Rork Practical Techniques [Part 2] — Monetization, Production Quality, CI/CD & Performance

import StoreKit
import SwiftUI
 
@MainActor
class PurchaseManager: ObservableObject {
  @Published var availableProducts: [Product] = []
  @Published var purchasedProductIDs: Set<String> = []
  @Published var isLoading = false
 
  private let productIDs = [
    "com.yourapp.subscription.monthly",
    "com.yourapp.subscription.annual",
    "com.yourapp.lifetime",
  ]
 
  init() {
    Task {
      await fetchProducts()
      await updatePurchasedProducts()
      await listenForTransactions()
    }
  }
 
  func fetchProducts() async {
    isLoading = true
    do {
      self.availableProducts = try await Product.products(for: productIDs)
    } catch {
      print("Failed to fetch products: \(error)")
    }
    isLoading = false
  }
 
  func purchase(_ product: Product) async throws -> Transaction? {
    let result = try await product.purchase()
 
    switch result {
    case .success(let verification):
      let transaction = try verification.payloadValue
      await updatePurchasedProducts()
      await transaction.finish()
      return transaction
 
    case .userCancelled:
      print("User cancelled purchase")
      return nil
 
    case .pending:
      print("Purchase pending - awaiting user action")
      return nil
 
    @unknown default:
      return nil
    }
  }
 
  func updatePurchasedProducts() async {
    var purchasedIDs: Set<String> = []
 
    for await result in Transaction.currentEntitlements {
      let transaction = try result.payloadValue
 
      if transaction.revocationDate == nil {
        purchasedIDs.insert(transaction.productID)
      }
    }
 
    self.purchasedProductIDs = purchasedIDs
  }
 
  func listenForTransactions() async {
    for await result in Transaction.updates {
      let transaction = try result.payloadValue
      await updatePurchasedProducts()
      await transaction.finish()
    }
  }
}
 
struct SubscriptionView: View {
  @ObservedObject var purchaseManager: PurchaseManager
  @State private var selectedProductID: String?
  @State private var showError = false
  @State private var errorMessage = ""
 
  var body: some View {
    VStack(spacing: 20) {
      Text("Get Premium")
        .font(.title)
        .fontWeight(.bold)
 
      ForEach(purchaseManager.availableProducts, id: \.id) { product in
        SubscriptionCard(
          product: product,
          isSelected: selectedProductID == product.id,
          onSelect: { selectedProductID = product.id },
          onPurchase: {
            Task {
              do {
                _ = try await purchaseManager.purchase(product)
              } catch {
                errorMessage = error.localizedDescription
                showError = true
              }
            }
          }
        )
      }
 
      if let selectedID = selectedProductID,
         let product = purchaseManager.availableProducts.first(where: { $0.id == selectedID }) {
        Button(action: {
          Task {
            do {
              _ = try await purchaseManager.purchase(product)
            } catch {
              errorMessage = error.localizedDescription
              showError = true
            }
          }
        }) {
          Text("Purchase")
            .fontWeight(.semibold)
            .frame(maxWidth: .infinity)
            .padding(12)
            .background(Color.blue)
            .foregroundColor(.white)
            .cornerRadius(8)
        }
      }
 
      Spacer()
    }
    .padding(16)
    .alert("Error", isPresented: $showError) {
      Button("OK") { showError = false }
    } message: {
      Text(errorMessage)
    }
  }
}

// lib/revenuecat.ts
import Purchases, {
  CustomerInfo,
  PurchasesError,
} from 'react-native-purchases';
 
// Initialize RevenueCat
export const initializeRevenueCat = async () => {
  Purchases.debugLogsEnabled = true;
 
  if (Platform.OS === 'ios') {
    await Purchases.configure({ apiKey: 'appl_YOUR_API_KEY' });
  } else if (Platform.OS === 'android') {
    await Purchases.configure({ apiKey: 'goog_YOUR_API_KEY' });
  }
};
 
// Fetch subscription offerings
export const fetchSubscriptionOfferings = async () => {
  try {
    const offerings = await Purchases.getOfferings();
 
    if (offerings.current != null) {
      const monthlyPackage = offerings.current.monthly;
      const annualPackage = offerings.current.annual;
      const lifetimePackage = offerings.current.lifetime;
 
      return {
        monthly: monthlyPackage?.product,
        annual: annualPackage?.product,
        lifetime: lifetimePackage?.product,
      };
    }
  } catch (error) {
    console.error('Error fetching offerings:', error);
  }
};
 
