#autoload

# Utility function for in-path completion.
# Supported arguments are: `-f', `-/', `-g <patterns>', `-J <group>',
# `-V <group>', `-W paths', `-X explanation', `-P prefix', `-S suffix',
# `-q', `-r remove-chars', `-R remove-func', and `-F <ignore>'. All but 
# the last have the same syntax and meaning as for `compgen' or
# `compadd', respectively. The `-F <ignore>' option may be used to give
# a list of suffixes either by giving the name of an array or
# literally by giving them in a string surrounded by parentheses. Files
# with one of the suffixes thus given are treated like files with one
# of the suffixes in the `fignore' array in normal completion.
#
# This function supports one configuration key:
#
#  path_expand
#    If this is set to a non-empty string, the partially typed path
#    from the line will be expanded as far as possible even if trailing
#    pathname components can not be completed.

local linepath realpath donepath prepath testpath exppath
local tmp1 tmp2 tmp3 tmp4 i orig pre suf tpre tsuf
local pats ignore group expl addpfx addsfx remsfx
local nm=$compstate[nmatches] menu

typeset -U prepaths exppaths

setopt localoptions nullglob rcexpandparam extendedglob
unsetopt markdirs globsubst shwordsplit nounset

exppaths=()
prepaths=('')
ignore=()
group=()
sopt='-'
gopt=''
pats=()
addpfx=()
addsfx=()
remsfx=()
expl=()

# Get the options.

while getopts "P:S:qr:R:W:F:J:V:X:f/g:" opt; do
  case "$opt" in
  P)     addpfx=(-P "$OPTARG")
         ;;
  S)     addsfx=(-S "$OPTARG")
         ;;
  q)     tmp1=yes
         ;;
  [rR])  remsfx=("-$opt" "$OPTARG")
         ;;
  W)     tmp1="$OPTARG"
         if [[ "$tmp1[1]" = '(' ]]; then
           prepaths=( ${^=tmp1[2,-2]}/ )
         else
           prepaths=( ${(P)=${tmp1}} )
           (( ! $#prepaths )) && prepaths=( ${tmp1}/ )
         fi
         (( ! $#prepaths )) && prepaths=( '' )
         ;;
  F)     tmp1="$OPTARG"
         if [[ "$tmp1[1]" = '(' ]]; then
           ignore=( ${^=tmp1[2,-2]}/ )
         else
           ignore=( ${(P)${tmp1}} )
         fi
	 (( $#ignore )) && ignore=(-F "( $ignore )")
         ;;
  [JV])  group=("-$opt" "$OPTARG")
         ;;
  X)     expl=(-X "$OPTARG")
         ;;
  f)     sopt="${sopt}f"
         pats=("$pats[@]" '*')
	 ;;
  /)     sopt="${sopt}/"
         pats=("$pats[@]" '*(-/)')
	 ;;
  g)     gopt='-g'
         pats=("$pats[@]" ${=OPTARG})
	 ;;
  esac
done

[[ -n "$tmp1" && $#addsfx -ne 0 ]] && addsfx[1]=-qS

# If we were given no file selection option, we behave as if we were given
# a `-f'.

if [[ "$sopt" = - ]]; then
  if [[ -z "$gopt" ]]; then
    sopt='-f'
    pats=('*')
  else
    unset sopt
  fi
fi

# We get the prefix and the suffix from the line and save the whole
# original string. Then we see if we will do menucompletion.

pre="$PREFIX"
suf="$SUFFIX"
orig="${PREFIX}${SUFFIX}"

[[ $compstate[insert] = (*menu|[0-9]*) || -n "$_comp_correct" ||
   ( $#compstate[pattern_match] -ne 0 &&
     "${orig#\~}" != "${${orig#\~}:q}" ) ]] && menu=yes

# We will first try normal completion called with `compgen', but only if we
# weren't given a `-F', `-r', or `-R' option or we are in the string.

if [[ -z "$suf" && $#ignore -eq 0 && $#remsfx -eq 0 &&
      -z "$_comp_correct" ]]; then
  # First build an array containing the `-W' option, if there is any and we
  # want to use it. We don't want to use it if the string from the command line
  # is a absolute path or relative to the current directory.

  if [[ -z "$prepaths[1]" || "$pre[1]" = [~/] || "$pre" = (.|..)/* ]]; then
    tmp1=()
  else
    tmp1=(-W "( $prepaths )")
  fi

