#![deny(unsafe_code)]
use crate::error::*;
use crate::graphics_permanent::{
  PermanentGraphicsState, GraphicsStateForReinit, QueueFamilyIndices
};
use crate::shader_data::{ VERTICES, INDICES, Vertex, UniformBlock };

use std::collections::BTreeSet;
use std::io::Cursor;
use std::ptr::copy_nonoverlapping;

use png::Decoder;
use vulkanalia::{ Device, Instance };
use vulkanalia::vk::{ self, Handle, HasBuilder, InstanceV1_0, DeviceV1_0,
                      KhrSwapchainExtensionDeviceCommands };
use winit::window::Window;


// TODO: use VK_KHR_swapchain_maintenance1 to put a fence on the presentation
// operation. doing that will remove the requirement that we have more
// simultaneous frames than images.
pub const N_SIMULTANEOUS_FRAMES: usize = 5;


//   The WindowDressing collects the Vulkan graphics objects which need to be
// regenerated or modified when the window changes in certain ways, such as
// resizing. The ones which don't need that are collected above, in
// PermanentGraphicsState.
#[derive(Debug)]
pub struct WindowDressing {
  pub swapchain: Swapchain,

  render_pass: vk::RenderPass,

  pipeline: vk::Pipeline,
  pipeline_layout: vk::PipelineLayout,

  framebuffers: Vec<vk::Framebuffer>,

  primary_command_pool: vk::CommandPool,
  transient_command_pool: vk::CommandPool,

  vertex_buffer: vk::Buffer,
  vertex_buffer_memory: vk::DeviceMemory,

  index_buffer: vk::Buffer,
  index_buffer_memory: vk::DeviceMemory,

  texture_image: vk::Image,
  texture_image_memory: vk::DeviceMemory,
  texture_image_view: vk::ImageView,

  uniform_buffers: Vec<vk::Buffer>,
  pub uniform_buffer_memory: Vec<vk::DeviceMemory>,

  descriptor_pool: vk::DescriptorPool,
  descriptor_sets: Vec<vk::DescriptorSet>,

  pub command_buffers: Vec<vk::CommandBuffer>,

  pub concurrency: Concurrency,
}

//   A swapchain is the generalized facility that is used to implement
// double buffering, triple buffering, rendering passes that feed into each
// other, and other things of that nature. It's a first-class thing but for
// now, we use at most one of it. We also support running without one.
#[derive(Debug)]
pub struct Swapchain {
  pub swapchain: vk::SwapchainKHR,
  images: Vec<vk::Image>,
  image_views: Vec<vk::ImageView>,
  format: vk::Format,
  pub extent: vk::Extent2D,
}

#[derive(Debug)]
pub struct Concurrency {
  pub image_available_semaphores: Vec<vk::Semaphore>,
  pub rendering_finished_semaphores: Vec<vk::Semaphore>,

  //   Okay, the lifetime management on the fences is really subtle. There is
  // one fence for each frame, and frame_fences holds the authoritative
  // reference to it.
  //
  //   There is one entry in image_fences for each image. The number of images
  // is not directly related to the number of frames; it will likely be
  // larger, but may be smaller or the same. At the start of execution, the
  // entries are all nulls. Each time an image is acquired from the swapchain,
  // the corresponding entry in image_fences is overwritten with a duplicate
  // of the frame fence. This happens during rendering of the frame, so the
  // frame fence is in the "signaled" state. It will be reset right before
  // submitting the queue, then signaled again when the submission completes.
  pub frame_fences: Vec<vk::Fence>,
  pub image_fences: Vec<vk::Fence>,
}


impl WindowDressing {
  pub fn new(permanent: &PermanentGraphicsState,
             for_reinit: &GraphicsStateForReinit)
      -> Result<Self>
  {
    let window = &permanent.window;
    let instance = &permanent.instance;
    let surface = &permanent.surface;
    let device = &permanent.device;
    let sampler = &permanent.sampler;
    let graphics_queue = &permanent.graphics_queue;
    let physical_device = &for_reinit.physical_device;
    let indices = &for_reinit.indices;
    let descriptor_set_layout = &for_reinit.descriptor_set_layout;

    let swapchain = init_swapchain(
            window, instance, surface, &physical_device, device, &indices)?;

    let render_pass = init_render_pass(device, &swapchain.format)?;

    let (pipeline_layout, pipeline)
            = init_pipeline(device, descriptor_set_layout, &swapchain.extent,
                            &render_pass)?;

    let framebuffers = init_framebuffers(
            device, &swapchain.extent, &swapchain.image_views, &render_pass)?;

    let (primary_command_pool, transient_command_pool)
            = init_command_pools(device, indices)?;

    let (vertex_buffer, vertex_buffer_memory)
            = init_vertex_buffer(instance, physical_device, device,
                                 graphics_queue, &transient_command_pool)?;
    let (index_buffer, index_buffer_memory)
            = init_index_buffer(instance, physical_device, device,
                                graphics_queue, &transient_command_pool)?;

    let (texture_image, texture_image_memory, texture_image_view)
            = init_texture(instance, physical_device, device,
                           graphics_queue, &transient_command_pool)?;

    let (uniform_buffers, uniform_buffer_memory)
            = init_uniform_buffers(instance, physical_device, device,
                                   swapchain.images.len())?;

    let descriptor_pool
            = init_descriptor_pool(device, swapchain.images.len())?;
    let descriptor_sets
            = init_descriptor_sets(device, descriptor_set_layout,
                                   &uniform_buffers, &descriptor_pool,
                                   swapchain.images.len(),
                                   &texture_image_view, sampler)?;

    let command_buffers = init_commands(
            device, &swapchain.extent, &framebuffers, &render_pass,
            &pipeline_layout, &pipeline, &vertex_buffer, &index_buffer,
            &descriptor_sets, &primary_command_pool)?;

    let concurrency = init_concurrency(device, &swapchain.images)?;

