unifed logic for function call / agent

[himself65]

Since gpt3.5/4 and Claude-3 are all support function calls, they have different way to use it. It's necessary to use a better way to handle it on the LlamaindexTS side to make user easy to switch without overhead.

type MessageRole = 'user' | 'ai' | 'system'
type MessageContentPart = MessageContentTextPart | MessageContentImagePart // ...
type Message = {
  role: MessageRole
  content: string | MessageContentPart[]
}

interface MessageInterop<LLMMessage> {
  toLLMMessage(messages: Message[]): LLMMessage[]
  fromAIMessage(message: LLMMessage[]): Message[]
}
interface LLM<LLMMessage> extends MessageInterop<LLMMessage> {
  // ...
}

type Tool<Input> = {
  handler: (input: Input) => string | Promise<string>
  metadata: {
    name: string
    // ... there should be json schema so that it could support zod
  }
}

type LLMFunctionCallEvent = LLMBaseEvent<'llm-function-call', {
  tool: Tool; // <-- should be BaseTool<Input>
  input: unknown // <-- should be Input
}>