Properties which handles by Drupal 7 default User Login Process - drupal

Question

I'm a new to Drupal but I just want to hack/customize the login function of Drupal 7, like hardcoding. As i have discovered that Drupal 7 login process is handling by user.module and its associated files.
I just wanna know which kinds of values or properties are returning or providing when a user logging/authentication process is done by providing just Username/Password.
The final properties it returns, to provide back to Drupal (along the whole authentication process) that I just noticed so far are:
{uid} of the attempted user
{rid} role id of the user
user email
user is blocked or not
then .. ?
The point is .. what other else?
Can i replace/modify the whole existing authentication process? (as i need)
For example, one of the default auth functions in user.module:
function user_authenticate($name, $password) {
..
return $uid;
}
For example, if i modify (hardcode) that function to connect to my other external database(s) and return {user id}, the Drupal will get one auth requirement {uid}. Then what other else to provide? User Role and .. etc etc ?
Like that .. what other functions and properties else should i touch and provide back to Drupal along the authentication process?

Answer 1

This is not an actual answer but I cannot post this as a comment.
Basically we do not hack core. So looking at the user.module's code will not help you very much than learning the hooks. For an example, It's difficult to get an idea about how to add some magic when a node is created by looking at the code of hook_nodeapi(). But if you check the docs and the return/input arguments, it's much easier to do the job.
I'd start by adding an extra submit handler to login form using hook_form_alter(). I have seen some other threads from you about your use case but unfortunately it's difficult to provide a sample code for you.. You can see how other modules implement extra authentication (e.g: http://bit.ly/LdRcm6). (See how Remember Me module adds a checkbox to login form and twitter module that allows twitter login).
Then, you can have Drupal to authenticate the user as normal, and your new custom functionality in addition the Drupal's authentication.
Drupal can even connect to external databases no matter if it's Drupal or not.
As you can see in many functions, they returns a Boolean value or sometimes, the user ID. user_load() is the function that loads a basic user object.
Remember it's modular. Some modules can include/remove/alter these values using hook_user_load(). user terms module and profile module is a perfect example here. It includes profile field information when other modules require user information.
A single user is not just a set of information. It can be modified during any part of the process. So do that. Use your module to provide information that your external site has.
{uid} of the attempted user
{rid} role id of the user
user email
user is blocked or not
user last login time.
user register date.
...
To see the entire object for your site, enter the following.
<pre>
<?php
$user_account = user_load (1);
print_r($user_account);
?>
</pre>
You can enter this code in a node create page where you have php filter used.
Without hardcoding, you can allow other modules to make use of these values. Even if your source database has no role ID, you can ive them a role ID, a user ID, and such.
Good luck!

Answer 2

Drupal is an extensible system. There is no need to do "hardcoding" in core modules like the "user" module. You should rather explore the hook system that allows extending the core (and also contributed) modules.
And in case you want to fetch user id's from a different database (I am not clear about this usecase), you can still use the roles, and other user data, from Drupal's database.