},
\   'save_conceallevel': {},
\   'save_concealcursor': {},
\   'save_modified': {},
\   'save_modifiable': {},
\   'save_readonly': {},
\   'save_undo': {},
\   'highlight_ids': {},
\ }

function! s:Hinter.new(hint_dict, config) abort
  let s = deepcopy(self)
  let s.config = a:config
  call s.init(a:hint_dict)
  return s
endfunction

function! s:Hinter.init(hint_dict) abort
  let win2pos2hint = s:create_win2pos2hint(a:hint_dict)
  let self.winnrs = sort(map(keys(win2pos2hint), 'str2nr(v:val)'))
  let self.win2pos2hint = win2pos2hint
  let self.w2l2c2h = s:win2pos2hint_to_w2l2c2h(win2pos2hint)
  let self.hl_target_ids = {}
  for winnr in self.winnrs
    let self.hl_target_ids[winnr] = []
  endfor
  call self._save_lines()
endfunction

function! s:Hinter.before() abort
  let self.highlight_id_cursor = matchadd('Cursor', '\%#', 101)
  call self.save_options()
  call self.disable_conceal_in_other_win()
endfunction

function! s:Hinter.after() abort
  call matchdelete(self.highlight_id_cursor)
  call self.restore_env()
  call self.restore_conceal_in_other_win()
endfunction

function! s:Hinter._save_lines() abort
  let nr = winnr()
  try
    for [winnr, pos2hint] in items(self.win2pos2hint)
      call s:move_to_win(winnr)
      let lnums = map(copy(keys(pos2hint)), 's:poskey2pos(v:val)[0]')
      let self.save_lines[winnr] = get(self.save_lines, winnr, {})
      for lnum in lnums
        let self.save_lines[winnr][lnum] = getline(lnum)
      endfor
    endfor
  finally
    call s:move_to_win(nr)
  endtry
endfunction

function! s:Hinter.restore_lines_for_win(winnr) abort
  let lnum2line = self.save_lines[a:winnr]
  for [lnum, line] in items(lnum2line)
    call s:setline(lnum, line)
  endfor
endfunction

function! s:Hinter.save_options() abort
  for winnr in self.winnrs
    let self.save_syntax[winnr] = getwinvar(winnr, '&syntax')
    let self.save_conceallevel[winnr] = getwinvar(winnr, '&conceallevel')
    let self.save_concealcursor[winnr] = getwinvar(winnr, '&concealcursor')
    let self.save_modified[winnr] = getwinvar(winnr, '&modified')
    let self.save_modifiable[winnr] = getwinvar(winnr, '&modifiable')
    let self.save_readonly[winnr] = getwinvar(winnr, '&readonly')
  endfor
endfunction

function! s:Hinter.restore_options() abort
  for winnr in self.winnrs
    call setwinvar(winnr, '&conceallevel', self.save_conceallevel[winnr])
    call setwinvar(winnr, '&concealcursor', self.save_concealcursor[winnr])
    call setwinvar(winnr, '&modified', self.save_modified[winnr])
    call setwinvar(winnr, '&modifiable', self.save_modifiable[winnr])
    call setwinvar(winnr, '&readonly', self.save_readonly[winnr])
  endfor
endfunction

function! s:Hinter.modify_env_for_win(winnr) abort
  let self.save_conceal = s:PHighlight.get('Conceal')
  let self.save_undo[a:winnr] = s:undo_lock.save()

  setlocal modifiable
  setlocal noreadonly

  if !s:can_preserve_syntax
    ownsyntax overwin
  endif

  setlocal conceallevel=2
  setlocal concealcursor=ncv

  let self.highlight_ids[a:winnr] = get(self.highlight_ids, a:winnr, [])
  if self.config.do_shade
    if !s:can_preserve_syntax
      syntax clear
    endif
    let self.highlight_ids[a:winnr] += [matchadd(self.config.highlight.shade, '\_.*', 100)]
  endif