    Ok(WindowDressing {
      swapchain,
      render_pass,
      pipeline,
      pipeline_layout,
      framebuffers,
      vertex_buffer,
      vertex_buffer_memory,
      index_buffer,
      index_buffer_memory,
      texture_image,
      texture_image_memory,
      texture_image_view,
      uniform_buffers,
      uniform_buffer_memory,
      descriptor_pool,
      descriptor_sets,
      primary_command_pool,
      transient_command_pool,
      command_buffers,
      concurrency,
    })
  }


  #[allow(unsafe_code)]
  pub fn reinit(&mut self, permanent: &PermanentGraphicsState,
                for_reinit: &GraphicsStateForReinit)
      -> Result<()>
  {
    let window = &permanent.window;
    let instance = &permanent.instance;
    let surface = &permanent.surface;
    let device = &permanent.device;
    let sampler = &permanent.sampler;
    let physical_device = &for_reinit.physical_device;
    let indices = &for_reinit.indices;
    let descriptor_set_layout = &for_reinit.descriptor_set_layout;

    unsafe { device.device_wait_idle() }.unwrap();

    self.destroy_replaceable(device);

    let swapchain = init_swapchain(
            window, instance, surface, &physical_device, device, &indices)?;

    let render_pass = init_render_pass(device, &swapchain.format)?;

    let (pipeline_layout, pipeline)
            = init_pipeline(device, descriptor_set_layout, &swapchain.extent,
                            &render_pass)?;

    let framebuffers = init_framebuffers(
            device, &swapchain.extent, &swapchain.image_views, &render_pass)?;

    let (uniform_buffers, uniform_buffer_memory)
            = init_uniform_buffers(instance, physical_device, device,
                                   swapchain.images.len())?;

    // Notice that we did NOT reuse the descriptor pool.
    let descriptor_pool
            = init_descriptor_pool(device, swapchain.images.len())?;

    let descriptor_sets
            = init_descriptor_sets(device, descriptor_set_layout,
                                   &uniform_buffers, &descriptor_pool,
                                   swapchain.images.len(),
                                   &self.texture_image_view, sampler)?;

    // Notice that we reused the command pool.
    let command_buffers = init_commands(
            device, &swapchain.extent, &framebuffers, &render_pass,
            &pipeline_layout, &pipeline, &self.vertex_buffer,
            &self.index_buffer, &descriptor_sets,
            &self.primary_command_pool)?;

    self.concurrency.image_fences.resize(swapchain.images.len(),
                                         vk::Fence::null());

    self.swapchain = swapchain;
    self.render_pass = render_pass;
    self.pipeline = pipeline;
    self.pipeline_layout = pipeline_layout;
    self.framebuffers = framebuffers;
    self.uniform_buffers = uniform_buffers;
    self.uniform_buffer_memory = uniform_buffer_memory;
    self.descriptor_pool = descriptor_pool;
    self.descriptor_sets = descriptor_sets;
    self.command_buffers = command_buffers;

    Ok(())
  }


  //   This relies on its caller to have already waited for the device to be
  // idle.
  #[allow(unsafe_code)]
  pub fn destroy(mut self, device: &Device) {
    self.destroy_replaceable(device);

    unsafe { device.destroy_buffer(self.vertex_buffer, None) };
    unsafe { device.free_memory(self.vertex_buffer_memory, None) };
    unsafe { device.destroy_buffer(self.index_buffer, None) };
    unsafe { device.free_memory(self.index_buffer_memory, None) };
    unsafe { device.destroy_image(self.texture_image, None) };
    unsafe { device.free_memory(self.texture_image_memory, None) };
    unsafe { device.destroy_image_view(self.texture_image_view, None) };

    for semaphore in self.concurrency.image_available_semaphores {
      unsafe { device.destroy_semaphore(semaphore, None) };
    }

    for semaphore in self.concurrency.rendering_finished_semaphores {
      unsafe { device.destroy_semaphore(semaphore, None) };
    }

    for fence in self.concurrency.frame_fences {
      unsafe { device.destroy_fence(fence, None) };
    }

    //   Notice that destroy_replaceable() freed the buffers in the pools, but
    // did not destroy the pools.
    unsafe { device.destroy_command_pool(self.primary_command_pool, None) };
    unsafe { device.destroy_command_pool(self.transient_command_pool, None) };
  }


  #[allow(unsafe_code)]
  fn destroy_replaceable(&mut self, device: &Device) {
    for framebuffer in &self.framebuffers {
      unsafe { device.destroy_framebuffer(*framebuffer, None) };
    }

    //   Notice that we free the buffers in the pool, but do not destroy the
    // pool itself. Notice also that we only do this for the primary command
    // pool, because that's the only one where we've kept track of the
    // buffers. We promise ourselves to free buffers in the transient pool
    // immediately after using them.
    unsafe {
      device.free_command_buffers(self.primary_command_pool,
                                  &self.command_buffers)
    };

    //   While the descriptor pool is also a pool, it has a preallocated size
    // which will be different next time. So, we destroy it all the way.
    unsafe { device.destroy_descriptor_pool(self.descriptor_pool, None) };

    //   Notice that, unlike the vertex and index buffers, we destroy and
    // re-create these on every reinitialization. That's because the number of
    // them depends on how many images the swapchain has.
    for buffer in &self.uniform_buffers {
      unsafe { device.destroy_buffer(*buffer, None) };
    }
    for memory in &self.uniform_buffer_memory {
      unsafe { device.free_memory(*memory, None) };
    }

    unsafe { device.destroy_pipeline(self.pipeline, None) };
    unsafe { device.destroy_pipeline_layout(self.pipeline_layout, None) };
    unsafe { device.destroy_render_pass(self.render_pass, None) };

    for view in &self.swapchain.image_views {
      unsafe { device.destroy_image_view(*view, None) };
    }

    unsafe { device.destroy_swapchain_khr(self.swapchain.swapchain, None) };
  }
}


#[allow(unsafe_code)]
fn init_swapchain(window: &Window, instance: &Instance,
                  surface: &vk::SurfaceKHR,
                  physical_device: &vk::PhysicalDevice, device: &Device,
                  indices: &QueueFamilyIndices)
    -> Result<Swapchain>
{
  let (capabilities, formats, presentation_modes)
          = PermanentGraphicsState::find_device_swapchain_features(
                instance, surface, physical_device)?.require()?;

  let format = pick_surface_format(&formats)?;

  let presentation_mode
          = pick_presentation_mode(&presentation_modes)?;
  let extent = pick_image_extent(window, capabilities)?;

  let mut image_count = capabilities.min_image_count + 1;
  if capabilities.max_image_count != 0 {
    image_count
        = image_count.clamp(0, capabilities.max_image_count);
  }

  let mut unique_queue_family_indices = BTreeSet::new();
  unique_queue_family_indices.insert(indices.graphics);
  unique_queue_family_indices.insert(indices.presentation);

