#compdef head ghead

local curcontext=$curcontext state state_descr line expl opts args ret=1
typeset -A opt_args

if _pick_variant gnu=GNU unix --version; then
  args=(
    '(-n --lines -c --bytes)'{-c+,--bytes=}'[print the first (or with -, all but the last) specified bytes]:number of bytes:->number'
    '(-n --lines -c --bytes)'{-n+,--lines=}'[print the first (or with -, all but the last) specified lines]:number of lines:->number'
    '(-q --quiet --silent -v --verbose)'{-q,--quiet,--silent}'[never print headers giving file names]'
    '(-q --quiet --silent -v --verbose)'{-v,--verbose}'[always print headers giving file names]'
    '(- *)--help[display help and exit]'
    '(- *)--version[output version information and exit]'
  )
else
  opts=(-A '-*')
  args=( '(-c)-n+[display the first specified lines]:number of lines' )
  case $OSTYPE in
    (freebsd*|darwin*|dragonfly*|netbsd*)
      args+=( '(-n)-c+[display the first specified bytes]:number of bytes' )
    ;|
    dragonfly*|netbsd*)
      args+=(
        '(-v)-q[never print headers giving file names]'
        '(-q)-v[always print headers giving file names]'
      )
    ;;
  esac
fi

_arguments -C -s -S $opts : $args '*:file:_files' && return 0

case $state in
  (number)
    local alts
    [[ -z $PREFIX ]] && alts=(
      'sign:sign:((-\:"print all but the last specified bytes/lines" +\:"print the first specified bytes/lines (default)"))'
    )
    compset -P '+'
    alts+=( 'numbers: :_numbers -N $state_descr b\:512 K\:1024 KB\:1000 M\:1024\^2 MB\:1000\^2 G\:1024\^3 GB\:1000\^3 T\:1024\^4 TB\:1000\^4' )
    _alternative $alts && ret=0
  ;;
esac

return ret