use super::metal_atlas::MetalAtlas;
use crate::{
    AtlasTextureId, Background, Bounds, ContentMask, DevicePixels, MonochromeSprite, PaintSurface,
    Path, PathVertex, PolychromeSprite, PrimitiveBatch, Quad, ScaledPixels, Scene, Shadow, Size,
    Surface, Underline, point, size,
};
use anyhow::Result;
use block::ConcreteBlock;
use cocoa::{
    base::{NO, YES},
    foundation::{NSSize, NSUInteger},
    quartzcore::AutoresizingMask,
};
use core_foundation::base::TCFType;
use core_video::{
    metal_texture::CVMetalTextureGetTexture, metal_texture_cache::CVMetalTextureCache,
    pixel_buffer::kCVPixelFormatType_420YpCbCr8BiPlanarFullRange,
};
use foreign_types::{ForeignType, ForeignTypeRef};
use metal::{
    CAMetalLayer, CommandQueue, MTLDrawPrimitivesIndirectArguments, MTLPixelFormat,
    MTLResourceOptions, NSRange,
};
use objc::{self, msg_send, sel, sel_impl};
use parking_lot::Mutex;
use std::{cell::Cell, ffi::c_void, mem, ptr, sync::Arc};

// Exported to metal
pub(crate) type PointF = crate::Point<f32>;

#[cfg(not(feature = "runtime_shaders"))]
const SHADERS_METALLIB: &[u8] = include_bytes!(concat!(env!("OUT_DIR"), "/shaders.metallib"));
#[cfg(feature = "runtime_shaders")]
const SHADERS_SOURCE_FILE: &str = include_str!(concat!(env!("OUT_DIR"), "/stitched_shaders.metal"));

pub type Context = Arc<Mutex<InstanceBufferPool>>;
pub type Renderer = MetalRenderer;

pub unsafe fn new_renderer(
    context: self::Context,
    _native_window: *mut c_void,
    _native_view: *mut c_void,
    _bounds: crate::Size<f32>,
    _transparent: bool,
) -> Renderer {
    MetalRenderer::new(context)
}

pub(crate) struct InstanceBufferPool {
    buffer_size: usize,
    buffers: Vec<metal::Buffer>,
}

impl Default for InstanceBufferPool {
    fn default() -> Self {
        Self {
            buffer_size: 2 * 1024 * 1024,
            buffers: Vec::new(),
        }
    }
}

pub(crate) struct InstanceBuffer {
    metal_buffer: metal::Buffer,
    size: usize,
}

impl InstanceBufferPool {
    pub(crate) fn reset(&mut self, buffer_size: usize) {
        self.buffer_size = buffer_size;
        self.buffers.clear();
    }

    pub(crate) fn acquire(&mut self, device: &metal::Device) -> InstanceBuffer {
        let buffer = self.buffers.pop().unwrap_or_else(|| {
            device.new_buffer(
                self.buffer_size as u64,
                MTLResourceOptions::StorageModeManaged,
            )
        });
        InstanceBuffer {
            metal_buffer: buffer,
            size: self.buffer_size,
        }
    }

    pub(crate) fn release(&mut self, buffer: InstanceBuffer) {
        if buffer.size == self.buffer_size {
            self.buffers.push(buffer.metal_buffer)
        }
    }
}

pub(crate) struct MetalRenderer {
    device: metal::Device,
    layer: metal::MetalLayer,
    presents_with_transaction: bool,
    command_queue: CommandQueue,
    path_pipeline_state: metal::RenderPipelineState,
    shadows_pipeline_state: metal::RenderPipelineState,
    quads_pipeline_state: metal::RenderPipelineState,
    underlines_pipeline_state: metal::RenderPipelineState,
    monochrome_sprites_pipeline_state: metal::RenderPipelineState,
    polychrome_sprites_pipeline_state: metal::RenderPipelineState,
    surfaces_pipeline_state: metal::RenderPipelineState,
    unit_vertices: metal::Buffer,
    #[allow(clippy::arc_with_non_send_sync)]
    instance_buffer_pool: Arc<Mutex<InstanceBufferPool>>,
    sprite_atlas: Arc<MetalAtlas>,
    core_video_texture_cache: core_video::metal_texture_cache::CVMetalTextureCache,
    sample_count: u64,
    msaa_texture: Option<metal::Texture>,
}

impl MetalRenderer {
    pub fn new(instance_buffer_pool: Arc<Mutex<InstanceBufferPool>>) -> Self {
        // Prefer low‐power integrated GPUs on Intel Mac. On Apple
        // Silicon, there is only ever one GPU, so this is equivalent to
        // `metal::Device::system_default()`.
        let mut devices = metal::Device::all();
        devices.sort_by_key(|device| (device.is_removable(), device.is_low_power()));
        let Some(device) = devices.pop() else {
            log::error!("unable to access a compatible graphics device");
            std::process::exit(1);
        };