  " XXX: other plugins specific handling
  if getbufvar('%', 'indentLine_enabled', 0)
    silent! syntax clear IndentLine
  endif
endfunction

function! s:Hinter.restore_env() abort
  call s:PHighlight.set('Conceal', self.save_conceal)
  let nr = winnr()
  try
    for winnr in self.winnrs
      call s:move_to_win(winnr)
      call self.restore_lines_for_win(winnr)
      call self.remove_hints(winnr)

      if !s:can_preserve_syntax && self.config.do_shade
        let &syntax = self.save_syntax[winnr]
      endif

      call self.save_undo[winnr].restore()

      for id in self.highlight_ids[winnr]
        call matchdelete(id)
      endfor

      " XXX: other plugins specific handling
      if getbufvar('%', 'indentLine_enabled', 0) && exists(':IndentLinesEnable') is# 2
        call setbufvar('%', 'indentLine_enabled', 0)
        :IndentLinesEnable
      endif
    endfor
  catch
    call s:throw(v:throwpoint . ' ' . v:exception)
  finally
    call s:move_to_win(nr)
  endtry

  call self.restore_options()
endfunction

let s:undo_lock = {}

function! s:undo_lock.save() abort
  let undo = deepcopy(self)
  call undo._save()
  return undo
endfunction

function! s:undo_lock._save() abort
  if undotree().seq_last == 0
    " if there are no undo history, disable undo feature by setting
    " 'undolevels' to -1 and restore it.
    let self.save_undolevels = &l:undolevels
    let &l:undolevels = -1
  elseif !s:Buffer.is_cmdwin()
    " command line window doesn't support :wundo.
    let self.undofile = tempname()
    execute 'wundo!' self.undofile
  else
    let self.is_cmdwin = s:TRUE
  endif
endfunction

function! s:undo_lock.restore() abort
  if has_key(self, 'save_undolevels')
    let &l:undolevels = self.save_undolevels
  endif
  if has_key(self, 'undofile') && filereadable(self.undofile)
    silent execute 'rundo' self.undofile
    call delete(self.undofile)
  endif
  if has_key(self, 'is_cmdwin')
    " XXX: it breaks undo history. AFAIK, there are no way to save and restore
    " undo history in commandline window.
    call self.undobreak()
  endif
endfunction

function! s:undo_lock.undobreak() abort
  let old_undolevels = &l:undolevels
  setlocal undolevels=-1
  keepjumps call setline('.', getline('.'))
  let &l:undolevels = old_undolevels
endfunction

function! s:Hinter.disable_conceal_in_other_win() abort
  let allwinnrs = s:Set.set(range(1, winnr('$')))
  let other_winnrs = allwinnrs.sub(self.winnrs).to_list()
  for w in other_winnrs
    if 'help' !=# getwinvar(w, '&buftype')
      call setwinvar(w, 'overwin_save_conceallevel', getwinvar(w, '&conceallevel'))
      call setwinvar(w, '&conceallevel', 0)
    endif
  endfor
endfunction

function! s:Hinter.restore_conceal_in_other_win() abort
  let allwinnrs = s:Set.set(range(1, winnr('$')))
  let other_winnrs = allwinnrs.sub(self.winnrs).to_list()
  for w in other_winnrs
    if 'help' !=# getwinvar(w, '&buftype')
      call setwinvar(w, '&conceallevel', getwinvar(w, 'overwin_save_conceallevel'))
    endif
  endfor
endfunction

