import { NextRequest, NextResponse } from 'next/server';
import { getStalwartCredentials } from '@/lib/stalwart/credentials';
import { configManager } from '@/lib/admin/config-manager';

export const runtime = 'nodejs';

/**
 * GET /api/ai/server/models — list models on the centrally-hosted `server`
 * class runtime (docs/AI-ASSISTANT-CONCEPT.md §2.1: "the same self-hosted
 * open-weight model stack as `local`... running on VNC's own infrastructure
 * instead of the user's laptop"). Tonight, `AI_SERVER_BASE_URL` stands in for
 * that infra with the Ollama already running on this developer's Mac — see
 * the module comment in lib/ai/entitlement.ts. Swapping to the real
 * EU/CH-hosted instance tomorrow is a config change, not a rewrite.
 *
 * Listing models is not a billable action (doc §10 point 1 — cosmetic), so
 * this only requires a valid session, not a seat.
 */
export async function GET(request: NextRequest) {
  const auth = await getStalwartCredentials(request);
  if (!auth) {
    return NextResponse.json({ error: 'not authenticated' }, { status: 401 });
  }

  const baseUrl = process.env.AI_SERVER_BASE_URL;
  if (!baseUrl) {
    return NextResponse.json({ error: 'AI server class is not configured' }, { status: 503 });
  }

  try {
    const res = await fetch(`${baseUrl.replace(/\/+$/, '')}/api/tags`);
    if (!res.ok) {
      return NextResponse.json({ error: `upstream returned ${res.status}` }, { status: 502 });
    }
    const body = (await res.json()) as { models?: Array<{ name: string; capabilities?: string[] }> };
    // Excludes embedding-only models (e.g. nomic-embed-text, used by
    // lib/ai/retrieval/mail-embeddings.ts) from the *chat* picker — Ollama
    // lists them in the same /api/tags response, but calling /api/chat with
    // one fails outright. `capabilities` absent (older Ollama) fails open
    // rather than hiding every model on an upgrade.
    let chatModels = (body.models ?? []).filter((m) => !m.capabilities || m.capabilities.includes('completion'));

    // Admin allow-list (docs/ADMIN-AI-POLICY-CONSOLE-SPEC.md §6). null = every
    // completion-capable model (today's behavior, unchanged).
    await configManager.ensureLoaded();
    const allowlist = configManager.getAiConsoleConfig().serverModelAllowlist;
    if (allowlist) {
      const allowed = new Set(allowlist);
      chatModels = chatModels.filter((m) => allowed.has(m.name));
    }

    return NextResponse.json({ models: chatModels.map((m) => m.name).filter(Boolean) });
  } catch (cause) {
    return NextResponse.json(
      { error: cause instanceof Error ? cause.message : 'AI server unreachable' },
      { status: 502 },
    );
  }
}