        let layer = metal::MetalLayer::new();
        layer.set_device(&device);
        layer.set_pixel_format(MTLPixelFormat::BGRA8Unorm);
        layer.set_opaque(false);
        layer.set_maximum_drawable_count(3);
        unsafe {
            let _: () = msg_send![&*layer, setAllowsNextDrawableTimeout: NO];
            let _: () = msg_send![&*layer, setNeedsDisplayOnBoundsChange: YES];
            let _: () = msg_send![
                &*layer,
                setAutoresizingMask: AutoresizingMask::WIDTH_SIZABLE
                    | AutoresizingMask::HEIGHT_SIZABLE
            ];
        }
        #[cfg(feature = "runtime_shaders")]
        let library = device
            .new_library_with_source(&SHADERS_SOURCE_FILE, &metal::CompileOptions::new())
            .expect("error building metal library");
        #[cfg(not(feature = "runtime_shaders"))]
        let library = device
            .new_library_with_data(SHADERS_METALLIB)
            .expect("error building metal library");

        fn to_float2_bits(point: PointF) -> u64 {
            let mut output = point.y.to_bits() as u64;
            output <<= 32;
            output |= point.x.to_bits() as u64;
            output
        }

        let unit_vertices = [
            to_float2_bits(point(0., 0.)),
            to_float2_bits(point(1., 0.)),
            to_float2_bits(point(0., 1.)),
            to_float2_bits(point(0., 1.)),
            to_float2_bits(point(1., 0.)),
            to_float2_bits(point(1., 1.)),
        ];
        let unit_vertices = device.new_buffer_with_data(
            unit_vertices.as_ptr() as *const c_void,
            mem::size_of_val(&unit_vertices) as u64,
            MTLResourceOptions::StorageModeManaged,
        );

        let sample_count = [4, 2, 1]
            .into_iter()
            .find(|count| device.supports_texture_sample_count(*count))
            .unwrap_or(1);

        let path_pipeline_state = build_pipeline_state(
            &device,
            &library,
            "paths",
            "path_vertex",
            "path_fragment",
            MTLPixelFormat::BGRA8Unorm,
            sample_count,
        );
        let shadows_pipeline_state = build_pipeline_state(
            &device,
            &library,
            "shadows",
            "shadow_vertex",
            "shadow_fragment",
            MTLPixelFormat::BGRA8Unorm,
            sample_count,
        );
        let quads_pipeline_state = build_pipeline_state(
            &device,
            &library,
            "quads",
            "quad_vertex",
            "quad_fragment",
            MTLPixelFormat::BGRA8Unorm,
            sample_count,
        );
        let underlines_pipeline_state = build_pipeline_state(
            &device,
            &library,
            "underlines",
            "underline_vertex",
            "underline_fragment",
            MTLPixelFormat::BGRA8Unorm,
            sample_count,
        );
        let monochrome_sprites_pipeline_state = build_pipeline_state(
            &device,
            &library,
            "monochrome_sprites",
            "monochrome_sprite_vertex",
            "monochrome_sprite_fragment",
            MTLPixelFormat::BGRA8Unorm,
            sample_count,
        );
        let polychrome_sprites_pipeline_state = build_pipeline_state(
            &device,
            &library,
            "polychrome_sprites",
            "polychrome_sprite_vertex",
            "polychrome_sprite_fragment",
            MTLPixelFormat::BGRA8Unorm,
            sample_count,
        );
        let surfaces_pipeline_state = build_pipeline_state(
            &device,
            &library,
            "surfaces",
            "surface_vertex",
            "surface_fragment",
            MTLPixelFormat::BGRA8Unorm,
            sample_count,
        );

        let command_queue = device.new_command_queue();
        let sprite_atlas = Arc::new(MetalAtlas::new(device.clone()));
        let core_video_texture_cache =
            CVMetalTextureCache::new(None, device.clone(), None).unwrap();
        let msaa_texture = create_msaa_texture(&device, &layer, sample_count);

        Self {
            device,
            layer,
            presents_with_transaction: false,
            command_queue,
            path_pipeline_state,
            shadows_pipeline_state,
            quads_pipeline_state,
            underlines_pipeline_state,
            monochrome_sprites_pipeline_state,
            polychrome_sprites_pipeline_state,
            surfaces_pipeline_state,
            unit_vertices,
            instance_buffer_pool,
            sprite_atlas,
            core_video_texture_cache,
            sample_count,
            msaa_texture,
        }
    }

    pub fn layer(&self) -> &metal::MetalLayerRef {
        &self.layer
    }

    pub fn layer_ptr(&self) -> *mut CAMetalLayer {
        self.layer.as_ptr()
    }

    pub fn sprite_atlas(&self) -> &Arc<MetalAtlas> {
        &self.sprite_atlas
    }

    pub fn set_presents_with_transaction(&mut self, presents_with_transaction: bool) {
        self.presents_with_transaction = presents_with_transaction;
        self.layer
            .set_presents_with_transaction(presents_with_transaction);
    }

