#compdef man apropos whatis

_man() {
  local dirs expl mrd awk

  if (( $words[(I)-M] == (( $CURRENT - 1 )) )); then
    _directories && return 0
  fi

  if [[ $service == man ]] && (( $words[(I)-l] + $words[(I)--local-file] )); then
    _files || return 0
  fi

  if (( ! $#_manpath )); then
    local mp
    mp=( ${(s.:.)$(manpath 2>/dev/null)} )
    [[ "$mp" == *:* ]] && mp=( ${(s.:.)mp} )
    if (( $#mp )); then
      _manpath=( $mp )
    elif (( $#manpath )); then
      _manpath=( $manpath )
    fi
  fi

  (( $#_manpath )) ||
      _manpath=( /usr/man(-/) /(opt|usr)/(pkg|dt|share|X11R6|local)/(cat|)man(-/) )

  integer index=$words[(I)-M]
  if (( index )); then
    local opt
    opt=$words[index+1]
    _manpath=($opt)
  fi

  # `sman' is the SGML manual directory for Solaris 7.
  # 1M is system administrator commands on SVR4

  mrd=(${^_manpath/\%L/${LANG:-En_US.ASCII}}/mandb(N))

  # $sect is from the command line, the "3p" in "man 3p memcpy".
  #   It may also be a |-joined (and later in the code "()"-enclosed) list of
  #   section names.
  #   TODO: disentangle this to always be an array.
  # $sect_dirname is from the filesystem, the "3" in "/usr/share/man/man3"
  # These are used by _man_pages
  local sect sect_dirname
  if [[ $OSTYPE = solaris* ]]; then
    sect=${${words[(R)-s*]#-s}:-$words[$words[(i)-s]+1]}
    sect="${sect//,/|}"
  elif [[ -n ${sect:=$words[$words[(i)-S]+1]} || -n ${sect:=$MANSECT} ]]; then
    sect="${sect//:/|}"
    sect="${sect//,/|}"
  elif (( CURRENT > 2 )); then
    case $words[2] in
      (-a) sect='*';;
      (-*) ;;
      (*)  sect=$words[2];;
    esac
  fi

  if [[ $sect = (<->*|1M|l|n) || $sect = *\|* ]]; then
    () {
      local -a sects=( ${(s.|.)sect} )
      if [[ $sect != (l|n) ]]; then
        sects=( ${sects%%[^0-9]#} )
      fi
      dirs=( $^_manpath/(sman|man|cat)${^sects}*/ )
    }
    if [[ $sect == *\|* ]]; then sect="($sect)"; fi
    awk="\$2 == \"$sect\" {print \$1}"
  else
    dirs=( $^_manpath/(sman|man|cat)*/ )
    awk='{print $1}'
  fi
  # Solaris 11 and on have a man-index directory that doesn't contain manpages
  dirs=( ${dirs:#*/man-index/} )
  if [[ $OSTYPE = solaris* && ( $words[CURRENT] = -s* || $words[CURRENT-1] == -s ) ]]; then
    [[ $words[CURRENT] = -s* ]] && compset -P '-s'
    sects=( ${(o)${dirs##*(man|cat)}%/} )
    _wanted sections expl 'section' compadd -a sects
  elif zstyle -t ":completion:${curcontext}:manuals" separate-sections; then
    typeset -U sects
    local ret=1

    sects=( ${(o)${dirs##*(man|cat)}%/} )

    (( $#sects )) || return 1

    _tags manuals.${^sects}
    while _tags; do
      for sect_dirname in $sects; do
        _requested manuals.$sect_dirname expl "manual page, section $sect_dirname" _man_pages &&
            ret=0
      done
      (( ret )) || return 0
    done
    ## To fall back to other sections' manpages when completing filenames, like
    ## the 'else' codepath does:
    #
    # if (( ret )) && [[ $PREFIX$SUFFIX == */* ]]; then
    #   sect_dirname=
    #   _wanted manuals expl 'manual page' _man_pages && return
    # fi

    return 1
  else
    sect_dirname=
    _wanted manuals expl 'manual page' _man_pages
  fi
}

_man_pages() {
  local pages sopt

  # What files corresponding to manual pages can end in.
  local suf='.((?|<->*)(|.gz|.bz2|.Z|.lzma))'

  if [[ $PREFIX$SUFFIX = */* ]]; then
    # Easy way to test for versions of man that allow file names.
    # This can't be a normal man page reference.
    # Try to complete by glob first.
    if [[ -n $sect_dirname ]]; then
      _path_files -g "*.*$sect_dirname*(|.gz|.bz2|.Z|.lzma)" "$expl[@]"
    else
      _path_files -g "*$suf" "$expl[@]" && return
      _path_files "$expl[@]"
    fi
    return $?
  fi

  pages=( ${(M)dirs:#*$sect_dirname/} )
  pages=( ${^pages}/"*$sect${sect:+"*"}" );
  pages=( ${^~pages}(N:t) )

  (($#mrd)) && pages[$#pages+1]=($(awk $awk $mrd))

  # Remove any compression suffix, then remove the minimum possible string
  # beginning with .<->: that handles problem cases like files called
  # `POSIX.1.5'.

  [[ $OSTYPE = solaris* ]] && sopt='-s '
  if ((CURRENT > 2)) ||
      ! zstyle -t ":completion:${curcontext}:manuals.$sect_dirname" insert-sections
  then
    compadd "$@" - ${pages%$~suf}
  else
    compadd "$@" -P "$sopt$sect_dirname " - ${pages%$~suf}
  fi
}

_man "$@"