import { NextRequest, NextResponse } from "next/server";
import { z } from "zod";
import { requireSession } from "@/lib/api-auth";
import { checkAndIncrementTierLimit, TierLimitError } from "@/lib/tiers";
import { applyRateLimit } from "@/lib/rate-limit";
import { substituteIngredient } from "@/lib/ai/features/substitute-ingredient";

const Schema = z.object({
  ingredient: z.string().min(1).max(200),
  recipeTitle: z.string().max(200).optional(),
  provider: z.enum(["openai", "anthropic", "openrouter", "ollama"]).optional(),
  model: z.string().optional(),
});

export async function POST(req: NextRequest) {
  const { session, response } = await requireSession();
  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 rateLimitRes = await applyRateLimit(`ai:substitute:${session!.user.id}`, 10, 60);
  if (rateLimitRes) return rateLimitRes;

  try {
    await checkAndIncrementTierLimit(session!.user.id, session!.user.tier as "free" | "pro", "aiCall");
  } catch (err) {
    if (err instanceof TierLimitError) {
      return NextResponse.json({ error: "AI call limit reached for your tier" }, { status: 403 });
    }
    throw err;
  }

  const context = parsed.data.recipeTitle
    ? `recipe "${parsed.data.recipeTitle}"`
    : "a general recipe";

  const substitutions = await substituteIngredient(
    parsed.data.ingredient,
    context,
    { provider: parsed.data.provider, model: parsed.data.model }
  );

  return NextResponse.json({ substitutions });
}