" ._pos2hint_to_line2col2hint() converts pos2hint to line2col2hint dict whose
" key is line number and whose value is list of tuple of col number to hint.
" line2col2hint is for show hint with replacing line by line.
" col should be sorted.
" @param {{string: list<char>}} pos2hint
" @return {number: [(number, list<char>)]}
function! s:Hinter._pos2hint_to_line2col2hint(pos2hint) abort
  let line2col2hint = {}
  let poskeys = sort(keys(a:pos2hint))
  for poskey in poskeys
    let [lnum, cnum] = s:poskey2pos(poskey)
    let line2col2hint[lnum] = get(line2col2hint, lnum, [])
    let line2col2hint[lnum] += [[cnum, a:pos2hint[poskey]]]
  endfor
  return line2col2hint
endfunction

function! s:Hinter.show_hint() abort
  let nr = winnr()
  try
    for winnr in self.winnrs
      call s:move_to_win(winnr)
      call self._show_hint_for_win(winnr)
    endfor
  finally
    call s:move_to_win(nr)
  endtry
endfunction

function! s:Hinter._show_hint_for_win(winnr) abort
  call self.modify_env_for_win(a:winnr)

  let hints = []
  for [lnum, col2hint] in items(self.w2l2c2h[a:winnr])
    let hints += self._show_hint_for_line(a:winnr, lnum, col2hint)
  endfor
  " Restore syntax and show hints after replacing all lines for performance.
  if !self.config.do_shade
    let &l:syntax = self.save_syntax[a:winnr]
  endif
  execute 'highlight! link Conceal' self.config.highlight.target
  for [lnum, cnum, char] in hints
    call self.show_hint_pos(lnum, cnum, char, a:winnr)
  endfor
endfunction

function! s:Hinter._show_hint_for_line(winnr, lnum, col2hint) abort
  let hints = [] " [lnum, cnum, char]
  let line = self.save_lines[a:winnr][a:lnum]
  let col_offset = 0
  let prev_cnum = -1
  let next_offset = 0
  for [cnum, hint] in a:col2hint
    let col_num = cnum + col_offset

    let is_consecutive = cnum is# prev_cnum + 1
    if !is_consecutive
      let col_num += next_offset
    else
      let save_next_offset = next_offset
    endif

    let [line, offset, next_offset] = self._replace_line_for_hint(a:lnum, col_num, line, hint)

    if is_consecutive
      let col_offset += save_next_offset
    endif
    let col_offset += offset

    let hints = [[a:lnum, col_num, hint[0]]] + hints
    if len(hint) > 1
      let hints = [[a:lnum, col_num + 1, hint[1]]] + hints
    endif

    let prev_cnum = cnum
  endfor
  call s:setline(a:lnum, line)
  return hints
endfunction

" ._replace_line_for_hint() replaces line to show hints.
" - It appends space if the line is empty
" - It replaces <Tab> to space if the target character is <Tab>
" - It replaces next target character if it's <Tab> and len(hint) > 1
" Replacing line changes col number, so it returns offset of col number.
" As for replaceing next target character, the timing to calculate offset
" depends on the col number of next hint in the same line, so it returns
" `next_offset` instead of returning offset all at once.
" @return {(string, number, number)} (line, offset, next_offset)
function! s:Hinter._replace_line_for_hint(lnum, col_num, line, hint) abort
  let line = a:line
  let col_num = a:col_num
  let do_replace_target = !(self.config.do_shade || s:can_preserve_syntax)
  let target = matchstr(line, '\%' . col_num .'c.')
  " Append one space for empty line or match at end of line
  if target is# ''
    let hintwidth = strdisplaywidth(join(a:hint[:1], ''))
    let char = do_replace_target ? ' ' : '.'
    let line .= repeat(char, hintwidth)
    return [line, hintwidth, 0]
  endif

  let offset = 0
  if target is# "\t"
    let [line, offset] = self._replace_tab_target(a:lnum, col_num, line)
  elseif strdisplaywidth(target) > 1
    let line = self._replace_text_to_space(line, a:lnum, col_num, strdisplaywidth(target))
    let offset = strdisplaywidth(target) - len(target)
  else
    if do_replace_target
      " The priority of :syn-cchar is always under the priority of keywords.
      " So, Hit-A-Hint replaces targets character with '.'.
      let space = '.'
      let line = substitute(line, '\%' . col_num . 'c.', space, '')
      let offset = len(space) - len(target)
    endif
  endif

  let next_offset = 0
  if len(a:hint) > 1 && target isnot# "\t"
    " pass [' '] as hint to stop recursion.
    let [line, next_offset, _] = self._replace_line_for_hint(a:lnum, col_num + offset + 1, line, [' '])
  endif
  return [line, offset, next_offset]
endfunction

