const admin = require("firebase-admin");
const { HttpsError, onCall } = require("firebase-functions/https");
const { onRequest } = require("firebase-functions/v2/https");
const { FieldValue } = require("firebase-admin/firestore");
const { refList } = require("../index");
const refsList = refList;
const {
  getStripeClient,
  buildCheckoutLineItems,
  ensureStripeCustomer,
  getReturnUrls,
  formatCheckoutSessionResponse,
  mapStripeErrorToHttps,
} = require("../helpers/stripe");
const { STRIPE_WEBHOOK_SECRET } = require("../config/keys");

const REGION = process.env.FIREBASE_REGION || "europe-west1";

const SUBSCRIPTION_PRICE_IDS = {
  monthly: [
    "price_1SPgitCzf2o5bDRdbnhLFx6f",
    "price_1SPgjCCzf2o5bDRdr08Xzp8u",
    "price_1SPgjaCzf2o5bDRdd9Xo2u26",
  ],
  annual: [
    "price_1SPgkDCzf2o5bDRdNGLVNeQ3",
    "price_1SPgkXCzf2o5bDRdejBVxEBY",
    "price_1SPgkqCzf2o5bDRdIcUwTDrm",
  ],
};

const ALL_SUBSCRIPTION_PRICE_IDS = Object.values(SUBSCRIPTION_PRICE_IDS).flat();

const SUBSCRIPTION_PRICE_METADATA = {
  price_1SPgitCzf2o5bDRdbnhLFx6f: {
    level: "starter",
    billingPeriod: "monthly",
  },
  price_1SPgjCCzf2o5bDRdr08Xzp8u: {
    level: "pro",
    billingPeriod: "monthly",
  },
  price_1SPgjaCzf2o5bDRdd9Xo2u26: {
    level: "premium",
    billingPeriod: "monthly",
  },
  price_1SPgkDCzf2o5bDRdNGLVNeQ3: {
    level: "starter",
    billingPeriod: "annual",
  },
  price_1SPgkXCzf2o5bDRdejBVxEBY: {
    level: "pro",
    billingPeriod: "annual",
  },
  price_1SPgkqCzf2o5bDRdIcUwTDrm: {
    level: "premium",
    billingPeriod: "annual",
  },
};

const COIN_PACK_PRODUCTS = [
  {
    productId: "prod_TMPPEXZ1wGk2cS",
    key: "starter",
    fallbackCoinAmount: 10,
  },
  {
    productId: "prod_TMPQ5SNdS47gY6",
    key: "pro",
    fallbackCoinAmount: 40,
  },
  {
    productId: "prod_TMPRpA0qQSHXj5",
    key: "premium",
    fallbackCoinAmount: 60,
  },
];

const COIN_PACK_PRODUCT_IDS = COIN_PACK_PRODUCTS.map(
  (pack) => pack.productId,
);

const COIN_PACK_PRODUCT_MAP = COIN_PACK_PRODUCTS.reduce(
  (acc, pack) => ({
    ...acc,
    [pack.productId]: pack,
  }),
  {},
);

const paymentsCollection = admin.firestore().collection("payments");
let cachedStripeWebhookSecret = null;
const PREMIUM_SUBSCRIPTION_STATUSES = new Set(["active", "trialing"]);

const getServerTimestamp = () => {
  if (typeof FieldValue?.serverTimestamp === "function") {
    return FieldValue.serverTimestamp();
  }
  if (admin.firestore?.FieldValue?.serverTimestamp) {
    return admin.firestore.FieldValue.serverTimestamp();
  }
  throw new HttpsError(
    "failed-precondition",
    "Firestore FieldValue.serverTimestamp indisponible.",
  );
};

const resolveStripeWebhookSecret = () => {
  if (cachedStripeWebhookSecret) {
    return cachedStripeWebhookSecret;
  }

  const envSecret =
    typeof process?.env?.STRIPE_WEBHOOK_SECRET === "string"
      ? process.env.STRIPE_WEBHOOK_SECRET.trim()
      : "";
  const inlineSecret =
    typeof STRIPE_WEBHOOK_SECRET === "string"
      ? STRIPE_WEBHOOK_SECRET.trim()
      : "";

