How to Write a shader with custom lighting?

I'm currently developing a procedural generated game which uses chunks made up of one mesh and a texture atlas to define each block on the mesh. I've always thought that i would never have to write my own shader and the default built in ones would be everything i need, but i have found that this is no longer true as i have no other choice but to write a shader for what my game needs.
I've never written a shader before and have been putting this back further and further developing other features instead but now i have come to the time where i should just get it over with and write the shader. I would like to get it done quickly so would it be possible to develop and learn the following within 24 hrs?

What i need in the shader:

• It needs to support both transparent and opaque textures for a texture atlas.
• It needs to not use unity's lighting i'm writing my own lighting system instead (I'm creating a lighting system similar to Minecraft's (https://minecraft.gamepedia.com/Light)).
• Related to the above point: it needs each face (2 triangles) to have a "lighting level" which defines how dark or light a face is.
• Each "lighting level" on the faces needs to be set by a script.

I've never written a shader before so i don't know if the above is possible, but could anyone suggest any tips or links to tutorials for writing a shader containing these features.

-Thanks for your time and help

 

first your script should store the "lighting level" to mesh's color data. And then your shader use the color data to multiply with texture color.