LMEMappeCatastaliApp/Platforms/Android/AndroidPlayBillingService.cs

using Android.BillingClient.Api;
using LMEMappeCatastaliApp.Services;
using Microsoft.Maui.ApplicationModel;

namespace LMEMappeCatastaliApp.Platforms.Android;

public sealed class AndroidPlayBillingService : Java.Lang.Object, IPlayBillingService, IPurchasesUpdatedListener
{
    private readonly SemaphoreSlim _connectionLock = new(1, 1);
    private readonly BillingClient _client;
    private TaskCompletionSource<PlayBillingResult>? _purchaseCompletion;

    public AndroidPlayBillingService()
    {
        var pendingPurchases = PendingPurchasesParams.NewBuilder()
            .EnableOneTimeProducts()
            .EnablePrepaidPlans()
            .Build();

        _client = BillingClient.NewBuilder(global::Android.App.Application.Context)
            .SetListener(this)
            .EnablePendingPurchases(pendingPurchases)
            .EnableAutoServiceReconnection()
            .Build();
    }

    public async Task<PlayBillingResult> RestoreAsync(CancellationToken cancellationToken = default)
    {
        try
        {
            await EnsureConnectedAsync(cancellationToken);
            var query = QueryPurchasesParams.NewBuilder()
                .SetProductType(BillingClient.ProductType.Subs)
                .Build();
            var result = await _client.QueryPurchasesAsync(query);
            if (result.Result.ResponseCode != BillingResponseCode.Ok)
            {
                return PlayBillingResult.Failed(ToMessage(result.Result));
            }

            var purchase = result.Purchases.FirstOrDefault(IsPurchasedProSubscription);
            if (purchase is null)
            {
                return PlayBillingResult.Base("Nessun abbonamento LME Pro attivo trovato su Google Play.");
            }

            var acknowledgement = await AcknowledgeIfNeededAsync(purchase);
            return acknowledgement ?? PlayBillingResult.Active("Abbonamento LME Pro ripristinato da Google Play.");
        }
        catch (OperationCanceledException)
        {
            throw;
        }
        catch (Exception error)
        {
            return PlayBillingResult.Failed($"Google Play Billing non disponibile: {error.GetBaseException().Message}");
        }
    }

    public async Task<PlayBillingResult> PurchaseAsync(string basePlanId, CancellationToken cancellationToken = default)
    {
        try
        {
            await EnsureConnectedAsync(cancellationToken);
            var product = QueryProductDetailsParams.Product.NewBuilder()
                .SetProductId(EntitlementService.ProductId)
                .SetProductType(BillingClient.ProductType.Subs)
                .Build();
            var query = QueryProductDetailsParams.NewBuilder()
                .SetProductList([product])
                .Build();
            var detailsResult = await _client.QueryProductDetailsAsync(query);
            if (detailsResult.Result.ResponseCode != BillingResponseCode.Ok)
            {
                return PlayBillingResult.Failed(ToMessage(detailsResult.Result));
            }

            var details = detailsResult.ProductDetailsList.FirstOrDefault();
            var offer = details?.GetSubscriptionOfferDetails()?
                .FirstOrDefault(item => item.BasePlanId == basePlanId && string.IsNullOrEmpty(item.OfferId));
            if (details is null || offer is null)
            {
                return PlayBillingResult.Failed("Piano LME Pro non disponibile. Verifica prodotto e base plan nella Play Console.");
            }

            var productParams = BillingFlowParams.ProductDetailsParams.NewBuilder()
                .SetProductDetails(details)
                .SetOfferToken(offer.OfferToken)
                .Build();
            var flow = BillingFlowParams.NewBuilder()
                .SetProductDetailsParamsList([productParams])
                .Build();
            var activity = Platform.CurrentActivity
                ?? throw new InvalidOperationException("Activity Android non disponibile.");

            var completion = new TaskCompletionSource<PlayBillingResult>(TaskCreationOptions.RunContinuationsAsynchronously);
            _purchaseCompletion = completion;
            using var registration = cancellationToken.Register(() => completion.TrySetCanceled(cancellationToken));
            var launchResult = _client.LaunchBillingFlow(activity, flow);
            if (launchResult.ResponseCode != BillingResponseCode.Ok)
            {
                _purchaseCompletion = null;
                return PlayBillingResult.Failed(ToMessage(launchResult));
            }

            return await completion.Task;
        }
        catch (OperationCanceledException)
        {
            throw;
        }
        catch (Exception error)
        {
            _purchaseCompletion = null;
            return PlayBillingResult.Failed($"Acquisto non avviato: {error.GetBaseException().Message}");
        }
    }

    public async void OnPurchasesUpdated(BillingResult billingResult, IList<Purchase>? purchases)
    {
        var completion = Interlocked.Exchange(ref _purchaseCompletion, null);
        if (completion is null)
        {
            return;
        }

        if (billingResult.ResponseCode == BillingResponseCode.UserCancelled)
        {
            completion.TrySetResult(PlayBillingResult.Cancelled("Acquisto annullato."));
            return;
        }

        if (billingResult.ResponseCode != BillingResponseCode.Ok)
        {
            completion.TrySetResult(PlayBillingResult.Failed(ToMessage(billingResult)));
            return;
        }

        var purchase = purchases?.FirstOrDefault(IsPurchasedProSubscription);
        if (purchase is null)
        {
            completion.TrySetResult(PlayBillingResult.Failed("Acquisto non ancora completato."));
            return;
        }

        var acknowledgement = await AcknowledgeIfNeededAsync(purchase);
        completion.TrySetResult(acknowledgement ?? PlayBillingResult.Active("Abbonamento LME Pro attivato."));
    }

    private async Task EnsureConnectedAsync(CancellationToken cancellationToken)
    {
        if (_client.IsReady)
        {
            return;
        }

        await _connectionLock.WaitAsync(cancellationToken);
        try
        {
            if (_client.IsReady)
            {
                return;
            }

            var result = await _client.StartConnectionAsync();
            if (result.ResponseCode != BillingResponseCode.Ok)
            {
                throw new InvalidOperationException(ToMessage(result));
            }
        }
        finally
        {
            _connectionLock.Release();
        }
    }

    private async Task<PlayBillingResult?> AcknowledgeIfNeededAsync(Purchase purchase)
    {
        if (purchase.IsAcknowledged)
        {
            return null;
        }

        var parameters = AcknowledgePurchaseParams.NewBuilder()
            .SetPurchaseToken(purchase.PurchaseToken)
            .Build();
        var result = await _client.AcknowledgePurchaseAsync(parameters);
        return result.ResponseCode == BillingResponseCode.Ok
            ? null
            : PlayBillingResult.Failed($"Acquisto trovato ma non confermato: {ToMessage(result)}");
    }

    private static bool IsPurchasedProSubscription(Purchase purchase) =>
        purchase.PurchaseState == PurchaseState.Purchased
        && purchase.Products.Contains(EntitlementService.ProductId);

    private static string ToMessage(BillingResult result) =>
        string.IsNullOrWhiteSpace(result.DebugMessage)
            ? $"Google Play Billing: {result.ResponseCode}."
            : result.DebugMessage;
}