  # Now call compgen.

  if [[ -z "$gopt" ]]; then
    compgen "$addpfx[@]" "$addsfx[@]" "$group[@]" "$expl[@]" "$tmp1[@]" $sopt
  else
    compgen "$addpfx[@]" "$addsfx[@]" "$group[@]" "$expl[@]" "$tmp1[@]" $sopt -g "$pats"
  fi

  # If this generated any matches, we don't want to do in-path completion.

  [[ compstate[nmatches] -eq nm ]] || return 0
fi

# If given no `-F' option, we want to use `fignore'.

(( $#ignore )) || ignore=(-F fignore)

# Now let's have a closer look at the string to complete.

if [[ "$pre[1]" = \~ ]]; then
  # It begins with `~', so remember anything before the first slash to be able
  # to report it to the completion code. Also get an expanded version of it
  # (in `realpath'), so that we can generate the matches. Then remove that
  # prefix from the string to complete, set `donepath' to build the correct
  # paths and make sure that the loop below is run only once with an empty
  # prefix path by setting `prepaths'.
  
  linepath="${pre%%/*}/"
  realpath=$~linepath
  [[ "$realpath" = "$linepath" ]] && return 1
  pre="${pre#*/}"
  orig="${orig#*/}"
  donepath=''
  prepaths=( '' )
else
  # If the string does not start with a `~' we don't remove a prefix from the
  # string.

  linepath=''
  realpath=''

  if [[ "$pre[1]" = / ]]; then
    # If it is a absolut path name, we remove the first slash and put it in
    # `donepath' meaning that we treat it as the path that was already handled.
    # Also, we don't use the paths from `-W'.

    pre="$pre[2,-1]"
    orig="$orig[2,-1]"
    donepath='/'
    prepaths=( '' )
  else
    # The common case, we just use the string as it is, unless it begins with
    # `./' or `../' in which case we don't use the paths from `-W'.
    
    [[ "$pre" = (.|..)/* ]] && prepaths=( '' )
    donepath=''
  fi
fi

# Now we generate the matches. First we loop over all prefix paths given
# with the `-W' option.

for prepath in "$prepaths[@]"; do

  # Get local copies of the prefix, suffix, and the prefix path to use
  # in the following loop, which walks through the pathname components
  # in the string from the line.

  tpre="$pre"
  tsuf="$suf"
  testpath="$donepath"

  tmp1=( "$prepath$realpath$donepath" )

  while true; do

    # Skip over `./' and `../'.

    if [[ "$tpre" = (.|..)/* ]]; then
      tmp1=( ${^tmp1}${tpre%%/*}/ )
      tpre="${tpre#*/}"
      continue
    fi

    # Get the prefix and suffix for matching.

    if [[ "$tpre" = */* ]]; then
      PREFIX="${tpre%%/*}"
      SUFFIX=""
    else
      PREFIX="${tpre}"
      SUFFIX="${tsuf%%/*}"
    fi

    # Get the matching files by globbing.

    if [[ "$tpre$tsuf" = */* ]]; then
      tmp1=( ${^tmp1}*(D/) )
    else
      tmp1=( ${^tmp1}${^~pats} )
    fi

    if [[ -n "$PREFIX$SUFFIX" ]]; then
      # See which of them match what's on the line.

      compadd -O tmp2 "$ignore[@]" - "${(@)tmp1##*/}"

      # If no file matches, save the expanded path and continue with
      # the outer loop.

      if [[ $#tmp2 -eq 0 ]]; then
 	if [[ "$tmp1[1]" = */* ]]; then
	  tmp2=( "${(@)tmp1#${prepath}${realpath}}" )
	  if [[ "$tmp2[1]" = */* ]]; then
	    exppaths=( "$exppaths[@]" ${^tmp2%/*}/${tpre}${tsuf} )
          else
	    exppaths=( "$exppaths[@]" ${tpre}${tsuf} )
	  fi
        fi
        continue 2
      fi

      # Remove all files that weren't matched.

      if [[ "$tmp1[1]" = */* ]]; then
        tmp1=( "${(@M)tmp1:#*/(${(j:|:)~${(@)tmp2:q}})}" )
      else
        tmp1=( "${(@M)tmp1:#(${(j:|:)~${(@)tmp2:q}})}" )
      fi
    elif (( ! $#tmp1 )); then
      continue 2
    fi

    # Step over to the next component, if any.

    if [[ "$tpre" = */* ]]; then
      tpre="${tpre#*/}"
    elif [[ "$tsuf" = */* ]]; then
      tpre="${tsuf#*/}"
      tsuf=""
    else
      break
    fi

