import { NextRequest, NextResponse } from 'next/server';
import type { ProviderId } from '@/types';
import { PROVIDER_MAP } from '@/lib/providers';

interface ModelsRequestBody {
  provider: ProviderId;
  apiKey?: string;
  baseUrl?: string;
}

export async function POST(req: NextRequest) {
  let body: ModelsRequestBody;
  try {
    body = await req.json();
  } catch {
    return NextResponse.json({ error: 'Invalid JSON' }, { status: 400 });
  }

  const { provider, apiKey, baseUrl } = body;
  const def = PROVIDER_MAP[provider];
  const base = baseUrl?.trim() || def.defaultBaseUrl;

  try {
    let models: string[] = [];

    if (provider === 'anthropic') {
      const key = apiKey?.trim() || process.env.ANTHROPIC_API_KEY;
      if (!key) {
        return NextResponse.json({ error: 'No API key — enter one above or set ANTHROPIC_API_KEY in .env.local' }, { status: 400 });
      }
      const res = await fetch('https://api.anthropic.com/v1/models?limit=100', {
        headers: {
          'x-api-key': key,
          'anthropic-version': '2023-06-01',
        },
      });
      if (!res.ok) {
        const text = await res.text().catch(() => '');
        return NextResponse.json({ error: `Anthropic: ${res.status} ${text}` }, { status: res.status });
      }
      const data = await res.json();
      models = (data.data ?? []).map((m: { id: string }) => m.id);
    }

    else if (provider === 'openrouter') {
      const headers: Record<string, string> = {};
      if (apiKey?.trim()) headers['Authorization'] = `Bearer ${apiKey.trim()}`;

      const res = await fetch('https://openrouter.ai/api/v1/models', { headers });
      if (!res.ok) {
        const text = await res.text().catch(() => '');
        return NextResponse.json({ error: `OpenRouter: ${res.status} ${text}` }, { status: res.status });
      }
      const data = await res.json();
      // Sort by id for easier browsing
      models = (data.data ?? [])
        .map((m: { id: string }) => m.id)
        .sort((a: string, b: string) => a.localeCompare(b));
    }

    else {
      // LM Studio and Ollama — OpenAI-compatible /v1/models
      const res = await fetch(`${base}/models`, {
        headers: { Authorization: 'Bearer none' },
        signal: AbortSignal.timeout(5000),
      });
      if (!res.ok) {
        const text = await res.text().catch(() => '');
        return NextResponse.json({ error: `${def.label}: ${res.status} ${text || 'Connection refused'}` }, { status: res.status });
      }
      const data = await res.json();
      models = (data.data ?? []).map((m: { id: string }) => m.id);
    }

    return NextResponse.json({ models });
  } catch (err) {
    const msg = err instanceof Error ? err.message : 'Unknown error';
    const isTimeout = msg.includes('timeout') || msg.includes('abort');
    return NextResponse.json(
      { error: isTimeout ? `Could not reach ${def.label} — is it running?` : msg },
      { status: 500 }
    );
  }
}