  const secret = envSecret || inlineSecret;
  if (!secret) {
    throw new Error("STRIPE_WEBHOOK_SECRET not configured");
  }

  cachedStripeWebhookSecret = secret;
  return cachedStripeWebhookSecret;
};

const toFirestoreTimestamp = (unixSeconds) => {
  if (typeof unixSeconds !== "number" || !Number.isFinite(unixSeconds)) {
    return null;
  }
  try {
    return admin.firestore.Timestamp.fromMillis(unixSeconds * 1000);
  } catch (error) {
    console.error(
      "[subscription-toFirestoreTimestamp] Conversion error",
      unixSeconds,
      error,
    );
    return null;
  }
};

const extractFirebaseUid = (metadata) => {
  if (!metadata || typeof metadata !== "object") {
    return null;
  }

  const candidates = [
    metadata.firebaseUID,
    metadata.firebaseUid,
    metadata.uid,
    metadata.userId,
  ];

  for (let index = 0; index < candidates.length; index += 1) {
    const candidate = candidates[index];
    if (typeof candidate === "string" && candidate.trim()) {
      return candidate.trim();
    }
  }

  return null;
};

const findUserByStripeCustomerId = async (customerId) => {
  if (!customerId || !refList?.users) {
    return { uid: null, userRef: null, userData: null };
  }

  try {
    const snapshot = await refList.users
      .where("stripeCustomerId", "==", customerId)
      .limit(1)
      .get();

    const doc = snapshot?.docs?.[0];
    if (doc?.id) {
      return {
        uid: doc.id,
        userRef: refList.users.doc(doc.id),
        userData: doc.data() || null,
      };
    }
  } catch (error) {
    console.error(
      "[subscription-findUserByStripeCustomerId] Query failed",
      customerId,
      error,
    );
  }

  return { uid: null, userRef: null, userData: null };
};

const resolveUserContext = async ({ metadata, customerId }) => {
  const metadataUid = extractFirebaseUid(metadata);
  if (metadataUid && refList?.users) {
    return {
      uid: metadataUid,
      userRef: refList.users.doc(metadataUid),
      userData: null,
    };
  }

  return findUserByStripeCustomerId(customerId);
};

const upsertPaymentDocument = async (docId, data = {}) => {
  if (!docId) {
    return null;
  }

  try {
    const docRef = paymentsCollection.doc(docId);
    const snapshot = await docRef.get();

    const payload = {
      ...data,
      updatedAt: getServerTimestamp(),
    };

    if (!snapshot.exists) {
      payload.createdAt = getServerTimestamp();
    }

    await docRef.set(payload, { merge: true });
    return docRef;
  } catch (error) {
    console.error(
      "[subscription-upsertPaymentDocument] Failed to persist payment",
      docId,
      error,
    );
    return null;
  }
};

const buildEventSnapshot = (type, referenceId) => ({
  type: type || null,
  referenceId: referenceId || null,
  receivedAt: getServerTimestamp(),
});

const buildSubscriptionPayload = (subscription) => {
  if (!subscription || typeof subscription !== "object") {
    return null;
  }

  const itemList = Array.isArray(subscription?.items?.data)
    ? subscription.items.data
    : [];

  const items = itemList.map((item) => {
    const stripePrice =
      item?.price && typeof item.price === "object" ? item.price : null;
    return {
      id: item?.id || null,
      priceId:
        stripePrice?.id ||
        (typeof item?.price === "string" ? item.price : null) ||
        null,
      productId: stripePrice?.product || null,
      currency: stripePrice?.currency || null,
      unitAmount: stripePrice?.unit_amount ?? null,
      recurring: stripePrice?.recurring || null,
      quantity: item?.quantity ?? null,
    };
  });

  const primaryItem = items[0] || null;

