namespace ytLive.Models;

/// <summary>
/// The one entitlement rule, as pure policy: what a build is allowed to emit.
///
/// <para><b>Why pixels and a frame rate rather than "720p".</b> The paid delta is output
/// quality, and a resolution name is a marketing word, not a measurable bound — 720p60 is
/// 921,600 pixels at twice the frame rate, and vertical 720×1280 is the same pixel count
/// with a different shape. A pixel budget plus a frame-rate ceiling expresses the same
/// promise without a lookup table that a new tier can quietly escape.</para>
///
/// <para><b>Fail closed.</b> Callers pass <c>pro: false</c> when entitlement is unknown,
/// unreadable or unresolved; the free profile is the default state, never the fallback
/// after an error.</para>
///
/// <para><b>This is not a feature gate.</b> Every feature, scene, overlay and the recording
/// itself stay available; only the emitted frame gets smaller. Never call it for anything
/// else — a cracked build buys almost nothing, which is the entire anti-piracy posture.</para>
/// </summary>
public static class OutputProfile
{
    /// <summary>Free ceiling: 921,600 px = 1280×720, i.e. one 720p frame.</summary>
    public const int FreeMaxPixels = 921_600;

    /// <summary>Free ceiling: 30 frames per second.</summary>
    public const int FreeMaxFps = 30;

    /// <summary>The named tier a capped build falls back to when nothing else qualifies.</summary>
    public const string FreeFallbackName = "720p30";

    /// <summary>Is this tier within the free budget? Pro may use anything shipped.</summary>
    public static bool IsAllowed(QualityOption tier, bool pro)
        => pro
           || (tier.Width * tier.Height <= FreeMaxPixels && tier.Fps <= FreeMaxFps);

    /// <summary>
    /// The tier a session will actually encode. A permitted selection passes through
    /// untouched (so Pro and the free tier's own 720p30 keep their exact bitrate); a
    /// disallowed one resolves to the best tier the budget allows — most pixels first, then
    /// most frames, then the cheapest bitrate — because silently encoding something the user
    /// did not pick is only acceptable if it is the closest legal thing to it.
    /// </summary>
    /// <param name="requested">What the dropdown says.</param>
    /// <param name="shipped">Every tier the build offers.</param>
    /// <param name="pro">Entitlement, already resolved. Unknown must be passed as false.</param>
    public static QualityOption Resolve(
        QualityOption requested, IEnumerable<QualityOption> shipped, bool pro)
    {
        if (IsAllowed(requested, pro)) return requested;

        var candidate = shipped
            .Where(tier => IsAllowed(tier, pro))
            .OrderByDescending(tier => tier.Width * tier.Height)
            .ThenByDescending(tier => tier.Fps)
            .ThenBy(tier => tier.Bitrate)
            .FirstOrDefault();

        // No shipped tier fits the budget: build the floor explicitly rather than trusting
        // the table. A build whose tiers were all redefined must still emit a legal frame.
        return candidate ?? new QualityOption(FreeFallbackName, FreeMaxFps, 6.0, 1280, 720);
    }
}