anything-llm/server/utils/helpers/chat/responses.js

const { v4: uuidv4 } = require("uuid");
const moment = require("moment");

function clientAbortedHandler(resolve, fullText) {
  console.log(
    "\x1b[43m\x1b[34m[STREAM ABORTED]\x1b[0m Client requested to abort stream. Exiting LLM stream handler early."
  );
  resolve(fullText);
  return;
}

// The default way to handle a stream response. Functions best with OpenAI.
// Currently used for LMStudio, LocalAI, Mistral API, and OpenAI
function handleDefaultStreamResponse(response, stream, responseProps) {
  const { uuid = uuidv4(), sources = [] } = responseProps;

  return new Promise((resolve) => {
    let fullText = "";
    let chunk = "";

    // Establish listener to early-abort a streaming response
    // in case things go sideways or the user does not like the response.
    // We preserve the generated text but continue as if chat was completed
    // to preserve previously generated content.
    const handleAbort = () => clientAbortedHandler(resolve, fullText);
    response.on("close", handleAbort);

    stream.data.on("data", (data) => {
      const lines = data
        ?.toString()
        ?.split("\n")
        .filter((line) => line.trim() !== "");

      for (const line of lines) {
        let validJSON = false;
        const message = chunk + line.replace(/^data: /, "");

        // JSON chunk is incomplete and has not ended yet
        // so we need to stitch it together. You would think JSON
        // chunks would only come complete - but they don't!
        try {
          JSON.parse(message);
          validJSON = true;
        } catch {}

        if (!validJSON) {
          // It can be possible that the chunk decoding is running away
          // and the message chunk fails to append due to string length.
          // In this case abort the chunk and reset so we can continue.
          // ref: https://github.com/Mintplex-Labs/anything-llm/issues/416
          try {
            chunk += message;
          } catch (e) {
            console.error(`Chunk appending error`, e);
            chunk = "";
          }
          continue;
        } else {
          chunk = "";
        }

        if (message == "[DONE]") {
          writeResponseChunk(response, {
            uuid,
            sources,
            type: "textResponseChunk",
            textResponse: "",
            close: true,
            error: false,
          });
          response.removeListener("close", handleAbort);
          resolve(fullText);
        } else {
          let finishReason = null;
          let token = "";
          try {
            const json = JSON.parse(message);
            token = json?.choices?.[0]?.delta?.content;
            finishReason = json?.choices?.[0]?.finish_reason || null;
          } catch {
            continue;
          }

          if (token) {
            fullText += token;
            writeResponseChunk(response, {
              uuid,
              sources: [],
              type: "textResponseChunk",
              textResponse: token,
              close: false,
              error: false,
            });
          }

          if (finishReason !== null) {
            writeResponseChunk(response, {
              uuid,
              sources,
              type: "textResponseChunk",
              textResponse: "",
              close: true,
              error: false,
            });
            response.removeListener("close", handleAbort);
            resolve(fullText);
          }
        }
      }
    });
  });
}

function convertToChatHistory(history = []) {
  const formattedHistory = [];
  history.forEach((history) => {
    const { prompt, response, createdAt, feedbackScore = null, id } = history;
    const data = JSON.parse(response);
    formattedHistory.push([
      {
        role: "user",
        content: prompt,
        sentAt: moment(createdAt).unix(),
      },
      {
        role: "assistant",
        content: data.text,
        sources: data.sources || [],
        chatId: id,
        sentAt: moment(createdAt).unix(),
        feedbackScore,
      },
    ]);
  });

  return formattedHistory.flat();
}

function convertToPromptHistory(history = []) {
  const formattedHistory = [];
  history.forEach((history) => {
    const { prompt, response } = history;
    const data = JSON.parse(response);
    formattedHistory.push([
      { role: "user", content: prompt },
      { role: "assistant", content: data.text },
    ]);
  });
  return formattedHistory.flat();
}

function writeResponseChunk(response, data) {
  response.write(`data: ${JSON.stringify(data)}\n\n`);
  return;
}

module.exports = {
  handleDefaultStreamResponse,
  convertToChatHistory,
  convertToPromptHistory,
  writeResponseChunk,
  clientAbortedHandler,
};