  return {
    id: subscription.id || null,
    status: subscription.status || null,
    customerId: subscription.customer || null,
    priceId: primaryItem?.priceId || null,
    productId: primaryItem?.productId || null,
    cancelAtPeriodEnd: subscription.cancel_at_period_end === true,
    cancelAt: toFirestoreTimestamp(subscription.cancel_at),
    canceledAt: toFirestoreTimestamp(subscription.canceled_at),
    createdAt: toFirestoreTimestamp(subscription.created),
    currentPeriodStart: toFirestoreTimestamp(subscription.current_period_start),
    currentPeriodEnd: toFirestoreTimestamp(subscription.current_period_end),
    endedAt: toFirestoreTimestamp(subscription.ended_at),
    trialStart: toFirestoreTimestamp(subscription.trial_start),
    trialEnd: toFirestoreTimestamp(subscription.trial_end),
    latestInvoiceId: subscription.latest_invoice || null,
    items,
    metadata: subscription.metadata || {},
  };
};

const handleCheckoutSessionCompleted = async (session, event) => {
  if (!session || typeof session !== "object") {
    return;
  }

  const firebaseUid = extractFirebaseUid(session.metadata);

  const paymentDocRef = await upsertPaymentDocument(session.id, {
    userId: firebaseUid || null,
    customerId: session.customer || null,
    subscriptionId: session.subscription || null,
    invoiceId: session.invoice || null,
    status: session.status || "completed",
    paymentStatus: session.payment_status || null,
    mode: session.mode || null,
    amountSubtotal: session.amount_subtotal ?? null,
    amountTotal: session.amount_total ?? null,
    currency: session.currency || null,
    metadata: session.metadata || {},
    completedAt: toFirestoreTimestamp(session.created),
    expiresAt: toFirestoreTimestamp(session.expires_at),
    paymentIntentId:
      typeof session.payment_intent === "string"
        ? session.payment_intent
        : null,
    lastEventType: event?.type || null,
    lastEventId: event?.id || null,
    lastEventAt: getServerTimestamp(),
  });

  const { userRef } = await resolveUserContext({
    metadata: session.metadata,
    customerId: session.customer,
  });

  if (userRef) {
    const lastEvent = buildEventSnapshot(event?.type, session.id);
    if (firebaseUid) {
      lastEvent.uid = firebaseUid;
    }

    const userUpdate = {
      lastStripeWebhookEvent: lastEvent,
    };

    if (session.customer) {
      userUpdate.stripeCustomerId = session.customer;
    }

    if (session.metadata?.subscriptionLevel) {
      userUpdate.premiumLevel = session.metadata.subscriptionLevel;
    }

    if (session.metadata?.subscriptionBillingPeriod) {
      userUpdate.premiumBillingPeriod =
        session.metadata.subscriptionBillingPeriod;
    }

    await userRef.set(userUpdate, { merge: true });
  }

  if (
    session.mode === "payment" &&
    (session.payment_status === "paid" ||
      session.payment_status === "no_payment_required") &&
    session.metadata?.purchaseType === "COIN_PACK" &&
    userRef
  ) {
    const coinAmountRaw = Number(session.metadata?.coinAmount || 0);
    const coinAmount = Number.isFinite(coinAmountRaw) ? coinAmountRaw : 0;

    if (coinAmount > 0 && paymentDocRef) {
      let paymentSnapshot = null;
      try {
        paymentSnapshot = await paymentDocRef.get();
      } catch (error) {
        console.warn(
          "[subscription-handleCheckoutSessionCompleted] Unable to read payment doc",
          session.id,
          error?.message || error,
        );
      }

      const alreadyGranted = Boolean(
        paymentSnapshot?.exists &&
          paymentSnapshot.data()?.coinPackGrantedAt,
      );

      if (!alreadyGranted) {
        await userRef.set(
          {
            coins: FieldValue.increment(coinAmount),
          },
          { merge: true },
        );

        await paymentDocRef.set(
          {
            coinPackGrantedAt: getServerTimestamp(),
            coinPackGrantedAmount: coinAmount,
            coinPackGrantedKey: session.metadata?.coinPackKey || null,
          },
          { merge: true },
        );
      }
    }
  }
};