  //   If there's only one queue, we use exclusive sharing mode, which
  // will allow things to work without locks. Otherwise we use concurrent
  // mode.
  let (ordered_indices, sharing_mode)
          = if unique_queue_family_indices.len() < 2
  {
    (vec![indices.graphics], vk::SharingMode::EXCLUSIVE)
  } else {
    (vec![indices.graphics, indices.presentation],
     vk::SharingMode::CONCURRENT)
  };

  let swapchain_info = vk::SwapchainCreateInfoKHR::builder()
          .surface(*surface)
          .min_image_count(image_count)
          .image_format(format.format)
          .image_color_space(format.color_space)
          .image_extent(extent)
          .image_array_layers(1)
          .image_usage(vk::ImageUsageFlags::COLOR_ATTACHMENT)
          .image_sharing_mode(sharing_mode)
          .queue_family_indices(&ordered_indices)
          .pre_transform(capabilities.current_transform)
          .composite_alpha(vk::CompositeAlphaFlagsKHR::OPAQUE)
          .present_mode(presentation_mode)
          .clipped(true)
          .old_swapchain(vk::SwapchainKHR::null());

  let swapchain = unsafe {
    device.create_swapchain_khr(&swapchain_info, None)
  }?;

  let images = unsafe {
    device.get_swapchain_images_khr(swapchain)
  }?;

  let mut image_views = Vec::new();
  for image in &images {
    let view = init_image_view(device, image, format.format)?;
    image_views.push(view);
  }

  Ok(Swapchain {
    swapchain, images, image_views,
    format: format.format,
    extent
  })
}


#[allow(unsafe_code)]
fn init_render_pass(device: &Device, format: &vk::Format)
    -> Result<vk::RenderPass>
{
  let color_attachment
          = vk::AttachmentDescription::builder()
                .format(*format)
                .samples(vk::SampleCountFlags::_1)
                .load_op(vk::AttachmentLoadOp::CLEAR)
                .store_op(vk::AttachmentStoreOp::STORE)
                .stencil_load_op(vk::AttachmentLoadOp::DONT_CARE)
                .stencil_store_op(vk::AttachmentStoreOp::DONT_CARE)
                .initial_layout(vk::ImageLayout::UNDEFINED)
                .final_layout(vk::ImageLayout::PRESENT_SRC_KHR);

  let color_attachment_reference
          = vk::AttachmentReference::builder()
                .attachment(0)
                .layout(vk::ImageLayout::COLOR_ATTACHMENT_OPTIMAL);

  let subpass_attachments = [color_attachment_reference];
  let subpass = vk::SubpassDescription::builder()
                    .pipeline_bind_point(vk::PipelineBindPoint::GRAPHICS)
                    .color_attachments(&subpass_attachments);

  let dependency
        = vk::SubpassDependency::builder()
              .src_subpass(vk::SUBPASS_EXTERNAL)
              .src_stage_mask(
                   vk::PipelineStageFlags::COLOR_ATTACHMENT_OUTPUT)
              .src_access_mask(vk::AccessFlags::empty())
              .dst_subpass(0)
              .dst_stage_mask(
                   vk::PipelineStageFlags::COLOR_ATTACHMENT_OUTPUT)
              .dst_access_mask(vk::AccessFlags::COLOR_ATTACHMENT_WRITE);

  let render_attachments = [color_attachment];
  let subpasses = [subpass];
  let dependencies = [dependency];
  let render_pass_info = vk::RenderPassCreateInfo::builder()
                             .attachments(&render_attachments)
                             .subpasses(&subpasses)
                             .dependencies(&dependencies);

  let render_pass = unsafe {
    device.create_render_pass(&render_pass_info, None)
  }?;

  Ok(render_pass)
}


#[allow(unsafe_code)]
fn init_pipeline(device: &Device,
                 descriptor_set_layout: &vk::DescriptorSetLayout,
                 extent: &vk::Extent2D, render_pass: &vk::RenderPass)
    -> Result<(vk::PipelineLayout, vk::Pipeline)>
{
  let vertex_binary = include_bytes!(
          concat!(env!("OUT_DIR"), "/shader.vert.spv"));
  let fragment_binary = include_bytes!(
          concat!(env!("OUT_DIR"), "/shader.frag.spv"));

  let vertex_module = PermanentGraphicsState::load_spirv_shader_module(
          device, vertex_binary)?;
  let fragment_module = PermanentGraphicsState::load_spirv_shader_module(
          device, fragment_binary)?;

  let vertex_stage_info = vk::PipelineShaderStageCreateInfo::builder()
                              .stage(vk::ShaderStageFlags::VERTEX)
                              .module(vertex_module)
                              .name(b"main\0");

  let fragment_stage_info = vk::PipelineShaderStageCreateInfo::builder()
                                .stage(vk::ShaderStageFlags::FRAGMENT)
                                .module(fragment_module)
                                .name(b"main\0");

  let binding_descriptions = [Vertex::<f32>::binding_description()];
  let attribute_descriptions = Vertex::<f32>::attribute_descriptions();
  let vertex_input_state_info
          = vk::PipelineVertexInputStateCreateInfo::builder()
                .vertex_binding_descriptions(&binding_descriptions)
                .vertex_attribute_descriptions(&attribute_descriptions);

  let input_assembly_state_info
          = vk::PipelineInputAssemblyStateCreateInfo::builder()
                .topology(vk::PrimitiveTopology::TRIANGLE_LIST)
                .primitive_restart_enable(false);