// Purchase subscription
export const purchaseSubscription = async (packageKey: string) => {
  try {
    const offerings = await Purchases.getOfferings();
 
    if (offerings.current != null) {
      const package_ = offerings.current[packageKey];
 
      if (package_ != null) {
        const customerInfo = await Purchases.purchasePackage(package_);
 
        // Purchase success - check subscription expiry
        const entitlements = customerInfo.entitlements.active;
        if (entitlements['premium'] != null) {
          console.log('Premium subscription activated');
          return { success: true, expiryDate: entitlements['premium'].expirationDate };
        }
      }
    }
  } catch (error) {
    if (error instanceof PurchasesError) {
      if (error.code === 'PurchaseCancelledError') {
        console.log('User cancelled purchase');
      } else {
        console.error('Purchase error:', error.message);
      }
    }
  }
};
 
// Check subscription status
export const checkSubscriptionStatus = async (): Promise<{
  isPremium: boolean;
  expiryDate?: string;
}> => {
  try {
    const customerInfo: CustomerInfo = await Purchases.getCustomerInfo();
 
    const hasPremium = customerInfo.entitlements.active['premium'] != null;
 
    if (hasPremium) {
      const expiryDate =
        customerInfo.entitlements.active['premium'].expirationDate;
      return {
        isPremium: true,
        expiryDate: expiryDate || undefined,
      };
    }
 
    return { isPremium: false };
  } catch (error) {
    console.error('Error checking subscription:', error);
    return { isPremium: false };
  }
};
 
// Set user ID (call on login)
export const setUserID = async (userID: string) => {
  await Purchases.logIn(userID);
};
 
// Logout
export const logoutUser = async () => {
  await Purchases.logOut();
};

// server/services/stripeService.ts
import Stripe from 'stripe';
 
const stripe = new Stripe(process.env.STRIPE_SECRET_KEY);
 
interface SubscriptionPlan {
  id: string;
  name: string;
  priceId: string;
  monthlyPrice: number;
  features: string[];
}
 
export const SUBSCRIPTION_PLANS: Record<string, SubscriptionPlan> = {
  monthly: {
    id: 'plan_monthly',
    name: 'Monthly Pro',
    priceId: 'price_monthly_usd',
    monthlyPrice: 4.99,
    features: ['Core features', 'Cloud sync', 'Priority support'],
  },
  annual: {
    id: 'plan_annual',
    name: 'Annual Pro',
    priceId: 'price_annual_usd',
    monthlyPrice: 3.33,
    features: ['All Monthly features', '25% discount'],
  },
  lifetime: {
    id: 'plan_lifetime',
    name: 'Lifetime Access',
    priceId: 'price_lifetime_usd',
    monthlyPrice: 39.99,
    features: ['Permanent access', 'All features', 'Unlimited support'],
  },
};
 
export const stripeService = {
  // Create Stripe customer
  async createCustomer(email: string, name: string) {
    const customer = await stripe.customers.create({
      email,
      name,
      metadata: {
        signupDate: new Date().toISOString(),
      },
    });
    return customer;
  },
 
  // Create subscription
  async createSubscription(
    customerId: string,
    planKey: 'monthly' | 'annual' | 'lifetime'
  ) {
    const plan = SUBSCRIPTION_PLANS[planKey];
 
    const subscription = await stripe.subscriptions.create({
      customer: customerId,
      items: [{ price: plan.priceId }],
      payment_behavior: 'default_incomplete',
      expand: ['latest_invoice.payment_intent'],
    });
 
    return subscription;
  },
 
  // Upgrade subscription
  async upgradeSubscription(
    subscriptionId: string,
    newPlanKey: 'monthly' | 'annual' | 'lifetime'
  ) {
    const subscription = await stripe.subscriptions.retrieve(subscriptionId);
    const plan = SUBSCRIPTION_PLANS[newPlanKey];
 
    const updated = await stripe.subscriptions.update(subscriptionId, {
      items: [
        {
          id: subscription.items.data[0].id,
          price: plan.priceId,
        },
      ],
      proration_behavior: 'create_prorations',
    });
 
    return updated;
  },
 
  // Cancel subscription
  async cancelSubscription(subscriptionId: string) {
    const canceled = await stripe.subscriptions.del(subscriptionId);
    return canceled;
  },
 
  // Get invoices
  async getInvoices(customerId: string) {
    const invoices = await stripe.invoices.list({
      customer: customerId,
      limit: 12,
    });
    return invoices.data;
  },
 
