import Stripe from "stripe";
import { eq, desc } from "drizzle-orm";
import { getDb, getSubscription, getUserById, updateSubscription, getConfigValue } from "../db.js";
import { subscriptions } from "../schema.js";

let stripeInstance: Stripe | null = null;
let stripeInstanceKey: string | null = null;

async function resolveStripeKey(): Promise<string | null> {
  const dbKey = await getConfigValue("STRIPE_SECRET_KEY");
  if (dbKey) return dbKey;
  return process.env.STRIPE_SECRET_KEY ?? null;
}

export async function getStripe(): Promise<Stripe> {
  const key = await resolveStripeKey();
  if (!key) {
    throw new Error("STRIPE_SECRET_KEY is not set");
  }
  if (stripeInstance && stripeInstanceKey === key) return stripeInstance;
  stripeInstance = new Stripe(key, {
    apiVersion: "2026-04-22.dahlia",
    typescript: true,
  });
  stripeInstanceKey = key;
  return stripeInstance;
}

export async function isStripeConfigured(): Promise<boolean> {
  const key = await resolveStripeKey();
  return Boolean(key);
}

async function resolvePriceId(envName: string, configKey: string): Promise<string | null> {
  const dbVal = await getConfigValue(configKey);
  if (dbVal) return dbVal;
  return process.env[envName] ?? null;
}

function publicBaseUrl(): string {
  const url = process.env.PUBLIC_BASE_URL ?? "";
  if (!url) {
    throw new Error("PUBLIC_BASE_URL is not set");
  }
  return url.replace(/\/$/, "");
}

async function ensureStripeCustomer(userId: number): Promise<string> {
  const sub = await getSubscription(userId);
  if (sub?.stripeCustomerId) return sub.stripeCustomerId;
  const user = await getUserById(userId);
  if (!user) throw new Error("User not found");
  const stripe = await getStripe();
  const customer = await stripe.customers.create({
    email: user.email,
    name: user.name ?? undefined,
    metadata: { userId: String(userId) },
  });
  await updateSubscription(userId, { stripeCustomerId: customer.id });
  return customer.id;
}

export async function createCheckoutSession(
  userId: number,
  priceId: string
): Promise<{ url: string; sessionId: string }> {
  const stripe = await getStripe();
  const customerId = await ensureStripeCustomer(userId);
  const base = publicBaseUrl();
  const session = await stripe.checkout.sessions.create({
    mode: "subscription",
    customer: customerId,
    line_items: [{ price: priceId, quantity: 1 }],
    success_url: `${base}/subscription/success?session_id={CHECKOUT_SESSION_ID}`,
    cancel_url: `${base}/subscription/cancel`,
    allow_promotion_codes: true,
    subscription_data: { metadata: { userId: String(userId) } },
    metadata: { userId: String(userId) },
  });
  if (!session.url) throw new Error("Stripe Checkout did not return a URL");
  return { url: session.url, sessionId: session.id };
}

export async function createPortalSession(userId: number): Promise<{ url: string }> {
  const stripe = await getStripe();
  const sub = await getSubscription(userId);
  if (!sub?.stripeCustomerId) {
    throw new Error("No Stripe customer for this user yet");
  }
  const base = publicBaseUrl();
  const portal = await stripe.billingPortal.sessions.create({
    customer: sub.stripeCustomerId,
    return_url: `${base}/dashboard/subscription`,
  });
  return { url: portal.url };
}

export async function getSubscriptionStatus(userId: number): Promise<{
  plan: "trial" | "basic" | "pro" | null;
  status: string | null;
  currentPeriodEnd: Date | null;
  trialEndsAt: Date | null;
  stripeCustomerId: string | null;
  stripeSubscriptionId: string | null;
} | null> {
  const sub = await getSubscription(userId);
  if (!sub) return null;
  return {
    plan: sub.plan,
    status: sub.status,
    currentPeriodEnd: sub.currentPeriodEnd,
    trialEndsAt: sub.trialEndsAt,
    stripeCustomerId: sub.stripeCustomerId,
    stripeSubscriptionId: sub.stripeSubscriptionId,
  };
}

async function planFromPriceId(priceId: string | null | undefined): Promise<"basic" | "pro"> {
  const proPriceId = await resolvePriceId("STRIPE_PRO_PRICE_ID", "STRIPE_PRO_PRICE_ID");
  if (priceId && proPriceId && priceId === proPriceId) return "pro";
  return "basic";
}

async function findUserBySubscriptionId(
  stripeSubscriptionId: string
): Promise<number | null> {
  const db = await getDb();
  const rows = await db
    .select()
    .from(subscriptions)
    .where(eq(subscriptions.stripeSubscriptionId, stripeSubscriptionId))
    .orderBy(desc(subscriptions.createdAt))
    .limit(1);
  return rows[0]?.userId ?? null;
}

async function findUserByCustomerId(stripeCustomerId: string): Promise<number | null> {
  const db = await getDb();
  const rows = await db
    .select()
    .from(subscriptions)
    .where(eq(subscriptions.stripeCustomerId, stripeCustomerId))
    .orderBy(desc(subscriptions.createdAt))
    .limit(1);
  return rows[0]?.userId ?? null;
}

