import { NextRequest, NextResponse } from "next/server";
import { z } from "zod";
import { generateText } from "ai";
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 { db, recipes, chatMessages, eq, and } from "@epicure/db";
import { getUserPrivateBio, buildUserBioContext } from "@/lib/ai/user-bio";
import { hasQuantity } from "@/lib/fractions";

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

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 recipe = await db.query.recipes.findFirst({
    where: and(eq(recipes.id, parsed.data.recipeId), eq(recipes.authorId, session!.user.id)),
    with: {
      ingredients: { orderBy: (t, { asc }) => asc(t.order) },
      steps: { orderBy: (t, { asc }) => asc(t.order) },
    },
  });

  if (!recipe) {
    return NextResponse.json({ error: "Recipe not found" }, { status: 404 });
  }

  const ingredientList = recipe.ingredients
    .map((ing) => [hasQuantity(ing.quantity) ? ing.quantity : null, ing.unit, ing.rawName, ing.note ? `(${ing.note})` : ""].filter(Boolean).join(" "))
    .join("\n");

  const stepList = recipe.steps
    .map((s, i) => `${i + 1}. ${s.instruction}`)
    .join("\n");

  const recipeContext = `
Recipe: ${recipe.title}
${recipe.description ? `Description: ${recipe.description}` : ""}
Difficulty: ${recipe.difficulty ?? "unknown"}
Prep: ${recipe.prepMins ?? 0}min | Cook: ${recipe.cookMins ?? 0}min | Servings: ${recipe.baseServings}

INGREDIENTS:
${ingredientList || "None listed"}

STEPS:
${stepList || "None listed"}
`.trim();

  const [configResult, privateBio] = await Promise.all([
    resolveAiConfigOrError(() => getModelConfigForUseCase(session!.user.id, "chat")),
    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" | "family", () =>
    generateText({
      model,
      system: `You are Epicure, a helpful culinary assistant. Answer questions about the following recipe concisely and accurately. 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 is not related to the recipe or cooking, politely redirect. Keep answers under 200 words. Respond in ${lang}.

${recipeContext}${bioContext}`,
      prompt: parsed.data.question,
    }), { skipQuota: aiConfig.isByok }
  );
  if (!result.ok) return result.response;

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

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