using System;
using System.Collections.Immutable;
using Sandbox;
using Sandbox.Rendering;
using Goo;

namespace Goo.Internal;

// Snapshot of a panel's resolved custom-draw state, written by the Applier and read by StatefulDrawPanel.Draw. All-default means no user custom draw.
internal readonly struct DrawState : IEquatable<DrawState>
{
    public readonly Material? Material;
    public readonly ImmutableArray<UniformValue> Uniforms;
    public readonly Action<CommandList, Rect>? Draw;

    public DrawState(Material? material, ImmutableArray<UniformValue> uniforms, Action<CommandList, Rect>? draw)
    {
        Material = material;
        Uniforms = uniforms;
        Draw = draw;
    }

    public static readonly DrawState Empty
        = new(null, ImmutableArray<UniformValue>.Empty, null);

    public bool IsEmpty => Material is null && Uniforms.IsDefaultOrEmpty && Draw is null;

    public bool Equals(DrawState other)
    {
        if (!ReferenceEquals(Material, other.Material)) return false;
        if (!ReferenceEquals(Draw, other.Draw)) return false;
        return UniformValue.SequenceEqual(Uniforms, other.Uniforms);
    }

    public override bool Equals(object? obj) => obj is DrawState s && Equals(s);
    public override int GetHashCode() => HashCode.Combine(Material, Uniforms.Length, Draw);
}