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// enable double clicking from the Macintosh Finder or the Windows Explorer
#target photoshop

const ScriptResult = 
{
    CANCEL: 'cancel' // quit, returning 'cancel' (dont localize) makes the actions palette not record our script
};

function exportGroups(document, folder, retina)
{
    var groups = document.layerSets;
    while (0 < groups.length)
    {
        var group = groups[0];
        if (group.visible)
        {
            var layer = group.merge();
            layer.copy(false);
            
            var tmpDoc = documents.add(document.width, document.height, 72, 'Untitled', NewDocumentMode.RGB, DocumentFill.TRANSPARENT);
            tmpDoc.paste(false);
            tmpDoc.trim(TrimType.TRANSPARENT);

            var file = new File(folder + '/' + layer.name + (retina ? '@2x.png' : '.png'));
            tmpDoc.saveAs (file, new PNGSaveOptions(), true);
            tmpDoc.close(SaveOptions.DONOTSAVECHANGES);
        }
        else
        {
            group.remove();
        }
    }
}

function main()
{
    if (0 == documents.length)
    {
        alert('No open documents');
        return ScriptResult.CANCEL;
    }
    
    var folder = Folder.selectDialog('Select destination folder', '~');
    if (null == folder) return ScriptResult.CANCEL;
    
    var document;
    
    document = activeDocument.duplicate();
    exportGroups(document, folder, true);
    document.close(SaveOptions.DONOTSAVECHANGES);
    
    document = activeDocument.duplicate();
    document.resizeImage('50%', '50%');
    exportGroups(document, folder, false);
    document.close(SaveOptions.DONOTSAVECHANGES);

    alert('Export finished successfully');
}

main();