# `LangchainPrompt.Prompt`
[🔗](https://github.com/exfoundry/langchain_prompt/blob/v0.1.0/lib/langchain_prompt/prompt.ex#L1)

Behaviour for a self-contained, reusable AI task.

A prompt module encapsulates everything needed for a specific AI operation:
what to ask (the prompts), how to ask it (the execution profile), and how to
process the answer (post-processing).

## Callbacks

- `set_profile/1` — returns a `LangchainPrompt.Profile` that selects the
  adapter and model configuration for this task.
- `generate_system_prompt/1` — returns the system prompt string, or `nil` to
  omit the system message (useful for models that don't support it).
- `generate_user_prompt/1` — returns the user prompt string, or `nil` for
  conversational prompts where the last message is already in `message_history`.
- `post_process/2` — transforms the raw `LangchainPrompt.Message` response
  into a domain value. Return `{:ok, result}` or `{:error, reason}`.

## Example

    defmodule MyApp.Prompts.Classify do
      @behaviour LangchainPrompt.Prompt

      @impl true
      def set_profile(_assigns), do: MyApp.AIProfiles.get(:fast)

      @impl true
      def generate_system_prompt(_assigns) do
        "Classify the sentiment as :positive, :neutral, or :negative. " <>
        "Reply with exactly one word."
      end

      @impl true
      def generate_user_prompt(%{text: text}), do: text

      @impl true
      def post_process(_assigns, %LangchainPrompt.Message{content: content}) do
        case String.trim(content) do
          "positive" -> {:ok, :positive}
          "neutral"  -> {:ok, :neutral}
          "negative" -> {:ok, :negative}
          other      -> {:error, {:unexpected_response, other}}
        end
      end
    end

# `generate_system_prompt`

```elixir
@callback generate_system_prompt(assigns :: map() | struct()) :: String.t() | nil
```

# `generate_user_prompt`

```elixir
@callback generate_user_prompt(assigns :: map() | struct()) :: String.t() | nil
```

# `post_process`

```elixir
@callback post_process(
  assigns :: map() | struct(),
  raw_response :: LangchainPrompt.Message.t()
) ::
  {:ok, any()} | {:error, any()}
```

# `set_profile`

```elixir
@callback set_profile(assigns :: map() | struct()) :: LangchainPrompt.Profile.t()
```

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