#autoload

# Utility function for in-path completion.
# First argument should be an complist-option (e.g. -f, -/, -g). The other
# arguments should be glob patterns, one per argument.
#
# E.g.: _path_files -g '*.tex' '*.texi'
#
# This is intended as a replacement for `complist -f', `complist -/', and
# `complist -g ...' (but don't use it with other options).
#
# You may also give the `-W <spec>' option as with `compctl' and `complist',
# but only as the first argument.
#
# This function also accepts an optional `-F <string>' option as its first
# argument or just after the `-W <spec>'. This can be used to define file
# name extension (a la `fignore'). Files with such an extension will not
# be considered possible completions.
#
# This function behaves as if you have a matcher definition like:
#   compctl -M 'r:|[-.,_/]=* r:|=* m:{a-z}={A-Z} m:-=_ m:.=,' \
#              'm:{a-z}={A-Z} l:|=* r:|=*'
# so you may want to modify this.

local nm prepaths str linepath realpath donepath patstr prepath testpath rest
local tmp1 collect tmp2 suffixes i ignore

setopt localoptions nullglob rcexpandparam globdots extendedglob
unsetopt markdirs globsubst shwordsplit nounset

# Get the optional `-W' option and its argument.
if [[ "$1" = -W ]]; then
  tmp1="$2"
  if [[ "$tmp1[1]" = '(' ]]; then
    prepaths=( $tmp1[2,-2]/ )
  else
    prepaths=( ${(P)${tmp1}} )
    [[ $#prepaths -eq 0 ]] && prepaths=( $tmp1/ )
  fi
  [[ $#prepaths -eq 0 ]] && prepaths=( '' )
  shift 2
else
  prepaths=( '' )
fi

# Get the optional `-F' option and its argument.
if [[ "$1" = -F ]]; then
  ignore=(-F "$2")
  shift 2
else
  ignore=''
fi

# str holds the whole string from the command line with a `*' between
# the prefix and the suffix.

str="${PREFIX:q}*${SUFFIX:q}"

# We will first try normal completion called with `complist', but only if we
# weren't given a `-F' option.

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

  # Now call complist.

  nm=$NMATCHES
  if [[ $# -eq 0 ]]; then
    complist "$tmp1[@]" -f
  elif [[ "$1" = -g ]]; then
    complist "$tmp1[@]" -g "$argv[2,-1]"
    shift
  else
    complist "$tmp1[@]" $1
    shift
  fi

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

  [[ -nmatches nm ]] || return

  # No `-F' option, so we want to use `fignore'.

  ignore=(-F fignore)
fi

# If we weren't given any file patterns as arguments, we trick ourselves
# into believing that we were given the pattern `*'. This is just to simplify
# the following code.

[[ -z "$1" ]] && 1='*'

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

if [[ "$str[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="${str%%/*}/"
  eval realpath\=path
  str="${str#*/}"
  donepath=''
  prepaths=( '' )
else
  # If the string does not start with a `~' we don't remove a prefix from the
  # string.

  liniepath=''
  realpath=''

  if [[ "$str[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'.

    str="$str[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'.
    
    [[ "$str" = (.|..)/* ]] && prepaths=( '' )
    donepath=''
  fi
fi

# First we skip over all pathname components in `str' which really exist in
# the file-system, so that `/usr/lib/l<TAB>' doesn't offer you `lib' and
# `lib5'. Pathname components skipped this way are taken from `str' and added
# to `donepath'.

while [[ "$str" = */* ]] do
  [[ -e "$realpath$donepath${str%%/*}" ]] || break
  donepath="$donepath${str%%/*}/"
  str="${str#*/}"
done

# Now build the glob pattern. As noted above, this function behaves as if
# a global matcher with two matching specifications are given.

if [[ -matcher 1 ]]; then
  patstr="$str:gs/,/*,/:gs/_/*_/:gs./.*/.:gs/-/*[-_]/:gs/./*[.,]/:gs-*[.,]*[.,]*/-../-:gs.**.*."
else
  patstr="${str%/*}/*${str##*/}*"
  patstr="$patstr:gs./.*/.:gs.**.*."
fi

