import { NextRequest, NextResponse } from "next/server";
import { z } from "zod";
import { generateText } from "ai";
import { db, chatMessages, aiConversations, sql } from "@epicure/db";
import { requireSessionOrApiKey } from "@/lib/api-auth";
import { applyRateLimit } from "@/lib/rate-limit";
import { withAiQuota, resolveAiConfigOrError } from "@/lib/ai/ai-error";
import { getModelConfigForUseCase } from "@/lib/ai/resolve-user-key";
import { resolveModel } from "@/lib/ai/factory";
import { getUserPrivateBio, buildUserBioContext } from "@/lib/ai/user-bio";

const Schema = z.object({
  question: z.string().min(1).max(500),
  conversationId: z.string().uuid().optional(),
});

const LANG: Record<string, string> = { en: "English", fr: "French" };

export async function POST(req: NextRequest) {
  const { session, response } = await requireSessionOrApiKey(req);
  if (response) return response;

  const body = await req.json() as unknown;
  const parsed = Schema.safeParse(body);
  if (!parsed.success) {
    return NextResponse.json({ error: "Validation error" }, { status: 400 });
  }

  const limited = await applyRateLimit(`rl:ai:${session!.user.id}`, 30, 60);
  if (limited) return limited;

  const [configResult, privateBio] = await Promise.all([
    resolveAiConfigOrError(() => getModelConfigForUseCase(session!.user.id, "text")),
    getUserPrivateBio(session!.user.id),
  ]);
  if (!configResult.ok) return configResult.response;
  const aiConfig = configResult.data;
  const model = resolveModel(aiConfig);
  const bioContext = buildUserBioContext(privateBio);
  const locale = (session!.user as { locale?: string }).locale ?? "en";
  const lang = LANG[locale] ?? "English";

  const result = await withAiQuota(session!.user.id, session!.user.tier as "free" | "pro", () =>
    generateText({
      model,
      system: `You are Epicure, a helpful culinary assistant answering general cooking questions — not tied to any specific recipe (techniques, substitutions, timing, equipment, food safety, etc). If asked who you are or what model/AI you're built on, say you're Epicure — never name the underlying model or provider. If a question has nothing to do with cooking or food, politely redirect. Keep answers under 200 words. Respond in ${lang}.${bioContext}`,
      prompt: parsed.data.question,
    }), { skipQuota: aiConfig.isByok }
  );
  if (!result.ok) return result.response;

  const { conversationId } = parsed.data;

  void db.insert(chatMessages).values([
    { id: crypto.randomUUID(), userId: session!.user.id, recipeId: null, conversationId, role: "user", content: parsed.data.question },
    { id: crypto.randomUUID(), userId: session!.user.id, recipeId: null, conversationId, role: "assistant", content: result.data.text },
  ]).catch((err) => console.error("[cooking-chat] failed to persist chat history", err));

  if (conversationId) {
    // Bumps updatedAt (for the conversation list's sort order) and, only if
    // this is the conversation's first message, auto-titles it from the
    // opening question — so users aren't left staring at "Untitled" entries;
    // they can still rename it later.
    void db.execute(sql`
      UPDATE ${aiConversations}
      SET updated_at = now(), title = COALESCE(title, ${parsed.data.question.slice(0, 60)})
      WHERE ${aiConversations.id} = ${conversationId} AND ${aiConversations.userId} = ${session!.user.id}
    `).catch((err) => console.error("[cooking-chat] failed to touch conversation", err));
  }

  return NextResponse.json({ answer: result.data.text });
}
