Sharing and Revocation
======================

Your client application must allow users to share files (see
:ref:`requirement_sharing_and_revoking`).

Your code should provide the following functionality:

- If Alice wants to share a file with Bob, Alice assembles an `accessToken` and
  sends this to Bob.

- Bob can use this access token to obtain full permission to the file, which
  should let Bob read, write, and share the file.

- After sharing a file with another user, Alice can revoke that user's access to
  the file. After revocation, the user should no longer have access to the file.

**Example**: Here is an example code snippet to help you understand the required
functionality.


.. code-block:: go

    u1, _ := InitUser("user_alice", "password1")
    u2, _ := InitUser("user_bob", "password2")

    f1 := []byte("content")

    u1.StoreFile("file_to_share_with_Bob", f1)
    accessToken, err := u1.ShareFile("file_to_share_with_Bob", "user_bob")

    u2.ReceiveFile("the_file_from_alice", "user_alice", accessToken)
    f2, _ = u2.LoadFile("the_file_from_alice")
    // f1 should be the same as f2

As demonstrated, after Alice gives Bob the access token, Bob can access the file
(under a filename of Bob's choice).