namespace SQLInsight.Licensing;

/// <summary>
/// Checks a license text offline. Never throws on bad input: an invalid license is a state, not an error, and never
/// stops monitoring.
/// </summary>
public sealed class LicenseVerifier(TrustedKeys keys, TimeProvider time)
{
    public static readonly TimeSpan GracePeriod = TimeSpan.FromDays(30);

    public LicenseStatus Check(string? licenseText)
    {
        if (string.IsNullOrWhiteSpace(licenseText))
        {
            return new LicenseStatus(LicenseState.None, null, "Ingen licens: Community. Al overvågning er gratis; Hub-synkronisering og prioriteret support kræver et abonnement.");
        }

        var license = SignedDocument.Verify<License>(licenseText, keys, l => l.KeyId);
        if (license is null)
        {
            return new LicenseStatus(LicenseState.Invalid, null, "Licensen er ugyldig: signaturen passer ikke, eller teksten er beskadiget. Overvågningen fortsætter.");
        }

        var now = time.GetUtcNow();
        if (now <= license.ExpiresAt)
        {
            return new LicenseStatus(LicenseState.Valid, license, $"{license.Plan} til {license.Customer}, gyldig til {license.ExpiresAt:yyyy-MM-dd}.");
        }

        return now <= license.ExpiresAt + GracePeriod
            ? new LicenseStatus(LicenseState.ExpiredInGrace, license, $"Licensen udløb {license.ExpiresAt:yyyy-MM-dd}. Hub-synkronisering fortsætter til {(license.ExpiresAt + GracePeriod):yyyy-MM-dd}; forny venligst.")
            : new LicenseStatus(LicenseState.Expired, license, $"Licensen udløb {license.ExpiresAt:yyyy-MM-dd}. Overvågningen fortsætter; Hub-synkronisering er stoppet.");
    }
}