chat_models.ts

import { type ClientOptions, OpenAI as OpenAIClient } from "openai";

import { CallbackManagerForLLMRun } from "@langchain/core/callbacks/manager";
import {
  AIMessage,
  AIMessageChunk,
  type BaseMessage,
  ChatMessage,
  ChatMessageChunk,
  FunctionMessageChunk,
  HumanMessageChunk,
  SystemMessageChunk,
  ToolMessage,
  ToolMessageChunk,
} from "@langchain/core/messages";
import {
  type ChatGeneration,
  ChatGenerationChunk,
  type ChatResult,
} from "@langchain/core/outputs";
import type { StructuredToolInterface } from "@langchain/core/tools";
import { getEnvironmentVariable } from "@langchain/core/utils/env";
import {
  BaseChatModel,
  type BaseChatModelParams,
} from "@langchain/core/language_models/chat_models";
import type { BaseFunctionCallOptions } from "@langchain/core/language_models/base";
import { NewTokenIndices } from "@langchain/core/callbacks/base";
import type {
  AzureOpenAIInput,
  OpenAICallOptions,
  OpenAIChatInput,
  OpenAICoreRequestOptions,
  LegacyOpenAIInput,
} from "./types.js";
import { type OpenAIEndpointConfig, getEndpoint } from "./utils/azure.js";
import { wrapOpenAIClientError, formatToOpenAITool } from "./utils/openai.js";
import {
  FunctionDef,
  formatFunctionDefinitions,
} from "./utils/openai-format-fndef.js";

export type { AzureOpenAIInput, OpenAICallOptions, OpenAIChatInput };

interface TokenUsage {
  completionTokens?: number;
  promptTokens?: number;
  totalTokens?: number;
}

interface OpenAILLMOutput {
  tokenUsage: TokenUsage;
}

// TODO import from SDK when available
type OpenAIRoleEnum = "system" | "assistant" | "user" | "function" | "tool";

type OpenAICompletionParam =
  OpenAIClient.Chat.Completions.ChatCompletionMessageParam;
type OpenAIFnDef = OpenAIClient.Chat.ChatCompletionCreateParams.Function;
type OpenAIFnCallOption = OpenAIClient.Chat.ChatCompletionFunctionCallOption;

function extractGenericMessageCustomRole(message: ChatMessage) {
  if (
    message.role !== "system" &&
    message.role !== "assistant" &&
    message.role !== "user" &&
    message.role !== "function" &&
    message.role !== "tool"
  ) {
    console.warn(`Unknown message role: ${message.role}`);
  }

  return message.role as OpenAIRoleEnum;
}

export function messageToOpenAIRole(message: BaseMessage): OpenAIRoleEnum {
  const type = message._getType();
  switch (type) {
    case "system":
      return "system";
    case "ai":
      return "assistant";
    case "human":
      return "user";
    case "function":
      return "function";
    case "tool":
      return "tool";
    case "generic": {
      if (!ChatMessage.isInstance(message))
        throw new Error("Invalid generic chat message");
      return extractGenericMessageCustomRole(message);
    }
    default:
      throw new Error(`Unknown message type: ${type}`);
  }
}

function openAIResponseToChatMessage(
  message: OpenAIClient.Chat.Completions.ChatCompletionMessage
): BaseMessage {
  switch (message.role) {
    case "assistant":
      return new AIMessage(message.content || "", {
        function_call: message.function_call,
        tool_calls: message.tool_calls,
      });
    default:
      return new ChatMessage(message.content || "", message.role ?? "unknown");
  }
}

function _convertDeltaToMessageChunk(
  // eslint-disable-next-line @typescript-eslint/no-explicit-any
  delta: Record<string, any>,
  defaultRole?: OpenAIRoleEnum
) {
  const role = delta.role ?? defaultRole;
  const content = delta.content ?? "";
  let additional_kwargs;
  if (delta.function_call) {
    additional_kwargs = {
      function_call: delta.function_call,
    };
  } else if (delta.tool_calls) {
    additional_kwargs = {
      tool_calls: delta.tool_calls,
    };
  } else {
    additional_kwargs = {};
  }
  if (role === "user") {
    return new HumanMessageChunk({ content });
  } else if (role === "assistant") {
    return new AIMessageChunk({ content, additional_kwargs });
  } else if (role === "system") {
    return new SystemMessageChunk({ content });
  } else if (role === "function") {
    return new FunctionMessageChunk({
      content,
      additional_kwargs,
      name: delta.name,
    });
  } else if (role === "tool") {
    return new ToolMessageChunk({
      content,
      additional_kwargs,
      tool_call_id: delta.tool_call_id,
    });
  } else {
    return new ChatMessageChunk({ content, role });
  }
}