  let viewport = vk::Viewport::builder()
                     .x(0.0)
                     .y(0.0)
                     .width(extent.width as f32)
                     .height(extent.height as f32)
                     .min_depth(0.0)
                     .max_depth(1.0);
  let viewports = [viewport];

  let scissor = vk::Rect2D::builder()
                     .offset(vk::Offset2D { x: 0, y: 0 })
                     .extent(*extent);
  let scissor_list = [scissor];

  let viewport_state_info = vk::PipelineViewportStateCreateInfo::builder()
                     .viewports(&viewports)
                     .scissors(&scissor_list);

  let rasterizer_state_info
          = vk::PipelineRasterizationStateCreateInfo::builder()
                .depth_clamp_enable(false)
                .rasterizer_discard_enable(false)
                .polygon_mode(vk::PolygonMode::FILL)
                .line_width(1.0)
                .cull_mode(vk::CullModeFlags::BACK)
                .front_face(vk::FrontFace::CLOCKWISE)
                .depth_bias_enable(false);

  let multisample_state_info
          = vk::PipelineMultisampleStateCreateInfo::builder()
                .sample_shading_enable(false)
                .rasterization_samples(vk::SampleCountFlags::_1);

  let blend_attachment_info
          = vk::PipelineColorBlendAttachmentState::builder()
                .color_write_mask(vk::ColorComponentFlags::all())
                .blend_enable(false)
                .src_color_blend_factor(vk::BlendFactor::ONE)
                .dst_color_blend_factor(vk::BlendFactor::ZERO)
                .color_blend_op(vk::BlendOp::ADD)
                .src_alpha_blend_factor(vk::BlendFactor::ONE)
                .dst_alpha_blend_factor(vk::BlendFactor::ZERO)
                .alpha_blend_op(vk::BlendOp::ADD);
  let blend_attachments = [blend_attachment_info];

  let blend_info = vk::PipelineColorBlendStateCreateInfo::builder()
                       .logic_op_enable(false)
                       .logic_op(vk::LogicOp::COPY)
                       .attachments(&blend_attachments)
                       .blend_constants([0.0, 0.0, 0.0, 0.0]);

  let layouts = [*descriptor_set_layout];
  let pipeline_layout_info = vk::PipelineLayoutCreateInfo::builder()
                                 .set_layouts(&layouts);

  let pipeline_layout = unsafe {
    device.create_pipeline_layout(&pipeline_layout_info, None)
  }?;

  let stages = [vertex_stage_info, fragment_stage_info];
  let pipeline_info
          = vk::GraphicsPipelineCreateInfo::builder()
                .stages(&stages)
                .vertex_input_state(&vertex_input_state_info)
                .input_assembly_state(&input_assembly_state_info)
                .viewport_state(&viewport_state_info)
                .rasterization_state(&rasterizer_state_info)
                .multisample_state(&multisample_state_info)
                .color_blend_state(&blend_info)
                .layout(pipeline_layout)
                .render_pass(*render_pass)
                .subpass(0);

  let pipeline = unsafe {
    device.create_graphics_pipelines(vk::PipelineCache::null(),
                                     &[pipeline_info], None)
  }?.0[0];

  unsafe {
    device.destroy_shader_module(vertex_module, None);
    device.destroy_shader_module(fragment_module, None);
  };

  Ok((pipeline_layout, pipeline))
}


#[allow(unsafe_code)]
fn init_framebuffers(device: &Device, extent: &vk::Extent2D,
                     swapchain_image_views: &Vec<vk::ImageView>,
                     render_pass: &vk::RenderPass)
    -> Result<Vec<vk::Framebuffer>>
{
  let mut framebuffers = Vec::new();

  for image_view in swapchain_image_views {
    let attachments = [*image_view];

    let framebuffer_info = vk::FramebufferCreateInfo::builder()
                               .render_pass(*render_pass)
                               .attachments(&attachments)
                               .width(extent.width)
                               .height(extent.height)
                               .layers(1);

    let framebuffer = unsafe {
      device.create_framebuffer(&framebuffer_info, None)
    }?;

    framebuffers.push(framebuffer);
  }

  Ok(framebuffers)
}


fn init_vertex_buffer(instance: &Instance,
                      physical_device: &vk::PhysicalDevice, device: &Device,
                      queue: &vk::Queue, command_pool: &vk::CommandPool)
    -> Result<(vk::Buffer, vk::DeviceMemory)>
{
  init_buffer(instance, physical_device, device, queue, command_pool,
              vk::BufferUsageFlags::VERTEX_BUFFER, &VERTICES)
}


fn init_index_buffer(instance: &Instance,
                     physical_device: &vk::PhysicalDevice, device: &Device,
                     queue: &vk::Queue, command_pool: &vk::CommandPool)
    -> Result<(vk::Buffer, vk::DeviceMemory)>
{
  init_buffer(instance, physical_device, device, queue, command_pool,
              vk::BufferUsageFlags::INDEX_BUFFER, INDICES)
}


#[allow(unsafe_code)]
fn init_texture(instance: &Instance,
                physical_device: &vk::PhysicalDevice, device: &Device,
                queue: &vk::Queue, command_pool: &vk::CommandPool)
    -> Result<(vk::Image, vk::DeviceMemory, vk::ImageView)>
{
  let png = include_bytes!("../textures/forest_leaves_04_diff.png");

  let decoder = Decoder::new(Cursor::new(png));
  let mut reader = decoder.read_info()?;

  let (width, height) = reader.info().size();

  let mut pixels = vec![0; reader.info().raw_bytes()];
  reader.next_frame(&mut pixels)?;

  let (staging_buffer, staging_memory, _byte_size)
          = stage_in_buffer(instance, physical_device, device, &pixels)?;

  let (image, image_memory)
          = allocate_image(instance, physical_device, device, width, height,
                           vk::Format::R8G8B8A8_SRGB,
                           vk::ImageTiling::OPTIMAL,
                           vk::ImageUsageFlags::SAMPLED
                               | vk::ImageUsageFlags::TRANSFER_DST,
                           vk::MemoryPropertyFlags::DEVICE_LOCAL)?;

