zsh/Completion/Base/Utility/_sep_parts

#autoload

# This function can be used to separately complete parts of strings
# where each part may be one of a set of matches and different parts
# have different sets.
# Arguments are alternately arrays and separator strings. Arrays may
# be given by name or literally as words separated by white space in
# parentheses, e.g.:
#
#  _sep_parts '(foo bar)' @ hosts
#
# This will make this function complete the strings `foo' and `bar'.
# If the string on the line contains a `@', the substring after it
# will be completed from the array `hosts'. Of course more arrays
# may be given, each preceded by another separator string.
#
# This function understands the `-J group', `-V group', and
# `-X explanation' options.

local str arr sep test testarr tmparr prefix suffixes autosuffix
local matchflags opt group expl nm=$compstate[nmatches] opre osuf opts matcher

# Get the options.

zparseopts -D -a opts 'J+:=group' 'V+:=group' P: F: S: r: R: q 1 2 o+: n \
    'x+:=expl' 'X+:=expl' 'M+:=matcher'

# Get the string from the line.

opre="$PREFIX"
osuf="$SUFFIX"
str="$PREFIX$SUFFIX"
SUFFIX=""
prefix=""

# Walk through the arguments to find the longest unambiguous prefix.

while [[ $# -gt 1 ]]; do
  # Get the next array and separator.
  arr="$1"
  sep="$2"

  if [[ "$arr[1]" == '(' ]]; then
    tmparr=( ${=arr[2,-2]} )
    arr=tmparr
  fi

  # Is the separator on the line?

  [[ "$str" != *${sep}* ]] && break

  # Get the matching array elements.

  PREFIX="${str%%(|\\)${sep}*}"
  builtin compadd -O testarr "$matcher[@]" -a "$arr"
  [[ $#testarr -eq 0 && -n "$_comp_correct" ]] &&
    compadd -O testarr "$matcher[@]" -a "$arr"

  # If there are no matches we give up. If there is more than one
  # match, this is the part we will complete.

  (( $#testarr )) || return 1
  [[ $#testarr -gt 1 ]] && break

  # Only one match, add it to the prefix and skip over it in `str',
  # continuing with the next array and separator.

  prefix="${prefix}${testarr[1]}${sep}"
  str="${str#*${sep}}"
  shift 2
done

# Get the array to work upon.

arr="$1"
if [[ "$arr[1]" == '(' ]]; then
  tmparr=( ${=arr[2,-2]} )
  arr=tmparr
fi

if [[ $# -le 1 || "$str" != *${2}* ]]; then
  # No more separators, build the matches.

  PREFIX="$str"
  builtin compadd -O testarr "$matcher[@]" -a "$arr"
  [[ $#testarr -eq 0 && -n "$_comp_correct" ]] &&
    compadd -O testarr "$matcher[@]" -a "$arr"
fi

[[ $#testarr -eq 0 || ${#testarr[1]} -eq 0 ]] && return 1

# Now we build the suffixes to give to the completion code.

shift
suffixes=("")
autosuffix=()

while [[ $# -gt 0 && "$str" == *${1}* ]]; do
  # Remove anything up to the suffix.

  str="${str#*${1}}"

  # Again, we get the string from the line up to the next separator
  # and build a pattern from it.

  if [[ $# -gt 2 ]]; then
    PREFIX="${str%%${3}*}"
  else
    PREFIX="$str"
  fi

  # We incrementally add suffixes by appending to them the separators
  # and the strings from the next array that match the pattern we built.

  arr="$2"
  if [[ "$arr[1]" == '(' ]]; then
    tmparr=( ${=arr[2,-2]} )
    arr=tmparr
  fi

  builtin compadd -O tmparr "$matcher[@]" -a "$arr"
  [[ $#tmparr -eq 0 && -n "$_comp_correct" ]] &&
    compadd -O tmparr "$matcher[@]" - "$arr"

  suffixes=("${(@)^suffixes[@]}${(q)1}${(@)^tmparr}")

  shift 2
done

# If we were given at least one more separator we make the completion
# code offer it by appending it as a autoremovable suffix.

(( $# )) && autosuffix=(-qS "${(q)1}")

# Add the matches for each of the suffixes.

PREFIX="$pre"
SUFFIX="$suf"
for i in "$suffixes[@]"; do
  compadd -U "$group[@]" "$expl[@]" "$autosuffix[@]" "$opts[@]" \
          -i "$IPREFIX" -I "$ISUFFIX" -p "$prefix" -s "$i" -a testarr
done

# This sets the return value to indicate that we added matches (or not).

[[ nm -ne compstate[nmatches] ]]