# `Wiztchta.Challenge`
[🔗](https://github.com/darth-jorge/wiztcha/blob/v0.1.0/lib/wiztchta/challenge.ex#L1)

Behaviour for challenge types, and the struct handed to templates.

A challenge type generates a `public` map (rendered to the user) and a
`secret` (kept inside the encrypted token), checks a response against the
secret, and renders its own UI.

## Writing a challenge type

    defmodule MyApp.ColorChallenge do
      @behaviour Wiztchta.Challenge
      use Phoenix.Component

      @impl true
      def generate(_opts), do: {%{"question" => "Type the word blue"}, "blue"}

      @impl true
      def valid?(secret, response, _opts), do: String.downcase(String.trim(response)) == secret

      @impl true
      def render(assigns) do
        ~H"""
        <label for={@id <> "-response"}>{@challenge.public["question"]}</label>
        <input type="text" id={@id <> "-response"} name={@name <> "[response]"} />
        """
      end
    end

`render/1` receives `@challenge` (this struct), `@id` (DOM id prefix) and
`@name` (form param prefix). The response must be submitted as
`@name <> "[response]"`; the token input is rendered for you.

Secrets are stored with `:erlang.term_to_binary/1`, so keep them small.

# `t`

```elixir
@type t() :: %Wiztchta.Challenge{public: map(), token: String.t(), type: module()}
```

# `generate`

```elixir
@callback generate(opts :: keyword()) :: {public :: map(), secret :: term()}
```

Returns `{public, secret}` for a new challenge.

# `render`

```elixir
@callback render(assigns :: map()) :: Phoenix.LiveView.Rendered.t()
```

Renders the challenge UI. See the module docs for available assigns.

# `valid?`

```elixir
@callback valid?(secret :: term(), response :: String.t(), opts :: keyword()) :: boolean()
```

Returns whether `response` solves the challenge described by `secret`.

---

*Consult [api-reference.md](api-reference.md) for complete listing*