KlugBilling

<extensions>
    <extensionID>com.klug.billing</extensionID>
</extensions>

import com.klug.billing.*;
import com.klug.billing.events.*;

var store:InAppBillingService = InAppBilling.service;

if ( InAppBilling.isSupported )   // iOS, Android
{
    store.addEventListener( InAppBillingEvent.SETUP_SUCCESS, onSetup );
    store.addEventListener( InAppBillingEvent.SETUP_FAILURE, onSetupFailed );
    store.addEventListener( PurchaseEvent.PURCHASES_UPDATED, onPurchasesUpdated );   // see 3

    var service:BillingService = new BillingService();
    if ( store.platform == "android" )
        service.setServiceType( InAppBillingServiceTypes.GOOGLE_PLAY_INAPP_BILLING )
               .setGooglePlayPublicKey( "MIIBIjANBgkqh..." );   // from the Play Console, Android only
    else
        service.setServiceType( InAppBillingServiceTypes.APPLE_INAPP_PURCHASE );
    store.setup( service );
}

function onSetup( e:InAppBillingEvent ):void
{
    store.checkAvailability( function( result:String ):void {
        if ( result == InAppBillingAvailability.AVAILABLE ) loadProducts();   // see 2
        else hideShop();   // e.g. purchases disabled by Screen Time
    });
}

function loadProducts():void
{
    store.addEventListener( ProductEvent.PRODUCTS_LOADED, onProducts );
    store.addEventListener( ProductEvent.PRODUCTS_FAILED, function( e:ProductEvent ):void {
        trace( "store not reachable: " + e.message );
    });
    // one-time products first, subscriptions second
    store.getProducts( [ "com.example.removeads" ],
                       [ "com.example.pro.monthly", "com.example.pro.yearly" ] );
}

function onProducts( e:ProductEvent ):void
{
    for each ( var p:Product in e.products )
    {
        // e.g. "Pro Yearly · 19,99 €" in the user's currency and language
        addShopButton( p.id, p.title + " · " + p.priceString );   // your app function
    }
}

function buy( productId:String ):void
{
    var request:PurchaseRequest = new PurchaseRequest().setProductId( productId );
    if ( store.checkPurchaseRequestValid( request ) ) store.makePurchase( request );
}

// every step of every transaction, also open ones from earlier sessions
function onPurchasesUpdated( e:PurchaseEvent ):void
{
    for each ( var p:Purchase in e.data )
    {
        switch ( p.transactionState )
        {
            case Purchase.STATE_PURCHASED:
            case Purchase.STATE_RESTORED:
                // iOS: p.transactionReceipt (app receipt)
                // Android: p.originalMessage + p.signature (Google's signed purchase data)
                verifyOnServer( p, function():void {   // your server call
                    unlock( p.productId );              // your app function
                    store.finishPurchase( p );          // close it, or the store sends it again
                });
                break;
            case Purchase.STATE_FAILED:
            case Purchase.STATE_CANCELLED:
                store.finishPurchase( p );
                break;
            case Purchase.STATE_DEFERRED:
                showHint( "Waiting for approval" );   // e.g. Ask to Buy
                break;
        }
    }
}

function restore():void
{
    if ( store.isGetPurchasesSupported )   // Android: list what the Google account owns
    {
        store.addEventListener( PurchaseEvent.GET_PURCHASES_COMPLETE, function( e:PurchaseEvent ):void {
            for each ( var p:Purchase in e.data ) unlock( p.productId );
        });
        store.getPurchases();
    }
    else   // iOS: restored transactions arrive in onPurchasesUpdated with STATE_RESTORED
    {
        store.addEventListener( PurchaseEvent.RESTORE_PURCHASES_SUCCESS, function( e:PurchaseEvent ):void {
            showHint( "Purchases restored" );
        });
        store.restorePurchases();
    }
}