#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' )
      ;;
  esac
fi

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

case $state in
  (number)
    local mlt sign digit
    mlt='multiplier:multiplier:((b\:512 K\:1024 KB\:1000 M\:1024\^2'
    mlt+=' MB\:1000\^2 G\:1024\^3 GB\:1000\^3 T\:1024\^4 TB\:1000\^4))'
    sign='sign:sign:((-\:"print all but the last specified bytes/lines"'
    sign+=' +\:"print the first specified bytes/lines (default)"))'
    digit='digits:digit:(0 1 2 3 4 5 6 7 8 9)'
    if compset -P '(-|+|)[0-9]##'; then
      _alternative $mlt $digit && ret=0
    elif [[ -z $PREFIX ]]; then
      _alternative $sign $digit && ret=0
    elif compset -P '(+|-)'; then
      _alternative $digit && ret=0
    fi
    ;;
esac

return ret