# `WardrikCore.Middleware`

Wraps every step of a turn: the turn itself, each model call, and each tool call.

Use it when every call needs the same treatment, such as policy, tracing, retries or a system
prompt.

    defmodule MyApp.NoShell do
      @behaviour WardrikCore.Middleware

      @impl true
      def call(%{step: {:tool_call, %{name: "shell"}}} = context, _next, _opts),
        do: {:ok, %{context | response: {:error, "No shell."}}}

      def call(context, next, _opts), do: next.(context)
    end

Give it to an agent as `middleware: [MyApp.NoShell]` or `middleware: [{MyApp.NoShell, opts}]`.
The first in the list runs outermost.

## Return values

  * `next.(context)` - carries on.
  * `{:ok, context}` - answers the step yourself, with `context.response` as the answer.
  * `{:park, reason, context}` - waits for a person. See `WardrikCore.resume/3`.
  * `{:error, reason}` - ends the step.

# `context`

```elixir
@type context() :: WardrikCore.Context.t()
```

# `next`

```elixir
@type next() :: (context() -> result())
```

# `result`

```elixir
@type result() :: {:ok, context()} | {:error, term()} | {:park, term(), context()}
```

# `call`

```elixir
@callback call(context(), next(), opts :: term()) :: result()
```

Handles one step. Call `next` to carry on, or return a result to stop.

---

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