conversation.ts

import { PromptTemplate } from "@langchain/core/prompts";
import { LLMChain, LLMChainInput } from "./llm_chain.js";
import { BufferMemory } from "../memory/buffer_memory.js";
import { Optional } from "../types/type-utils.js";

export const DEFAULT_TEMPLATE = `The following is a friendly conversation between a human and an AI. The AI is talkative and provides lots of specific details from its context. If the AI does not know the answer to a question, it truthfully says it does not know.

Current conversation:
{history}
Human: {input}
AI:`;

/**
 * A class for conducting conversations between a human and an AI. It
 * extends the {@link LLMChain} class.
 * @example
 * ```typescript
 * const model = new ChatOpenAI({});
 * const chain = new ConversationChain({ llm: model });
 *
 * // Sending a greeting to the conversation chain
 * const res1 = await chain.call({ input: "Hi! I'm Jim." });
 * console.log({ res1 });
 *
 * // Following up with a question in the conversation
 * const res2 = await chain.call({ input: "What's my name?" });
 * console.log({ res2 });
 * ```
 */
export class ConversationChain extends LLMChain {
  static lc_name() {
    return "ConversationChain";
  }

  constructor({
    prompt,
    outputKey,
    memory,
    ...rest
  }: Optional<LLMChainInput, "prompt">) {
    super({
      prompt:
        prompt ??
        new PromptTemplate({
          template: DEFAULT_TEMPLATE,
          inputVariables: ["history", "input"],
        }),
      outputKey: outputKey ?? "response",
      memory: memory ?? new BufferMemory(),
      ...rest,
    });
  }
}