Handles wizard step navigation events.

How a wizard moves

The template draws every step and shows the current one; Next is the form's submit button, so Enter in a field presses it too. MishkaGervaz.Form.Web.Events handles the form's submit by step:

• on any step but the last, it validates what the form holds and calls advance/2, which moves to the next step when can_advance?/2 allows it. A step it refuses is marked :error and shows the errors of its own fields (step_errors/2), never another step's, and they follow what is typed until the step moves on. Nothing is saved.
• on the last step, it saves. A save that fails on a field of another step calls goto_errors/2, which moves the form to the first step holding an error, marks every step holding one :error, and sends the parent LiveView {:put_flash, :error, message}, the message naming the step to check.

Back (prev_step) moves to the previous step. Every step stays in the form, so nothing typed on either is lost.

Overridable Functions

• can_advance?/2 - Check if user can move to next step
• advance/2 - Move to the next step
• go_back/2 - Move to the previous step
• goto_step/3 - Jump to a specific step (tabs mode)
• goto_errors/2 - Move a form whose save failed to the step holding the error

User Override

defmodule MyApp.Form.StepHandler do
  use MishkaGervaz.Form.Web.Events.StepHandler

  def can_advance?(state, current_step) do
    # Custom step validation
    super(state, current_step)
  end
end

Top-level helpers find_next_step/2, find_prev_step/2, step_exists?/2, step_fields/2 and step_errors/2 are public so user overrides can reuse them.

See MishkaGervaz.Form.Web.Events, MishkaGervaz.Form.Web.State (for :current_step, :step_states, :wizard_history), and the sibling sub-handlers.