import { NextRequest, NextResponse } from "next/server";
import { z } from "zod";
import { and, eq } from "@epicure/db";
import { db, recipes, recipeIngredients, recipeSteps, recipeVariations } from "@epicure/db";
import { requireSessionOrApiKey } from "@/lib/api-auth";
import { applyRateLimit } from "@/lib/rate-limit";
import { withAiQuota, resolveAiConfigOrError } from "@/lib/ai/ai-error";
import { adaptRecipe } from "@/lib/ai/features/adapt-recipe";
import { withUserKey } from "@/lib/ai/resolve-user-key";
import { getUserPrivateBio } from "@/lib/ai/user-bio";
import { checkTierLimitInTransaction, TierLimitError } from "@/lib/tiers";
import { isRecipeUnchanged } from "@/lib/recipe-diff";

const Schema = z.object({
  excludeIngredients: z.array(z.string()).default([]),
  extraConstraints: z.string().max(500).optional(),
  provider: z.enum(["openai", "anthropic", "openrouter", "ollama"]).optional(),
  model: z.string().optional(),
});

type Params = { params: Promise<{ id: string }> };

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

  const userId = session!.user.id;
  const limited = await applyRateLimit(`rl:ai:${userId}`, 10, 60);
  if (limited) return limited;

  const { id } = await params;

  const recipe = await db.query.recipes.findFirst({
    where: and(eq(recipes.id, id)),
    with: {
      ingredients: { orderBy: (t, { asc }) => asc(t.order) },
      steps: { orderBy: (t, { asc }) => asc(t.order) },
    },
  });
  if (!recipe || (recipe.visibility === "private" && recipe.authorId !== userId)) {
    return NextResponse.json({ error: "Not found" }, { status: 404 });
  }

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

  if (parsed.data.excludeIngredients.length === 0 && !parsed.data.extraConstraints?.trim()) {
    return NextResponse.json({ error: "Provide at least one constraint" }, { status: 400 });
  }

  const [configResult, privateBio] = await Promise.all([
    resolveAiConfigOrError(() => withUserKey(userId, { provider: parsed.data.provider, model: parsed.data.model })),
    getUserPrivateBio(userId),
  ]);
  if (!configResult.ok) return configResult.response;
  const aiConfig = configResult.data;

  const locale = (session!.user as { locale?: string }).locale ?? "en";

  const result = await withAiQuota(userId, session!.user.tier as "free" | "pro" | "family", () =>
    adaptRecipe(
      {
        title: recipe.title,
        description: recipe.description,
        baseServings: recipe.baseServings,
        ingredients: recipe.ingredients,
        steps: recipe.steps,
      },
      {
        excludeIngredients: parsed.data.excludeIngredients,
        extraConstraints: parsed.data.extraConstraints,
      },
      { ...aiConfig, userContext: privateBio ?? undefined },
      locale
    ), { skipQuota: aiConfig.isByok }
  );
  if (!result.ok) return result.response;
  const adapted = result.data;

  // The AI sometimes "adapts" a recipe into something byte-for-byte
  // identical (e.g. it decides the constraints are already satisfied) —
  // don't persist a duplicate recipe/variation when nothing actually changed.
  if (isRecipeUnchanged(recipe, adapted)) {
    return NextResponse.json({ id: recipe.id, adaptationNotes: adapted.adaptationNotes, unchanged: true });
  }

  const newId = crypto.randomUUID();
  const now = new Date();

  try {
    await db.transaction(async (tx) => {
      await checkTierLimitInTransaction(tx, userId, session!.user.tier as "free" | "pro" | "family", "recipe");
      await tx.insert(recipes).values({
        id: newId,
        authorId: userId,
        title: adapted.title,
        description: adapted.description,
        baseServings: adapted.baseServings,
        visibility: "private",
        language: locale,
        difficulty: adapted.difficulty,
        prepMins: adapted.prepMins,
        cookMins: adapted.cookMins,
        dietaryTags: adapted.dietaryTags ?? {},
        aiGenerated: true,
        createdAt: now,
        updatedAt: now,
      });

      if (adapted.ingredients.length > 0) {
        await tx.insert(recipeIngredients).values(
          adapted.ingredients.map((ing, i) => ({
            id: crypto.randomUUID(),
            recipeId: newId,
            rawName: ing.rawName,
            quantity: ing.quantity !== undefined ? String(ing.quantity) : undefined,
            unit: ing.unit,
            note: ing.note,
            order: i,
          }))
        );
      }

      if (adapted.steps.length > 0) {
        await tx.insert(recipeSteps).values(
          adapted.steps.map((step, i) => ({
            id: crypto.randomUUID(),
            recipeId: newId,
            instruction: step.instruction,
            timerSeconds: step.timerSeconds,
            order: i,
          }))
        );
      }

      await tx.insert(recipeVariations).values({
        id: crypto.randomUUID(),
        parentRecipeId: recipe.id,
        childRecipeId: newId,
        description: adapted.adaptationNotes,
        aiGenerated: true,
        createdAt: now,
      });
    });
  } catch (err) {
    if (err instanceof TierLimitError) {
      return NextResponse.json({ error: "Recipe limit reached for your tier" }, { status: 403 });
    }
    return NextResponse.json({ error: "Failed to save the adapted recipe. Please try again." }, { status: 500 });
  }

  return NextResponse.json({ id: newId, adaptationNotes: adapted.adaptationNotes });
}