const handleCustomerSubscriptionEvent = async (subscription, event) => {
  if (!subscription || typeof subscription !== "object") {
    return;
  }

  const subscriptionPayload = buildSubscriptionPayload(subscription);

  await upsertPaymentDocument(subscription.id, {
    customerId: subscription.customer || null,
    subscriptionId: subscription.id || null,
    status: subscription.status || null,
    mode: "subscription",
    priceId: subscriptionPayload?.priceId || null,
    productId: subscriptionPayload?.productId || null,
    cancelAtPeriodEnd: subscriptionPayload?.cancelAtPeriodEnd ?? null,
    currentPeriodStart: subscriptionPayload?.currentPeriodStart || null,
    currentPeriodEnd: subscriptionPayload?.currentPeriodEnd || null,
    metadata: subscription.metadata || {},
    lastEventType: event?.type || null,
    lastEventId: event?.id || null,
    lastEventAt: getServerTimestamp(),
  });

  const { uid, userRef } = await resolveUserContext({
    metadata: subscription.metadata,
    customerId: subscription.customer,
  });

  if (!userRef) {
    console.warn(
      "[subscription-handleCustomerSubscriptionEvent] User not resolved",
      subscription.customer,
      event?.type,
    );
    return;
  }

  const lastEvent = buildEventSnapshot(event?.type, subscription.id);
  if (uid) {
    lastEvent.uid = uid;
  }

  const priceMeta = getSubscriptionMetaFromPrice(
    subscriptionPayload?.priceId,
  );
  const metadataLevel = subscription.metadata?.subscriptionLevel || null;
  const metadataPeriod =
    subscription.metadata?.subscriptionBillingPeriod || null;
  const resolvedLevel = metadataLevel || priceMeta?.level || null;
  const resolvedPeriod = metadataPeriod || priceMeta?.billingPeriod || null;

  const isPremium = subscription.status
    ? PREMIUM_SUBSCRIPTION_STATUSES.has(subscription.status)
    : false;

  const userUpdate = {
    stripeSubscription: subscriptionPayload,
    stripeSubscriptionStatus: subscription.status || null,
    stripeSubscriptionUpdatedAt: getServerTimestamp(),
    isPremium,
    lastStripeWebhookEvent: lastEvent,
  };

  if (subscriptionPayload?.customerId) {
    userUpdate.stripeCustomerId = subscriptionPayload.customerId;
  }

  if (resolvedLevel && isPremium) {
    userUpdate.premiumLevel = resolvedLevel;
  } else if (!isPremium) {
    userUpdate.premiumLevel = null;
  }

  if (isPremium && resolvedPeriod) {
    userUpdate.premiumBillingPeriod = resolvedPeriod;
  } else if (!isPremium) {
    userUpdate.premiumBillingPeriod = null;
  }

  await userRef.set(userUpdate, { merge: true });
};

const handleInvoiceEvent = async (invoice, event) => {
  if (!invoice || typeof invoice !== "object") {
    return;
  }

  const firebaseUid = extractFirebaseUid(invoice.metadata);
  const eventType = event?.type || null;

  await upsertPaymentDocument(invoice.id, {
    userId: firebaseUid || null,
    customerId: invoice.customer || null,
    subscriptionId: invoice.subscription || null,
    status: invoice.status || null,
    paymentStatus:
      eventType === "invoice.payment_failed"
        ? "failed"
        : invoice.status || null,
    amountDue: invoice.amount_due ?? null,
    amountPaid: invoice.amount_paid ?? null,
    amountRemaining: invoice.amount_remaining ?? null,
    currency: invoice.currency || null,
    invoiceNumber: invoice.number || null,
    hostedInvoiceUrl: invoice.hosted_invoice_url || null,
    invoicePdf: invoice.invoice_pdf || null,
    billingReason: invoice.billing_reason || null,
    metadata: invoice.metadata || {},
    periodStart: toFirestoreTimestamp(invoice.period_start),
    periodEnd: toFirestoreTimestamp(invoice.period_end),
    paidAt: toFirestoreTimestamp(invoice.status_transitions?.paid_at),
    lastEventType: eventType,
    lastEventId: event?.id || null,
    lastEventAt: getServerTimestamp(),
    mode: "invoice",
  });