    pub fn update_drawable_size(&mut self, size: Size<DevicePixels>) {
        let size = NSSize {
            width: size.width.0 as f64,
            height: size.height.0 as f64,
        };
        unsafe {
            let _: () = msg_send![
                self.layer(),
                setDrawableSize: size
            ];
        }

        self.msaa_texture = create_msaa_texture(&self.device, &self.layer, self.sample_count);
    }

    pub fn update_transparency(&self, _transparent: bool) {
        // todo(mac)?
    }

    pub fn destroy(&self) {
        // nothing to do
    }

    pub fn draw(&mut self, scene: &Scene) {
        let layer = self.layer.clone();
        let viewport_size = layer.drawable_size();
        let viewport_size: Size<DevicePixels> = size(
            (viewport_size.width.ceil() as i32).into(),
            (viewport_size.height.ceil() as i32).into(),
        );
        let drawable = if let Some(drawable) = layer.next_drawable() {
            drawable
        } else {
            log::error!(
                "failed to retrieve next drawable, drawable size: {:?}",
                viewport_size
            );
            return;
        };

        loop {
            let mut instance_buffer = self.instance_buffer_pool.lock().acquire(&self.device);

            let command_buffer =
                self.draw_primitives(scene, &mut instance_buffer, drawable, viewport_size);

            match command_buffer {
                Ok(command_buffer) => {
                    let instance_buffer_pool = self.instance_buffer_pool.clone();
                    let instance_buffer = Cell::new(Some(instance_buffer));
                    let block = ConcreteBlock::new(move |_| {
                        if let Some(instance_buffer) = instance_buffer.take() {
                            instance_buffer_pool.lock().release(instance_buffer);
                        }
                    });
                    let block = block.copy();
                    command_buffer.add_completed_handler(&block);

                    if self.presents_with_transaction {
                        command_buffer.commit();
                        command_buffer.wait_until_scheduled();
                        drawable.present();
                    } else {
                        command_buffer.present_drawable(drawable);
                        command_buffer.commit();
                    }
                    return;
                }
                Err(err) => {
                    log::error!(
                        "failed to render: {}. retrying with larger instance buffer size",
                        err
                    );
                    let mut instance_buffer_pool = self.instance_buffer_pool.lock();
                    let buffer_size = instance_buffer_pool.buffer_size;
                    if buffer_size >= 256 * 1024 * 1024 {
                        log::error!("instance buffer size grew too large: {}", buffer_size);
                        break;
                    }
                    instance_buffer_pool.reset(buffer_size * 2);
                    log::info!(
                        "increased instance buffer size to {}",
                        instance_buffer_pool.buffer_size
                    );
                }
            }
        }
    }

    fn draw_primitives(
        &mut self,
        scene: &Scene,
        instance_buffer: &mut InstanceBuffer,
        drawable: &metal::MetalDrawableRef,
        viewport_size: Size<DevicePixels>,
    ) -> Result<metal::CommandBuffer> {
        let command_queue = self.command_queue.clone();
        let command_buffer = command_queue.new_command_buffer();
        let mut instance_offset = 0;
        let render_pass_descriptor = metal::RenderPassDescriptor::new();
        let color_attachment = render_pass_descriptor
            .color_attachments()
            .object_at(0)
            .unwrap();

        if let Some(msaa_texture_ref) = self.msaa_texture.as_deref() {
            color_attachment.set_texture(Some(msaa_texture_ref));
            color_attachment.set_load_action(metal::MTLLoadAction::Clear);
            color_attachment.set_store_action(metal::MTLStoreAction::MultisampleResolve);
            color_attachment.set_resolve_texture(Some(drawable.texture()));
        } else {
            color_attachment.set_load_action(metal::MTLLoadAction::Clear);
            color_attachment.set_texture(Some(drawable.texture()));
            color_attachment.set_store_action(metal::MTLStoreAction::Store);
        }

        let alpha = if self.layer.is_opaque() { 1. } else { 0. };
        color_attachment.set_clear_color(metal::MTLClearColor::new(0., 0., 0., alpha));
        let command_encoder = command_buffer.new_render_command_encoder(render_pass_descriptor);

        command_encoder.set_viewport(metal::MTLViewport {
            originX: 0.0,
            originY: 0.0,
            width: i32::from(viewport_size.width) as f64,
            height: i32::from(viewport_size.height) as f64,
            znear: 0.0,
            zfar: 1.0,
        });

