frienderer 0.3.0

// come on it's just OpenGL
#![allow(clippy::missing_safety_doc)]

use glam::UVec2;
use glow::HasContext;

use crate::is_opengl_debug_enabled;

pub fn slice_as_bytes<T>(slice: &[T]) -> &[u8] {
	unsafe { std::slice::from_raw_parts(slice.as_ptr() as *const u8, size_of_val(slice)) }
}

// --- debugging ---

pub unsafe fn push_debug_group(gl: &glow::Context, message: &str) {
	if is_opengl_debug_enabled() {
		unsafe {
			gl.push_debug_group(glow::DEBUG_SOURCE_APPLICATION, 0, message);
		}
	}
}

pub unsafe fn pop_debug_group(gl: &glow::Context) {
	if is_opengl_debug_enabled() {
		unsafe {
			gl.pop_debug_group();
		}
	}
}

// --- shader compilation ---

pub unsafe fn create_shader_program(gl: &glow::Context, vert_source: &str, frag_source: &str) -> glow::Program {
	unsafe {
		let vert_shader = gl.create_shader(glow::VERTEX_SHADER).unwrap();
		{
			gl.shader_source(vert_shader, vert_source);
			gl.compile_shader(vert_shader);
		}
		verify_shader(gl, vert_shader, "vert");

		let frag_shader = gl.create_shader(glow::FRAGMENT_SHADER).unwrap();
		{
			gl.shader_source(frag_shader, frag_source);
			gl.compile_shader(frag_shader);
		}
		verify_shader(gl, frag_shader, "frag");

		let program = gl.create_program().unwrap();
		{
			gl.attach_shader(program, vert_shader);
			gl.attach_shader(program, frag_shader);

			gl.link_program(program);
			gl.use_program(Some(program));

			gl.delete_shader(vert_shader);
			gl.delete_shader(frag_shader);
		}
		verify_program(gl, program);

		program
	}
}

pub unsafe fn verify_shader(gl: &glow::Context, shader: glow::Shader, ty: &str) {
	unsafe {
		if !gl.get_shader_compile_status(shader) {
			let log = gl.get_shader_info_log(shader);

			if !log.is_empty() {
				#[cfg(feature = "logging")]
				tracing::error!("SHADER COMPILE ERROR ({ty}): {log}");
			}
		}
	}
}

pub unsafe fn verify_program(gl: &glow::Context, program: glow::Program) {
	unsafe {
		if !gl.get_program_link_status(program) {
			let log = gl.get_program_info_log(program);

			if !log.is_empty() {
				#[cfg(feature = "logging")]
				tracing::error!("PROGRAM LINK ERROR: {log}");
			}
		}
	}
}

// --- framebuffers and textures ---

#[repr(C)]
#[derive(Debug, Clone)]
pub struct Framebuffer {
	pub fbo: glow::Framebuffer,
	pub texture: glow::Texture,
	pub size: UVec2,
}

pub unsafe fn create_framebuffer(
	gl: &glow::Context,
	name: &str,
	size: UVec2,
	wrapping: TextureWrapping,
) -> Framebuffer {
	unsafe {
		let fbo = gl.create_framebuffer().unwrap();
		gl.bind_framebuffer(glow::FRAMEBUFFER, Some(fbo));

		let texture = gl.create_texture().unwrap();
		upload_texture(
			gl,
			texture,
			size.x,
			size.y,
			None,
			wrapping,
			TextureInterpolation::Nearest,
		);

		gl.framebuffer_texture_2d(
			glow::FRAMEBUFFER,
			glow::COLOR_ATTACHMENT0,
			glow::TEXTURE_2D,
			Some(texture),
			0,
		);

		if gl.check_framebuffer_status(glow::FRAMEBUFFER) != glow::FRAMEBUFFER_COMPLETE {
			#[cfg(feature = "logging")]
			tracing::error!("{name} framebuffer ({}x{}) not complete", size.x, size.y);
		}

		Framebuffer { fbo, texture, size }
	}
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
#[allow(unused)]
pub enum TextureWrapping {
	/// The integer part of the coordinate will be ignored and a repeating pattern is formed.
	Repeat,
	/// The texture will also be repeated, but it will be mirrored when the integer part of the coordinate is odd.
	MirroredRepeat,
	/// The coordinate will simply be clamped between 0 and 1.
	ClampToEdge,
	/// The coordinates that fall outside the range will be given a specified border color.
	ClampToBorder,
}

impl TextureWrapping {
	pub fn to_glenum(self) -> u32 {
		match self {
			TextureWrapping::Repeat => glow::REPEAT,
			TextureWrapping::MirroredRepeat => glow::MIRRORED_REPEAT,
			TextureWrapping::ClampToEdge => glow::CLAMP_TO_EDGE,
			TextureWrapping::ClampToBorder => glow::CLAMP_TO_BORDER,
		}
	}
}

#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
pub enum TextureInterpolation {
	Nearest,
	Linear,
}

impl TextureInterpolation {
	fn to_glenum(self) -> u32 {
		match self {
			TextureInterpolation::Nearest => glow::NEAREST,
			TextureInterpolation::Linear => glow::LINEAR,
		}
	}
}

pub unsafe fn upload_texture(
	gl: &glow::Context,
	texture: glow::Texture,
	width: u32,
	height: u32,
	pixels: Option<&[u8]>,
	wrapping: TextureWrapping,
	interpolation: TextureInterpolation,
) {
	let clamp = wrapping.to_glenum();
	let interpolation = interpolation.to_glenum();

	unsafe {
		gl.bind_texture(glow::TEXTURE_2D, Some(texture));

		gl.tex_image_2d(
			glow::TEXTURE_2D,
			0,
			glow::RGBA8 as i32,
			width as i32,
			height as i32,
			0,
			glow::RGBA,
			glow::UNSIGNED_BYTE,
			glow::PixelUnpackData::Slice(pixels),
		);

		gl.tex_parameter_i32(glow::TEXTURE_2D, glow::TEXTURE_MIN_FILTER, interpolation as i32);
		gl.tex_parameter_i32(glow::TEXTURE_2D, glow::TEXTURE_MAG_FILTER, interpolation as i32);
		gl.tex_parameter_i32(glow::TEXTURE_2D, glow::TEXTURE_WRAP_S, clamp as i32);
		gl.tex_parameter_i32(glow::TEXTURE_2D, glow::TEXTURE_WRAP_T, clamp as i32);
	}
}

pub unsafe fn upload_subtexture(
	gl: &glow::Context,
	texture: glow::Texture,
	x: u32,
	y: u32,
	width: u32,
	height: u32,
	pixels: Option<&[u8]>,
) {
	unsafe {
		gl.bind_texture(glow::TEXTURE_2D, Some(texture));
		gl.tex_sub_image_2d(
			glow::TEXTURE_2D,
			0,
			x as i32,
			y as i32,
			width as i32,
			height as i32,
			glow::RGBA,
			glow::UNSIGNED_BYTE,
			glow::PixelUnpackData::Slice(pixels),
		);
	}
}