function toDate(epochSeconds: number | null | undefined): Date | null {
  if (!epochSeconds) return null;
  return new Date(epochSeconds * 1000);
}

function mapStripeStatus(
  s: Stripe.Subscription.Status
): "trialing" | "active" | "past_due" | "canceled" | "expired" {
  switch (s) {
    case "trialing":
      return "trialing";
    case "active":
      return "active";
    case "past_due":
    case "unpaid":
      return "past_due";
    case "canceled":
      return "canceled";
    case "incomplete":
    case "incomplete_expired":
    case "paused":
      return "expired";
    default:
      return "expired";
  }
}

async function syncSubscriptionFromStripe(
  userId: number,
  subscription: Stripe.Subscription
): Promise<void> {
  const item = subscription.items.data[0];
  const priceId = item?.price?.id ?? null;
  const plan = await planFromPriceId(priceId);
  const status = mapStripeStatus(subscription.status);
  await updateSubscription(userId, {
    stripeSubscriptionId: subscription.id,
    stripeCustomerId:
      typeof subscription.customer === "string"
        ? subscription.customer
        : subscription.customer.id,
    stripePriceId: priceId,
    plan,
    status,
    currentPeriodStart: toDate(item?.current_period_start ?? null),
    currentPeriodEnd: toDate(item?.current_period_end ?? null),
    canceledAt: toDate(subscription.canceled_at),
  });
}

export async function handleWebhook(event: Stripe.Event): Promise<void> {
  const stripe = await getStripe();
  switch (event.type) {
    case "checkout.session.completed": {
      const session = event.data.object as Stripe.Checkout.Session;
      const userIdRaw = session.metadata?.userId;
      const userId = userIdRaw ? Number(userIdRaw) : null;
      if (!userId || Number.isNaN(userId)) return;
      if (typeof session.subscription === "string") {
        const sub = await stripe.subscriptions.retrieve(session.subscription);
        await syncSubscriptionFromStripe(userId, sub);
      }
      break;
    }
    case "customer.subscription.created":
    case "customer.subscription.updated": {
      const sub = event.data.object as Stripe.Subscription;
      const metaUserId = sub.metadata?.userId ? Number(sub.metadata.userId) : null;
      let userId = metaUserId && !Number.isNaN(metaUserId) ? metaUserId : null;
      if (!userId) {
        userId = await findUserBySubscriptionId(sub.id);
      }
      if (!userId) {
        const customerId =
          typeof sub.customer === "string" ? sub.customer : sub.customer.id;
        userId = await findUserByCustomerId(customerId);
      }
      if (!userId) return;
      await syncSubscriptionFromStripe(userId, sub);
      break;
    }
    case "customer.subscription.deleted": {
      const sub = event.data.object as Stripe.Subscription;
      let userId = await findUserBySubscriptionId(sub.id);
      if (!userId) {
        const customerId =
          typeof sub.customer === "string" ? sub.customer : sub.customer.id;
        userId = await findUserByCustomerId(customerId);
      }
      if (!userId) return;
      await updateSubscription(userId, {
        status: "canceled",
        canceledAt: toDate(sub.canceled_at) ?? new Date(),
      });
      break;
    }
    case "invoice.paid": {
      const invoice = event.data.object as Stripe.Invoice;
      const subRef = invoice.parent?.subscription_details?.subscription ?? null;
      const subscriptionId =
        typeof subRef === "string" ? subRef : subRef?.id ?? null;
      const customerId =
        typeof invoice.customer === "string"
          ? invoice.customer
          : invoice.customer?.id ?? null;
      let userId: number | null = null;
      if (subscriptionId) userId = await findUserBySubscriptionId(subscriptionId);
      if (!userId && customerId) userId = await findUserByCustomerId(customerId);
      if (!userId || !subscriptionId) return;
      const sub = await stripe.subscriptions.retrieve(subscriptionId);
      await syncSubscriptionFromStripe(userId, sub);
      break;
    }
    case "invoice.payment_failed": {
      const invoice = event.data.object as Stripe.Invoice;
      const customerId =
        typeof invoice.customer === "string"
          ? invoice.customer
          : invoice.customer?.id ?? null;
      if (!customerId) return;
      const userId = await findUserByCustomerId(customerId);
      if (!userId) return;
      await updateSubscription(userId, { status: "past_due" });
      break;
    }
    default:
      break;
  }
}

export async function verifyAndConstructEvent(
  rawBody: Buffer,
  signature: string
): Promise<Stripe.Event> {
  const stripe = await getStripe();
  const secret = (await getConfigValue("STRIPE_WEBHOOK_SECRET")) ?? process.env.STRIPE_WEBHOOK_SECRET;
  if (!secret) {
    throw new Error("STRIPE_WEBHOOK_SECRET is not set");
  }
  return stripe.webhooks.constructEvent(rawBody, signature, secret);
}