using System.Numerics;

namespace AcDream.App.Rendering;

/// <summary>
/// Result of a camera spring-arm sweep: the collided eye position AND the cell the swept
/// viewer-sphere ended in (retail <c>viewer_cell = sphere_path.curr_cell</c>, update_viewer
/// pc:92871). The cell is graph-tracked by the transition — no AABB, no grace frames — so it
/// is the robust per-frame "which cell is the camera in?" answer that roots the render.
/// </summary>
public readonly record struct CameraSweepResult(Vector3 Eye, uint ViewerCellId);

/// <summary>
/// Sweeps a small sphere from the camera pivot (player head) toward the
/// desired eye and returns the stopped (non-penetrating) eye + its cell. The seam that
/// lets <see cref="RetailChaseCamera"/> collide its eye without depending on
/// the physics engine directly (and stay unit-testable with a fake).
/// </summary>
public interface ICameraCollisionProbe
{
    /// <summary>
    /// Roll a collision sphere from <paramref name="pivot"/> to
    /// <paramref name="desiredEye"/>; return the position it reaches without
    /// penetrating geometry AND the cell it ended in. Mirrors retail
    /// <c>SmartBox::update_viewer</c>: when <paramref name="cellId"/> is indoor the
    /// sweep's start cell is seated at the pivot, and when there is no start cell or
    /// the sweep fails the eye snaps to <paramref name="playerPos"/> (retail
    /// <c>set_viewer(player_pos)</c>, viewer cell null).
    /// </summary>
    CameraSweepResult SweepEye(Vector3 pivot, Vector3 desiredEye, uint cellId, uint selfEntityId, Vector3 playerPos);
}