function convertMessagesToOpenAIParams(messages: BaseMessage[]) {
  // TODO: Function messages do not support array content, fix cast
  return messages.map(
    (message) =>
      ({
        role: messageToOpenAIRole(message),
        content: message.content,
        name: message.name,
        function_call: message.additional_kwargs.function_call,
        tool_calls: message.additional_kwargs.tool_calls,
        tool_call_id: (message as ToolMessage).tool_call_id,
      } as OpenAICompletionParam)
  );
}

export interface ChatOpenAICallOptions
  extends OpenAICallOptions,
    BaseFunctionCallOptions {
  tools?: StructuredToolInterface[] | OpenAIClient.ChatCompletionTool[];
  tool_choice?: OpenAIClient.ChatCompletionToolChoiceOption;
  promptIndex?: number;
  response_format?: { type: "json_object" };
  seed?: number;
}

/**
 * Wrapper around OpenAI large language models that use the Chat endpoint.
 *
 * To use you should have the `openai` package installed, with the
 * `OPENAI_API_KEY` environment variable set.
 *
 * To use with Azure you should have the `openai` package installed, with the
 * `AZURE_OPENAI_API_KEY`,
 * `AZURE_OPENAI_API_INSTANCE_NAME`,
 * `AZURE_OPENAI_API_DEPLOYMENT_NAME`
 * and `AZURE_OPENAI_API_VERSION` environment variable set.
 * `AZURE_OPENAI_BASE_PATH` is optional and will override `AZURE_OPENAI_API_INSTANCE_NAME` if you need to use a custom endpoint.
 *
 * @remarks
 * Any parameters that are valid to be passed to {@link
 * https://platform.openai.com/docs/api-reference/chat/create |
 * `openai.createChatCompletion`} can be passed through {@link modelKwargs}, even
 * if not explicitly available on this class.
 * @example
 * ```typescript
 * // Create a new instance of ChatOpenAI with specific temperature and model name settings
 * const model = new ChatOpenAI({
 *   temperature: 0.9,
 *   modelName: "ft:gpt-3.5-turbo-0613:{ORG_NAME}::{MODEL_ID}",
 * });
 *
 * // Invoke the model with a message and await the response
 * const message = await model.invoke("Hi there!");
 *
 * // Log the response to the console
 * console.log(message);
 *
 * ```
 */
export class ChatOpenAI<
    CallOptions extends ChatOpenAICallOptions = ChatOpenAICallOptions
  >
  extends BaseChatModel<CallOptions>
  implements OpenAIChatInput, AzureOpenAIInput
{
  static lc_name() {
    return "ChatOpenAI";
  }

  get callKeys() {
    return [
      ...super.callKeys,
      "options",
      "function_call",
      "functions",
      "tools",
      "tool_choice",
      "promptIndex",
      "response_format",
      "seed",
    ];
  }

  lc_serializable = true;

  get lc_secrets(): { [key: string]: string } | undefined {
    return {
      openAIApiKey: "OPENAI_API_KEY",
      azureOpenAIApiKey: "AZURE_OPENAI_API_KEY",
      organization: "OPENAI_ORGANIZATION",
    };
  }

  get lc_aliases(): Record<string, string> {
    return {
      modelName: "model",
      openAIApiKey: "openai_api_key",
      azureOpenAIApiVersion: "azure_openai_api_version",
      azureOpenAIApiKey: "azure_openai_api_key",
      azureOpenAIApiInstanceName: "azure_openai_api_instance_name",
      azureOpenAIApiDeploymentName: "azure_openai_api_deployment_name",
    };
  }

  temperature = 1;

  topP = 1;

  frequencyPenalty = 0;

  presencePenalty = 0;

  n = 1;

  logitBias?: Record<string, number>;

  modelName = "gpt-3.5-turbo";

  modelKwargs?: OpenAIChatInput["modelKwargs"];

  stop?: string[];

  user?: string;

  timeout?: number;

  streaming = false;

  maxTokens?: number;

  openAIApiKey?: string;

  azureOpenAIApiVersion?: string;

  azureOpenAIApiKey?: string;

  azureOpenAIApiInstanceName?: string;

  azureOpenAIApiDeploymentName?: string;