# Finally, generate the matches. First we loop over all the paths from `-W'.
# Note that in this loop `str' is used as a modifyable version of `patstr'
# and `testpath' is a modifyable version of `donepath'.

for prepath in "$prepaths[@]"; do
  str="$patstr"
  testpath="$donepath"

  # The second loop tests the components of the path in `str' to get the
  # possible matches.

  while [[ "$str" = */* ]] do
    # `rest' is the pathname after the first slash that is left. In `tmp1'
    # we get the globbing matches for the pathname component currently
    # handled.

    rest="${str#*/}"
    tmp1="${prepath}${realpath}${testpath}(#l)${str%%/*}(-/)"
    tmp1=( $~tmp1 )

    if [[ $#tmp1 -eq 0 ]]; then
      # If this didn't produce any matches, we don't need to test this path
      # any further, so continue with the next `-W' path, if any.

      continue 2
    elif [[ $#tmp1 -gt 1 ]]; then
      # If it produced more than one match, we want to remove those which
      # don't have possible following pathname components matching the 
      # rest of the string we are completing. (The case with only one
      # match is handled below.)
      # In `collect' we will collect those of the produced pathnames that
      # have a matching possible path-suffix. In `suffixes' we build an
      # array containing strings build from the rest of the string to 
      # complete and the glob patterns we were given as arguments.

      collect=()
      suffixes=( $rest$@ )
      suffixes=( "${(@)suffixes:gs.**.*.}" )

      # In the loop the prefixes from the `tmp1' array produced above and
      # the suffixes we just built are used to produce possible matches
      # via globbing.

      for i in $tmp1; do
        tmp2=( $~i/(#l)$~suffixes )
        [[ $#tmp2 -ne 0 ]] && collect=( $collect $i )
      done

      # If this test showed that none of the matches from the glob in `tmp1'
      # has a possible sub-path matching what's on the line, we give up and
      # continue with the next `-W' path.

      if [[ $#collect -eq 0 ]]; then
        continue 2
      elif [[ $#collect -ne 1 ]]; then
        # If we have more than one possible match, this means that the
	# pathname component currently handled is ambiguous, so we give
	# it to the completion code.
	# First we build the full path prefix in `tmp1'.

        tmp1="$prepath$realpath$testpath"

	# Now produce all matching pathnames in `collect'.

        collect=( $~collect/(#l)$~suffixes )

	# And then remove the common path prefix from all these matches.

        collect=( ${collect#$tmp1} )

	# Finally, we add all these matches with the common (unexpanded)
	# pathprefix (the `-p' option), the path-prefix (the `-W' option)
	# to allow the completion code to test file type, and the path-
	# suffix (the `-s' option). We also tell the completion code that
	# these are file names and that `fignore' should be used as usual
	# (the `-f' and `-F' options).

        for i in $collect; do
          compadd -p "$linepath$testpath" -W "$tmp1" -s "/${i#*/}" -f "$ignore[@]" - "${i%%/*}"
        done

	# We have just finished handling all the matches from above, so we
	# can continue with the next `-W' path.

	continue 2
      fi
      # We reach this point if only one of the path prefixes in `tmp1'
      # has a existing path-suffix matching the string from the line.
      # In this case we accept this match and continue with the next
      # path-name component.

      tmp1=( "$collect[1]" )
    fi
    # This is also reached if the first globbing produced only one match
    # in this case we just continue with the next pathname component, too.

    tmp1="$tmp1[1]"
    testpath="$testpath${tmp1##*/}/"
    str="$rest"
  done

  # We are here if all pathname components except the last one (which is still
  # not tested) are unambiguous. So we add matches with the full path prefix, 
  # no path suffix, the `-W' we are currently handling, all the matches we
  # can produce in this directory, if any.

  tmp1="$prepath$realpath$testpath"
  suffixes=( $str$@ )
  suffixes=( "${(@)suffixes:gs.**.*.}" )
  tmp2=( $~tmp1(#l)$~suffixes )
  compadd -p "$linepath$testpath" -W "$prepath$realpath$testpath" -f "$ignore[@]" - ${tmp2#$tmp1}
done