namespace LMEMappeCatastaliApp.Services;

public sealed class EntitlementService(
    ManualLicenseService manualLicenses,
    IPlayBillingService playBilling,
    PlayPurchaseVerificationService purchaseVerification)
{
    public const string ProductId = "lme_pro";
    public const string MonthlyBasePlanId = "monthly";
    public const string YearlyBasePlanId = "yearly";
    public const int BaseDrawingObjectLimit = 15;

    private const string GoogleProActivePreference = "entitlement_google_pro_active";
    private const string GoogleExpiresAtPreference = "entitlement_google_pro_expires_at";
    private const string GoogleLastVerifiedAtPreference = "entitlement_google_pro_last_verified_at";
    private static readonly TimeSpan OfflineGracePeriod = TimeSpan.FromDays(7);
    private static readonly HashSet<string> ProFeatures = new(StringComparer.Ordinal)
    {
        AppFeatures.ProjectArchive,
        AppFeatures.Export,
        AppFeatures.CloudSync,
        AppFeatures.OfflineMaps,
        AppFeatures.AdvancedGeometry,
        AppFeatures.GpsTrail,
        AppFeatures.FiducialPoints
    };

    public bool IsGoogleProActive { get; private set; }
    public DateTimeOffset? GoogleExpiresAt { get; private set; }
    public DateTimeOffset? GoogleLastVerifiedAt { get; private set; }
    public ManualLicenseInfo? ManualLicense => manualLicenses.Current;
    public string? ManualLicenseError => manualLicenses.LastError;

    public bool HasGoogleProAccess
    {
        get
        {
            var now = DateTimeOffset.UtcNow;
            if (!IsGoogleProActive || GoogleExpiresAt is { } expiresAt && expiresAt <= now)
            {
                return false;
            }

            return GoogleLastVerifiedAt is null
                || now - GoogleLastVerifiedAt <= OfflineGracePeriod;
        }
    }

    public bool HasManualProAccess => manualLicenses.HasActiveLicense;
    public bool HasProAccess => HasGoogleProAccess || HasManualProAccess;

    public string PlanLabel => HasProAccess
        ? HasGoogleProAccess && HasManualProAccess ? "LME Pro (Google + manuale)"
        : HasGoogleProAccess ? "LME Pro (Google Play)"
        : "LME Pro (licenza manuale)"
        : "Base";

    public bool RequiresPro(string feature) => ProFeatures.Contains(feature);
    public bool CanUse(string feature) => !RequiresPro(feature) || HasProAccess;

    public Task<IReadOnlyList<PlaySubscriptionPlan>> GetSubscriptionPlansAsync(
        CancellationToken cancellationToken = default) =>
        playBilling.GetSubscriptionPlansAsync(cancellationToken);

    public async Task LoadAsync()
    {
        IsGoogleProActive = Preferences.Default.Get(GoogleProActivePreference, false);
        GoogleExpiresAt = ReadDate(GoogleExpiresAtPreference);
        GoogleLastVerifiedAt = ReadDate(GoogleLastVerifiedAtPreference);
        await manualLicenses.LoadAsync();
    }

    public void ApplyVerifiedGooglePro(DateTimeOffset? expiresAt)
    {
        IsGoogleProActive = true;
        GoogleExpiresAt = expiresAt;
        GoogleLastVerifiedAt = DateTimeOffset.UtcNow;
        SaveGoogleState();
    }

    public void ApplyGoogleBase()
    {
        IsGoogleProActive = false;
        GoogleExpiresAt = null;
        GoogleLastVerifiedAt = DateTimeOffset.UtcNow;
        SaveGoogleState();
    }

    public Task<ManualLicenseActivationResult> ActivateManualLicenseAsync(string? token) =>
        manualLicenses.ActivateAsync(token);

    public Task RemoveManualLicenseAsync() => manualLicenses.RemoveAsync();

    public async Task<PlayBillingResult> RestorePurchasesAsync()
    {
        var result = await playBilling.RestoreAsync();
        return await ApplyPlayBillingResultAsync(result);
    }

    public async Task<PlayBillingResult> PurchaseGoogleProAsync(string basePlanId)
    {
        var result = await playBilling.PurchaseAsync(basePlanId);
        return await ApplyPlayBillingResultAsync(result);
    }

    private async Task<PlayBillingResult> ApplyPlayBillingResultAsync(PlayBillingResult result)
    {
        if (!result.Completed)
        {
            return result;
        }

        if (result.HasActiveSubscription)
        {
            if (!string.IsNullOrWhiteSpace(result.PurchaseToken))
            {
                var verification = await purchaseVerification.VerifyAsync(result.PurchaseToken);
                if (verification.Verified)
                {
                    if (verification.Active)
                    {
                        ApplyVerifiedGooglePro(verification.ExpiresAt);
                        return result with
                        {
                            Message = string.IsNullOrWhiteSpace(verification.Message)
                                ? result.Message
                                : verification.Message
                        };
                    }

                    ApplyGoogleBase();
                    return PlayBillingResult.Base(string.IsNullOrWhiteSpace(verification.Message)
                        ? "L'abbonamento Google Play non risulta attivo."
                        : verification.Message);
                }

                if (purchaseVerification.IsRequired)
                {
                    return PlayBillingResult.Failed(verification.Message);
                }
            }

            ApplyVerifiedGooglePro(null);
        }
        else
        {
            ApplyGoogleBase();
        }

        return result;
    }

    private void SaveGoogleState()
    {
        Preferences.Default.Set(GoogleProActivePreference, IsGoogleProActive);
        WriteDate(GoogleExpiresAtPreference, GoogleExpiresAt);
        WriteDate(GoogleLastVerifiedAtPreference, GoogleLastVerifiedAt);
    }

    private static DateTimeOffset? ReadDate(string key)
    {
        var value = Preferences.Default.Get(key, string.Empty);
        return DateTimeOffset.TryParse(value, out var parsed) ? parsed : null;
    }

    private static void WriteDate(string key, DateTimeOffset? value)
    {
        if (value is null)
        {
            Preferences.Default.Remove(key);
            return;
        }

        Preferences.Default.Set(key, value.Value.ToString("O"));
    }
}

public static class AppFeatures
{
    public const string CadastreMap = "cadastre-map";
    public const string BasicSearch = "basic-search";
    public const string DrawingMeasurements = "drawing-measurements";
    public const string ProjectArchive = "project-archive";
    public const string Export = "export";
    public const string CloudSync = "cloud-sync";
    public const string OfflineMaps = "offline-maps";
    public const string AdvancedGeometry = "advanced-geometry";
    public const string GpsTrail = "gps-trail";
    public const string FiducialPoints = "fiducial-points";
}