2 files changed, 407 insertions, 0 deletions
diff --git a/resources/src/lib.rs b/resources/src/lib.rs
new file mode 100644
index 0000000..9cbbba0
--- /dev/null
+++ b/resources/src/lib.rs
@@ -0,0 +1,13 @@
+#![feature(new_uninit, let_chains)]
+#![warn(clippy::nursery, clippy::pedantic)]
+#![allow(clippy::module_name_repetitions)]
+
+pub mod texture;
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
+pub enum Priority {
+	Unnecessary,
+	Possible(u8),
+	Eventual(u8),
+	Urgent,
+}
diff --git a/resources/src/texture.rs b/resources/src/texture.rs
new file mode 100644
index 0000000..3a5bf3e
--- /dev/null
+++ b/resources/src/texture.rs
@@ -0,0 +1,394 @@
+use std::cmp::Reverse;
+use std::mem;
+use std::path::Path;
+use std::sync::atomic::{AtomicBool, AtomicUsize, Ordering};
+use std::sync::Arc;
+
+use dashmap::DashMap;
+use image::ImageBuffer;
+use parking_lot::Mutex;
+use thiserror::Error;
+
+use crate::Priority;
+
+/// The next texture ID
+static NEXT_TEXTURE_ID: AtomicUsize = AtomicUsize::new(0);
+
+/// A unique identifier for a texture
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+pub struct TextureId(usize);
+
+impl TextureId {
+	fn new() -> Self {
+		Self(NEXT_TEXTURE_ID.fetch_add(1, Ordering::Relaxed))
+	}
+}
+
+/// These are the formats supported by the renderer.
+// TODO make these feature-enabled
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
+#[non_exhaustive]
+pub enum ImageFormat {
+	Bmp,
+	Ico,
+	Farbfeld,
+}
+
+impl From<ImageFormat> for image::ImageFormat {
+	fn from(format: ImageFormat) -> Self {
+		match format {
+			ImageFormat::Bmp => Self::Bmp,
+			ImageFormat::Ico => Self::Ico,
+			ImageFormat::Farbfeld => Self::Farbfeld,
+		}
+	}
+}
+
+#[derive(Debug, Error)]
+#[error("{}", .0)]
+pub struct DecodingError(#[from] image::error::DecodingError);
+
+#[allow(clippy::missing_const_for_fn)]
+fn convert_image_decoding(e: image::ImageError) -> DecodingError {
+	if let image::ImageError::Decoding(de) = e {
+		de.into()
+	} else {
+		unreachable!("No other error should be possible")
+	}
+}
+
+#[derive(Debug, Error)]
+pub enum LoadError {
+	#[error("{}", .0)]
+	Decoding(#[from] DecodingError),
+	#[error("{}", .0)]
+	Io(#[from] std::io::Error),
+}
+
+fn convert_image_load_error(e: image::ImageError) -> LoadError {
+	match e {
+		image::ImageError::Decoding(de) => LoadError::Decoding(de.into()),
+		image::ImageError::IoError(ioe) => ioe.into(),
+		_ => unreachable!("No other error should be possible"),
+	}
+}
+
+pub type Rgba16Texture = image::ImageBuffer<image::Rgba<u16>, Box<[u16]>>;
+
+fn vec_image_to_box(vec_image: image::ImageBuffer<image::Rgba<u16>, Vec<u16>>) -> Rgba16Texture {
+	let width = vec_image.width();
+	let height = vec_image.height();
+	let buf = vec_image.into_raw().into_boxed_slice();
+	ImageBuffer::from_raw(width, height, buf).expect("image buffer is too small")
+}
+
+/// Get the size, in bytes, of the texture
+#[allow(clippy::missing_const_for_fn)]
+fn texture_size(image: &Rgba16Texture) -> usize {
+	image.len() * mem::size_of::<image::Rgba<u16>>()
+}
+
+/// A texture from disk
+struct TextureFile {
+	path: Box<Path>,
+	texture: Option<Arc<Rgba16Texture>>,
+}
+
+impl TextureFile {
+	/// This doesn't load the texture
+	#[allow(clippy::missing_const_for_fn)]
+	fn new(path: impl AsRef<Path>) -> Self {
+		Self {
+			path: path.as_ref().into(),
+			texture: None,
+		}
+	}
+
+	const fn is_loaded(&self) -> bool {
+		self.texture.is_some()
+	}
+
+	fn load(&mut self) -> Result<&Rgba16Texture, LoadError> {
+		if self.texture.is_none() {
+			log::warn!("{} was not pre-loaded", self.path.to_string_lossy());
+			let texture = image::open(&self.path).map_err(convert_image_load_error)?;
+			let texture = texture.to_rgba16();
+			let texture = Arc::new(vec_image_to_box(texture));
+			self.texture = Some(texture);
+		}
+
+		Ok(self.texture.as_ref().expect("the texture wasn't loaded"))
+	}
+
+	fn loaded_texture(&self) -> Option<&Rgba16Texture> {
+		self.texture.as_deref()
+	}
+
+	fn is_used(&self) -> bool {
+		let Some(arc) = &self.texture else { return false };
+		Arc::strong_count(arc) > 1
+	}
+
+	/// Unloads the texture from memory if it isn't being used
+	fn unload(&mut self) {
+		if !self.is_used() {
+			self.texture = None;
+		}
+	}
+
+	/// The amount of heap memory used, in bytes. This returns 0 if the texture
+	/// hasn't been loaded yet.