  azureOpenAIBasePath?: string;

  organization?: string;

  private client: OpenAIClient;

  private clientConfig: ClientOptions;

  constructor(
    fields?: Partial<OpenAIChatInput> &
      Partial<AzureOpenAIInput> &
      BaseChatModelParams & {
        configuration?: ClientOptions & LegacyOpenAIInput;
      },
    /** @deprecated */
    configuration?: ClientOptions & LegacyOpenAIInput
  ) {
    super(fields ?? {});

    this.openAIApiKey =
      fields?.openAIApiKey ?? getEnvironmentVariable("OPENAI_API_KEY");

    this.azureOpenAIApiKey =
      fields?.azureOpenAIApiKey ??
      getEnvironmentVariable("AZURE_OPENAI_API_KEY");

    if (!this.azureOpenAIApiKey && !this.openAIApiKey) {
      throw new Error("OpenAI or Azure OpenAI API key not found");
    }

    this.azureOpenAIApiInstanceName =
      fields?.azureOpenAIApiInstanceName ??
      getEnvironmentVariable("AZURE_OPENAI_API_INSTANCE_NAME");

    this.azureOpenAIApiDeploymentName =
      fields?.azureOpenAIApiDeploymentName ??
      getEnvironmentVariable("AZURE_OPENAI_API_DEPLOYMENT_NAME");

    this.azureOpenAIApiVersion =
      fields?.azureOpenAIApiVersion ??
      getEnvironmentVariable("AZURE_OPENAI_API_VERSION");

    this.azureOpenAIBasePath =
      fields?.azureOpenAIBasePath ??
      getEnvironmentVariable("AZURE_OPENAI_BASE_PATH");

    this.organization =
      fields?.configuration?.organization ??
      getEnvironmentVariable("OPENAI_ORGANIZATION");

    this.modelName = fields?.modelName ?? this.modelName;
    this.modelKwargs = fields?.modelKwargs ?? {};
    this.timeout = fields?.timeout;

    this.temperature = fields?.temperature ?? this.temperature;
    this.topP = fields?.topP ?? this.topP;
    this.frequencyPenalty = fields?.frequencyPenalty ?? this.frequencyPenalty;
    this.presencePenalty = fields?.presencePenalty ?? this.presencePenalty;
    this.maxTokens = fields?.maxTokens;
    this.n = fields?.n ?? this.n;
    this.logitBias = fields?.logitBias;
    this.stop = fields?.stop;
    this.user = fields?.user;

    this.streaming = fields?.streaming ?? false;

    if (this.azureOpenAIApiKey) {
      if (!this.azureOpenAIApiInstanceName && !this.azureOpenAIBasePath) {
        throw new Error("Azure OpenAI API instance name not found");
      }
      if (!this.azureOpenAIApiDeploymentName) {
        throw new Error("Azure OpenAI API deployment name not found");
      }
      if (!this.azureOpenAIApiVersion) {
        throw new Error("Azure OpenAI API version not found");
      }
      this.openAIApiKey = this.openAIApiKey ?? "";
    }

    this.clientConfig = {
      apiKey: this.openAIApiKey,
      organization: this.organization,
      baseURL: configuration?.basePath ?? fields?.configuration?.basePath,
      dangerouslyAllowBrowser: true,
      defaultHeaders:
        configuration?.baseOptions?.headers ??
        fields?.configuration?.baseOptions?.headers,
      defaultQuery:
        configuration?.baseOptions?.params ??
        fields?.configuration?.baseOptions?.params,
      ...configuration,
      ...fields?.configuration,
    };
  }

  /**
   * Get the parameters used to invoke the model
   */
  invocationParams(
    options?: this["ParsedCallOptions"]
  ): Omit<OpenAIClient.Chat.ChatCompletionCreateParams, "messages"> {
    function isStructuredToolArray(
      tools?: unknown[]
    ): tools is StructuredToolInterface[] {
      return (
        tools !== undefined &&
        tools.every((tool) =>
          Array.isArray((tool as StructuredToolInterface).lc_namespace)
        )
      );
    }
    const params: Omit<
      OpenAIClient.Chat.ChatCompletionCreateParams,
      "messages"
    > = {
      model: this.modelName,
      temperature: this.temperature,
      top_p: this.topP,
      frequency_penalty: this.frequencyPenalty,
      presence_penalty: this.presencePenalty,
      max_tokens: this.maxTokens === -1 ? undefined : this.maxTokens,
      n: this.n,
      logit_bias: this.logitBias,
      stop: options?.stop ?? this.stop,
      user: this.user,
      stream: this.streaming,
      functions: options?.functions,
      function_call: options?.function_call,
      tools: isStructuredToolArray(options?.tools)
        ? options?.tools.map(formatToOpenAITool)
        : options?.tools,
      tool_choice: options?.tool_choice,
      response_format: options?.response_format,
      seed: options?.seed,
      ...this.modelKwargs,
    };
    return params;
  }

