#![allow(unsafe_code)]
use crate::error::*;

use std::mem::size_of;
use std::ptr::copy_nonoverlapping;

use vulkanalia::{ Device, Instance };
use vulkanalia::vk::{ self, Handle, HasBuilder, InstanceV1_0, DeviceV1_0 };


#[allow(unsafe_code)]
pub 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))
}


pub 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)]
pub 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)]
pub 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)]
pub 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)]
pub 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)]
pub 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(())
}