  change_image_layout(device, queue, command_pool, &image,
                      vk::Format::R8G8B8A8_SRGB,
                      vk::ImageLayout::UNDEFINED,
                      vk::ImageLayout::TRANSFER_DST_OPTIMAL)?;

  copy_buffer_to_image(device, queue, command_pool, &staging_buffer, &image,
                       width, height)?;

  change_image_layout(device, queue, command_pool, &image,
                      vk::Format::R8G8B8A8_SRGB,
                      vk::ImageLayout::TRANSFER_DST_OPTIMAL,
                      vk::ImageLayout::SHADER_READ_ONLY_OPTIMAL)?;

  let view = init_image_view(device, &image, vk::Format::R8G8B8A8_SRGB)?;

  unsafe { device.destroy_buffer(staging_buffer, None) };
  unsafe { device.free_memory(staging_memory, None) };

  Ok((image, image_memory, view))
}


fn init_uniform_buffers(instance: &Instance,
                        physical_device: &vk::PhysicalDevice, device: &Device,
                        count: usize)
    -> Result<(Vec<vk::Buffer>, Vec<vk::DeviceMemory>)>
{
  let mut buffers = Vec::new();
  let mut all_memory = Vec::new();

  for _ in 0 .. count {
    let (buffer, memory) = allocate_buffer(
            instance, physical_device, device,
            size_of::<UniformBlock<f32>>() as vk::DeviceSize,
            vk::BufferUsageFlags::UNIFORM_BUFFER,
            vk::MemoryPropertyFlags::HOST_COHERENT
            | vk::MemoryPropertyFlags::HOST_VISIBLE)?;
    buffers.push(buffer);
    all_memory.push(memory);
  }

  Ok((buffers, all_memory))
}


#[allow(unsafe_code)]
fn init_buffer<T>(instance: &Instance,
                  physical_device: &vk::PhysicalDevice, device: &Device,
                  queue: &vk::Queue, command_pool: &vk::CommandPool,
                  usage: vk::BufferUsageFlags, contents: &[T])
    -> Result<(vk::Buffer, vk::DeviceMemory)>
{
  let (staging_buffer, staging_memory, size)
          = stage_in_buffer(instance, physical_device, device, contents)?;

  let final_usage = vk::BufferUsageFlags::TRANSFER_DST | usage;
  let final_memory_flags = vk::MemoryPropertyFlags::DEVICE_LOCAL;
  let (final_buffer, device_memory)
          = allocate_buffer(instance, physical_device, device,
                            size as vk::DeviceSize, final_usage,
                            final_memory_flags)?;

  copy_buffer(device, queue, command_pool, &staging_buffer, &final_buffer,
              size as vk::DeviceSize)?;

  unsafe { device.destroy_buffer(staging_buffer, None) };
  unsafe { device.free_memory(staging_memory, None) };

  Ok((final_buffer, device_memory))
}


#[allow(unsafe_code)]
fn init_descriptor_pool(device: &Device, count: usize)
    -> Result<vk::DescriptorPool>
{
  let uniform_block_size = vk::DescriptorPoolSize::builder()
          .type_(vk::DescriptorType::UNIFORM_BUFFER)
          .descriptor_count(count as u32);

  let sampler_size = vk::DescriptorPoolSize::builder()
          .type_(vk::DescriptorType::COMBINED_IMAGE_SAMPLER)
          .descriptor_count(count as u32);

  let sizes = [uniform_block_size, sampler_size];
  let pool_info = vk::DescriptorPoolCreateInfo::builder()
          .pool_sizes(&sizes)
          .max_sets(count as u32);
  let pool = unsafe { device.create_descriptor_pool(&pool_info, None) }?;

  Ok(pool)
}


#[allow(unsafe_code)]
fn init_descriptor_sets(device: &Device, layout: &vk::DescriptorSetLayout,
                        buffers: &Vec<vk::Buffer>, pool: &vk::DescriptorPool,
                        count: usize, texture_image_view: &vk::ImageView,
                        sampler: &vk::Sampler)
    -> Result<Vec<vk::DescriptorSet>>
{
  let layouts = vec![*layout; count];
  let set_info = vk::DescriptorSetAllocateInfo::builder()
          .descriptor_pool(*pool)
          .set_layouts(&layouts);
  let sets = unsafe { device.allocate_descriptor_sets(&set_info) }?;

  for index in 0 .. count {
    let buffer_info = vk::DescriptorBufferInfo::builder()
            .buffer(buffers[index])
            .offset(0)
            .range(size_of::<UniformBlock<f32>>() as vk::DeviceSize);

    let buffer_info_list = [buffer_info];
    let uniform_block_write_info = vk::WriteDescriptorSet::builder()
            .dst_set(sets[index])
            .dst_binding(0)
            .dst_array_element(0)
            .descriptor_type(vk::DescriptorType::UNIFORM_BUFFER)
            .buffer_info(&buffer_info_list);

    let image_info = vk::DescriptorImageInfo::builder()
            .image_layout(vk::ImageLayout::SHADER_READ_ONLY_OPTIMAL)
            .image_view(*texture_image_view)
            .sampler(*sampler);
    let image_info_list = [image_info];
    let sampler_write_info = vk::WriteDescriptorSet::builder()
            .dst_set(sets[index])
            .dst_binding(1)
            .dst_array_element(0)
            .descriptor_type(vk::DescriptorType::COMBINED_IMAGE_SAMPLER)
            .image_info(&image_info_list);

    let write_info_list = [uniform_block_write_info, sampler_write_info];
    let copy_info_list: [vk::CopyDescriptorSet; 0] = [];

    unsafe {
      device.update_descriptor_sets(&write_info_list, &copy_info_list)
    };
  }

