#!/hint/zsh

if zmodload -s zsh/pcre; then
  setopt localoptions rematch_pcre
fi

local key qtype tmp query_string
typeset -g _ftb_query=
-ftb-zstyle -a query-string query_string || query_string=(prefix input first)
for qtype in $query_string; do
  if [[ $qtype == prefix ]]; then
    # find the longest common prefix among descriptions
    local -a keys=(${_ftb_compcap%$'\2'*})
    tmp=$keys[1]
    local MATCH match mbegin mend prefix=(${(s::)tmp})
    for key in ${keys:1}; do
      (( $#tmp )) || break
      [[ $key == $tmp* ]] && continue
      # interpose characters from the current common prefix and $key and see how
      # many pairs of equal characters we get at the start of the resulting string
      [[ ${(j::)${${(s::)key[1,$#tmp]}:^prefix}} =~ '^(((.)\3)*)' ]]
      # truncate common prefix and maintain loop invariant: ${(s::)tmp} == $prefix
      tmp[$#MATCH/2+1,-1]=""
      prefix[$#MATCH/2+1,-1]=()
    done
  elif [[ $qtype == input ]]; then
    local fv=${_ftb_compcap[1]#*$'\2'}
    local -A v=("${(@0)fv}")
    tmp=$v[PREFIX]
    if (( $RBUFFER[(i)$v[SUFFIX]] != 1 )); then
      tmp=${tmp/%$v[SUFFIX]}
    fi
    tmp=${${tmp#$v[hpre]}#$v[apre]}
  fi
  if (( $query_string[(I)longest] )); then
    (( $#tmp > $#_ftb_query )) && _ftb_query=$tmp
  elif [[ -n $tmp ]]; then
    _ftb_query=$tmp && break
  fi
done