= Use-case 0001 — Register new account =

'''Initiating actor:''' Visitor

'''Other actors:''' —

A new person creates an account on !EduBerza so they can later log in as a Trader. The system validates input, refuses duplicates, and stores a hashed password.

== Scenario ==

 1. Visitor chooses "Register" from the anonymous menu.
 2. System prompts for username, email, full name and password.
 3. Visitor enters values.
 4. System validates:
   * username, email, password are non-empty.
   * email contains `@`.
   * password is at least 6 characters.
 5. System checks whether the chosen username or email already exists:

{{{
SELECT EXISTS (
    SELECT 1 FROM project.users
     WHERE username = $1 OR email = $2
);
}}}

 6. If the row exists, system informs the user and the scenario ends. Otherwise it creates the account:

{{{
INSERT INTO project.users (username, email, full_name, password_hash, available_balance)
VALUES ($1, $2, $3, encode(digest($4, 'sha256'), 'hex'), 0);
}}}

 7. System confirms success and returns to the anonymous menu; Visitor can then proceed to UC0002.

=== Alternate flow 3a — invalid email ===

If step 4 fails email validation, system shows "Invalid email." and scenario returns to step 2.

=== Alternate flow 5a — duplicate ===

If step 5 returns `true`, system shows "Username or email already taken." and scenario ends.