  const { userRef } = await resolveUserContext({
    metadata: invoice.metadata,
    customerId: invoice.customer,
  });

  if (userRef) {
    const lastEvent = buildEventSnapshot(eventType, invoice.id);
    if (firebaseUid) {
      lastEvent.uid = firebaseUid;
    }
    await userRef.set(
      {
        lastStripeWebhookEvent: lastEvent,
      },
      { merge: true },
    );
  }
};

const handlePaymentIntentEvent = async (paymentIntent, event) => {
  if (!paymentIntent || typeof paymentIntent !== "object") {
    return;
  }

  const firebaseUid = extractFirebaseUid(paymentIntent.metadata);

  await upsertPaymentDocument(paymentIntent.id, {
    userId: firebaseUid || null,
    customerId: paymentIntent.customer || null,
    status: paymentIntent.status || null,
    paymentStatus: paymentIntent.status || null,
    amountTotal: paymentIntent.amount ?? null,
    amountReceived: paymentIntent.amount_received ?? null,
    currency: paymentIntent.currency || null,
    description: paymentIntent.description || null,
    metadata: paymentIntent.metadata || {},
    latestChargeId: paymentIntent.latest_charge || null,
    paymentMethodId:
      typeof paymentIntent.payment_method === "string"
        ? paymentIntent.payment_method
        : null,
    createdAtFromStripe: toFirestoreTimestamp(paymentIntent.created),
    succeededAt: toFirestoreTimestamp(
      paymentIntent.status_transitions?.succeeded_at,
    ),
    canceledAt: toFirestoreTimestamp(
      paymentIntent.status_transitions?.canceled_at,
    ),
    lastEventType: event?.type || null,
    lastEventId: event?.id || null,
    lastEventAt: getServerTimestamp(),
    mode: "payment",
  });

  const { userRef } = await resolveUserContext({
    metadata: paymentIntent.metadata,
    customerId: paymentIntent.customer,
  });

  if (userRef) {
    const lastEvent = buildEventSnapshot(event?.type, paymentIntent.id);
    if (firebaseUid) {
      lastEvent.uid = firebaseUid;
    }
    await userRef.set(
      {
        lastStripeWebhookEvent: lastEvent,
      },
      { merge: true },
    );
  }
};

const handleStripeWebhookEvent = async ({ event }) => {
  if (!event || typeof event !== "object") {
    return;
  }

  switch (event.type) {
    case "checkout.session.completed":
      await handleCheckoutSessionCompleted(event.data?.object, event);
      break;
    case "customer.subscription.created":
    case "customer.subscription.updated":
    case "customer.subscription.deleted":
      await handleCustomerSubscriptionEvent(event.data?.object, event);
      break;
    case "invoice.paid":
    case "invoice.payment_failed":
      await handleInvoiceEvent(event.data?.object, event);
      break;
    case "payment_intent.succeeded":
    case "payment_intent.payment_failed":
      await handlePaymentIntentEvent(event.data?.object, event);
      break;
    default:
      console.log(
        "[subscription-handleStripeWebhookEvent] Unhandled event type",
        event.type,
      );
  }
};

const handleStripeWebhook = onRequest({ region: REGION }, async (req, res) => {
  if (req.method !== "POST") {
    res.set("Allow", "POST");
    res.status(405).send("Méthode non autorisée");
    return;
  }

  let stripe = null;
  try {
    stripe = getStripeClient();
  } catch (error) {
    console.error(
      "[subscription-handleStripeWebhook] Stripe client error",
      error,
    );
    res.status(500).send("Client Stripe indisponible");
    return;
  }

  const signature = req.headers["stripe-signature"];
  if (!signature) {
    res.status(400).send("En-tête stripe-signature manquant");
    return;
  }

  let rawBody = null;
  if (Buffer.isBuffer(req.rawBody)) {
    rawBody = req.rawBody;
  } else {
    console.warn(
      "[subscription-handleStripeWebhook] rawBody indisponible, utilisation d'un fallback JSON stringify",
    );
    rawBody = Buffer.from(JSON.stringify(req.body || {}));
  }