  // Check payment status
  async getPaymentStatus(customerId: string) {
    const invoices = await stripe.invoices.list({
      customer: customerId,
      limit: 1,
    });
 
    const latestInvoice = invoices.data[0];
    if (!latestInvoice) return null;
 
    return {
      status: latestInvoice.status,
      amount: latestInvoice.amount_due,
      dueDate: latestInvoice.due_date,
    };
  },
};

# eas.json
{
  "build": {
    "preview": {
      "android": {
        "buildType": "apk"
      },
      "ios": {
        "buildType": "simulator"
      }
    },
    "preview2": {
      "android": {
        "buildType": "apk"
      },
      "ios": {
        "buildType": "simulator"
      }
    },
    "preview3": {
      "developmentClient": true
    },
    "production": {}
  },
  "submit": {
    "production": {
      "android": {
        "serviceAccount": "@env GOOGLE_SERVICE_ACCOUNT"
      },
      "ios": {
        "appleTeamId": "@env APPLE_TEAM_ID",
        "appleId": "@env APPLE_ID",
        "appleIdPassword": "@env APPLE_PASSWORD"
      }
    }
  }
}

#!/bin/bash
 
# Build iOS and Android
eas build --platform ios --wait
eas build --platform android --wait
 
# Submit to stores
eas submit --platform ios --latest
eas submit --platform android --latest

// e2e/tasks.e2e.js
describe('Task Management Flow', () => {
  beforeAll(async () => {
    await device.launchApp();
  });
 
  beforeEach(async () => {
    await device.reloadReactNative();
  });
 
  it('should create and complete a task', async () => {
    // Login
    await element(by.id('emailInput')).typeText('user@test.com');
    await element(by.id('passwordInput')).typeText('password123');
    await element(by.text('Login')).tap();
 
    // Wait for home screen
    await waitFor(element(by.id('taskList')))
      .toBeVisible()
      .withTimeout(5000);
 
    // Create task
    await element(by.id('addTaskButton')).tap();
    await element(by.id('taskTitle')).typeText('Complete report');
    await element(by.id('taskDescription')).typeText('Finish quarterly report');
    await element(by.text('Create')).tap();
 
    // Verify task appears
    await expect(element(by.text('Complete report'))).toBeVisible();
 
    // Complete task
    await element(by.text('Complete report')).tap();
    await waitFor(element(by.id('completeCheckbox')))
      .toBeVisible()
      .withTimeout(5000);
    await element(by.id('completeCheckbox')).multiTap();
 
    // Verify completion
    await expect(element(by.id('completedTaskBadge'))).toBeVisible();
  });
 
  it('should filter tasks by priority', async () => {
    // Open filter menu
    await element(by.id('filterButton')).tap();
 
    // Select high priority
    await element(by.id('priorityHigh')).tap();
    await element(by.text('Apply')).tap();
 
    // Verify filtered results
    await expect(element(by.text('High priority task'))).toBeVisible();
    await expect(element(by.text('Low priority task'))).not.toBeVisible();
  });
 
  it('should handle offline scenario', async () => {
    // Simulate offline
    await device.setAirplaneMode(true);
 
    // Create task offline
    await element(by.id('addTaskButton')).tap();
    await element(by.id('taskTitle')).typeText('Offline task');
    await element(by.text('Create')).tap();
 
    // Verify local storage
    await expect(element(by.text('Offline task'))).toBeVisible();
 
    // Go online
    await device.setAirplaneMode(false);
 
    // Verify sync
    await waitFor(element(by.id('syncBadge')))
      .not.toBeVisible()
      .withTimeout(10000);
  });
});

// Memoization for expensive calculations
const TaskListOptimized = React.memo(({ tasks, onTaskPress }) => {
  const sortedTasks = useMemo(() => {
    return tasks.sort((a, b) => {
      const priorityOrder = { high: 0, medium: 1, low: 2 };
      return priorityOrder[a.priority] - priorityOrder[b.priority];
    });
  }, [tasks]);
 
  const renderTask = useCallback(({ item }) => (
    <TaskItem task={item} onPress={() => onTaskPress(item.id)} />
  ), [onTaskPress]);
 
  return (
    <FlatList
      data={sortedTasks}
      renderItem={renderTask}
      keyExtractor={(item) => item.id}
      maxToRenderPerBatch={5}
      updateCellsBatchingPeriod={100}
      removeClippedSubviews={true}
      initialNumToRender={10}
    />
  );
});
 