  Ok(sets)
}


#[allow(unsafe_code)]
fn init_command_pools(device: &Device, indices: &QueueFamilyIndices)
    -> Result<(vk::CommandPool, vk::CommandPool)>
{
  let command_pool_info = vk::CommandPoolCreateInfo::builder()
                              .flags(vk::CommandPoolCreateFlags::empty())
                              .queue_family_index(indices.graphics);

  let primary = unsafe {
    device.create_command_pool(&command_pool_info, None)
  }?;

  command_pool_info.flags(vk::CommandPoolCreateFlags::TRANSIENT);
  let transient = unsafe {
    device.create_command_pool(&command_pool_info, None)
  }?;

  Ok((primary, transient))
}


#[allow(unsafe_code)]
fn init_commands(device: &Device,
                 extent: &vk::Extent2D,
                 framebuffers: &Vec<vk::Framebuffer>,
                 render_pass: &vk::RenderPass,
                 pipeline_layout: &vk::PipelineLayout,
                 pipeline: &vk::Pipeline,
                 vertex_buffer: &vk::Buffer,
                 index_buffer: &vk::Buffer,
                 descriptor_sets: &Vec<vk::DescriptorSet>,
                 command_pool: &vk::CommandPool)
    -> Result<Vec<vk::CommandBuffer>>
{
  let command_buffer_allocation_info
          = vk::CommandBufferAllocateInfo::builder()
                .command_pool(*command_pool)
                .level(vk::CommandBufferLevel::PRIMARY)
                .command_buffer_count(framebuffers.len() as u32);
  let command_buffers = unsafe {
    device.allocate_command_buffers(&command_buffer_allocation_info)
  }?;

  for (index, framebuffer) in framebuffers.iter().enumerate() {
    let command_buffer = command_buffers[index];

    let inheritance_info = vk::CommandBufferInheritanceInfo::builder();

    let command_buffer_begin_info = vk::CommandBufferBeginInfo::builder()
            .flags(vk::CommandBufferUsageFlags::empty())
            .inheritance_info(&inheritance_info);

    unsafe {
      device.begin_command_buffer(command_buffer, &command_buffer_begin_info)
    }?;

    let render_area = vk::Rect2D::builder()
                          .offset(vk::Offset2D::default())
                          .extent(*extent);

    let clear_value = vk::ClearValue {
      color: vk::ClearColorValue {
        float32: [0.0, 0.0, 0.0, 1.0]
      }
    };
    let clear_values = [clear_value];

    let begin_pass_info = vk::RenderPassBeginInfo::builder()
                              .render_pass(*render_pass)
                              .framebuffer(*framebuffer)
                              .render_area(render_area)
                              .clear_values(&clear_values);

    unsafe {
      device.cmd_begin_render_pass(command_buffer, &begin_pass_info,
                                   vk::SubpassContents::INLINE)
    };

    unsafe {
      device.cmd_bind_pipeline(command_buffer,
                               vk::PipelineBindPoint::GRAPHICS,
                               *pipeline)
    };

    unsafe {
      device.cmd_bind_vertex_buffers(command_buffer, 0,
                                     &[*vertex_buffer], &[0])
    };

    unsafe {
      device.cmd_bind_index_buffer(command_buffer, *index_buffer, 0,
                                   vk::IndexType::UINT16)
    };

    unsafe {
      device.cmd_bind_descriptor_sets(command_buffer,
                                      vk::PipelineBindPoint::GRAPHICS,
                                      *pipeline_layout,
                                      0,
                                      &[descriptor_sets[index]],
                                      &[])
    };

    unsafe {
      device.cmd_draw_indexed(command_buffer, INDICES.len() as u32,
                              1, 0, 0, 0)
    };

    unsafe { device.cmd_end_render_pass(command_buffer) };

    unsafe { device.end_command_buffer(command_buffer) }?;
  }

  Ok(command_buffers)
}


#[allow(unsafe_code)]
fn init_concurrency(device: &Device,
                    swapchain_images: &Vec<vk::Image>)
    -> Result<Concurrency>
{
  let semaphore_info = vk::SemaphoreCreateInfo::builder();
  let fence_info = vk::FenceCreateInfo::builder()
                       .flags(vk::FenceCreateFlags::SIGNALED);

  let mut image_available_semaphores = Vec::new();
  let mut rendering_finished_semaphores = Vec::new();
  let mut frame_fences = Vec::new();
  for _ in 0 .. N_SIMULTANEOUS_FRAMES {
    image_available_semaphores.push(unsafe {
      device.create_semaphore(&semaphore_info, None)
    }?);

    rendering_finished_semaphores.push(unsafe {
      device.create_semaphore(&semaphore_info, None)
    }?);

    frame_fences.push(unsafe {
      device.create_fence(&fence_info, None)
    }?);
  }

  let mut image_fences = Vec::new();
  for _ in 0 .. swapchain_images.len() {
    image_fences.push(vk::Fence::null());
  }

  Ok(Concurrency {
    image_available_semaphores,
    rendering_finished_semaphores,
    frame_fences,
    image_fences: image_fences,
  })
}


#[allow(unsafe_code)]
fn init_image_view(device: &Device, image: &vk::Image, format: vk::Format)
    -> Result<vk::ImageView>
{
  let components = vk::ComponentMapping::builder()
                       .r(vk::ComponentSwizzle::IDENTITY)
                       .g(vk::ComponentSwizzle::IDENTITY)
                       .b(vk::ComponentSwizzle::IDENTITY)
                       .a(vk::ComponentSwizzle::IDENTITY);

  let subresource_range = vk::ImageSubresourceRange::builder()
                              .aspect_mask(vk::ImageAspectFlags::COLOR)
                              .base_mip_level(0)
                              .level_count(1)
                              .base_array_layer(0)
                              .layer_count(1);

  let view_info = vk::ImageViewCreateInfo::builder()
                      .image(*image)
                      .view_type(vk::ImageViewType::_2D)
                      .format(format)
                      .components(components)
                      .subresource_range(subresource_range);

  let view = unsafe {
    device.create_image_view(&view_info, None)
  }?;