        for batch in scene.batches() {
            let ok = match batch {
                PrimitiveBatch::Shadows(shadows) => self.draw_shadows(
                    shadows,
                    instance_buffer,
                    &mut instance_offset,
                    viewport_size,
                    command_encoder,
                ),
                PrimitiveBatch::Quads(quads) => self.draw_quads(
                    quads,
                    instance_buffer,
                    &mut instance_offset,
                    viewport_size,
                    command_encoder,
                ),
                PrimitiveBatch::Paths(paths) => self.draw_paths(
                    paths,
                    instance_buffer,
                    &mut instance_offset,
                    viewport_size,
                    command_encoder,
                ),
                PrimitiveBatch::Underlines(underlines) => self.draw_underlines(
                    underlines,
                    instance_buffer,
                    &mut instance_offset,
                    viewport_size,
                    command_encoder,
                ),
                PrimitiveBatch::MonochromeSprites {
                    texture_id,
                    sprites,
                } => self.draw_monochrome_sprites(
                    texture_id,
                    sprites,
                    instance_buffer,
                    &mut instance_offset,
                    viewport_size,
                    command_encoder,
                ),
                PrimitiveBatch::PolychromeSprites {
                    texture_id,
                    sprites,
                } => self.draw_polychrome_sprites(
                    texture_id,
                    sprites,
                    instance_buffer,
                    &mut instance_offset,
                    viewport_size,
                    command_encoder,
                ),
                PrimitiveBatch::Surfaces(surfaces) => self.draw_surfaces(
                    surfaces,
                    instance_buffer,
                    &mut instance_offset,
                    viewport_size,
                    command_encoder,
                ),
            };

            if !ok {
                command_encoder.end_encoding();
                anyhow::bail!(
                    "scene too large: {} paths, {} shadows, {} quads, {} underlines, {} mono, {} poly, {} surfaces",
                    scene.paths.len(),
                    scene.shadows.len(),
                    scene.quads.len(),
                    scene.underlines.len(),
                    scene.monochrome_sprites.len(),
                    scene.polychrome_sprites.len(),
                    scene.surfaces.len(),
                );
            }
        }

        command_encoder.end_encoding();

        instance_buffer.metal_buffer.did_modify_range(NSRange {
            location: 0,
            length: instance_offset as NSUInteger,
        });
        Ok(command_buffer.to_owned())
    }

    fn draw_shadows(
        &self,
        shadows: &[Shadow],
        instance_buffer: &mut InstanceBuffer,
        instance_offset: &mut usize,
        viewport_size: Size<DevicePixels>,
        command_encoder: &metal::RenderCommandEncoderRef,
    ) -> bool {
        if shadows.is_empty() {
            return true;
        }
        align_offset(instance_offset);

        command_encoder.set_render_pipeline_state(&self.shadows_pipeline_state);
        command_encoder.set_vertex_buffer(
            ShadowInputIndex::Vertices as u64,
            Some(&self.unit_vertices),
            0,
        );
        command_encoder.set_vertex_buffer(
            ShadowInputIndex::Shadows as u64,
            Some(&instance_buffer.metal_buffer),
            *instance_offset as u64,
        );
        command_encoder.set_fragment_buffer(
            ShadowInputIndex::Shadows as u64,
            Some(&instance_buffer.metal_buffer),
            *instance_offset as u64,
        );

        command_encoder.set_vertex_bytes(
            ShadowInputIndex::ViewportSize as u64,
            mem::size_of_val(&viewport_size) as u64,
            &viewport_size as *const Size<DevicePixels> as *const _,
        );

        let shadow_bytes_len = mem::size_of_val(shadows);
        let buffer_contents =
            unsafe { (instance_buffer.metal_buffer.contents() as *mut u8).add(*instance_offset) };

        let next_offset = *instance_offset + shadow_bytes_len;
        if next_offset > instance_buffer.size {
            return false;
        }

        unsafe {
            ptr::copy_nonoverlapping(
                shadows.as_ptr() as *const u8,
                buffer_contents,
                shadow_bytes_len,
            );
        }

        command_encoder.draw_primitives_instanced(
            metal::MTLPrimitiveType::Triangle,
            0,
            6,
            shadows.len() as u64,
        );
        *instance_offset = next_offset;
        true
    }

    fn draw_quads(
        &self,
        quads: &[Quad],
        instance_buffer: &mut InstanceBuffer,
        instance_offset: &mut usize,
        viewport_size: Size<DevicePixels>,
        command_encoder: &metal::RenderCommandEncoderRef,
    ) -> bool {
        if quads.is_empty() {
            return true;
        }
        align_offset(instance_offset);

        command_encoder.set_render_pipeline_state(&self.quads_pipeline_state);
        command_encoder.set_vertex_buffer(
            QuadInputIndex::Vertices as u64,
            Some(&self.unit_vertices),
            0,
        );
        command_encoder.set_vertex_buffer(
            QuadInputIndex::Quads as u64,
            Some(&instance_buffer.metal_buffer),
            *instance_offset as u64,
        );
        command_encoder.set_fragment_buffer(
            QuadInputIndex::Quads as u64,
            Some(&instance_buffer.metal_buffer),
            *instance_offset as u64,
        );

        command_encoder.set_vertex_bytes(
            QuadInputIndex::ViewportSize as u64,
            mem::size_of_val(&viewport_size) as u64,
            &viewport_size as *const Size<DevicePixels> as *const _,
        );

