Spotlight on texture to highlight specific part with GLSL shaders

I am trying to highlight the pattern of the image texture when spotlight moves on that part. and main texture will be visible as background. spotlight will be moving continuously over the mesh surface.

currently when spotlight moves over the texture and it shows the bump image (pattern image) with black color as well. I am trying to achieve as it should highlight only pattern part of the image and show original main image as well in background.

live code link : Glitch :・゚✧

any help or guidance on this would be greatly appreciated.

current output :

trying to achieve :

many thanks to @manthrax. solved now

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