  Ok(view)
}


fn pick_surface_format(available_formats: &Vec<vk::SurfaceFormatKHR>)
    -> Result<vk::SurfaceFormatKHR>
{
  for format in available_formats {
    if format.format == vk::Format::B8G8R8A8_SRGB
       && format.color_space == vk::ColorSpaceKHR::SRGB_NONLINEAR
    {
      return Ok(format.clone());
    }
  }

  return Ok(available_formats[0].clone());
}


fn pick_presentation_mode(_available_modes: &Vec<vk::PresentModeKHR>)
    -> Result<vk::PresentModeKHR>
{
  // It's guaranteed to have this one.
  return Ok(vk::PresentModeKHR::FIFO);
}


fn pick_image_extent(window: &Window,
                     capabilities: vk::SurfaceCapabilitiesKHR)
    -> Result<vk::Extent2D>
{
  if capabilities.current_extent.width != u32::MAX
     && capabilities.current_extent.height != u32::MAX
  {
    Ok(capabilities.current_extent)
  } else {
    let window_size = window.inner_size();

    let width = window_size.width
                           .clamp(capabilities.min_image_extent.width,
                                  capabilities.max_image_extent.width);
    let height = window_size.height
                            .clamp(capabilities.min_image_extent.height,
                                   capabilities.max_image_extent.height);

    Ok(vk::Extent2D::builder().width(width).height(height).build())
  }
}


#[allow(unsafe_code)]
fn pick_memory_type(instance: &Instance,
                    physical_device: &vk::PhysicalDevice,
                    properties: &vk::MemoryPropertyFlags,
                    requirements: &vk::MemoryRequirements)
    -> Result<u32>
{
  let memory_map = unsafe {
    instance.get_physical_device_memory_properties(*physical_device)
  };

  //   So. The memory_type_bits field is a map of which indices are suitable,
  // based on the buffer our caller passed to
  // get_buffer_memory_requirements(). Yes, that means there's a hard cap on
  // how many memory types there can be, based on the size of the bitfield.
  for index in 0 .. memory_map.memory_type_count {
    if requirements.memory_type_bits & (1 << index) == 0 {
      continue;
    }

    let memory_type = memory_map.memory_types[index as usize];

    if memory_type.property_flags.contains(*properties) {
      return Ok(index);
    }
  }

  Err(Error {
    message: "The system has no suitable memory for a buffer.".to_string()
  })
}


#[allow(unsafe_code)]
fn stage_in_buffer<T>(instance: &Instance,
                      physical_device: &vk::PhysicalDevice, device: &Device,
                      contents: &[T])
    -> Result<(vk::Buffer, vk::DeviceMemory, usize)>
{
  let size = size_of::<T>() * contents.len();

  let staging_usage = vk::BufferUsageFlags::TRANSFER_SRC;
  let staging_memory_flags = vk::MemoryPropertyFlags::HOST_COHERENT
                             | vk::MemoryPropertyFlags::HOST_VISIBLE;
  let (staging_buffer, staging_memory)
          = allocate_buffer(instance, physical_device, device,
                            size as vk::DeviceSize, staging_usage,
                            staging_memory_flags)?;

  let host_memory = unsafe {
    device.map_memory(staging_memory, 0, size as vk::DeviceSize,
                      vk::MemoryMapFlags::empty())
  }?;

  unsafe {
    copy_nonoverlapping(contents.as_ptr(), host_memory.cast(), contents.len())
  };

  unsafe { device.unmap_memory(staging_memory) };

  Ok((staging_buffer, staging_memory, size))
}


#[allow(unsafe_code)]
fn allocate_buffer(instance: &Instance,
                   physical_device: &vk::PhysicalDevice, device: &Device,
                   size: vk::DeviceSize, usage: vk::BufferUsageFlags,
                   memory_flags: vk::MemoryPropertyFlags)
    -> Result<(vk::Buffer, vk::DeviceMemory)>
{
  let buffer_info = vk::BufferCreateInfo::builder()
                        .size(size)
                        .usage(usage)
                        .sharing_mode(vk::SharingMode::EXCLUSIVE);

  let buffer = unsafe { device.create_buffer(&buffer_info, None) }?;

  //   The requirements are mostly what you'd think: size and alignment. The
  // bits field is something special; see pick_memory_type() for the
  // explanation. Despite the simplicity of this data, Vulkan wants to be the
  // one to tell us about it, and we let it.
  let requirements = unsafe { device.get_buffer_memory_requirements(buffer) };

  let type_index = pick_memory_type(instance, physical_device,
                                    &memory_flags, &requirements)?;

  let memory_info = vk::MemoryAllocateInfo::builder()
                        .allocation_size(requirements.size)
                        .memory_type_index(type_index);

  let device_memory = unsafe { device.allocate_memory(&memory_info, None) }?;

  unsafe { device.bind_buffer_memory(buffer, device_memory, 0) }?;

  Ok((buffer, device_memory))
}


#[allow(unsafe_code)]
fn copy_buffer(device: &Device, queue: &vk::Queue,
               command_pool: &vk::CommandPool, source: &vk::Buffer,
               destination: &vk::Buffer, size: vk::DeviceSize)
    -> Result<()>
{
  let command_buffer = begin_transient_commands(device, command_pool)?;

  let copy_info = vk::BufferCopy::builder().size(size);
  unsafe {
    device.cmd_copy_buffer(command_buffer, *source, *destination,
                           &[copy_info])
  };

  end_transient_commands(command_buffer, device, queue, command_pool)?;

  Ok(())
}


#[allow(unsafe_code)]
fn allocate_image(instance: &Instance, physical_device: &vk::PhysicalDevice,
                  device: &Device, width: u32, height: u32,
                  format: vk::Format, tiling: vk::ImageTiling,
                  usage: vk::ImageUsageFlags,
                  memory_flags: vk::MemoryPropertyFlags)
    -> Result<(vk::Image, vk::DeviceMemory)>
{
  let image_info = vk::ImageCreateInfo::builder()
          .image_type(vk::ImageType::_2D)
          .extent(vk::Extent3D { width, height, depth: 1 })
          .mip_levels(1)
          .array_layers(1)
          .format(format)
          .tiling(tiling)
          .initial_layout(vk::ImageLayout::UNDEFINED)
          .usage(usage)
          .sharing_mode(vk::SharingMode::EXCLUSIVE)
          .samples(vk::SampleCountFlags::_1)
          .flags(vk::ImageCreateFlags::empty());
  let image = unsafe { device.create_image(&image_info, None) }?;

  let requirements = unsafe { device.get_image_memory_requirements(image) };

  let type_index = pick_memory_type(instance, physical_device,
                                    &memory_flags, &requirements)?;

  let image_memory_info = vk::MemoryAllocateInfo::builder()
          .allocation_size(requirements.size)
          .memory_type_index(type_index);
  let image_memory = unsafe {
    device.allocate_memory(&image_memory_info, None)
  }?;

  unsafe { device.bind_image_memory(image, image_memory, 0) }?;

