using System;
using Silk.NET.OpenGL;

namespace AcDream.App.Rendering;

/// <summary>
/// Two persistent GL sampler objects (Repeat + ClampToEdge) created once
/// per GL context. Renderers <see cref="GL.BindSampler"/> the appropriate
/// one to a texture unit instead of mutating per-texture
/// <c>GL_TEXTURE_WRAP_S/T</c> state — sampler state overrides the
/// texture's own wrap parameters, so two renderers can share the same
/// texture handle but sample it with different wrap modes safely.
///
/// <para>
/// Ported from
/// <c>references/WorldBuilder/Chorizite.OpenGLSDLBackend/OpenGLGraphicsDevice.cs:115-132</c>.
/// Filter modes match <see cref="TextureCache"/>'s upload defaults
/// (Linear / Linear, no mipmaps) so binding either sampler doesn't
/// change the visual filtering behavior — only the wrap behavior at
/// UVs outside [0, 1].
/// </para>
///
/// <para>
/// Lifetime: created once at GL init, disposed with the GL context.
/// Anything that binds a sampler MUST unbind it (<c>BindSampler(unit, 0)</c>)
/// before yielding to a renderer that doesn't use samplers, otherwise
/// the bound sampler's wrap mode will silently override that renderer's
/// per-texture wrap state.
/// </para>
/// </summary>
public sealed class SamplerCache : IDisposable
{
    private readonly GL _gl;

    /// <summary>Sampler with WrapS = WrapT = Repeat. The default for textures uploaded by <see cref="TextureCache"/>.</summary>
    public uint Wrap { get; }

    /// <summary>Sampler with WrapS = WrapT = ClampToEdge. Used by sky meshes whose authored UVs are strictly in [0, 1] to avoid bilinear-filter bleed at seam edges.</summary>
    public uint Clamp { get; }

    public SamplerCache(GL gl)
    {
        _gl = gl ?? throw new ArgumentNullException(nameof(gl));

        Wrap = _gl.GenSampler();
        _gl.SamplerParameter(Wrap, SamplerParameterI.WrapS, (int)TextureWrapMode.Repeat);
        _gl.SamplerParameter(Wrap, SamplerParameterI.WrapT, (int)TextureWrapMode.Repeat);
        _gl.SamplerParameter(Wrap, SamplerParameterI.MinFilter, (int)TextureMinFilter.Linear);
        _gl.SamplerParameter(Wrap, SamplerParameterI.MagFilter, (int)TextureMagFilter.Linear);

        Clamp = _gl.GenSampler();
        _gl.SamplerParameter(Clamp, SamplerParameterI.WrapS, (int)TextureWrapMode.ClampToEdge);
        _gl.SamplerParameter(Clamp, SamplerParameterI.WrapT, (int)TextureWrapMode.ClampToEdge);
        _gl.SamplerParameter(Clamp, SamplerParameterI.MinFilter, (int)TextureMinFilter.Linear);
        _gl.SamplerParameter(Clamp, SamplerParameterI.MagFilter, (int)TextureMagFilter.Linear);
    }

    public void Dispose()
    {
        if (Wrap != 0) _gl.DeleteSampler(Wrap);
        if (Clamp != 0) _gl.DeleteSampler(Clamp);
    }
}