nextjs-chat-gpt/app/api/chat/route.ts

import {
  streamText,
  convertToModelMessages,
  stepCountIs,
  pruneMessages,
} from 'ai';
import { getChatModel } from '@/services/chat/model';
import { getChatInstructions } from '@/services/chat/instructions';
import { chatTools } from '@/services/chat/tools';
import { isOpenRouterModelId } from '@/lib/openrouter';

export const maxDuration = 300;

export async function POST(request: Request) {
  try {
    const { messages, modelId } = await request.json();

    if (modelId !== undefined && !isOpenRouterModelId(modelId)) {
      return Response.json({ error: 'Select a supported model' }, { status: 400 });
    }

    if (!process.env.OPENROUTER_API_KEY) {
      return Response.json(
        { error: 'OPENROUTER_API_KEY is not configured' },
        { status: 503 }
      );
    }

    const model = getChatModel(modelId);

    const webSearchEnabled = Boolean(process.env.FIRECRAWL_API_KEY);

    const instructions = getChatInstructions(webSearchEnabled);

    const convertedMessages = await convertToModelMessages(messages);

    const prunedMessages = pruneMessages({
      messages: convertedMessages,
      reasoning: 'all',
      toolCalls: 'none',
    });

    const result = streamText({
      model,
      instructions,
      messages: prunedMessages,
      abortSignal: request.signal,
      tools: webSearchEnabled ? chatTools : {},
      stopWhen: stepCountIs(20),
      onError: ({ error }) => {
        if (!request.signal.aborted) console.error('Chat stream error:', error);
      },
      providerOptions: {
        openrouter: {
          reasoning: {
            enabled: true,
            effort: 'medium',
          },
        },
      },
    });

    return result.toUIMessageStreamResponse({
      sendReasoning: true,
      headers: { 'Cache-Control': 'no-cache, no-transform' },
      onError: () => 'The response was interrupted. Please try again.',
    });
  } catch (error) {
    console.error('Chat API error:', error);
    return new Response(
      JSON.stringify({ error: 'Failed to process chat request' }),
      {
        status: 500,
        headers: { 'Content-Type': 'application/json' },
      }
    );
  }
}