Shift layer in Photoshop up or down - photoshop

Question

Whilst shifting a layer up or down in Photoshop is quite easy - just drag it wherever you want in code it's proving to be a little more difficult:
// Switch off any dialog boxes
displayDialogs = DialogModes.ALL; // OFF
shift_layer(-1);
// Set Display Dialogs back to normal
displayDialogs = DialogModes.ALL; // NORMAL
// function SHIFT LAYER (direction)
// --------------------------------------------------------
function shift_layer(direction)
{
// direction = 1 Moves layer up 1 place to top
// direction = -1 Moves layer down 1 place to background
if(direction == undefined) return -1;
var where = (direction > 0) ? ElementPlacement.PLACEBEFORE : ElementPlacement.PLACEAFTER;
var currentActiveLayer = app.activeDocument.activeLayer;
var idx = get_layer_index(currentActiveLayer);
// Get a reference to the active layer
var layerRef = app.activeDocument.layers[idx-direction];
// Move the new layer set to after the previously first layer
currentActiveLayer.move(layerRef, where);
}
function get_layer_index(ref)
{
var numOfArtLayers = app.activeDocument.layers.length;
// work from the top of the stack down!
for (var i = numOfArtLayers -1; i >= 0; i--)
{
var tempLayer = app.activeDocument.layers[i];
if (tempLayer == ref) return i;
}
}
Whilst this works it does do when there are no groups (layer sets) in the PSD file. I'm stumped how to do this as the layer index (when groups are involved) are somewhat convoluted. it's gett the layer reference that's proving difficult
Assuming that you cannot rely on using layer names and group names.
Any ideas?
I've had a look at using scriptlistener code (thanks Sergey Kritskiy)
// =======================================================
var idmove = charIDToTypeID( "move" );
var desc23 = new ActionDescriptor();
var idnull = charIDToTypeID( "null" );
var ref15 = new ActionReference();
var idLyr = charIDToTypeID( "Lyr " );
var idOrdn = charIDToTypeID( "Ordn" );
var idTrgt = charIDToTypeID( "Trgt" );
ref15.putEnumerated( idLyr, idOrdn, idTrgt );
desc23.putReference( idnull, ref15 );
var idT = charIDToTypeID( "T " );
var ref16 = new ActionReference();
var idLyr = charIDToTypeID( "Lyr " );
ref16.putIndex( idLyr, 2 );
desc23.putReference( idT, ref16 );
var idAdjs = charIDToTypeID( "Adjs" );
desc23.putBoolean( idAdjs, false );
var idVrsn = charIDToTypeID( "Vrsn" );
desc23.putInteger( idVrsn, 5 );
var idLyrI = charIDToTypeID( "LyrI" );
var list9 = new ActionList();
list9.putInteger( 3 );
desc23.putList( idLyrI, list9 );
executeAction( idmove, desc23, DialogModes.NO );
Which doesn't really get us anywhere. But if we compare it to moving a layer up and then turning it into a function there are three values that seem to control the outcome. What they do? Nobody knows.
function shift(a,b,c)
{
var idmove = charIDToTypeID( "move" );
var desc23 = new ActionDescriptor();
var idnull = charIDToTypeID( "null" );
var ref15 = new ActionReference();
var idLyr = charIDToTypeID( "Lyr " );
var idOrdn = charIDToTypeID( "Ordn" );
var idTrgt = charIDToTypeID( "Trgt" );
ref15.putEnumerated( idLyr, idOrdn, idTrgt );
desc23.putReference( idnull, ref15 );
var idT = charIDToTypeID( "T " );
var ref16 = new ActionReference();
var idLyr = charIDToTypeID( "Lyr " );
ref16.putIndex( idLyr, a ); //2
desc23.putReference( idT, ref16 );
var idAdjs = charIDToTypeID( "Adjs" );
desc23.putBoolean( idAdjs, false );
var idVrsn = charIDToTypeID( "Vrsn" );
desc23.putInteger( idVrsn, b ); //2
var idLyrI = charIDToTypeID( "LyrI" );
var list11 = new ActionList();
list11.putInteger( c ); //3
desc23.putList( idLyrI, list11 );
executeAction( idmove, desc23, DialogModes.NO );
}
These where my results:
// Original layer order 0,1,2,3,4,5,6
// shift_down(1, 1, 1) // 3, 0, 1, 2, 4, 5, 6
// shift_down(1, 2, 2) // 3, 0, 1, 2, 4, 5, 6
// shift_down(2, 1, 1) // 0, 3, 1, 2, 4, 5, 6
// shift_down(3, 1, 1) // 0, 1, 3, 2, 4, 5, 6
// shift_down(3, 0, 0) // 0, 1, 3, 2, 4, 5, 6
// shift_down(3, 0, 1) // 0, 1, 3, 2, 4, 5, 6
// shift_down(3, 1, 0) // 0, 1, 3, 2, 4, 5, 6
// shift_down(4, 0, 0) // 0, 1, 2, 3, 4, 5, 6 // does nothing
// shift_down(5, 0, 0) // 0, 1, 2, 3, 4, 5, 6 // does nothing
// shift_down(4, 1, 1) // 0, 1, 2, 3, 4, 5, 6 // does nothing
// shift_down(4, 0, 4) // 0, 1, 2, 3, 4, 5, 6 // does nothing
// shift_down(4, 4, 4) // 0, 1, 2, 3, 4, 5, 6 // does nothing
// shift_down(5, 5, 4) // 0, 1, 2, 3, 4, 5, 6 // does nothing
// shift_down(6, 5, 4) // 0, 1, 2, 4, 3, 5, 6 // Move up
When moving down, the first parameter seems to be the layer index.
However in order to move up, that parameter needs to be 6.
Confused :(