nuxt__ui/docs/server/api/completion.post.ts

import { streamText } from 'ai'
import { gateway } from '@ai-sdk/gateway'

export default defineEventHandler(async (event) => {
  const { prompt, mode, language } = await readBody(event)
  if (!prompt) {
    throw createError({ statusCode: 400, message: 'Prompt is required' })
  }

  let system: string
  let maxOutputTokens: number

  const preserveMarkdown = 'IMPORTANT: Preserve all markdown formatting (bold, italic, links, etc.) exactly as in the original.'

  switch (mode) {
    case 'fix':
      system = `You are a writing assistant. Fix all spelling and grammar errors in the given text. ${preserveMarkdown} Only output the corrected text, nothing else.`
      maxOutputTokens = 500
      break
    case 'extend':
      system = `You are a writing assistant. Extend the given text with more details, examples, and explanations while maintaining the same style. ${preserveMarkdown} Only output the extended text, nothing else.`
      maxOutputTokens = 500
      break
    case 'reduce':
      system = `You are a writing assistant. Make the given text more concise by removing unnecessary words while keeping the meaning. ${preserveMarkdown} Only output the reduced text, nothing else.`
      maxOutputTokens = 300
      break
    case 'simplify':
      system = `You are a writing assistant. Simplify the given text to make it easier to understand, using simpler words and shorter sentences. ${preserveMarkdown} Only output the simplified text, nothing else.`
      maxOutputTokens = 400
      break
    case 'summarize':
      system = 'You are a writing assistant. Summarize the given text concisely while keeping the key points. Only output the summary, nothing else.'
      maxOutputTokens = 200
      break
    case 'translate':
      system = `You are a writing assistant. Translate the given text to ${language || 'English'}. ${preserveMarkdown} Only output the translated text, nothing else.`
      maxOutputTokens = 500
      break
    case 'continue':
    default:
      system = `You are a writing assistant providing inline autocompletions.
CRITICAL RULES:
- Output ONLY the NEW text that comes AFTER the user's input
- NEVER repeat any words from the end of the user's text
- Keep completions short (1 sentence max)
- Match the tone and style of the existing text
- ${preserveMarkdown}`
      maxOutputTokens = 25
      break
  }

  return streamText({
    model: gateway('anthropic/claude-haiku-4.5'),
    system,
    prompt,
    maxOutputTokens
  }).toTextStreamResponse()
})