#![deny(unsafe_code)]
use crate::error::*;
use crate::graphics::{ Permanent, ForReinit, WindowDressing, Texture };
use crate::shader_data::UniformBlock;

use std::mem::size_of;

use vulkanalia::Device;
use vulkanalia::vk::{ self, HasBuilder, DeviceV1_0 };


//   Frame is a state object that collects the Vulkan graphics objects which
// are used as part of rendering and which need to exist in multiples, one for
// each frame that can be rendered in parallel (see N_SIMULTANEOUS_FRAMES in
// window_dressing.rs). As with WindowDressing, these need to be regenerated
// or modified when the window changes.
#[derive(Debug)]
pub struct Frame {
  pub framebuffer: vk::Framebuffer,
  pub command_buffer: vk::CommandBuffer,
  pub descriptor_set: vk::DescriptorSet,
}


impl Frame {
  //   The lifecycle stuff for Frame is a little different. The Vulkan API to
  // allocate and deallocate command buffers is designed on the assumption you
  // want to handle a few of them simultaneously. That is in fact what we want,
  // so the interfaces to new() and reinit() work on Vec<Frame> instead of on
  // an indidivual Frame.
  pub fn new(permanent: &Permanent, for_reinit: &ForReinit,
             window_dressing: &WindowDressing, texture: &Texture,
             render_pass: &vk::RenderPass)
      -> Result<Vec<Self>>
  {
    let device = &permanent.device;
    let primary_command_pool = &permanent.primary_command_pool;
    let descriptor_set_layout = &for_reinit.descriptor_set_layout;
    let swapchain = &window_dressing.swapchain;
    let color_image_view = &window_dressing.color_image_view;
    let depth_image_view = &window_dressing.depth_image_view;
    let uniform_buffers = &window_dressing.uniform_buffers;
    let descriptor_pool = &window_dressing.descriptor_pool;
    let sampler = &window_dressing.sampler;

    let count = swapchain.image_views.len();

    let command_buffers = init_command_buffers(count, device,
                                               primary_command_pool)?;

    let descriptor_sets
            = init_descriptor_sets(count, device, descriptor_set_layout,
                                   &uniform_buffers, &descriptor_pool,
                                   &texture.image_view, &sampler)?;

    let mut frames = Vec::new();
    for (index, color_resolve_image_view)
        in swapchain.image_views.iter().enumerate()
    {
      let framebuffer = init_framebuffer(
              device, &swapchain.extent, &color_image_view, &depth_image_view,
              color_resolve_image_view, &render_pass)?;

      frames.push(Frame {
        command_buffer: command_buffers[index],
        descriptor_set: descriptor_sets[index],
        framebuffer,
      });
    }

    Ok(frames)
  }

  // See new() in regard to the Vec.
  pub fn reinit(frames: &mut Vec<Self>, permanent: &Permanent,
                for_reinit: &ForReinit, window_dressing: &WindowDressing,
                texture: &Texture, render_pass: &vk::RenderPass)
      -> Result<()>
  {
    let device = &permanent.device;
    let primary_command_pool = &permanent.primary_command_pool;
    let descriptor_set_layout = &for_reinit.descriptor_set_layout;
    let swapchain = &window_dressing.swapchain;
    let color_image_view = &window_dressing.color_image_view;
    let depth_image_view = &window_dressing.depth_image_view;
    let uniform_buffers = &window_dressing.uniform_buffers;
    let descriptor_pool = &window_dressing.descriptor_pool;
    let sampler = &window_dressing.sampler;

    frames.clear();

    let count = swapchain.image_views.len();

    // Notice that we reused the command pool.
    let command_buffers = init_command_buffers(count, device,
                                               primary_command_pool)?;

    let descriptor_sets
            = init_descriptor_sets(count, device, descriptor_set_layout,
                                   &uniform_buffers, &descriptor_pool,
                                   &texture.image_view, sampler)?;

    for (index, color_resolve_image_view)
        in swapchain.image_views.iter().enumerate()
    {
      let framebuffer = init_framebuffer(
              device, &swapchain.extent, &color_image_view, &depth_image_view,
              color_resolve_image_view, &render_pass)?;

      frames.push(Frame {
        command_buffer: command_buffers[index],
        descriptor_set: descriptor_sets[index],
        framebuffer,
      });
    }

    Ok(())
  }
}


#[allow(unsafe_code)]
fn init_framebuffer(device: &Device, extent: &vk::Extent2D,
                     color_image_view: &vk::ImageView,
                     depth_image_view: &vk::ImageView,
                     color_resolve_image_view: &vk::ImageView,
                     render_pass: &vk::RenderPass)
    -> Result<vk::Framebuffer>
{
  let attachments = [*color_image_view,
                     *depth_image_view,
                     *color_resolve_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)
  }?;

  Ok(framebuffer)
}


#[allow(unsafe_code)]
fn init_command_buffers(count: usize, device: &Device,
                        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(count as u32);
  let command_buffers = unsafe {
    device.allocate_command_buffers(&command_buffer_allocation_info)
  }?;

  Ok(command_buffers)
}


#[allow(unsafe_code)]
fn init_descriptor_sets(count: usize, device: &Device,
                        layout: &vk::DescriptorSetLayout,
                        buffers: &Vec<vk::Buffer>, pool: &vk::DescriptorPool,
                        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 sampler_image_info = vk::DescriptorImageInfo::builder()
            .sampler(*sampler);
    let sampler_image_info_list = [sampler_image_info];
    let sampler_write_info = vk::WriteDescriptorSet::builder()
            .dst_set(sets[index])
            .dst_binding(1)
            .dst_array_element(0)
            .descriptor_type(vk::DescriptorType::SAMPLER)
            .image_info(&sampler_image_info_list);

    let texture_image_info = vk::DescriptorImageInfo::builder()
            .image_layout(vk::ImageLayout::SHADER_READ_ONLY_OPTIMAL)
            .image_view(*texture_image_view);
    let texture_image_info_list = [texture_image_info];
    let texture_write_info = vk::WriteDescriptorSet::builder()
            .dst_set(sets[index])
            .dst_binding(2)
            .dst_array_element(0)
            .descriptor_type(vk::DescriptorType::SAMPLED_IMAGE)
            .image_info(&texture_image_info_list);

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

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

  Ok(sets)
}