Plugin creating page templates

Hi all,

I’d like to create a portfolio plugin that will have portfolio custom post type and taxonomies. I’d like the plugin to add to the user’s theme page template files for presenting all portfolio items, also a template for the single portfolio item page.

What’s the best way to do this?

As far as page template files are part of the theme is not a good idea to write files in the theme’s folder. Plus the plugin can’t know the structure of every theme, so basically it can’t know how to build the template file so it does not break.

Any help is much appreciated.

Thanks ??