next-ai-draw-io/lib/langfuse.ts

import { LangfuseClient } from "@langfuse/client"
import { observe, updateActiveTrace } from "@langfuse/tracing"
import * as api from "@opentelemetry/api"

// Singleton LangfuseClient instance for direct API calls
let langfuseClient: LangfuseClient | null = null

export function getLangfuseClient(): LangfuseClient | null {
    if (!process.env.LANGFUSE_PUBLIC_KEY || !process.env.LANGFUSE_SECRET_KEY) {
        return null
    }

    if (!langfuseClient) {
        langfuseClient = new LangfuseClient({
            publicKey: process.env.LANGFUSE_PUBLIC_KEY,
            secretKey: process.env.LANGFUSE_SECRET_KEY,
            baseUrl: process.env.LANGFUSE_BASEURL,
        })
    }

    return langfuseClient
}

// Check if Langfuse is configured
export function isLangfuseEnabled(): boolean {
    return !!process.env.LANGFUSE_PUBLIC_KEY
}

// Update trace with input data at the start of request
export function setTraceInput(params: {
    input: string
    sessionId?: string
    userId?: string
}) {
    if (!isLangfuseEnabled()) return

    updateActiveTrace({
        name: "chat",
        input: params.input,
        sessionId: params.sessionId,
        userId: params.userId,
    })
}

// Update trace with output and end the span
export function setTraceOutput(
    output: string,
    usage?: { promptTokens?: number; completionTokens?: number },
) {
    if (!isLangfuseEnabled()) return

    updateActiveTrace({ output })

    const activeSpan = api.trace.getActiveSpan()
    if (activeSpan) {
        // Manually set usage attributes since AI SDK Bedrock streaming doesn't provide them
        if (usage?.promptTokens) {
            activeSpan.setAttribute("ai.usage.promptTokens", usage.promptTokens)
            activeSpan.setAttribute(
                "gen_ai.usage.input_tokens",
                usage.promptTokens,
            )
        }
        if (usage?.completionTokens) {
            activeSpan.setAttribute(
                "ai.usage.completionTokens",
                usage.completionTokens,
            )
            activeSpan.setAttribute(
                "gen_ai.usage.output_tokens",
                usage.completionTokens,
            )
        }
        activeSpan.end()
    }
}

// Get telemetry config for streamText
export function getTelemetryConfig(params: {
    sessionId?: string
    userId?: string
}) {
    if (!isLangfuseEnabled()) return undefined

    return {
        isEnabled: true,
        // Disable automatic input recording to avoid uploading large base64 images to Langfuse media
        // User text input is recorded manually via setTraceInput
        recordInputs: false,
        recordOutputs: true,
        metadata: {
            sessionId: params.sessionId,
            userId: params.userId,
        },
    }
}

// Wrap a handler with Langfuse observe
export function wrapWithObserve<T>(
    handler: (req: Request) => Promise<T>,
): (req: Request) => Promise<T> {
    if (!isLangfuseEnabled()) {
        return handler
    }

    return observe(handler, { name: "chat", endOnExit: false })
}