  let event = null;
  try {
    const webhookSecret = resolveStripeWebhookSecret();
    event = stripe.webhooks.constructEvent(rawBody, signature, webhookSecret);
  } catch (error) {
    console.error(
      "[subscription-handleStripeWebhook] Signature invalide",
      error?.message || error,
    );
    res.status(400).send(`Signature invalide: ${error?.message || "Webhook"}`);
    return;
  }

  try {
    await handleStripeWebhookEvent({ event, stripe });
    res.status(200).json({ received: true });
  } catch (error) {
    console.error(
      "[subscription-handleStripeWebhook] Traitement échoué",
      event?.id,
      error,
    );
    res.status(500).send("Erreur lors du traitement du webhook");
  }
});

const sanitizePriceId = (value) => {
  if (typeof value !== "string") {
    return "";
  }
  return value.trim();
};

const formatPlan = (price, priceId) => {
  if (!price || typeof price !== "object") {
    return null;
  }

  const product =
    typeof price.product === "object" && price.product !== null
      ? price.product
      : {};

  return {
    id: price.id || priceId,
    priceId: price.id || priceId,
    active: price.active !== false,
    currency: price.currency || "eur",
    unitAmount: price.unit_amount,
    unitAmountDecimal: price.unit_amount_decimal,
    transformQuantity: price.transform_quantity || null,
    recurring: price.recurring || null,
    nickname: price.nickname || null,
    billingScheme: price.billing_scheme || null,
    product: {
      id: product.id || null,
      name: product.name || "",
      description: product.description || "",
      metadata: product.metadata || {},
    },
  };
};

const formatCoinPack = ({ product, price, fallback = {} }) => {
  if (!product || typeof product !== "object") {
    return null;
  }

  const resolvedPrice =
    price ||
    (typeof product.default_price === "object" && product.default_price) ||
    null;

  const priceId =
    (resolvedPrice && resolvedPrice.id) ||
    (typeof product.default_price === "string"
      ? product.default_price
      : null);

  const rawCoinAmount =
    product?.metadata?.coins ??
    product?.metadata?.coinAmount ??
    fallback.fallbackCoinAmount ??
    0;

  const coinAmount =
    typeof rawCoinAmount === "string"
      ? parseInt(rawCoinAmount, 10)
      : Number(rawCoinAmount);

  return {
    productId: product.id,
    priceId,
    name: product.name || "",
    description: product.description || "",
    coinAmount:
      Number.isFinite(coinAmount) && coinAmount > 0 ? coinAmount : 0,
    currency:
      resolvedPrice?.currency ||
      (typeof resolvedPrice?.currency === "string"
        ? resolvedPrice.currency.toLowerCase()
        : "eur"),
    unitAmount: resolvedPrice?.unit_amount ?? null,
    metadata: product.metadata || {},
  };
};

const getSubscriptionMetaFromPrice = (priceId) => {
  if (typeof priceId !== "string") {
    return null;
  }
  return SUBSCRIPTION_PRICE_METADATA[priceId] || null;
};

const listSubscriptionPlans = onCall({ region: REGION }, async () => {
  try {
    const stripe = getStripeClient();

    const entries = await Promise.all(
      Object.entries(SUBSCRIPTION_PRICE_IDS).map(async ([period, priceIds]) => {
        const periodPlans = await Promise.all(
          priceIds.map(async (priceId) => {
            try {
              const price = await stripe.prices.retrieve(priceId, {
                expand: ["product"],
              });
              return formatPlan(price, priceId);
            } catch (error) {
              console.error(
                `[subscription-listSubscriptionPlans] Impossible de récupérer ${priceId}`,
                error?.message || error,
              );
              return null;
            }
          }),
        );

        return [period, periodPlans.filter(Boolean)];
      }),
    );

    return {
      plans: Object.fromEntries(entries),
    };
  } catch (error) {
    console.error("[subscription-listSubscriptionPlans] error", error);
    throw mapStripeErrorToHttps(
      error,
      "Impossible de récupérer les abonnements Stripe.",
    );
  }
});

