# `X402.Extensions.AuthHints.Adapter`
[🔗](https://github.com/cardotrejos/x402/blob/v0.9.0/lib/x402/extensions/auth_hints/adapter.ex#L1)

`X402.Extension` adapter advertising the `auth-hints` extension.

    plug X402.Plug.PaymentGate,
      routes: [...],
      extensions: [
        {X402.Extensions.AuthHints.Adapter,
         auth_requirements: [
           [accept_indexes: [1], methods: [X402.Extensions.AuthHints.oauth2(...)]]
         ]}
      ]

Every 402 response advertises `X402.Extensions.AuthHints.extension/1`
for the configured requirements, minus any index that falls outside
the requirements actually offered to the request (a hook may have
replaced them); a requirement left without indexes is not advertised,
and neither is the extension when nothing remains. A context without
requirements advertises the configuration unchanged.

The hints only announce what the route expects. Checking the
credentials a client then presents is the application's job, in the
handler or in a plug ahead of the gate.

# `advertise`
*since 0.9.0* 

```elixir
@spec advertise(
  keyword(),
  X402.Hooks.RequestContext.t()
) :: map() | nil
```

Advertises the configured requirements, dropping indexes outside the
request's requirements.

## Examples

    iex> {:ok, opts} = X402.Extensions.AuthHints.Adapter.init(
    ...>   auth_requirements: [[accept_indexes: [0, 1], methods: [X402.Extensions.AuthHints.sign_in_with_x()]]]
    ...> )
    iex> context = X402.Hooks.RequestContext.new(requirements: [%{"scheme" => "exact"}])
    iex> X402.Extensions.AuthHints.Adapter.advertise(opts, context)["info"]
    %{"authRequirements" => [%{"acceptIndexes" => [0], "methods" => [%{"type" => "sign-in-with-x"}]}]}

    iex> {:ok, opts} = X402.Extensions.AuthHints.Adapter.init(
    ...>   auth_requirements: [[accept_indexes: [3], methods: [X402.Extensions.AuthHints.sign_in_with_x()]]]
    ...> )
    iex> context = X402.Hooks.RequestContext.new(requirements: [%{"scheme" => "exact"}])
    iex> X402.Extensions.AuthHints.Adapter.advertise(opts, context)
    nil

# `init`
*since 0.9.0* 

```elixir
@spec init(keyword()) :: {:ok, keyword()} | {:error, String.t()}
```

Validates the adapter options.

## Options

* `:auth_requirements` - Required. The requirements, as accepted by `X402.Extensions.AuthHints.extension/1`.

## Examples

    iex> requirements = [[accept_indexes: [1], methods: [X402.Extensions.AuthHints.sign_in_with_x()]]]
    iex> {:ok, opts} = X402.Extensions.AuthHints.Adapter.init(auth_requirements: requirements)
    iex> opts[:auth_requirements]["info"]["authRequirements"]
    [%{"acceptIndexes" => [1], "methods" => [%{"type" => "sign-in-with-x"}]}]

    iex> {:error, message} = X402.Extensions.AuthHints.Adapter.init(auth_requirements: [[accept_indexes: [], methods: []]])
    iex> message =~ "accept indexes"
    true

    iex> {:error, message} = X402.Extensions.AuthHints.Adapter.init([])
    iex> message =~ ":auth_requirements"
    true

# `key`
*since 0.9.0* 

```elixir
@spec key() :: String.t()
```

Returns `"auth-hints"`.

## Examples

    iex> X402.Extensions.AuthHints.Adapter.key()
    "auth-hints"

---

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