+	fn allocated_size(&self) -> usize {
+		self.texture.as_ref().map_or(0, |t| texture_size(t))
+	}
+}
+
+enum TextureBuffer {
+	Memory(Arc<Rgba16Texture>),
+	Disk(TextureFile),
+}
+
+struct Texture {
+	priority: Priority,
+	queued_priority: Arc<Mutex<Option<Priority>>>,
+	buffer: TextureBuffer,
+}
+
+impl Texture {
+	fn from_buffer(texture: Rgba16Texture) -> Self {
+		Self {
+			priority: Priority::Urgent, // indicates that it can't be unloaded
+			queued_priority: Arc::new(Mutex::new(None)),
+			buffer: TextureBuffer::Memory(Arc::new(texture)),
+		}
+	}
+
+	fn from_path(path: impl AsRef<Path>, priority: Priority) -> Self {
+		Self {
+			priority,
+			queued_priority: Arc::new(Mutex::new(None)),
+			buffer: TextureBuffer::Disk(TextureFile::new(path)),
+		}
+	}
+
+	const fn priority(&self) -> Priority {
+		self.priority
+	}
+
+	fn _set_priority(buffer: &TextureBuffer, src: &mut Priority, priority: Priority) -> bool {
+		// memory textures and textures in use should always be urgent
+		if let TextureBuffer::Disk(disk) = buffer && !disk.is_used() {
+			*src = priority;
+			true
+		} else {
+			false
+		}
+	}
+
+	fn unqueue_priority(&mut self) {
+		let mut queued_priority = self.queued_priority.lock();
+		let unqueued_priority = queued_priority.unwrap_or(Priority::Unnecessary);
+
+		if Self::_set_priority(&self.buffer, &mut self.priority, unqueued_priority) {
+			*queued_priority = None;
+		}
+	}
+
+	fn set_priority(&mut self, priority: Priority) {
+		Self::_set_priority(&self.buffer, &mut self.priority, priority);
+	}
+
+	fn load_texture(&mut self) -> Result<&Rgba16Texture, LoadError> {
+		match &mut self.buffer {
+			TextureBuffer::Memory(ref texture) => Ok(texture),
+			TextureBuffer::Disk(file) => file.load(),
+		}
+	}
+
+	/// If the texture is loaded, return it.
+	fn loaded_texture(&self) -> Option<&Rgba16Texture> {
+		match &self.buffer {
+			TextureBuffer::Memory(ref texture) => Some(texture),
+			TextureBuffer::Disk(file) => file.loaded_texture(),
+		}
+	}
+
+	fn unload(&mut self) {
+		if let TextureBuffer::Disk(file) = &mut self.buffer {
+			file.unload();
+		}
+	}
+
+	/// The amount of heap memory used for the texture, if any
+	fn allocated_size(&self) -> usize {
+		match &self.buffer {
+			TextureBuffer::Memory(texture) => texture_size(texture),
+			TextureBuffer::Disk(file) => file.allocated_size(),
+		}
+	}
+
+	const fn is_loaded(&self) -> bool {
+		match &self.buffer {
+			TextureBuffer::Memory(_) => true,
+			TextureBuffer::Disk(file) => file.is_loaded(),
+		}
+	}
+}
+
+pub struct TextureManager {
+	textures: DashMap<TextureId, Texture>,
+	max_size: usize,
+	needs_atlas_update: AtomicBool,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct TextureManagerConfig {
+	/// The initial capacity of the texture manager. This defaults to 500 textures.
+	pub initial_capacity: usize,
+	/// The maximum amount of heap usage acceptable. Defaults to 10 MiB.
