LMEMappeCatastaliProApp/Services/PlayPurchaseVerificationService.cs

using System.Net.Http.Json;
using System.Reflection;

namespace LMEMappeCatastaliApp.Services;

public sealed class PlayPurchaseVerificationService
{
    private const string EndpointMetadataKey = "PlayBillingVerificationUrl";
    private const string RequiredMetadataKey = "PlayBillingVerificationRequired";
    private readonly HttpClient _httpClient = new() { Timeout = TimeSpan.FromSeconds(20) };

    public bool IsConfigured => VerificationEndpoint is not null;
    public bool IsRequired => ReadMetadata(RequiredMetadataKey).Equals("true", StringComparison.OrdinalIgnoreCase);

    private static Uri? VerificationEndpoint
    {
        get
        {
            var value = ReadMetadata(EndpointMetadataKey);
            return Uri.TryCreate(value, UriKind.Absolute, out var endpoint)
                && endpoint.Scheme == Uri.UriSchemeHttps
                ? endpoint
                : null;
        }
    }

    public async Task<PlayPurchaseVerificationResult> VerifyAsync(
        string purchaseToken,
        CancellationToken cancellationToken = default)
    {
        var endpoint = VerificationEndpoint;
        if (endpoint is null)
        {
            return PlayPurchaseVerificationResult.NotConfigured();
        }

        try
        {
            using var response = await _httpClient.PostAsJsonAsync(endpoint, new
            {
                packageName = AppInfo.Current.PackageName,
                productId = EntitlementService.ProductId,
                purchaseToken
            }, cancellationToken);
            if (!response.IsSuccessStatusCode)
            {
                return PlayPurchaseVerificationResult.Failed(
                    $"Verifica acquisto non disponibile ({(int)response.StatusCode}).");
            }

            var result = await response.Content.ReadFromJsonAsync<VerificationResponse>(cancellationToken);
            return result is null
                ? PlayPurchaseVerificationResult.Failed("Risposta di verifica acquisto non valida.")
                : new(true, true, result.Active, result.ExpiresAt, result.Message ?? string.Empty);
        }
        catch (OperationCanceledException) when (!cancellationToken.IsCancellationRequested)
        {
            return PlayPurchaseVerificationResult.Failed("Il server di verifica acquisti non ha risposto in tempo.");
        }
        catch (Exception error)
        {
            return PlayPurchaseVerificationResult.Failed(
                $"Verifica acquisto non disponibile: {error.GetBaseException().Message}");
        }
    }

    private static string ReadMetadata(string key) =>
        typeof(PlayPurchaseVerificationService).Assembly
            .GetCustomAttributes<AssemblyMetadataAttribute>()
            .FirstOrDefault(attribute => attribute.Key == key)?.Value?.Trim() ?? string.Empty;

    private sealed record VerificationResponse(bool Active, DateTimeOffset? ExpiresAt, string? Message);
}

public sealed record PlayPurchaseVerificationResult(
    bool Configured,
    bool Verified,
    bool Active,
    DateTimeOffset? ExpiresAt,
    string Message)
{
    public static PlayPurchaseVerificationResult NotConfigured() =>
        new(false, false, false, null, "Server di verifica acquisti non configurato.");

    public static PlayPurchaseVerificationResult Failed(string message) =>
        new(true, false, false, null, message);
}