--- /dev/null
+USING: accessors arrays combinators.short-circuit grouping kernel lists
+lists.lazy locals math math.functions math.parser math.ranges
+models.product monads random sequences sets ui ui.gadgets.controls
+ui.gadgets.layout models.combinators ui.gadgets.alerts vectors fry
+ui.gadgets.labels shuffle ;
+IN: sudokus
+
+: row ( index -- row ) 1 + 9 / ceiling ;
+: col ( index -- col ) 9 mod 1 + ;
+: sq ( index -- square ) [ row ] [ col ] bi [ 3 / ceiling ] bi@ 2array ;
+: near ( a pos -- ? ) { [ [ row ] same? ] [ [ col ] same? ] [ [ sq ] same? ] } 2|| ;
+: nth-or-lower ( n seq -- elt ) [ length 1 - 2dup > [ nip ] [ drop ] if ] keep nth ;
+
+:: solutions ( puzzle random? -- solutions )
+ f puzzle random? [ indices [ f ] [ random? swap nth-or-lower ] if-empty ] [ index ] if
+ [ :> pos
+ 1 9 [a,b] 80 <iota> [ pos near ] filter [ puzzle nth ] map prune diff
+ [ 1array puzzle pos cut-slice rest surround ] map >list [ random? solutions ] bind
+ ] [ puzzle list-monad return ] if* ;
+
+: solution ( puzzle random? -- solution ) dupd solutions dup +nil+ = [ drop "Unsolvable" alert* ] [ nip car ] if ;
+: hint ( puzzle -- puzzle' ) [ [ f swap indices random dup ] [ f solution ] bi nth ] keep swapd >vector [ set-nth ] keep ;
+: create ( difficulty -- puzzle ) 81 [ f ] replicate
+ 40 random solution [ [ f swap [ length random ] keep set-nth ] curry times ] keep ;
+
+: do-sudoku ( -- ) [ [
+ [
+ 81 [ "" ] replicate <basic> switch-models [ [ <basic> ] map 9 group [ 3 group ] map 3 group
+ [ [ [ <spacer> [ [ <model-field> ->% 2 [ string>number ] fmap ]
+ map <spacer> ] map concat ] <hbox> , ] map concat <spacer> ] map concat <product>
+ [ "Difficulty:" <label> , "1" <basic> <model-field> -> [ string>number 1 or 1 + 10 * ] fmap
+ "Generate" <model-border-btn> -> updates [ create ] fmap <spacer>
+ "Hint" <model-border-btn> -> "Solve" <model-border-btn> -> ] <hbox> ,
+ roll [ swap updates ] curry bi@
+ [ [ hint ] fmap ] [ [ f solution ] fmap ] bi* 3array merge [ [ [ number>string ] [ "" ] if* ] map ] fmap
+ ] bind
+ ] with-self , ] <vbox> { 280 220 } >>pref-dim
+ "Sudoku Sleuth" open-window ] with-ui ;
+
+MAIN: do-sudoku