3D Platformer Camera

Hello, I am currently working on a 3D platformer type game in Unity. However, I've been running into problems with the camera. The effect I am trying to achieve is similar to games such as Crash Bandicoot : Twinsanity, and the Spyro the Dragon series.

What I need the camera to do:

*Follow the player keeping relatively the same distance

*Rotate towards the direction of the player

*Be able to manually rotate camera around player

*Have camera detect walls and other objects then adjust its position so it doesn't clip through them

*When the player walks towards the camera, it shouldn't back up, but instead just continue to look at the character until it walks past it. Then it would snap back to the player

I am not asking for anyone to write me a script, I just need guidance and information on where to start and a basic what to do.

Thanks.