using System;
using System.Numerics;

namespace AcDream.Core.Lighting;

/// <summary>
/// Retail light-source kinds (r13 §12.1).
/// </summary>
public enum LightKind
{
    Directional = 0,  // sun, moon — no position, infinite range
    Point       = 1,  // torch, fireplace, spell aura
    Spot        = 2,  // cone-shaped (rare in AC, used for a few specific lamps)
}

/// <summary>
/// Per-frame light record. Used by <see cref="LightManager"/> and fed to
/// the shader UBO on every draw call.
///
/// <para>
/// Retail semantics (r13 §10.2):
/// <list type="bullet">
///   <item><description>
///     Hard cutoff at <see cref="Range"/> — no smoothstep, no distance
///     attenuation inside the range. "Crisp bubble of illumination."
///   </description></item>
///   <item><description>
///     Max 8 active lights (<see cref="LightManager.MaxActiveLights"/>),
///     ranked by distance-to-viewer. Slot 0 is reserved for the sun.
///   </description></item>
///   <item><description>
///     <see cref="IsLit"/> latches the <c>SetLightHook</c> value so
///     animations can toggle a light on/off (torch being lit, light
///     crystal activating).
///   </description></item>
/// </list>
/// </para>
/// </summary>
public sealed class LightSource
{
    public LightKind Kind;
    public Vector3   WorldPosition;
    public Vector3   WorldForward;    // for Spot/Directional
    public Vector3   ColorLinear = Vector3.One;   // R,G,B in [0,1], pre-brightness
    public float     Intensity = 1f;
    public float     Range = 10f;     // metres, hard cutoff
    public float     ConeAngle = 0f;  // radians, Spot only
    public uint      OwnerId;         // attached entity id; 0 = world-global
    public uint      CellId;          // owning cell id (0xLLLLNNNN); 0 = cell-less/global (viewer fill, sun).
                                      // Retail carries this on the RenderLight (insert_light arg6, +0x6c) for the
                                      // cross-cell block-offset distance math. #176 correction (2026-07-06): it is
                                      // NOT a pool filter — retail collects from ALL resident cells
                                      // (CEnvCell::visible_cell_table = the loaded-cell registry, not the flood);
                                      // acdream keeps the tag for probes ([indoor-light]/[seam-*]) + future parity.
    public bool      IsLit = true;    // SetLightHook latch
    public bool      IsDynamic;       // #143: true = D3D hardware path (1/d att, range×1.5);
                                      // false = static dat-baked bake (1/d³, range×1.3)

    // Cached each frame by LightManager.
    public float DistSq;
}

/// <summary>
/// Per-cell ambient + sun state. For outdoor cells this comes from the
/// R12 sky state; for indoor cells the EnvCell dat carries a per-cell
/// ambient override (r13 §3).
/// </summary>
public readonly record struct CellAmbientState(
    Vector3 AmbientColor,
    Vector3 SunColor,
    Vector3 SunDirection);