! Copyright (C) 2017 Jon Harper.
! See http://factorcode.org/license.txt for BSD license.
USING: assocs combinators kernel math math.order math.statistics
sequences splitting ;
IN: aoc.2017.11

: biggest-absolute ( a b -- a/b )
  2dup [ abs ] bi@ [ min ] keep = [ drop ] [ nip ] if ;
: (hexdist) ( a b c -- n )
biggest-absolute [ abs ] bi@ + ;
: hexdist ( a b c -- n )
{ 
  { [ 3dup [ sgn ] tri@ over [ = ] 2bi@ and ] [ (hexdist) ] }
  { [ 2over [ sgn ] bi@ = ] [ rot (hexdist) ] }
  [ -rot (hexdist) ]
} cond ;

: p1 ( str -- dist )
    "," split histogram
    [ [ "n" "s" ] dip [ at 0 or ] curry bi@ - ]
    [ [ "nw" "se" ] dip [ at 0 or ] curry bi@ - ]
    [ [ "ne" "sw" ] dip [ at 0 or ] curry bi@ - ]
    tri hexdist ;

: inccount ( a b c str -- a' b' c' )
{
  { "n" [ [ 1 + ] 2dip ] }
  { "s" [ [ 1 - ] 2dip ] }
  { "nw" [ [ 1 + ] dip  ] }
  { "se" [ [ 1 - ] dip ] }
  { "ne" [ 1 + ] }
  { "sw" [ 1 - ] }
} case ;

: p2 ( str -- dist )
    "," split [ 0 0 0 ] dip
    [ inccount 3dup hexdist ] map supremum [ 3drop ] dip ;