        let quad_bytes_len = mem::size_of_val(quads);
        let buffer_contents =
            unsafe { (instance_buffer.metal_buffer.contents() as *mut u8).add(*instance_offset) };

        let next_offset = *instance_offset + quad_bytes_len;
        if next_offset > instance_buffer.size {
            return false;
        }

        unsafe {
            ptr::copy_nonoverlapping(quads.as_ptr() as *const u8, buffer_contents, quad_bytes_len);
        }

        command_encoder.draw_primitives_instanced(
            metal::MTLPrimitiveType::Triangle,
            0,
            6,
            quads.len() as u64,
        );
        *instance_offset = next_offset;
        true
    }

    fn draw_paths(
        &self,
        paths: &[Path<ScaledPixels>],
        instance_buffer: &mut InstanceBuffer,
        instance_offset: &mut usize,
        viewport_size: Size<DevicePixels>,
        command_encoder: &metal::RenderCommandEncoderRef,
    ) -> bool {
        if paths.is_empty() {
            return true;
        }

        command_encoder.set_render_pipeline_state(&self.path_pipeline_state);

        unsafe {
            let base_addr = instance_buffer.metal_buffer.contents();
            let mut p = (base_addr as *mut u8).add(*instance_offset);
            let mut draw_indirect_commands = Vec::with_capacity(paths.len());

            // copy vertices
            let vertices_offset = (p as usize) - (base_addr as usize);
            let mut first_vertex = 0;
            for (i, path) in paths.iter().enumerate() {
                if (p as usize) - (base_addr as usize)
                    + (mem::size_of::<PathVertex<ScaledPixels>>() * path.vertices.len())
                    > instance_buffer.size
                {
                    return false;
                }

                for v in &path.vertices {
                    *(p as *mut PathVertex<ScaledPixels>) = PathVertex {
                        xy_position: v.xy_position,
                        content_mask: ContentMask {
                            bounds: path.content_mask.bounds,
                        },
                    };
                    p = p.add(mem::size_of::<PathVertex<ScaledPixels>>());
                }

                draw_indirect_commands.push(MTLDrawPrimitivesIndirectArguments {
                    vertexCount: path.vertices.len() as u32,
                    instanceCount: 1,
                    vertexStart: first_vertex,
                    baseInstance: i as u32,
                });
                first_vertex += path.vertices.len() as u32;
            }

            // copy sprites
            let sprites_offset = (p as u64) - (base_addr as u64);
            if (p as usize) - (base_addr as usize) + (mem::size_of::<PathSprite>() * paths.len())
                > instance_buffer.size
            {
                return false;
            }
            for path in paths {
                *(p as *mut PathSprite) = PathSprite {
                    bounds: path.bounds,
                    color: path.color,
                };
                p = p.add(mem::size_of::<PathSprite>());
            }

            // copy indirect commands
            let icb_bytes_len = mem::size_of_val(draw_indirect_commands.as_slice());
            let icb_offset = (p as u64) - (base_addr as u64);
            if (p as usize) - (base_addr as usize) + icb_bytes_len > instance_buffer.size {
                return false;
            }
            ptr::copy_nonoverlapping(
                draw_indirect_commands.as_ptr() as *const u8,
                p,
                icb_bytes_len,
            );
            p = p.add(icb_bytes_len);

            // draw path
            command_encoder.set_vertex_buffer(
                PathInputIndex::Vertices as u64,
                Some(&instance_buffer.metal_buffer),
                vertices_offset as u64,
            );

            command_encoder.set_vertex_bytes(
                PathInputIndex::ViewportSize as u64,
                mem::size_of_val(&viewport_size) as u64,
                &viewport_size as *const Size<DevicePixels> as *const _,
            );

            command_encoder.set_vertex_buffer(
                PathInputIndex::Sprites as u64,
                Some(&instance_buffer.metal_buffer),
                sprites_offset,
            );

            command_encoder.set_fragment_buffer(
                PathInputIndex::Sprites as u64,
                Some(&instance_buffer.metal_buffer),
                sprites_offset,
            );

            for i in 0..paths.len() {
                command_encoder.draw_primitives_indirect(
                    metal::MTLPrimitiveType::Triangle,
                    &instance_buffer.metal_buffer,
                    icb_offset
                        + (i * std::mem::size_of::<MTLDrawPrimitivesIndirectArguments>()) as u64,
                );
            }

