import { NextRequest, NextResponse } from "next/server";
import { z } from "zod";
import { db, recipes, recipeIngredients, recipeSteps, mealPlans, mealPlanEntries, pantryItems, userNutritionGoals, eq, and } from "@epicure/db";
import { requireSessionOrApiKey } from "@/lib/api-auth";
import { applyRateLimit } from "@/lib/rate-limit";
import { getDefaultProviderWithKey } from "@/lib/ai/resolve-user-key";
import { withAiQuota, resolveAiConfigOrError } from "@/lib/ai/ai-error";
import { checkTierLimitInTransaction, TierLimitError } from "@/lib/tiers";
import { generateMealPlan } from "@/lib/ai/features/generate-meal-plan";
import { getUserPrivateBio } from "@/lib/ai/user-bio";

const DAYS = ["mon", "tue", "wed", "thu", "fri", "sat", "sun"] as const;

const Schema = z.object({
  weekStart: z.string().regex(/^\d{4}-\d{2}-\d{2}$/),
  dietaryPrefs: z.string().max(200).optional(),
  servings: z.number().int().min(1).max(20).default(2),
  days: z.array(z.enum(DAYS)).min(1).max(7).default([...DAYS]),
  usePantry: z.boolean().default(false),
  pantryMode: z.boolean().default(false),
  difficulty: z.enum(["easy", "medium", "hard"]).optional(),
  targetNutritionGoals: z.boolean().default(false),
});

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", issues: parsed.error.issues }, { status: 400 });
  }

  const limited = await applyRateLimit(`rl:ai:${session!.user.id}`, 3, 60);
  if (limited) return limited;

  const userId = session!.user.id;
  const locale = (session!.user as { locale?: string }).locale ?? "en";
  const [configResult, privateBio] = await Promise.all([
    resolveAiConfigOrError(() => getDefaultProviderWithKey(userId, "mealPlan")),
    getUserPrivateBio(userId),
  ]);
  if (!configResult.ok) return configResult.response;
  const config = configResult.data;

  // pantryMode forces usePantry on so pantry items are always fetched when maximizing pantry use
  const effectiveUsePantry = parsed.data.usePantry || parsed.data.pantryMode;

  // Optionally fetch pantry items
  let pantryItemNames: string[] = [];
  if (effectiveUsePantry) {
    const pantry = await db
      .select({ rawName: pantryItems.rawName })
      .from(pantryItems)
      .where(eq(pantryItems.userId, userId));
    pantryItemNames = pantry.map((p) => p.rawName);
  }

  // Optionally fetch the user's nutrition goals to nudge the AI toward them.
  // Silently ignored (no-op) if the user hasn't set any goals — no need to
  // fail the whole generation over a missing preference.
  let nutritionGoals: { caloriesKcal?: number | null; proteinG?: number | null; carbsG?: number | null; fatG?: number | null } | undefined;
  if (parsed.data.targetNutritionGoals) {
    const goals = await db.query.userNutritionGoals.findFirst({
      where: eq(userNutritionGoals.userId, userId),
    });
    if (goals && (goals.caloriesKcal || goals.proteinG || goals.carbsG || goals.fatG)) {
      nutritionGoals = {
        caloriesKcal: goals.caloriesKcal,
        proteinG: goals.proteinG,
        carbsG: goals.carbsG,
        fatG: goals.fatG,
      };
    }
  }

  const result = await withAiQuota(userId, session!.user.tier as "free" | "pro" | "family", () =>
    generateMealPlan(
      {
        dietaryPrefs: parsed.data.dietaryPrefs,
        servings: parsed.data.servings,
        pantryItems: pantryItemNames,
        days: parsed.data.days,
        pantryMode: parsed.data.pantryMode,
        difficulty: parsed.data.difficulty,
        nutritionGoals,
      },
      { ...config, userContext: privateBio ?? undefined },
      locale
    ), { skipQuota: config.isByok }
  );
  if (!result.ok) return result.response;
  const plan = result.data;

  // Ensure meal plan row exists for the week
  let mealPlan = await db.query.mealPlans.findFirst({
    where: and(eq(mealPlans.userId, userId), eq(mealPlans.weekStart, parsed.data.weekStart)),
  });

  if (!mealPlan) {
    const planId = crypto.randomUUID();
    await db.insert(mealPlans).values({ id: planId, userId, weekStart: parsed.data.weekStart });
    mealPlan = { id: planId, userId, weekStart: parsed.data.weekStart, createdAt: new Date() };
  }

  const createdEntries: Array<{ id: string; day: string; mealType: string; recipeId: string; recipeTitle: string }> = [];

  try {
    await db.transaction(async (tx) => {
    // Each plan entry creates a draft recipe — check the recipe limit covers
    // all of them before inserting anything.
    await checkTierLimitInTransaction(tx, userId, session!.user.tier as "free" | "pro" | "family", "recipe", plan.entries.length);
    for (const entry of plan.entries) {
      // Create draft recipe
      const recipeId = crypto.randomUUID();
      await tx.insert(recipes).values({
        id: recipeId,
        authorId: userId,
        title: entry.recipe.title,
        description: entry.recipe.description,
        baseServings: entry.servings,
        visibility: "private",
        language: locale,
        aiGenerated: true,
        difficulty: entry.recipe.difficulty ?? null,
        prepMins: entry.recipe.prepMins ?? null,
        cookMins: entry.recipe.cookMins ?? null,
      });

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

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

      // Remove any existing entry for this day+mealType, then insert new
      const existingEntry = await tx.query.mealPlanEntries.findFirst({
        where: and(
          eq(mealPlanEntries.mealPlanId, mealPlan!.id),
          eq(mealPlanEntries.day, entry.day),
          eq(mealPlanEntries.mealType, entry.mealType)
        ),
      });

      if (existingEntry) {
        await tx.delete(mealPlanEntries).where(eq(mealPlanEntries.id, existingEntry.id));
      }

      const entryId = crypto.randomUUID();
      await tx.insert(mealPlanEntries).values({
        id: entryId,
        mealPlanId: mealPlan!.id,
        day: entry.day,
        mealType: entry.mealType,
        recipeId,
        servings: entry.servings,
      });

      createdEntries.push({ id: entryId, day: entry.day, mealType: entry.mealType, recipeId, recipeTitle: entry.recipe.title });
    }
    });
  } catch (err) {
    if (err instanceof TierLimitError) {
      return NextResponse.json({ error: "Recipe limit reached for your tier" }, { status: 403 });
    }
    throw err;
  }

  return NextResponse.json({ weekStart: parsed.data.weekStart, entries: createdEntries });
}