pages/api/vector-search.ts

import type { NextRequest } from 'next/server'
import { createClient } from '@supabase/supabase-js'
import { codeBlock, oneLine } from 'common-tags'
import GPT3Tokenizer from 'gpt3-tokenizer'
import {
  Configuration,
  OpenAIApi,
  CreateModerationResponse,
  CreateEmbeddingResponse,
  ChatCompletionRequestMessage,
} from 'openai-edge'
import { OpenAIStream, StreamingTextResponse } from 'ai'
import { ApplicationError, UserError } from '@/lib/errors'

const openAiKey = process.env.OPENAI_KEY
const supabaseUrl = process.env.NEXT_PUBLIC_SUPABASE_URL
const supabaseServiceKey = process.env.SUPABASE_SERVICE_ROLE_KEY

const config = new Configuration({
  apiKey: openAiKey,
})
const openai = new OpenAIApi(config)

export const runtime = 'edge'

export default async function handler(req: NextRequest) {
  try {
    if (!openAiKey) {
      throw new ApplicationError('Missing environment variable OPENAI_KEY')
    }

    if (!supabaseUrl) {
      throw new ApplicationError('Missing environment variable SUPABASE_URL')
    }

    if (!supabaseServiceKey) {
      throw new ApplicationError('Missing environment variable SUPABASE_SERVICE_ROLE_KEY')
    }

    const requestData = await req.json()

    if (!requestData) {
      throw new UserError('Missing request data')
    }

    const { prompt: query } = requestData

    if (!query) {
      throw new UserError('Missing query in request data')
    }

    const supabaseClient = createClient(supabaseUrl, supabaseServiceKey)

    // Moderate the content to comply with OpenAI T&C
    const sanitizedQuery = query.trim()
    const moderationResponse: CreateModerationResponse = await openai
      .createModeration({ input: sanitizedQuery })
      .then((res) => res.json())

    const [results] = moderationResponse.results

    if (results.flagged) {
      throw new UserError('Flagged content', {
        flagged: true,
        categories: results.categories,
      })
    }

    // Create embedding from query
    const embeddingResponse = await openai.createEmbedding({
      model: 'text-embedding-ada-002',
      input: sanitizedQuery.replaceAll('\n', ' '),
    })

    if (embeddingResponse.status !== 200) {
      throw new ApplicationError('Failed to create embedding for question', embeddingResponse)
    }

    const {
      data: [{ embedding }],
    }: CreateEmbeddingResponse = await embeddingResponse.json()

    const { error: matchError, data: pageSections } = await supabaseClient.rpc(
      'match_page_sections',
      {
        embedding,
        match_threshold: 0.78,
        match_count: 10,
        min_content_length: 50,
      }
    )

    if (matchError) {
      throw new ApplicationError('Failed to match page sections', matchError)
    }

    const tokenizer = new GPT3Tokenizer({ type: 'gpt3' })
    let tokenCount = 0
    let contextText = ''

    for (let i = 0; i < pageSections.length; i++) {
      const pageSection = pageSections[i]
      const content = pageSection.content
      const encoded = tokenizer.encode(content)
      tokenCount += encoded.text.length

      if (tokenCount >= 1500) {
        break
      }

      contextText += `${content.trim()}\n---\n`
    }

    const prompt = codeBlock`
      ${oneLine`
        You are a very enthusiastic Supabase representative who loves
        to help people! Given the following sections from the Supabase
        documentation, answer the question using only that information,
        outputted in markdown format. If you are unsure and the answer
        is not explicitly written in the documentation, say
        "Sorry, I don't know how to help with that."
      `}

      Context sections:
      ${contextText}

      Question: """
      ${sanitizedQuery}
      """

      Answer as markdown (including related code snippets if available):
    `

    const chatMessage: ChatCompletionRequestMessage = {
      role: 'user',
      content: prompt,
    }

    const response = await openai.createChatCompletion({
      model: 'gpt-3.5-turbo',
      messages: [chatMessage],
      max_tokens: 512,
      temperature: 0,
      stream: true,
    })

    if (!response.ok) {
      const error = await response.json()
      throw new ApplicationError('Failed to generate completion', error)
    }

    // Transform the response into a readable stream
    const stream = OpenAIStream(response)

    // Return a StreamingTextResponse, which can be consumed by the client
    return new StreamingTextResponse(stream)
  } catch (err: unknown) {
    if (err instanceof UserError) {
      return new Response(
        JSON.stringify({
          error: err.message,
          data: err.data,
        }),
        {
          status: 400,
          headers: { 'Content-Type': 'application/json' },
        }
      )
    } else if (err instanceof ApplicationError) {
      // Print out application errors with their additional data
      console.error(`${err.message}: ${JSON.stringify(err.data)}`)
    } else {
      // Print out unexpected errors as is to help with debugging
      console.error(err)
    }

    // TODO: include more response info in debug environments
    return new Response(
      JSON.stringify({
        error: 'There was an error processing your request',
      }),
      {
        status: 500,
        headers: { 'Content-Type': 'application/json' },
      }
    )
  }
}