! Copyright © 2008 Reginald Keith Ford II
! 24, the Factor game!

USING: kernel random namespaces shuffle sequences
parser io math prettyprint combinators continuations
arrays words quotations accessors math.parser backtrack assocs ;

IN: 24-game
SYMBOL: commands
: nop ( -- ) ;
: do-something ( a b -- c ) { + - * } amb-execute ;
: maybe-swap ( a b -- a b ) { nop swap } amb-execute ;
: some-rots ( a b c -- a b c )
    #! Try each permutation of 3 elements.
    { nop rot -rot swap spin swapd } amb-execute ;
: makes-24? ( a b c d -- ? )
        [
            some-rots do-something
            some-rots do-something
            maybe-swap do-something
            24 =
        ]
        [ 4drop ]
    if-amb ;
: q ( -- obj ) "quit" ;
: show-commands ( -- ) "Commands: " write commands get unparse print ;
: report ( vector -- ) unparse print show-commands ;
: give-help ( -- ) "Command not found..." print show-commands ;
: find-word ( string choices -- word ) [ name>> = ] with find nip ;
: obtain-word ( -- word )
    readln commands get find-word dup
    [ drop give-help obtain-word ] unless ;
: done? ( vector -- t/f ) 1 swap length = ;
: victory? ( vector -- t/f ) { 24 } = ;
: apply-word ( vector word -- array ) 1quotation with-datastack >array ;
: update-commands ( vector -- )
    length 3 <
        [ commands [ \ rot swap remove ] change ]
        [ ]
    if ;
DEFER: check-status
: quit-game ( vector -- ) drop "you're a quitter" print ;
: quit? ( vector -- t/f ) last "quit" = ;
: end-game ( vector -- )
    dup victory? 
        [ drop "You WON!" ]
        [ pop number>string " is not 24... You lose." append ]
    if print ;
    
! The following two words are mutually recursive,
! providing the repl loop of the game
: repeat ( vector -- )
    dup report obtain-word apply-word dup update-commands check-status  ;
: check-status ( object -- )
    dup done?
        [ end-game ] 
        [ dup quit? [ quit-game ] [ repeat ] if ]
    if ;
: build-quad ( -- array ) 4 [ 10 random ] replicate ;
: 24-able? ( quad -- t/f ) [ makes-24? ] with-datastack first ;
: 24-able ( -- vector ) build-quad dup 24-able? [ drop build-quad ] unless ;
: set-commands ( -- ) { + - * / rot swap q } commands set ;
: play-game ( -- ) set-commands 24-able repeat ;
MAIN: play-game