#![deny(unsafe_code)]
use crate::error::*;
use crate::assets::asset;
use crate::graphics::{
  Permanent, ForReinit, WindowDressing, Frame, Model, Texture
};
use crate::shader_data::{ Vertex, VertexPushBlock };

use std::mem::size_of;

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


//   Render is a state object that collects the Vulkan graphics objects which
// need to be regenerated or modified when the window changes, as with
// WindowDressing, and which are also used as part of rendering.
#[derive(Debug)]
pub struct Render {
  pub render_pass: vk::RenderPass,

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

  pub model: Option<Model>,

  pub per_frame: Vec<Frame>,
}


impl Render {
  pub fn new(permanent: &Permanent, for_reinit: &ForReinit,
             window_dressing: &WindowDressing, texture: &Texture)
      -> Result<Self>
  {
    let device = &permanent.device;
    let sample_count = for_reinit.sample_count;
    let descriptor_set_layout = &for_reinit.descriptor_set_layout;
    let swapchain = &window_dressing.swapchain;
    let depth_format = &window_dressing.depth_format;

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

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

    let per_frame = Frame::new(permanent, for_reinit, window_dressing,
                               texture, &render_pass)?;

    let model = None;

    Ok(Render {
      render_pass,
      pipeline,
      pipeline_layout,
      model,
      per_frame,
    })
  }

  //   This relies on its caller to have already waited for the device to be
  // idle.
  pub fn reinit(&mut self,
                permanent: &Permanent, for_reinit: &ForReinit,
                window_dressing: &WindowDressing, texture: &Texture)
      -> Result<()>
  {
    self.destroy_replaceable(permanent);

    let device = &permanent.device;
    let sample_count = for_reinit.sample_count;
    let descriptor_set_layout = &for_reinit.descriptor_set_layout;
    let swapchain = &window_dressing.swapchain;
    let depth_format = &window_dressing.depth_format;

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

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

    Frame::reinit(&mut self.per_frame, permanent, for_reinit, window_dressing,
                  texture, &render_pass)?;

    self.render_pass = render_pass;
    self.pipeline = pipeline;
    self.pipeline_layout = pipeline_layout;

    Ok(())
  }

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

    if let Some(model) = self.model {
      model.destroy(&permanent.device);
    }
  }

  #[allow(unsafe_code)]
  fn destroy_replaceable(&mut self, permanent: &Permanent) {
    let device = &permanent.device;

    let mut command_buffers = Vec::new();
    for frame in &self.per_frame {
      unsafe { device.destroy_framebuffer(frame.framebuffer, None) };

      command_buffers.push(frame.command_buffer);
    }

    //   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(permanent.primary_command_pool,
                                  &command_buffers)
    };

    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) };
  }

  pub fn set_model(&mut self, model: Model) {
    self.model = Some(model);
  }
}


#[allow(unsafe_code)]
fn init_render_pass(device: &Device, sample_count: vk::SampleCountFlags,
                    color_format: &vk::Format, depth_format: &vk::Format)
    -> Result<vk::RenderPass>
{
  let color_attachment = vk::AttachmentDescription::builder()
          .format(*color_format)
          .samples(sample_count)
          .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::COLOR_ATTACHMENT_OPTIMAL);

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

  let depth_attachment = vk::AttachmentDescription::builder()
          .format(*depth_format)
          .samples(sample_count)
          .load_op(vk::AttachmentLoadOp::CLEAR)
          .store_op(vk::AttachmentStoreOp::DONT_CARE)
          .stencil_load_op(vk::AttachmentLoadOp::DONT_CARE)
          .stencil_store_op(vk::AttachmentStoreOp::DONT_CARE)
          .initial_layout(vk::ImageLayout::UNDEFINED)
          .final_layout(vk::ImageLayout::DEPTH_STENCIL_ATTACHMENT_OPTIMAL);

  let depth_attachment_reference = vk::AttachmentReference::builder()
          .attachment(1)
          .layout(vk::ImageLayout::DEPTH_STENCIL_ATTACHMENT_OPTIMAL);

  let color_resolve_attachment = vk::AttachmentDescription::builder()
          .format(*color_format)
          .samples(vk::SampleCountFlags::_1)
          .load_op(vk::AttachmentLoadOp::DONT_CARE)
          .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_resolve_attachment_reference = vk::AttachmentReference::builder()
          .attachment(2)
          .layout(vk::ImageLayout::COLOR_ATTACHMENT_OPTIMAL);

  let color_attachments = [color_attachment_reference];
  let resolve_attachments = [color_resolve_attachment_reference];
  let subpass = vk::SubpassDescription::builder()
          .pipeline_bind_point(vk::PipelineBindPoint::GRAPHICS)
          .color_attachments(&color_attachments)
          .depth_stencil_attachment(&depth_attachment_reference)
          .resolve_attachments(&resolve_attachments);

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

  let render_attachments = [color_attachment,
                            depth_attachment,
                            color_resolve_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, sample_count: vk::SampleCountFlags,
                 render_pass: &vk::RenderPass)
    -> Result<(vk::PipelineLayout, vk::Pipeline)>
{
  let vertex_binary = asset("shaders/shader.vert.spv")?;
  let fragment_binary = asset("shaders/shader.frag.spv")?;

  let vertex_module = Permanent::load_spirv_shader_module(
          device, vertex_binary)?;
  let fragment_module = Permanent::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(sample_count);

  let depth_state_info = vk::PipelineDepthStencilStateCreateInfo::builder()
          .depth_test_enable(true)
          .depth_write_enable(true)
          .depth_compare_op(vk::CompareOp::LESS)
          .depth_bounds_test_enable(false)
          .min_depth_bounds(0.0)
          .max_depth_bounds(1.0)
          .stencil_test_enable(false);

  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 vertex_push_constant_range = vk::PushConstantRange::builder()
          .stage_flags(vk::ShaderStageFlags::VERTEX)
          .offset(0)
          .size(size_of::<VertexPushBlock<f32>>() as u32);

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

  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)
          .depth_stencil_state(&depth_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))
}