+	pub max_size: usize,
+}
+
+impl Default for TextureManagerConfig {
+	fn default() -> Self {
+		Self {
+			initial_capacity: 500,
+			max_size: 10 * 1024 * 1024, // 10 MiB
+		}
+	}
+}
+
+impl TextureManager {
+	/// Create a new `TextureManager` with the given config options.
+	#[must_use]
+	pub fn new(config: &TextureManagerConfig) -> Self {
+		let textures = DashMap::with_capacity(config.initial_capacity);
+
+		Self {
+			textures,
+			max_size: config.max_size,
+			needs_atlas_update: AtomicBool::new(false),
+		}
+	}
+
+	/// Load textures into memory that will be needed soon. Unload unnecessary textures
+	pub fn cache_files(&self) {
+		let mut textures: Vec<_> = self
+			.textures
+			.iter_mut()
+			.map(|mut t| {
+				t.value_mut().unqueue_priority();
+				t
+			})
+			.collect();
+		textures.sort_by_key(|t2| Reverse(t2.priority()));
+
+		let max_size = self.max_size;
+		let mut total_size = 0;
+
+		for texture in &mut textures {
+			drop(texture.load_texture());
+			total_size += texture.allocated_size();
+			if total_size > max_size && texture.priority() != Priority::Urgent {
+				texture.unload();
+				return;
+			}
+		}
+	}
+
+	/// Loads a texture from memory in the given format.
+	///
+	/// # Errors
+	///
+	/// This returns `Expected(DecodingError)` if the given buffer was invalid
+	/// for the given format.
+	pub fn load_from_memory(
+		&self,
+		buf: &[u8],
+		format: ImageFormat,
+	) -> Result<TextureId, DecodingError> {
+		let id = TextureId::new();
+		let texture = image::load_from_memory_with_format(buf, format.into());
+		let texture = texture.map_err(convert_image_decoding)?;
+		let texture = texture.into_rgba16();
+		let texture = vec_image_to_box(texture);
+		let texture = Texture::from_buffer(texture);
+
+		self.textures.insert(id, texture);
+		self.needs_atlas_update.store(true, Ordering::Release);
+
+		Ok(id)
+	}
+
+	/// Loads a texture from disk.
+	///
+	/// # Errors
+	///
+	/// This returns an error if `priority` is set to [`Priority::Urgent`] but
+	/// there was an error in loading the file to a texture.
+	pub fn load_from_file(
+		&self,
+		path: impl AsRef<Path>,
+		priority: Priority,
+	) -> Result<TextureId, LoadError> {
+		let id = TextureId::new();
+		let mut texture = Texture::from_path(path, priority);
+
+		if priority == Priority::Urgent {
+			match texture.load_texture() {
+				Ok(_) => {
+					self.textures.insert(id, texture);
+					self.needs_atlas_update.store(true, Ordering::Release);
+				}
+				Err(e) => {
+					self.textures.insert(id, texture);
+					return Err(e);
+				}
+			}
+		} else {
+			self.textures.insert(id, texture);
+		}
+
+		Ok(id)
+	}
+
+	/// Loads a texture from disk.
+	///
+	/// # Errors
+	///
+	/// This returns an error if `priority` is set to [`Priority::Urgent`] but
+	/// there was an error in loading the file to a texture.
+	pub fn set_priority(&self, id: TextureId, priority: Priority) -> Result<(), LoadError> {
+		let mut texture = self.textures.get_mut(&id).expect("invalid texture id");
+		texture.set_priority(priority);
+
+		if !texture.is_loaded() && priority == Priority::Urgent {
+			let mut texture = self.textures.get_mut(&id).expect("invalid texture id");
+			texture.load_texture()?;
+			self.needs_atlas_update.store(true, Ordering::Release);
+		}
+
+		Ok(())
+	}
+
+	/// This returns `true` if a texture has been set to have an urgent
+	/// priority since the last time this function was called.
+	pub fn needs_atlas_update(&self) -> bool {
+		self.needs_atlas_update.fetch_and(false, Ordering::AcqRel)
+	}
+
+	/// Load a texture into memory, if it hasn't been already. Then return a
+	/// copy of the texture.
+	///
+	/// # Errors
+	///
+	/// This returns an error if an error occurs in loading the texture from
+	/// disk, such as the file not existing, or not being a valid texture.
+	pub fn load_texture(&self, id: TextureId) -> Result<Rgba16Texture, LoadError> {
+		self.textures
+			.get_mut(&id)
+			.expect("the TextureId was invalid")
+			.load_texture()
+			.cloned()
+	}
+}