const listCoinPacks = onCall({ region: REGION }, async () => {
  try {
    const stripe = getStripeClient();

    const packs = await Promise.all(
      COIN_PACK_PRODUCTS.map(async (pack) => {
        try {
          const product = await stripe.products.retrieve(pack.productId, {
            expand: ["default_price"],
          });

          let resolvedPrice = null;
          if (typeof product?.default_price === "string") {
            resolvedPrice = await stripe.prices.retrieve(
              product.default_price,
            );
          } else if (
            product?.default_price &&
            typeof product.default_price === "object"
          ) {
            resolvedPrice = product.default_price;
          }

          return formatCoinPack({
            product,
            price: resolvedPrice,
            fallback: pack,
          });
        } catch (error) {
          console.error(
            "[subscription-listCoinPacks] Unable to retrieve product",
            pack.productId,
            error?.message || error,
          );
          return null;
        }
      }),
    );

    return {
      packs: packs.filter(Boolean),
    };
  } catch (error) {
    console.error("[subscription-listCoinPacks] error", error);
    throw mapStripeErrorToHttps(
      error,
      "Impossible de récupérer les packs de pièces.",
    );
  }
});

const createSubscriptionCheckoutSession = onCall(
  { region: REGION },
  async (request) => {
    try {
      const uid = request?.auth?.uid;
      if (!uid) {
        throw new HttpsError(
          "unauthenticated",
          "Connecte-toi pour souscrire un abonnement.",
        );
      }

      const rawPriceId = request?.data?.priceId;
      const priceId = sanitizePriceId(rawPriceId);
      if (!priceId) {
        throw new HttpsError(
          "invalid-argument",
          "Un identifiant de prix Stripe est requis.",
        );
      }

      if (!ALL_SUBSCRIPTION_PRICE_IDS.includes(priceId)) {
        throw new HttpsError(
          "invalid-argument",
          `L'identifiant de prix ${priceId} n'est pas pris en charge.`,
        );
      }

      const stripe = getStripeClient();

      const priceMeta = getSubscriptionMetaFromPrice(priceId) || {};

      const { lineItems, summary } = await buildCheckoutLineItems(
        [
          {
            priceID: priceId,
            quantity: 1,
            isRenewable: true,
          },
        ],
        { stripe },
      );

      const { successUrl, cancelUrl } = getReturnUrls(
        request?.data?.returnUrls,
      );

      const { customerId } = await ensureStripeCustomer({
        uid,
        stripe,
        refsList: refList,
        createIfMissing: true,
      });

      if (!customerId) {
        throw new HttpsError(
          "failed-precondition",
          "Impossible de retrouver le client Stripe associé.",
        );
      }

      const session = await stripe.checkout.sessions.create({
        mode: "subscription",
        customer: customerId,
        line_items: lineItems,
        success_url: successUrl,
        cancel_url: cancelUrl,
        allow_promotion_codes: true,
        metadata: {
          firebaseUID: uid,
          priceId,
          purchaseType: "SUBSCRIPTION",
          subscriptionLevel: priceMeta.level || null,
          subscriptionBillingPeriod: priceMeta.billingPeriod || null,
        },
      });

      await paymentsCollection.doc(session.id).set(
        {
          userId: uid,
          customerId,
          status: session.status || "created",
          mode: "subscription",
          createdAt: getServerTimestamp(),
          updatedAt: getServerTimestamp(),
          sessionId: session.id,
          sessionUrl: session.url,
          lineItems: summary,
          amountSubtotal: session.amount_subtotal,
          amountTotal: session.amount_total,
          currency: session.currency,
          paymentStatus: session.payment_status,
          metadata: session.metadata || {},
        },
        { merge: true },
      );

      return formatCheckoutSessionResponse(session);
    } catch (error) {
      console.error(
        "[subscription-createSubscriptionCheckoutSession] error",
        error,
      );
      if (error instanceof HttpsError) {
        throw error;
      }
      throw mapStripeErrorToHttps(
        error,
        "Impossible de créer la session d'abonnement Stripe.",
      );
    }
  },
);