            *instance_offset = (p as usize) - (base_addr as usize);
        }

        true
    }

    fn draw_underlines(
        &self,
        underlines: &[Underline],
        instance_buffer: &mut InstanceBuffer,
        instance_offset: &mut usize,
        viewport_size: Size<DevicePixels>,
        command_encoder: &metal::RenderCommandEncoderRef,
    ) -> bool {
        if underlines.is_empty() {
            return true;
        }
        align_offset(instance_offset);

        command_encoder.set_render_pipeline_state(&self.underlines_pipeline_state);
        command_encoder.set_vertex_buffer(
            UnderlineInputIndex::Vertices as u64,
            Some(&self.unit_vertices),
            0,
        );
        command_encoder.set_vertex_buffer(
            UnderlineInputIndex::Underlines as u64,
            Some(&instance_buffer.metal_buffer),
            *instance_offset as u64,
        );
        command_encoder.set_fragment_buffer(
            UnderlineInputIndex::Underlines as u64,
            Some(&instance_buffer.metal_buffer),
            *instance_offset as u64,
        );

        command_encoder.set_vertex_bytes(
            UnderlineInputIndex::ViewportSize as u64,
            mem::size_of_val(&viewport_size) as u64,
            &viewport_size as *const Size<DevicePixels> as *const _,
        );

        let underline_bytes_len = mem::size_of_val(underlines);
        let buffer_contents =
            unsafe { (instance_buffer.metal_buffer.contents() as *mut u8).add(*instance_offset) };

        let next_offset = *instance_offset + underline_bytes_len;
        if next_offset > instance_buffer.size {
            return false;
        }

        unsafe {
            ptr::copy_nonoverlapping(
                underlines.as_ptr() as *const u8,
                buffer_contents,
                underline_bytes_len,
            );
        }

        command_encoder.draw_primitives_instanced(
            metal::MTLPrimitiveType::Triangle,
            0,
            6,
            underlines.len() as u64,
        );
        *instance_offset = next_offset;
        true
    }

    fn draw_monochrome_sprites(
        &self,
        texture_id: AtlasTextureId,
        sprites: &[MonochromeSprite],
        instance_buffer: &mut InstanceBuffer,
        instance_offset: &mut usize,
        viewport_size: Size<DevicePixels>,
        command_encoder: &metal::RenderCommandEncoderRef,
    ) -> bool {
        if sprites.is_empty() {
            return true;
        }
        align_offset(instance_offset);

        let sprite_bytes_len = mem::size_of_val(sprites);
        let buffer_contents =
            unsafe { (instance_buffer.metal_buffer.contents() as *mut u8).add(*instance_offset) };

        let next_offset = *instance_offset + sprite_bytes_len;
        if next_offset > instance_buffer.size {
            return false;
        }

        let texture = self.sprite_atlas.metal_texture(texture_id);
        let texture_size = size(
            DevicePixels(texture.width() as i32),
            DevicePixels(texture.height() as i32),
        );
        command_encoder.set_render_pipeline_state(&self.monochrome_sprites_pipeline_state);
        command_encoder.set_vertex_buffer(
            SpriteInputIndex::Vertices as u64,
            Some(&self.unit_vertices),
            0,
        );
        command_encoder.set_vertex_buffer(
            SpriteInputIndex::Sprites as u64,
            Some(&instance_buffer.metal_buffer),
            *instance_offset as u64,
        );
        command_encoder.set_vertex_bytes(
            SpriteInputIndex::ViewportSize as u64,
            mem::size_of_val(&viewport_size) as u64,
            &viewport_size as *const Size<DevicePixels> as *const _,
        );
        command_encoder.set_vertex_bytes(
            SpriteInputIndex::AtlasTextureSize as u64,
            mem::size_of_val(&texture_size) as u64,
            &texture_size as *const Size<DevicePixels> as *const _,
        );
        command_encoder.set_fragment_buffer(
            SpriteInputIndex::Sprites as u64,
            Some(&instance_buffer.metal_buffer),
            *instance_offset as u64,
        );
        command_encoder.set_fragment_texture(SpriteInputIndex::AtlasTexture as u64, Some(&texture));

        unsafe {
            ptr::copy_nonoverlapping(
                sprites.as_ptr() as *const u8,
                buffer_contents,
                sprite_bytes_len,
            );
        }

        command_encoder.draw_primitives_instanced(
            metal::MTLPrimitiveType::Triangle,
            0,
            6,
            sprites.len() as u64,
        );
        *instance_offset = next_offset;
        true
    }

    fn draw_polychrome_sprites(
        &self,
        texture_id: AtlasTextureId,
        sprites: &[PolychromeSprite],
        instance_buffer: &mut InstanceBuffer,
        instance_offset: &mut usize,
        viewport_size: Size<DevicePixels>,
        command_encoder: &metal::RenderCommandEncoderRef,
    ) -> bool {
        if sprites.is_empty() {
            return true;
        }
        align_offset(instance_offset);