" @return {(line, offset)}
function! s:Hinter._replace_tab_target(lnum, col_num, line) abort
  let space_len = s:tab2spacelen(a:line, a:col_num)
  let line = self._replace_text_to_space(a:line, a:lnum, a:col_num, space_len)
  return [line, space_len - 1]
endfunction

function! s:Hinter._replace_text_to_space(line, lnum, col_num, len) abort
  let target = printf('\%%%dc.', a:col_num)
  let line = substitute(a:line, target, repeat(' ', a:len), '')
  return line
endfunction

function! s:Hinter.show_hint_pos(lnum, cnum, char, winnr) abort
  let p = '\%'. a:lnum . 'l\%'. a:cnum . 'c.'
  if s:can_preserve_syntax
    let self.hl_target_ids[a:winnr] += [matchadd('Conceal', p, 101, -1, {'conceal': a:char})]
  else
    exec "syntax match HitAHintTarget '". p . "' contains=NONE containedin=.* conceal cchar=". a:char
  endif
endfunction

function! s:Hinter.remove_hints(winnr) abort
  if s:can_preserve_syntax
    for id in self.hl_target_ids[a:winnr]
      call matchdelete(id)
    endfor
  else
    " Clear syntax defined by Hit-A-Hint motion before restoring syntax.
    syntax clear HitAHintTarget
  endif
endfunction

" @param {number} col_num col_num is 1 origin like col()
function! s:tab2spacelen(line, col_num) abort
  let before_line = a:col_num > 2 ? a:line[: a:col_num - 2]
  \   : a:col_num is# 2 ? a:line[0]
  \   : ''
  let vcol_num = 1
  for c in split(before_line, '\zs')
    let vcol_num += c is# "\t" ? s:_virtual_tab2spacelen(vcol_num) : len(c)
  endfor
  return s:_virtual_tab2spacelen(vcol_num)
endfunction

function! s:_virtual_tab2spacelen(col_num) abort
  return &tabstop - ((a:col_num - 1) % &tabstop)
endfunction

function! s:win2pos2hint_to_w2l2c2h(win2pos2hint) abort
  let w2l2c2h = {}
  for [winnr, pos2hint] in items(a:win2pos2hint)
    let w2l2c2h[winnr] = s:pos2hint_to_line2col2hint(pos2hint)
  endfor
  return w2l2c2h
endfunction

" s:pos2hint_to_line2col2hint() converts pos2hint to line2col2hint dict whose
" key is line number and whose value is list of tuple of col number to hint.
" line2col2hint is for show hint with replacing line by line.
" col should be sorted.
" @param {{string: list<char>}} pos2hint
" @return {number: [(number, list<char>)]}
function! s:pos2hint_to_line2col2hint(pos2hint) abort
  let line2col2hint = {}
  let poskeys = sort(keys(a:pos2hint))
  for poskey in poskeys
    let [lnum, cnum] = s:poskey2pos(poskey)
    let line2col2hint[lnum] = get(line2col2hint, lnum, [])
    let line2col2hint[lnum] += [[cnum, a:pos2hint[poskey]]]
  endfor
  return line2col2hint
endfunction

" @param {number} winnr
function! s:move_to_win(winnr) abort
  if a:winnr !=# winnr()
    execute 'noautocmd' a:winnr . 'wincmd w'
  endif
endfunction