const createCoinPackCheckoutSession = onCall(
  { region: REGION },
  async (request) => {
    try {
      const uid = request?.auth?.uid;
      if (!uid) {
        throw new HttpsError(
          "unauthenticated",
          "Connecte-toi pour acheter un pack de pièces.",
        );
      }

      const rawProductId = request?.data?.productId;
      const productId =
        typeof rawProductId === "string" ? rawProductId.trim() : "";

      if (!productId) {
        throw new HttpsError(
          "invalid-argument",
          "Un identifiant de produit Stripe est requis.",
        );
      }

      if (!COIN_PACK_PRODUCT_IDS.includes(productId)) {
        throw new HttpsError(
          "invalid-argument",
          `Le produit ${productId} n'est pas un pack de pièces autorisé`,
        );
      }

      const stripe = getStripeClient();

      const product = await stripe.products.retrieve(productId, {
        expand: ["default_price"],
      });

      let resolvedPrice = null;
      if (typeof product?.default_price === "string") {
        resolvedPrice = await stripe.prices.retrieve(product.default_price);
      } else if (
        product?.default_price &&
        typeof product.default_price === "object"
      ) {
        resolvedPrice = product.default_price;
      }

      const coinPack = formatCoinPack({
        product,
        price: resolvedPrice,
        fallback: COIN_PACK_PRODUCT_MAP[productId],
      });

      if (!coinPack?.priceId) {
        throw new HttpsError(
          "failed-precondition",
          "Impossible de déterminer le prix Stripe pour ce pack.",
        );
      }

      const { successUrl, cancelUrl } = getReturnUrls(
        request?.data?.returnUrls,
      );

      const { customerId } = await ensureStripeCustomer({
        uid,
        stripe,
        refsList,
        createIfMissing: true,
      });

      if (!customerId) {
        throw new HttpsError(
          "failed-precondition",
          "Impossible de retrouver le client Stripe associé.",
        );
      }

      const session = await stripe.checkout.sessions.create({
        mode: "payment",
        customer: customerId,
        line_items: [
          {
            price: coinPack.priceId,
            quantity: 1,
          },
        ],
        success_url: successUrl,
        cancel_url: cancelUrl,
        allow_promotion_codes: false,
        metadata: {
          firebaseUID: uid,
          purchaseType: "COIN_PACK",
          coinPackProductId: coinPack.productId,
          coinPackPriceId: coinPack.priceId,
          coinAmount: coinPack.coinAmount,
          coinPackKey: COIN_PACK_PRODUCT_MAP[productId]?.key || null,
        },
      });

      await paymentsCollection.doc(session.id).set(
        {
          userId: uid,
          customerId,
          status: session.status || "created",
          mode: "payment",
          createdAt: getServerTimestamp(),
          updatedAt: getServerTimestamp(),
          sessionId: session.id,
          sessionUrl: session.url,
          lineItems: [
            {
              productId: coinPack.productId,
              priceId: coinPack.priceId,
              quantity: 1,
              coinAmount: coinPack.coinAmount,
            },
          ],
          amountSubtotal: session.amount_subtotal,
          amountTotal: session.amount_total,
          currency: session.currency,
          paymentStatus: session.payment_status,
          metadata: session.metadata || {},
        },
        { merge: true },
      );

      return formatCheckoutSessionResponse(session);
    } catch (error) {
      console.error(
        "[subscription-createCoinPackCheckoutSession] error",
        error,
      );
      if (error instanceof HttpsError) {
        throw error;
      }
      throw mapStripeErrorToHttps(
        error,
        "Impossible de créer la session d'achat de pièces.",
      );
    }
  },
);

exports.listSubscriptionPlans = listSubscriptionPlans;
exports.createSubscriptionCheckoutSession = createSubscriptionCheckoutSession;
exports.listCoinPacks = listCoinPacks;
exports.createCoinPackCheckoutSession = createCoinPackCheckoutSession;
exports.handleStripeWebhook = handleStripeWebhook;