! use source and destination component-order to shuffle color components
! fills with 255 if destination component was not found in the source.
! 
! example usage / tests:
! [ B{ 0 3 } ]
! [ B{ 0 1 2 3 4 5 } RGB R permute ] unit-test
! 
! [ B{ 0 1 2 255 3 4 5 255 } ]
! [ B{ 0 1 2 3 4 5 } RGB RGBA permute ] unit-test
! 
! [ B{ 2 1 0 5 4 3 } ]
! [ B{ 0 1 2 3 4 5 } RGB BGR permute ] unit-test

<PRIVATE

CONSTANT: don't-care 3

: permutation ( src dst -- seq n )
    [
        swap '[ _ index [ don't-care ] unless* ] { } map-as
        4 don't-care pad-tail
    ] keep length ;

: pad4 ( seq -- newseq ) 4 255 pad-tail ;

: permute ( byte-array src-order dst-order -- byte-array )
   [ name>> [ length ] keep ] [ name>> ] bi*
   permutation [ group ] 2dip '[ pad4 _ vshuffle _ head ] map concat ;

: (reorder-colors) ( image src-order dest-order -- image )
    [ permute ] 2curry change-bitmap ;

PRIVATE>

: reorder-colors ( image component-order -- image )
    [
        [ component-type>> ubyte-components assert= ]
        [ dup component-order>> ] bi
    ] dip (reorder-colors) ;