// Component memoization
const TaskItem = React.memo(({ task, onPress }) => (
  <TouchableOpacity onPress={onPress} style={styles.item}>
    <Text>{task.title}</Text>
  </TouchableOpacity>
));

// lib/offlineSync.ts
import SQLite from 'react-native-sqlite-storage';
import * as CRDT from 'automerge';
 
const db = SQLite.openDatabase({
  name: 'taskapp.db',
  location: 'default',
});
 
interface SyncableTask {
  id: string;
  title: string;
  status: 'todo' | 'in_progress' | 'done';
  version: number;
  lastModified: number;
  needsSync: boolean;
}
 
export const offlineSync = {
  // Save task locally (CRDT-enabled)
  async saveLocalTask(task: SyncableTask) {
    return new Promise((resolve, reject) => {
      db.transaction((tx) => {
        tx.executeSql(
          'INSERT OR REPLACE INTO tasks (id, title, status, version, lastModified, needsSync) VALUES (?, ?, ?, ?, ?, ?)',
          [task.id, task.title, task.status, task.version, task.lastModified, task.needsSync ? 1 : 0],
          () => resolve(task),
          (_, error) => reject(error)
        );
      });
    });
  },
 
  // Get unsync'd tasks
  async getUnsyncedTasks(): Promise<SyncableTask[]> {
    return new Promise((resolve, reject) => {
      db.transaction((tx) => {
        tx.executeSql(
          'SELECT * FROM tasks WHERE needsSync = 1',
          [],
          (_, result) => {
            const tasks = [];
            for (let i = 0; i < result.rows.length; i++) {
              tasks.push(result.rows.item(i));
            }
            resolve(tasks);
          },
          (_, error) => reject(error)
        );
      });
    });
  },
 
  // Sync with server when online
  async syncWithServer() {
    const unsyncedTasks = await this.getUnsyncedTasks();
 
    for (const task of unsyncedTasks) {
      try {
        // Upload to Supabase
        const { error } = await supabase
          .from('tasks')
          .upsert({ ...task, needsSync: false });
 
        if (!error) {
          // Mark as synced locally
          await this.markSynced(task.id);
        }
      } catch (err) {
        console.error('Sync error:', err);
      }
    }
  },
 
  // Mark as synced
  async markSynced(taskId: string) {
    return new Promise((resolve, reject) => {
      db.transaction((tx) => {
        tx.executeSql(
          'UPDATE tasks SET needsSync = 0 WHERE id = ?',
          [taskId],
          () => resolve(true),
          (_, error) => reject(error)
        );
      });
    });
  },
};

// lib/geminaChatService.ts
import { GoogleGenerativeAI } from '@google/generative-ai';
 
const genAI = new GoogleGenerativeAI(process.env.GEMINI_API_KEY);
 
export const geminaChatService = {
  async *streamChat(userMessage: string, conversationHistory: Array<{ role: string; content: string }>) {
    try {
      const model = genAI.getGenerativeModel({ model: 'gemini-2.5-pro' });
 
      const messages = [
        ...conversationHistory.map(msg => ({
          role: msg.role === 'user' ? 'user' : 'model',
          parts: [{ text: msg.content }],
        })),
        {
          role: 'user',
          parts: [{ text: userMessage }],
        },
      ];
 
      const chat = model.startChat({
        history: messages.slice(0, -1),
      });
 
      const result = await chat.sendMessageStream(userMessage);
 
      for await (const chunk of result.stream) {
        const text = chunk.text();
        yield text;  // Yield each chunk for UI update
      }
    } catch (error) {
      console.error('Gemini API error:', error);
      throw error;
    }
  },
};
 
// React component using streaming
const ChatScreen = () => {
  const [messages, setMessages] = useState([]);
  const [input, setInput] = useState('');
  const [isLoading, setIsLoading] = useState(false);
 
  const handleSendMessage = async () => {
    if (!input.trim()) return;
 
    const userMessage = input;
    setMessages(prev => [...prev, { role: 'user', content: userMessage }]);
    setInput('');
    setIsLoading(true);
 
    let assistantMessage = '';
 
    try {
      for await (const chunk of geminaChatService.streamChat(userMessage, messages)) {
        assistantMessage += chunk;
        setMessages(prev => {
          const newMessages = [...prev];
          if (newMessages[newMessages.length - 1]?.role === 'assistant') {
            newMessages[newMessages.length - 1].content = assistantMessage;
          } else {
            newMessages.push({ role: 'assistant', content: assistantMessage });
          }
          return newMessages;
        });
      }
    } catch (error) {
      console.error('Chat error:', error);
    } finally {
      setIsLoading(false);
    }
  };
 