  /** @ignore */
  _identifyingParams(): Omit<
    OpenAIClient.Chat.ChatCompletionCreateParams,
    "messages"
  > & {
    model_name: string;
  } & ClientOptions {
    return {
      model_name: this.modelName,
      ...this.invocationParams(),
      ...this.clientConfig,
    };
  }

  async *_streamResponseChunks(
    messages: BaseMessage[],
    options: this["ParsedCallOptions"],
    runManager?: CallbackManagerForLLMRun
  ): AsyncGenerator<ChatGenerationChunk> {
    const messagesMapped: OpenAICompletionParam[] =
      convertMessagesToOpenAIParams(messages);
    const params = {
      ...this.invocationParams(options),
      messages: messagesMapped,
      stream: true as const,
    };
    let defaultRole: OpenAIRoleEnum | undefined;
    const streamIterable = await this.completionWithRetry(params, options);
    for await (const data of streamIterable) {
      const choice = data?.choices[0];
      if (!choice) {
        continue;
      }

      const { delta } = choice;
      if (!delta) {
        continue;
      }
      const chunk = _convertDeltaToMessageChunk(delta, defaultRole);
      defaultRole = delta.role ?? defaultRole;
      const newTokenIndices = {
        prompt: options.promptIndex ?? 0,
        completion: choice.index ?? 0,
      };
      if (typeof chunk.content !== "string") {
        console.log(
          "[WARNING]: Received non-string content from OpenAI. This is currently not supported."
        );
        continue;
      }
      const generationChunk = new ChatGenerationChunk({
        message: chunk,
        text: chunk.content,
        generationInfo: newTokenIndices,
      });
      yield generationChunk;
      // eslint-disable-next-line no-void
      void runManager?.handleLLMNewToken(
        generationChunk.text ?? "",
        newTokenIndices,
        undefined,
        undefined,
        undefined,
        { chunk: generationChunk }
      );
    }
    if (options.signal?.aborted) {
      throw new Error("AbortError");
    }
  }

  /**
   * Get the identifying parameters for the model
   *
   */
  identifyingParams() {
    return this._identifyingParams();
  }

  /** @ignore */
  async _generate(
    messages: BaseMessage[],
    options: this["ParsedCallOptions"],
    runManager?: CallbackManagerForLLMRun
  ): Promise<ChatResult> {
    const tokenUsage: TokenUsage = {};
    const params = this.invocationParams(options);
    const messagesMapped: OpenAICompletionParam[] =
      convertMessagesToOpenAIParams(messages);

    if (params.stream) {
      const stream = this._streamResponseChunks(messages, options, runManager);
      const finalChunks: Record<number, ChatGenerationChunk> = {};
      for await (const chunk of stream) {
        const index =
          (chunk.generationInfo as NewTokenIndices)?.completion ?? 0;
        if (finalChunks[index] === undefined) {
          finalChunks[index] = chunk;
        } else {
          finalChunks[index] = finalChunks[index].concat(chunk);
        }
      }
      const generations = Object.entries(finalChunks)
        .sort(([aKey], [bKey]) => parseInt(aKey, 10) - parseInt(bKey, 10))
        .map(([_, value]) => value);

      const { functions, function_call } = this.invocationParams(options);

      // OpenAI does not support token usage report under stream mode,
      // fallback to estimation.