  Ok((image, image_memory))
}


#[allow(unsafe_code)]
fn copy_buffer_to_image(device: &Device, queue: &vk::Queue,
                        command_pool: &vk::CommandPool, source: &vk::Buffer,
                        destination: &vk::Image, width: u32, height: u32)
    -> Result<()>
{
  let command_buffer = begin_transient_commands(device, command_pool)?;

  let subresource_layers = vk::ImageSubresourceLayers::builder()
          .aspect_mask(vk::ImageAspectFlags::COLOR)
          .mip_level(0)
          .base_array_layer(0)
          .layer_count(1);

  let copy_info = vk::BufferImageCopy::builder()
          .buffer_offset(0)
          .buffer_row_length(0)
          .buffer_image_height(0)
          .image_subresource(subresource_layers)
          .image_offset(vk::Offset3D { x: 0, y: 0, z: 0 })
          .image_extent(vk::Extent3D { width, height, depth: 1 });

  unsafe {
    device.cmd_copy_buffer_to_image(command_buffer, *source, *destination,
                                    vk::ImageLayout::TRANSFER_DST_OPTIMAL,
                                    &[copy_info])
  };

  end_transient_commands(command_buffer, device, queue, command_pool)?;

  Ok(())
}


#[allow(unsafe_code)]
fn change_image_layout(device: &Device, queue: &vk::Queue,
                       command_pool: &vk::CommandPool, image: &vk::Image,
                       format: vk::Format, old: vk::ImageLayout,
                       new: vk::ImageLayout)
    -> Result<()>
{
  let command_buffer = begin_transient_commands(device, command_pool)?;

  let subresource_range = vk::ImageSubresourceRange::builder()
                              .aspect_mask(vk::ImageAspectFlags::COLOR)
                              .base_mip_level(0)
                              .level_count(1)
                              .base_array_layer(0)
                              .layer_count(1);

  //   Notionally this is a property that our caller is in a better position
  // to know than we are, but in practice the nature of the transition
  // strongly implies a particular phase of the image's lifecycle, so we just
  // compute it here.
  let (source_access, source_stage, destination_access, destination_stage)
          = match (old, new)
  {
    (vk::ImageLayout::UNDEFINED, vk::ImageLayout::TRANSFER_DST_OPTIMAL)
        => (vk::AccessFlags::empty(),
            vk::PipelineStageFlags::TOP_OF_PIPE,
            vk::AccessFlags::TRANSFER_WRITE,
            vk::PipelineStageFlags::TRANSFER),
    (vk::ImageLayout::TRANSFER_DST_OPTIMAL,
     vk::ImageLayout::SHADER_READ_ONLY_OPTIMAL)
        => (vk::AccessFlags::TRANSFER_WRITE,
            vk::PipelineStageFlags::TRANSFER,
            vk::AccessFlags::SHADER_READ,
            vk::PipelineStageFlags::FRAGMENT_SHADER),
    _ => return Err(Error {
      message:
          format!("Don't know how to change from image layout {:?} to {:?}",
                  old, new)
    })
  };

  let barrier_info = vk::ImageMemoryBarrier::builder()
        .image(*image)
        .subresource_range(subresource_range)
        .old_layout(old)
        .new_layout(new)
        .src_queue_family_index(vk::QUEUE_FAMILY_IGNORED)
        .dst_queue_family_index(vk::QUEUE_FAMILY_IGNORED)
        .src_access_mask(source_access)
        .dst_access_mask(destination_access);

  unsafe {
    device.cmd_pipeline_barrier(command_buffer,
                                source_stage, destination_stage,
                                vk::DependencyFlags::empty(),
                                &[] as &[vk::MemoryBarrier],
                                &[] as &[vk::BufferMemoryBarrier],
                                &[barrier_info])
  };

  end_transient_commands(command_buffer, device, queue, command_pool)?;

  Ok(())
}


#[allow(unsafe_code)]
fn begin_transient_commands(device: &Device, command_pool: &vk::CommandPool)
    -> Result<vk::CommandBuffer>
{
  let command_buffer_allocation_info
          = vk::CommandBufferAllocateInfo::builder()
                .command_pool(*command_pool)
                .level(vk::CommandBufferLevel::PRIMARY)
                .command_buffer_count(1);
  let command_buffer = unsafe {
    device.allocate_command_buffers(&command_buffer_allocation_info)
  }?[0];

  let command_buffer_begin_info = vk::CommandBufferBeginInfo::builder()
          .flags(vk::CommandBufferUsageFlags::ONE_TIME_SUBMIT);

  unsafe {
    device.begin_command_buffer(command_buffer, &command_buffer_begin_info)
  }?;

  Ok(command_buffer)
}


#[allow(unsafe_code)]
fn end_transient_commands(command_buffer: vk::CommandBuffer,
                          device: &Device, queue: &vk::Queue,
                          command_pool: &vk::CommandPool)
    -> Result<()>
{
  unsafe { device.end_command_buffer(command_buffer) }?;

  let command_buffers = [command_buffer];
  let submit_info = vk::SubmitInfo::builder()
          .command_buffers(&command_buffers);
  unsafe { device.queue_submit(*queue, &[submit_info], vk::Fence::null()) }?;

  unsafe { device.queue_wait_idle(*queue) }?;

  unsafe { device.free_command_buffers(*command_pool, &command_buffers) };

  Ok(())
}