  return (
    <View style={styles.container}>
      <FlatList
        data={messages}
        renderItem={({ item }) => (
          <View style={[styles.message, item.role === 'user' ? styles.userMessage : styles.aiMessage]}>
            <Text>{item.content}</Text>
          </View>
        )}
        keyExtractor={(_, index) => index.toString()}
      />
      <View style={styles.inputContainer}>
        <TextInput
          style={styles.input}
          value={input}
          onChangeText={setInput}
          placeholder="Type your message..."
          multiline
          editable={!isLoading}
        />
        <Button title="Send" onPress={handleSendMessage} disabled={isLoading} />
      </View>
    </View>
  );
};
 
const styles = StyleSheet.create({
  container: {
    flex: 1,
    backgroundColor: '#fff',
  },
  message: {
    padding: 12,
    marginVertical: 4,
    marginHorizontal: 8,
    borderRadius: 8,
    maxWidth: '85%',
  },
  userMessage: {
    alignSelf: 'flex-end',
    backgroundColor: '#0066cc',
  },
  aiMessage: {
    alignSelf: 'flex-start',
    backgroundColor: '#f0f0f0',
  },
  inputContainer: {
    flexDirection: 'row',
    padding: 12,
    borderTopWidth: 1,
    borderTopColor: '#e0e0e0',
  },
  input: {
    flex: 1,
    borderWidth: 1,
    borderColor: '#ccc',
    borderRadius: 8,
    paddingHorizontal: 12,
    paddingVertical: 8,
    marginRight: 8,
  },
});

// Growth strategy hooks
export const growthService = {
  // App launch - show onboarding
  async showOnboarding() {
    const user = await authService.getCurrentUser();
    if (!user) return;
 
    const { data: profile } = await supabase
      .from('user_profiles')
      .select('onboarding_completed')
      .eq('id', user.id)
      .single();
 
    if (!profile?.onboarding_completed) {
      // Show onboarding flow
      showOnboardingModal();
    }
  },
 
  // Prompt for app store review at right moment
  async requestReview() {
    const { data: userStats } = await supabase
      .from('user_stats')
      .select('tasks_completed, days_active')
      .single();
 
    // Ask after 10 tasks completed and 3+ days active
    if (userStats.tasks_completed >= 10 && userStats.days_active >= 3) {
      requestAppStoreReview();
    }
  },
 
  // Share feature prompt
  async promptShare() {
    const { data: userStats } = await supabase
      .from('user_stats')
      .select('teams_created')
      .single();
 
    if (userStats.teams_created >= 1) {
      promptForSharing('Invite teammates and collaborate on tasks!');
    }
  },
 
  // Freemium upsell at right moment
  async promptUpgrade() {
    const { data: userStats } = await supabase
      .from('user_stats')
      .select('projects_created')
      .single();
 
    if (userStats.projects_created >= 3) {
      showUpgradePrompt('Unlock unlimited projects with Pro');
    }
  },
};

// StoreKit 2 + ATT paywall gate
import StoreKit
import AppTrackingTransparency
 
@MainActor
final class PaywallGate: ObservableObject {
    @Published private(set) var paywallReady = false
    private let minSessions = 3
    private let minActiveSeconds: TimeInterval = 90
 
    private var sessions: Int { UserDefaults.standard.integer(forKey: "pw.sessions") }
    private var activeSeconds: TimeInterval {
        UserDefaults.standard.double(forKey: "pw.activeSeconds")
    }
 
    func recordSession() {
        UserDefaults.standard.set(sessions + 1, forKey: "pw.sessions")
    }
 
    func recordActive(_ seconds: TimeInterval) {
        UserDefaults.standard.set(activeSeconds + seconds, forKey: "pw.activeSeconds")
    }
 
    func evaluate() async {
        guard sessions >= minSessions, activeSeconds >= minActiveSeconds else { return }
        let status = await ATTrackingManager.requestTrackingAuthorization()
        // Always resolve the ATT prompt first, then unlock the paywall.
        await MainActor.run { self.paywallReady = (status == .authorized || status == .denied) }
    }
}

import Purchases, { CustomerInfo } from 'react-native-purchases';
import AsyncStorage from '@react-native-async-storage/async-storage';
 
