# LangSchema

Converts an abstract schema into JSON schemas required by various AI providers, minimizing code changes when switching providers.

## Design Goals

LangSchema aims to define an abstract schema that can be commonly applied across different AI providers, allowing you to switch providers without modifying your original schema. While provider-specific features are not entirely excluded, supporting every custom feature is not the primary goal. Instead, LangSchema prioritizes raising errors when a schema might implicitly behave incorrectly due to differences between providers, making such issues explicit and easier to fix.

## Concepts

- **Abstract Schema**: A subset of JSON Schema that is primarily used to define structured outputs or function parameters for AI providers. It aims to maintain an independent expression without being tied to any specific provider. For an example, see [schema.ex](https://github.com/nallwhy/lang_schema/blob/main/test/support/schema.ex).
- **JSON Schema**: The concrete output generated by converting the abstract schema to match the specific requirements of each AI provider.

## Supported AI providers

- OpenAI
  - [LangSchema.Converter.OpenAI.ChatCompletion](./lib/lang_schema/converter/openai/chat_completion.ex)
  - [LangSchema.Converter.OpenAI.Function](./lib/lang_schema/converter/openai/function.ex)
- Gemini
  - [LangSchema.Converter.Gemini](./lib/lang_schema/converter/gemini.ex)

## Writing a Custom Converter

You can create your own converter for a new AI provider by implementing the `LangSchema.Converter` behaviour.

Here's a simple example based on the OpenAI converter:

```elixir
defmodule MyApp.LangSchema.Converter.MyProvider do
  use LangSchema.Converter

  @impl LangSchema.Converter
  def wrap(json_schema, opts) do
    name = Keyword.get(opts, :name, "response")

    %{
      "name" => name,
      "schema" => json_schema
    }
  end

  @impl LangSchema.Converter
  def types() do
    # Add type converters
    %{
      integer: MyApp.LangSchema.Type.MyProvider.Integer,
      number: MyApp.LangSchema.Type.MyProvider.Number,
      string: MyApp.LangSchema.Type.MyProvider.String,
      array: MyApp.LangSchema.Type.MyProvider.Array,
      object: MyApp.LangSchema.Type.MyProvider.Object
    }
  end

  @impl LangSchema.Converter
  def allowed_combinations() do
    # List only the combinations your provider supports, e.g., :any_of, :one_of, :all_of
    [:any_of] 
  end

  @impl LangSchema.Converter
  def keywords() do
    %{
      # Add keyword converters
      nullable: MyApp.LangSchema.Keyword.MyProvider.Nullable
    }
  end
end
```

## Installation

The package can be installed by adding `lang_schema` to your list of dependencies
in `mix.exs`:

```elixir
def deps do
  [
    {:lang_schema, "~> 0.1.0"}
  ]
end
```

## Relationship with Elixir LangChain

Elixir [LangChain](https://hex.pm/packages/langchain) library provides support for function calling by accepting a `json_schema`.
LangSchema is designed so that the output of each converter’s `wrap/2` function can be directly used as a json_schema in LangChain without additional modifications.