USING: splitting random-weighted grouping random fry hashtables ;
  
: add-line ( chain line -- chain )
    " " split 2 clump [ first2 1 swap associate swap associate [ '[ swap _ [ H{ } clone or [ '[ swap _ at+ ] assoc-each ] keep ] change-at ] assoc-each ] keep ] each ;

: sentence ( chain word -- response )
    tuck 1 -rot [ dupd swap at dup [ >alist [ swap ] assoc-map random-weighted* ] [ ] if rot 1+ dup 15 < [ -rot ] dip dupd and ] [ dup ] [ 3drop ] produce swap prefix " " join CHAR: . suffix [ 1 head >upper ] [ rest ] bi append ;