let s:subword_motion = ""
let s:subword_nosave = 0

" Return the type of meta-word (i.e. camelCase, snake_case). If
" a:prefer_camel is set, then a word like ThisIs_A_MixOfCamel_And_Snake will
" some_snake_cae SomeCamelCase SOME_CONSTANT_CASE
" return 'camel', otherwise it'll return 'snake'.
function! s:detect_word_type(prefer_camel, word) abort
  let is_camel = 0
  if a:word =~ '[a-z][A-Z]'
    let is_camel = 1

    if a:prefer_camel
      " The word contains a camelCase boundary.
      return 'camel'
    endif
  endif

  if a:word =~ '_\|\W'
    " The word contains a sake_case boundary.
    return 'snake'
  endif

  if is_camel
    return 'camel'
  endif

  " There is not discernible type, it's probably just a single word.
  return 'word'
endfunction

" Move the cursor to the next subowrd.
function! subwords#next(vis, forward)
  if ! s:subword_nosave
    if a:forward
      let s:subword_motion = 'next'
    else
      let s:subword_motion = 'prev'
    endif
  endif

  let i = 0
  while i < v:count1
    call search(
          \ '\([a-z]\zs[A-Z]\ze\)\|\(\W\|_\)\zs\w\ze', (a:forward ? '' : 'b'))
    let i += 1
  endwhile

  let s:subword_nosave = 0
endfunction

" Zero-match the next subword baundary for repeatable cin- and cin_ commands.
function! subwords#visual_beginning(prefer_camel, around)
  return subwords#visual(a:prefer_camel, a:around) . "oi v"
endfunction

" Visually highlights a subword.
"
" If a:prefer_camel is set, then WordsLike_This will be interpreted with
" camelCase.
"
" if a:around is set, the highlight around the subword (otherwise highlight the
" inner subword).
function! subwords#visual(prefer_camel, around)

  " Detect the type of the word.
  let word = expand("<cword>")
  let t = s:detect_word_type(a:prefer_camel, word)

  let expr = ''

  if t == 'camel'
    let expr = 'v'

    let line = getline('.')
    let c = col('.') - 1
    let i = 0

    while line[c] =~ '[a-z]' && c >= 0
      let c -= 1
      let i += 1
    endwhile

    " camelCase

    if c >= 0 && ! (line[c] =~ '[A-Z_]')
      " If we are at the beginning of the meta word, the don't go back too far.
      let i -= 1
    endif

    if i > 0
      let expr .= printf("%dh", i)
    endif

    let expr .= 'o'

    let c = col('.') - 1
    let i = 0

    if line[c] =~ '[A-Z_]'
      " Actually on the starting capital letter, include it, but start counting
      " from the next character.
      let i += 1
      let c += 1
    endif

    while  c < len(line) && line[c] =~ '[a-z]'
      let c += 1
      let i += 1
    endwhile

    if i > 1
      let expr .= printf("%dl", i - 1)
    endif

  elseif t == "snake"
    let expr = 'v'

    let line = getline('.')
    let c = col('.') - 1
    let i = 0

    while c >= 0 && !( line[c] =~ '\W' ) && line[c] != '_'
      let c -= 1
      let i += 1
    endwhile

    let lhs_under = c >= 0 && line[c] == '_'

    let i -= 1
    let c += 1

    if i > 0
      let expr .= printf('%dho', i)
    endif

    let c = col('.') - 1
    let i = 0

    while c < len(line) && !(line[c] =~ '\W') && line[c] != '_'
      let c += 1
      let i += 1
    endwhile

    let rhs_under = c < len(line) && line[c] == '_'

    let i -= 1
    let c -= 1

    if i > 0
      let expr .= printf('%dl', i)
    endif

    if a:around
      if rhs_under
        let expr .= 'l'
      elseif lhs_under
        let expr .= 'oho'
      endif
    endif


  elseif t == "word"
    " Just a word? Easy peasy.
    let expr = 'viw'
  endif

  return expr
endfunction!

" Clear the subword motion. (used for replacement TtfF)
function! subwords#clear_mark()
  let s:subword_motion = ""
  return ''
endfunction

function! subwords#repeat(char)
  if s:subword_motion == ''
    return a:char
  endif

  let mot = (s:subword_motion == 'next') != (a:char == ',')

  let s:subword_nosave = 1
  if mot
    return "\<Plug>(next-subword)"
  else
    return "\<Plug>(prev-subword)"
  endif
endfunction