        let texture = self.sprite_atlas.metal_texture(texture_id);
        let texture_size = size(
            DevicePixels(texture.width() as i32),
            DevicePixels(texture.height() as i32),
        );
        command_encoder.set_render_pipeline_state(&self.polychrome_sprites_pipeline_state);
        command_encoder.set_vertex_buffer(
            SpriteInputIndex::Vertices as u64,
            Some(&self.unit_vertices),
            0,
        );
        command_encoder.set_vertex_buffer(
            SpriteInputIndex::Sprites as u64,
            Some(&instance_buffer.metal_buffer),
            *instance_offset as u64,
        );
        command_encoder.set_vertex_bytes(
            SpriteInputIndex::ViewportSize as u64,
            mem::size_of_val(&viewport_size) as u64,
            &viewport_size as *const Size<DevicePixels> as *const _,
        );
        command_encoder.set_vertex_bytes(
            SpriteInputIndex::AtlasTextureSize as u64,
            mem::size_of_val(&texture_size) as u64,
            &texture_size as *const Size<DevicePixels> as *const _,
        );
        command_encoder.set_fragment_buffer(
            SpriteInputIndex::Sprites as u64,
            Some(&instance_buffer.metal_buffer),
            *instance_offset as u64,
        );
        command_encoder.set_fragment_texture(SpriteInputIndex::AtlasTexture as u64, Some(&texture));

        let sprite_bytes_len = mem::size_of_val(sprites);
        let buffer_contents =
            unsafe { (instance_buffer.metal_buffer.contents() as *mut u8).add(*instance_offset) };

        let next_offset = *instance_offset + sprite_bytes_len;
        if next_offset > instance_buffer.size {
            return false;
        }

        unsafe {
            ptr::copy_nonoverlapping(
                sprites.as_ptr() as *const u8,
                buffer_contents,
                sprite_bytes_len,
            );
        }

        command_encoder.draw_primitives_instanced(
            metal::MTLPrimitiveType::Triangle,
            0,
            6,
            sprites.len() as u64,
        );
        *instance_offset = next_offset;
        true
    }

    fn draw_surfaces(
        &mut self,
        surfaces: &[PaintSurface],
        instance_buffer: &mut InstanceBuffer,
        instance_offset: &mut usize,
        viewport_size: Size<DevicePixels>,
        command_encoder: &metal::RenderCommandEncoderRef,
    ) -> bool {
        command_encoder.set_render_pipeline_state(&self.surfaces_pipeline_state);
        command_encoder.set_vertex_buffer(
            SurfaceInputIndex::Vertices as u64,
            Some(&self.unit_vertices),
            0,
        );
        command_encoder.set_vertex_bytes(
            SurfaceInputIndex::ViewportSize as u64,
            mem::size_of_val(&viewport_size) as u64,
            &viewport_size as *const Size<DevicePixels> as *const _,
        );

        for surface in surfaces {
            let texture_size = size(
                DevicePixels::from(surface.image_buffer.get_width() as i32),
                DevicePixels::from(surface.image_buffer.get_height() as i32),
            );

            assert_eq!(
                surface.image_buffer.get_pixel_format(),
                kCVPixelFormatType_420YpCbCr8BiPlanarFullRange
            );

            let y_texture = self
                .core_video_texture_cache
                .create_texture_from_image(
                    surface.image_buffer.as_concrete_TypeRef(),
                    None,
                    MTLPixelFormat::R8Unorm,
                    surface.image_buffer.get_width_of_plane(0),
                    surface.image_buffer.get_height_of_plane(0),
                    0,
                )
                .unwrap();
            let cb_cr_texture = self
                .core_video_texture_cache
                .create_texture_from_image(
                    surface.image_buffer.as_concrete_TypeRef(),
                    None,
                    MTLPixelFormat::RG8Unorm,
                    surface.image_buffer.get_width_of_plane(1),
                    surface.image_buffer.get_height_of_plane(1),
                    1,
                )
                .unwrap();

            align_offset(instance_offset);
            let next_offset = *instance_offset + mem::size_of::<Surface>();
            if next_offset > instance_buffer.size {
                return false;
            }

            command_encoder.set_vertex_buffer(
                SurfaceInputIndex::Surfaces as u64,
                Some(&instance_buffer.metal_buffer),
                *instance_offset as u64,
            );
            command_encoder.set_vertex_bytes(
                SurfaceInputIndex::TextureSize as u64,
                mem::size_of_val(&texture_size) as u64,
                &texture_size as *const Size<DevicePixels> as *const _,
            );
            // let y_texture = y_texture.get_texture().unwrap().
            command_encoder.set_fragment_texture(SurfaceInputIndex::YTexture as u64, unsafe {
                let texture = CVMetalTextureGetTexture(y_texture.as_concrete_TypeRef());
                Some(metal::TextureRef::from_ptr(texture as *mut _))
            });
            command_encoder.set_fragment_texture(SurfaceInputIndex::CbCrTexture as u64, unsafe {
                let texture = CVMetalTextureGetTexture(cb_cr_texture.as_concrete_TypeRef());
                Some(metal::TextureRef::from_ptr(texture as *mut _))
            });

            unsafe {
                let buffer_contents = (instance_buffer.metal_buffer.contents() as *mut u8)
                    .add(*instance_offset)
                    as *mut SurfaceBounds;
                ptr::write(
                    buffer_contents,
                    SurfaceBounds {
                        bounds: surface.bounds,
                        content_mask: surface.content_mask.clone(),
                    },
                );
            }