" @param {regex} pattern
" @return {{winnr: list<list<(number,number))>}}
function! s:overwin.gather_poses_overwin(pattern) abort
  return s:wincall(function('s:gather_poses'), [a:pattern])
endfunction

" s:gather_poses() aggregates patterm matched positions in visible current
" window for both direction excluding poses in fold.
" @return {{list<list<(number,number))>}}
function! s:gather_poses(pattern) abort
  let f = s:gather_visible_matched_poses(a:pattern, s:DIRECTION.forward, s:TRUE)
  let b = s:gather_visible_matched_poses(a:pattern, s:DIRECTION.backward, s:FALSE)
  return filter(f + b, '!s:is_in_fold(v:val[0])')
endfunction

" s:gather_visible_matched_poses() aggregates pattern matched positions in visible current
" window.
" @param {regex} pattern
" @param {enum<DIRECTION>} direction see s:DIRECTION
" @param {bool} allow_cursor_pos_match
" @return {list<list<(number,number)>>} positions
function! s:gather_visible_matched_poses(pattern, direction, allow_cursor_pos_match) abort
  let stop_line = line(a:direction is# s:DIRECTION.forward ? 'w$' : 'w0')
  let search_flag = (a:direction is# s:DIRECTION.forward ? '' : 'b')
  let c_flag = a:allow_cursor_pos_match ? 'c' : ''
  let view = winsaveview()
  let poses = []
  keepjumps let pos = searchpos(a:pattern, c_flag . search_flag, stop_line)
  while pos != [0, 0]
    let poses += [pos]
    keepjumps let pos = searchpos(a:pattern, search_flag, stop_line)
  endwhile
  call winrestview(view)
  return poses
endfunction

" @param {{winnr: list<list<(number,number))>}} winnr2poses
" @param {number?} first_winnr the top winnr poses in returned list
" @return {list<{list<(winnr, (number,number))}>}
function! s:winnr2poses_to_list(winnr2poses, ...) abort
  let first_winnr = get(a:, 1, winnr())
  let first_winnr_poses = []
  let other_poses = []
  for [winnr_str, poses] in items(a:winnr2poses)
    let winnr = str2nr(winnr_str)
    if winnr is# first_winnr
      let first_winnr_poses = map(copy(poses), '[winnr, v:val]')
    else
      let other_poses += map(copy(poses), '[winnr, v:val]')
    endif
  endfor
  return first_winnr_poses + other_poses
endfunction

" @param {number} lnum line number
function! s:is_in_fold(lnum) abort
  return foldclosed(a:lnum) != -1
endfunction

" @param {funcref} func
" @param {arglist} list<S>
" @param {dict?} dict for :h call()
" @return {{winnr: <T>}}
function! s:wincall(func, arglist, ...) abort
  let dict = get(a:, 1, {})
  let r = {}
  let start_winnr = winnr()
  let r[start_winnr] = call(a:func, a:arglist, dict)
  if s:Buffer.is_cmdwin()
    return r
  endif
  noautocmd wincmd w
  while winnr() isnot# start_winnr
    let r[winnr()] = call(a:func, a:arglist, dict)
    noautocmd wincmd w
  endwhile
  return r
endfunction

" deepextend (nest: 1)
function! s:deepextend(expr1, expr2) abort
  let expr2 = copy(a:expr2)
  for [k, V] in items(a:expr1)
    if (type(V) is type({}) || type(V) is type([])) && has_key(expr2, k)
      let a:expr1[k] = extend(a:expr1[k], expr2[k])
      unlet expr2[k]
    endif
    unlet V
  endfor
  return extend(a:expr1, expr2)
endfunction

function! s:setline(lnum, text) abort
  if getline(a:lnum) isnot# a:text
    call setline(a:lnum, a:text)
  endif
endfunction

function! s:throw(message) abort
  throw 'vital: HitAHint.Motion: ' . a:message
endfunction