! Copyright (C) 2022 Keldan Chapman.
! See http://factorcode.org/license.txt for BSD license.
USING: kernel AOC prettyprint splitting sequences.extras
       math math.vectors math.parser sequences sets ;
IN: AOC.2022.14

CONSTANT: sand-origin { 500 0 }

: build-path ( map a b -- map )
    [ "," split [ dec> ] map ] bi@ 2dup v- [ sgn ] map
    rot '[ dup _ = not ] swap '[ [ over adjoin ] keep _ v+ ] while drop ;

: build-map ( input -- hashmap )
    HS{ } clone swap split-lines [
        " -> " split-subseq [ 1 f 1 reach <step-slice> [ build-path ] 2each
        ] keep first "," split [ dec> ] map over adjoin
    ] each ;

: sand ( hashmap limit -- pos ) sand-origin
    [ 2dup second > [ { { 0 1 } { -1 1 } { 1 1 } } over '[ _ v+ [ reach in? not ] keep and ] map sift
        [ nip f ] [ first nip ] if-empty ] [ nip f ] if
    ] [ ] while* nip ;

: sand-fall ( input limitquot islimit notlimit -- result )
    [ build-map [ cardinality ] keep ] 3dip [ call ] 2dip
    '[ 2dup sand 2dup second = _ _ if ] [ ] while
    drop cardinality swap - ; inline

: part-1 ( input -- result )
    [ dup members [ second ] map supremum ]
    [ drop f ] [ pick adjoin t ] sand-fall ;

: part-2 ( input -- result )
    [ dup members [ second ] map supremum 1 + ]
    [ pick adjoin t ] [ [ pick adjoin ] keep sand-origin = not ] sand-fall ;

MAIN: [ 14 read-day-input [ part-1 . ] [ part-2 . ] bi ]