            command_encoder.draw_primitives(metal::MTLPrimitiveType::Triangle, 0, 6);
            *instance_offset = next_offset;
        }
        true
    }
}

fn build_pipeline_state(
    device: &metal::DeviceRef,
    library: &metal::LibraryRef,
    label: &str,
    vertex_fn_name: &str,
    fragment_fn_name: &str,
    pixel_format: metal::MTLPixelFormat,
    sample_count: u64,
) -> metal::RenderPipelineState {
    let vertex_fn = library
        .get_function(vertex_fn_name, None)
        .expect("error locating vertex function");
    let fragment_fn = library
        .get_function(fragment_fn_name, None)
        .expect("error locating fragment function");

    let descriptor = metal::RenderPipelineDescriptor::new();
    descriptor.set_label(label);
    descriptor.set_vertex_function(Some(vertex_fn.as_ref()));
    descriptor.set_fragment_function(Some(fragment_fn.as_ref()));
    descriptor.set_sample_count(sample_count);
    let color_attachment = descriptor.color_attachments().object_at(0).unwrap();
    color_attachment.set_pixel_format(pixel_format);
    color_attachment.set_blending_enabled(true);
    color_attachment.set_rgb_blend_operation(metal::MTLBlendOperation::Add);
    color_attachment.set_alpha_blend_operation(metal::MTLBlendOperation::Add);
    color_attachment.set_source_rgb_blend_factor(metal::MTLBlendFactor::SourceAlpha);
    color_attachment.set_source_alpha_blend_factor(metal::MTLBlendFactor::One);
    color_attachment.set_destination_rgb_blend_factor(metal::MTLBlendFactor::OneMinusSourceAlpha);
    color_attachment.set_destination_alpha_blend_factor(metal::MTLBlendFactor::One);

    device
        .new_render_pipeline_state(&descriptor)
        .expect("could not create render pipeline state")
}

// Align to multiples of 256 make Metal happy.
fn align_offset(offset: &mut usize) {
    *offset = (*offset).div_ceil(256) * 256;
}

fn create_msaa_texture(
    device: &metal::Device,
    layer: &metal::MetalLayer,
    sample_count: u64,
) -> Option<metal::Texture> {
    let viewport_size = layer.drawable_size();
    let width = viewport_size.width.ceil() as u64;
    let height = viewport_size.height.ceil() as u64;

    if width == 0 || height == 0 {
        return None;
    }

    if sample_count <= 1 {
        return None;
    }

    let texture_descriptor = metal::TextureDescriptor::new();
    texture_descriptor.set_texture_type(metal::MTLTextureType::D2Multisample);

    // MTLStorageMode default is `shared` only for Apple silicon GPUs. Use `private` for Apple and Intel GPUs both.
    // Reference: https://developer.apple.com/documentation/metal/choosing-a-resource-storage-mode-for-apple-gpus
    texture_descriptor.set_storage_mode(metal::MTLStorageMode::Private);

    texture_descriptor.set_width(width);
    texture_descriptor.set_height(height);
    texture_descriptor.set_pixel_format(layer.pixel_format());
    texture_descriptor.set_usage(metal::MTLTextureUsage::RenderTarget);
    texture_descriptor.set_sample_count(sample_count);

    let metal_texture = device.new_texture(&texture_descriptor);
    Some(metal_texture)
}

#[repr(C)]
enum ShadowInputIndex {
    Vertices = 0,
    Shadows = 1,
    ViewportSize = 2,
}

#[repr(C)]
enum QuadInputIndex {
    Vertices = 0,
    Quads = 1,
    ViewportSize = 2,
}

#[repr(C)]
enum UnderlineInputIndex {
    Vertices = 0,
    Underlines = 1,
    ViewportSize = 2,
}

#[repr(C)]
enum SpriteInputIndex {
    Vertices = 0,
    Sprites = 1,
    ViewportSize = 2,
    AtlasTextureSize = 3,
    AtlasTexture = 4,
}

#[repr(C)]
enum SurfaceInputIndex {
    Vertices = 0,
    Surfaces = 1,
    ViewportSize = 2,
    TextureSize = 3,
    YTexture = 4,
    CbCrTexture = 5,
}

#[repr(C)]
enum PathInputIndex {
    Vertices = 0,
    ViewportSize = 1,
    Sprites = 2,
}

#[derive(Clone, Debug, Eq, PartialEq)]
#[repr(C)]
pub struct PathSprite {
    pub bounds: Bounds<ScaledPixels>,
    pub color: Background,
}

#[derive(Clone, Debug, Eq, PartialEq)]
#[repr(C)]
pub struct SurfaceBounds {
    pub bounds: Bounds<ScaledPixels>,
    pub content_mask: ContentMask<ScaledPixels>,
}