    # There are more components, so add a slash to the files we are
    # collecting.

    tmp1=( ${^tmp1}/ )
  done

  # The next loop searches the first ambiguous component.

  tmp3="$pre$suf"
  tmp1=( "${(@)tmp1#${prepath}${realpath}${testpath}}" )

  while true; do

    # First we check if some of the files match the original string
    # for this component. If there are some we remove all other
    # names. This avoid having `foo' complete to `foo' and `foobar'.

    if [[ "$tmp3" = */* ]]; then
      tmp4=( "${(@M)tmp1:#${tmp3%%/*}/*}" )
      if (( $#tmp4 )); then
        tmp1=( "$tmp4[@]" )
      fi
    fi

    # Next we see if this component is ambiguous.

    if [[ "$tmp3" = */* ]]; then
      tmp4=( "${(@)tmp1:#${tmp1[1]%%/*}/*}" )
    else
      tmp4=( "${(@)tmp1:#${tmp1[1]}}" )
    fi

    if (( $#tmp4 )); then

      # It is. For menucompletion we now add the possible completions
      # for this component with the unambigous prefix we have built
      # and the rest of the string from the line as the suffix.
      # For normal completion we add the rests of the filenames
      # collected as the suffixes to make the completion code expand
      # it as far as possible.

      if [[ -n $menu ]]; then
        if [[ "$tmp3" = */* ]]; then
	  compadd -Uf -p "$linepath$testpath" -s "/${tmp3#*/}" \
	          -W "$prepath$realpath$testpath" "$ignore[@]" \
		  "$addpfx[@]" "$addsfx[@]" "$remsfx[@]" \
		  "$group[@]" "$expl[@]" -i "$IPREFIX" -I "$ISUFFIX" \
		  - "${(@)tmp1%%/*}"
	else
	  compadd -Uf -p "$linepath$testpath" \
	          -W "$prepath$realpath$testpath" "$ignore[@]" \
		   "$addpfx[@]" "$addsfx[@]" "$remsfx[@]" \
		   "$group[@]" "$expl[@]" -i "$IPREFIX" -I "$ISUFFIX" \
		   - "$tmp1[@]"
	fi
      else
        if [[ "$tmp3" = */* ]]; then
          for i in "$tmp1[@]"; do
	    compadd -Uf -p "$linepath$testpath" -s "/${i#*/}" \
		    -W "$prepath$realpath$testpath" "$ignore[@]" \
		    "$addpfx[@]" "$addsfx[@]" "$remsfx[@]" -M 'r:|/=* r:|=*' \
		    "$group[@]" "$expl[@]" -i "$IPREFIX" -I "$ISUFFIX" \
		    - "${i%%/*}"
	  done
        else
	  compadd -Uf -p "$linepath$testpath" \
		  -W "$prepath$realpath$testpath" "$ignore[@]" \
		  "$addpfx[@]" "$addsfx[@]" "$remsfx[@]" \
		  "$group[@]" "$expl[@]" -i "$IPREFIX" -I "$ISUFFIX" \
		  - "$tmp1[@]"
        fi
      fi
      tmp4=-
      break
    fi

    # If we have checked all components, we stop now and add the 
    # strings collected after the loop.

    if [[ "$tmp3" != */* ]]; then
      tmp4=""
      break
    fi

    # Otherwise we add the unambiguous component to `testpath' and
    # take it from the filenames.

    testpath="${testpath}${tmp1[1]%%/*}/"
    tmp1=( "${(@)tmp1#*/}" )

    tmp3="${tmp3#*/}"
  done

  if [[ -z "$tmp4" ]]; then
    compadd -Uf -p "$linepath$testpath" \
	    -W "$prepath$realpath$testpath" "$ignore[@]" \
	    "$addpfx[@]" "$addsfx[@]" "$remsfx[@]" \
	    "$group[@]" "$expl[@]" -i "$IPREFIX" -I "$ISUFFIX" \
	    - "$tmp1[@]"
  fi
done

# If we are configured to expand paths as far as possible and we collected
# expanded paths that are different from the string on the line, we add
# them as possible matches.

exppaths=( "${(@)exppaths:#$orig}" )

if [[ -n "$compconfig[path_expand]" &&
      $#exppaths -ne 0 && nm -eq compstate[nmatches] ]]; then
  compadd -U -S '' "$group[@]" "$expl[@]" -i "$IPREFIX" -I "$ISUFFIX" \
          -p "$linepath" - "${(@)exppaths}"
fi

[[ nm -eq compstate[nmatches] ]]