      const promptTokenUsage = await this.getEstimatedTokenCountFromPrompt(
        messages,
        functions,
        function_call
      );
      const completionTokenUsage = await this.getNumTokensFromGenerations(
        generations
      );

      tokenUsage.promptTokens = promptTokenUsage;
      tokenUsage.completionTokens = completionTokenUsage;
      tokenUsage.totalTokens = promptTokenUsage + completionTokenUsage;
      return { generations, llmOutput: { estimatedTokenUsage: tokenUsage } };
    } else {
      const data = await this.completionWithRetry(
        {
          ...params,
          stream: false,
          messages: messagesMapped,
        },
        {
          signal: options?.signal,
          ...options?.options,
        }
      );
      const {
        completion_tokens: completionTokens,
        prompt_tokens: promptTokens,
        total_tokens: totalTokens,
      } = data?.usage ?? {};

      if (completionTokens) {
        tokenUsage.completionTokens =
          (tokenUsage.completionTokens ?? 0) + completionTokens;
      }

      if (promptTokens) {
        tokenUsage.promptTokens = (tokenUsage.promptTokens ?? 0) + promptTokens;
      }

      if (totalTokens) {
        tokenUsage.totalTokens = (tokenUsage.totalTokens ?? 0) + totalTokens;
      }

      const generations: ChatGeneration[] = [];
      for (const part of data?.choices ?? []) {
        const text = part.message?.content ?? "";
        const generation: ChatGeneration = {
          text,
          message: openAIResponseToChatMessage(
            part.message ?? { role: "assistant" }
          ),
        };
        if (part.finish_reason) {
          generation.generationInfo = { finish_reason: part.finish_reason };
        }
        generations.push(generation);
      }
      return {
        generations,
        llmOutput: { tokenUsage },
      };
    }
  }

  /**
   * Estimate the number of tokens a prompt will use.
   * Modified from: https://github.com/hmarr/openai-chat-tokens/blob/main/src/index.ts
   */
  private async getEstimatedTokenCountFromPrompt(
    messages: BaseMessage[],
    functions?: OpenAIFnDef[],
    function_call?: "none" | "auto" | OpenAIFnCallOption
  ): Promise<number> {
    // It appears that if functions are present, the first system message is padded with a trailing newline. This
    // was inferred by trying lots of combinations of messages and functions and seeing what the token counts were.

    let tokens = (await this.getNumTokensFromMessages(messages)).totalCount;

    // If there are functions, add the function definitions as they count towards token usage
    if (functions && function_call !== "auto") {
      const promptDefinitions = formatFunctionDefinitions(
        functions as unknown as FunctionDef[]
      );
      tokens += await this.getNumTokens(promptDefinitions);
      tokens += 9; // Add nine per completion
    }

    // If there's a system message _and_ functions are present, subtract four tokens. I assume this is because
    // functions typically add a system message, but reuse the first one if it's already there. This offsets
    // the extra 9 tokens added by the function definitions.
    if (functions && messages.find((m) => m._getType() === "system")) {
      tokens -= 4;
    }

    // If function_call is 'none', add one token.
    // If it's a FunctionCall object, add 4 + the number of tokens in the function name.
    // If it's undefined or 'auto', don't add anything.
    if (function_call === "none") {
      tokens += 1;
    } else if (typeof function_call === "object") {
      tokens += (await this.getNumTokens(function_call.name)) + 4;
    }

    return tokens;
  }

  /**
   * Estimate the number of tokens an array of generations have used.
   */
  private async getNumTokensFromGenerations(generations: ChatGeneration[]) {
    const generationUsages = await Promise.all(
      generations.map(async (generation) => {
        if (generation.message.additional_kwargs?.function_call) {
          return (await this.getNumTokensFromMessages([generation.message]))
            .countPerMessage[0];
        } else {
          return await this.getNumTokens(generation.message.content);
        }
      })
    );

    return generationUsages.reduce((a, b) => a + b, 0);
  }

  async getNumTokensFromMessages(messages: BaseMessage[]) {
    let totalCount = 0;
    let tokensPerMessage = 0;
    let tokensPerName = 0;

    // From: https://github.com/openai/openai-cookbook/blob/main/examples/How_to_format_inputs_to_ChatGPT_models.ipynb
    if (this.modelName === "gpt-3.5-turbo-0301") {
      tokensPerMessage = 4;
      tokensPerName = -1;
    } else {
      tokensPerMessage = 3;
      tokensPerName = 1;
    }

    const countPerMessage = await Promise.all(
      messages.map(async (message) => {
        const textCount = await this.getNumTokens(message.content);
        const roleCount = await this.getNumTokens(messageToOpenAIRole(message));
        const nameCount =
          message.name !== undefined
            ? tokensPerName + (await this.getNumTokens(message.name))
            : 0;
        let count = textCount + tokensPerMessage + roleCount + nameCount;

