Bridges Peri schemas and Phoenix forms.

Validates (and coerces) raw params with Peri.decode/3, wraps the result in a Peri.Form struct, and converts it into a Phoenix.HTML.Form through the Phoenix.HTML.FormData protocol, so schemas plug directly into Phoenix.Component.form/1 and the <.input> component without Ecto.

LiveView round trip

@schema %{
  name: {:required, :string},
  age: {:coerce, :string, {:integer, {:gte, 18}}}
}

def mount(_params, _session, socket) do
  {:ok, assign(socket, form: Peri.Phoenix.to_form(@schema))}
end

def handle_event("validate", %{"peri" => params}, socket) do
  {:noreply, assign(socket, form: Peri.Phoenix.to_form(@schema, params))}
end

def handle_event("save", %{"peri" => params}, socket) do
  case Peri.decode(@schema, params) do
    {:ok, data} -> # persist, redirect...
    {:error, _} -> {:noreply, assign(socket, form: Peri.Phoenix.to_form(@schema, params))}
  end
end

And in the template:

<.form for={@form} phx-change="validate" phx-submit="save">
  <.input field={@form[:name]} label="Name" />
  <.input field={@form[:age]} type="number" label="Age" />
</.form>