const ENT_KEY = 'rc.entitlement.snapshot.v2';
 
type EntitlementSnapshot = {
  isPro: boolean;
  expiresAt: number | null;
  fetchedAt: number;
};
 
export async function loadEntitlementSnapshot(): Promise<EntitlementSnapshot> {
  const raw = await AsyncStorage.getItem(ENT_KEY);
  if (raw) return JSON.parse(raw);
  return { isPro: false, expiresAt: null, fetchedAt: 0 };
}
 
export async function refreshEntitlement(): Promise<EntitlementSnapshot> {
  const info: CustomerInfo = await Purchases.getCustomerInfo();
  const pro = info.entitlements.active['pro'];
  const snap: EntitlementSnapshot = {
    isPro: !!pro,
    expiresAt: pro?.expirationDate ? new Date(pro.expirationDate).getTime() : null,
    fetchedAt: Date.now(),
  };
  await AsyncStorage.setItem(ENT_KEY, JSON.stringify(snap));
  return snap;
}
 
// On boot: trust the snapshot, refresh in the background
export async function bootstrapEntitlement() {
  const snap = await loadEntitlementSnapshot();
  // UI immediately reflects snap.isPro
  refreshEntitlement().catch(() => {/* offline: keep cached value */});
  return snap;
}

// e2e/helpers/wait.js
const TIMEOUT = 8000;
 
async function waitForElementByID(id, timeout = TIMEOUT) {
  await waitFor(element(by.id(id)))
    .toBeVisible()
    .withTimeout(timeout);
  return element(by.id(id));
}
 
async function waitAndTap(id) {
  const el = await waitForElementByID(id);
  await el.tap();
}
 
module.exports = { waitForElementByID, waitAndTap };

#!/usr/bin/env bash
# scripts/staged-rollout.sh
set -euo pipefail
 
CHANNEL="${1:-production}"
SENTRY_PROJECT="${2:-rork-app}"
THRESHOLD="0.997"  # crash-free sessions 99.7%
 
step() {
  local pct="$1"
  echo "→ raising ${CHANNEL} to ${pct}%"
  eas update --channel "$CHANNEL" --target-rollout "$pct" --non-interactive
}
 
health() {
  curl -s -H "Authorization: Bearer ${SENTRY_AUTH_TOKEN}" \
    "https://sentry.io/api/0/projects/${SENTRY_ORG}/${SENTRY_PROJECT}/sessions/" \
    | jq -r '.groups[0].totals."crash_free_sessions" // 1.0'
}
 
step 2
sleep 4h
[[ "$(health)" > "$THRESHOLD" ]] || { echo "halt"; exit 1; }
step 25
sleep 8h
[[ "$(health)" > "$THRESHOLD" ]] || { echo "halt"; exit 1; }
step 50
sleep 24h
[[ "$(health)" > "$THRESHOLD" ]] || { echo "halt"; exit 1; }
step 100
echo "✅ 100% rollout complete"

import * as Y from 'yjs';
import { openDatabase } from 'react-native-sqlite-storage';
 
const db = openDatabase({ name: 'app.db', location: 'default' });
 
export async function persistDoc(name: string, doc: Y.Doc) {
  const update = Y.encodeStateAsUpdate(doc);
  await db.transaction(tx => {
    tx.executeSql(
      'INSERT OR REPLACE INTO ydocs(name, update_b64) VALUES(?, ?)',
      [name, Buffer.from(update).toString('base64')]
    );
  });
}
 
export async function restoreDoc(name: string): Promise<Y.Doc> {
  const doc = new Y.Doc();
  const [_, results] = await db.executeSql(
    'SELECT update_b64 FROM ydocs WHERE name = ?', [name]
  );
  if (results.rows.length > 0) {
    const buf = Buffer.from(results.rows.item(0).update_b64, 'base64');
    Y.applyUpdate(doc, new Uint8Array(buf));
  }
  return doc;
}

type Bidder = {
  id: string;
  fillRate: number;       // 0..1
  ecpm: number;           // USD
  avgLoadMs: number;
};
 
export function rankBidders(bidders: Bidder[]): Bidder[] {
  return [...bidders].sort((a, b) => score(b) - score(a));
}
 
function score(b: Bidder): number {
  let s = b.ecpm;
  if (b.fillRate < 0.8) s *= 0.7;
  if (b.avgLoadMs > 3000) s *= 0.5;
  return s * b.fillRate;
}