        // From: https://github.com/hmarr/openai-chat-tokens/blob/main/src/index.ts messageTokenEstimate
        const openAIMessage = message;
        if (openAIMessage._getType() === "function") {
          count -= 2;
        }
        if (openAIMessage.additional_kwargs?.function_call) {
          count += 3;
        }
        if (openAIMessage?.additional_kwargs.function_call?.name) {
          count += await this.getNumTokens(
            openAIMessage.additional_kwargs.function_call?.name
          );
        }
        if (openAIMessage.additional_kwargs.function_call?.arguments) {
          count += await this.getNumTokens(
            // Remove newlines and spaces
            JSON.stringify(
              JSON.parse(
                openAIMessage.additional_kwargs.function_call?.arguments
              )
            )
          );
        }

        totalCount += count;
        return count;
      })
    );

    totalCount += 3; // every reply is primed with <|start|>assistant<|message|>

    return { totalCount, countPerMessage };
  }

  /**
   * Calls the OpenAI API with retry logic in case of failures.
   * @param request The request to send to the OpenAI API.
   * @param options Optional configuration for the API call.
   * @returns The response from the OpenAI API.
   */
  async completionWithRetry(
    request: OpenAIClient.Chat.ChatCompletionCreateParamsStreaming,
    options?: OpenAICoreRequestOptions
  ): Promise<AsyncIterable<OpenAIClient.Chat.Completions.ChatCompletionChunk>>;

  async completionWithRetry(
    request: OpenAIClient.Chat.ChatCompletionCreateParamsNonStreaming,
    options?: OpenAICoreRequestOptions
  ): Promise<OpenAIClient.Chat.Completions.ChatCompletion>;

  async completionWithRetry(
    request:
      | OpenAIClient.Chat.ChatCompletionCreateParamsStreaming
      | OpenAIClient.Chat.ChatCompletionCreateParamsNonStreaming,
    options?: OpenAICoreRequestOptions
  ): Promise<
    | AsyncIterable<OpenAIClient.Chat.Completions.ChatCompletionChunk>
    | OpenAIClient.Chat.Completions.ChatCompletion
  > {
    const requestOptions = this._getClientOptions(options);
    return this.caller.call(async () => {
      try {
        const res = await this.client.chat.completions.create(
          request,
          requestOptions
        );
        return res;
      } catch (e) {
        const error = wrapOpenAIClientError(e);
        throw error;
      }
    });
  }

  private _getClientOptions(options: OpenAICoreRequestOptions | undefined) {
    if (!this.client) {
      const openAIEndpointConfig: OpenAIEndpointConfig = {
        azureOpenAIApiDeploymentName: this.azureOpenAIApiDeploymentName,
        azureOpenAIApiInstanceName: this.azureOpenAIApiInstanceName,
        azureOpenAIApiKey: this.azureOpenAIApiKey,
        azureOpenAIBasePath: this.azureOpenAIBasePath,
        baseURL: this.clientConfig.baseURL,
      };

      const endpoint = getEndpoint(openAIEndpointConfig);
      const params = {
        ...this.clientConfig,
        baseURL: endpoint,
        timeout: this.timeout,
        maxRetries: 0,
      };
      if (!params.baseURL) {
        delete params.baseURL;
      }

      this.client = new OpenAIClient(params);
    }
    const requestOptions = {
      ...this.clientConfig,
      ...options,
    } as OpenAICoreRequestOptions;
    if (this.azureOpenAIApiKey) {
      requestOptions.headers = {
        "api-key": this.azureOpenAIApiKey,
        ...requestOptions.headers,
      };
      requestOptions.query = {
        "api-version": this.azureOpenAIApiVersion,
        ...requestOptions.query,
      };
    }
    return requestOptions;
  }

  _llmType() {
    return "openai";
  }

  /** @ignore */
  _combineLLMOutput(...llmOutputs: OpenAILLMOutput[]): OpenAILLMOutput {
    return llmOutputs.reduce<{
      [key in keyof OpenAILLMOutput]: Required<OpenAILLMOutput[key]>;
    }>(
      (acc, llmOutput) => {
        if (llmOutput && llmOutput.tokenUsage) {
          acc.tokenUsage.completionTokens +=
            llmOutput.tokenUsage.completionTokens ?? 0;
          acc.tokenUsage.promptTokens += llmOutput.tokenUsage.promptTokens ?? 0;
          acc.tokenUsage.totalTokens += llmOutput.tokenUsage.totalTokens ?? 0;
        }
        return acc;
      },
      {
        tokenUsage: {
          completionTokens: 0,
          promptTokens: 0,
          totalTokens: 0,
        },
      }
    );
  }
}