How could I possibly make a cannon that works with redstone and fuel?

I really need help with this, it has been really really complicated but i just cant get it to work; I have the models and the textures, they all look awesome, but i just cant get the cannon to work how i want it to. I know this is complicated, so...

I want to make a cannon that works with fuel, my idea for it is that you need to add the ammo for the cannon, and on another slot of the cannon you add the fuel, then you activate it with redstone and the cannon throws a cannonball, i already have the cannon ball throw action by making a ranged item with no creative entry, but i cant get it to work like i want it to, any ideas on how i could possibly make this? I am really determined to finish it, i need it, but i dont know very well how to use the right procedures. Thanks in advance to anyone who would like to help me.