// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.

use deno_core::error::type_error;
use deno_core::error::AnyError;
use deno_core::futures::channel::oneshot;
use deno_core::op2;
use deno_core::OpState;
use deno_core::Resource;
use deno_core::ResourceId;
use std::borrow::Cow;
use std::cell::RefCell;
use std::rc::Rc;
use std::time::Duration;
use wgpu_core::resource::BufferAccessResult;

use super::error::DomExceptionOperationError;
use super::error::WebGpuResult;

pub(crate) struct WebGpuBuffer(
  pub(crate) super::Instance,
  pub(crate) wgpu_core::id::BufferId,
);
impl Resource for WebGpuBuffer {
  fn name(&self) -> Cow<str> {
    "webGPUBuffer".into()
  }

  fn close(self: Rc<Self>) {
    gfx_select!(self.1 => self.0.buffer_drop(self.1, true));
  }
}

struct WebGpuBufferMapped(*mut u8, usize);
impl Resource for WebGpuBufferMapped {
  fn name(&self) -> Cow<str> {
    "webGPUBufferMapped".into()
  }
}

#[op2]
#[serde]
pub fn op_webgpu_create_buffer(
  state: &mut OpState,
  #[smi] device_rid: ResourceId,
  #[string] label: Cow<str>,
  #[number] size: u64,
  usage: u32,
  mapped_at_creation: bool,
) -> Result<WebGpuResult, AnyError> {
  let instance = state.borrow::<super::Instance>();
  let device_resource = state
    .resource_table
    .get::<super::WebGpuDevice>(device_rid)?;
  let device = device_resource.1;

  let descriptor = wgpu_core::resource::BufferDescriptor {
    label: Some(label),
    size,
    usage: wgpu_types::BufferUsages::from_bits(usage)
      .ok_or_else(|| type_error("usage is not valid"))?,
    mapped_at_creation,
  };

  gfx_put!(device => instance.device_create_buffer(
    device,
    &descriptor,
    None
  ) => state, WebGpuBuffer)
}

#[op2(async)]
#[serde]
pub async fn op_webgpu_buffer_get_map_async(
  state: Rc<RefCell<OpState>>,
  #[smi] buffer_rid: ResourceId,
  #[smi] device_rid: ResourceId,
  mode: u32,
  #[number] offset: u64,
  #[number] size: u64,
) -> Result<WebGpuResult, AnyError> {
  let (sender, receiver) = oneshot::channel::<BufferAccessResult>();

  let device;
  {
    let state_ = state.borrow();
    let instance = state_.borrow::<super::Instance>();
    let buffer_resource =
      state_.resource_table.get::<WebGpuBuffer>(buffer_rid)?;
    let buffer = buffer_resource.1;
    let device_resource = state_
      .resource_table
      .get::<super::WebGpuDevice>(device_rid)?;
    device = device_resource.1;

    let callback = Box::new(move |status| {
      sender.send(status).unwrap();
    });

    // TODO(lucacasonato): error handling
    let maybe_err = gfx_select!(buffer => instance.buffer_map_async(
            buffer,
            offset,
            Some(size),
            wgpu_core::resource::BufferMapOperation {
                host: match mode {
                    1 => wgpu_core::device::HostMap::Read,
                    2 => wgpu_core::device::HostMap::Write,
                    _ => unreachable!(),
                },
                callback: Some(wgpu_core::resource::BufferMapCallback::from_rust(callback)),
            }
        ))
        .err();

    if maybe_err.is_some() {
      return Ok(WebGpuResult::maybe_err(maybe_err));
    }
  }

  let done = Rc::new(RefCell::new(false));
  let done_ = done.clone();
  let device_poll_fut = async move {
    while !*done.borrow() {
      {
        let state = state.borrow();
        let instance = state.borrow::<super::Instance>();
        gfx_select!(device => instance.device_poll(device, wgpu_types::Maintain::wait()))
                    .unwrap();
      }
      tokio::time::sleep(Duration::from_millis(10)).await;
    }
    Ok::<(), AnyError>(())
  };

  let receiver_fut = async move {
    receiver.await??;
    let mut done = done_.borrow_mut();
    *done = true;
    Ok::<(), AnyError>(())
  };

  tokio::try_join!(device_poll_fut, receiver_fut)?;

  Ok(WebGpuResult::empty())
}

#[op2]
#[serde]
pub fn op_webgpu_buffer_get_mapped_range(
  state: &mut OpState,
  #[smi] buffer_rid: ResourceId,
  #[number] offset: u64,
  #[number] size: Option<u64>,
  #[buffer] buf: &mut [u8],
) -> Result<WebGpuResult, AnyError> {
  let instance = state.borrow::<super::Instance>();
  let buffer_resource = state.resource_table.get::<WebGpuBuffer>(buffer_rid)?;
  let buffer = buffer_resource.1;

  let (slice_pointer, range_size) =
    gfx_select!(buffer => instance.buffer_get_mapped_range(
      buffer,
      offset,
      size
    ))
    .map_err(|e| DomExceptionOperationError::new(&e.to_string()))?;

  // SAFETY: guarantee to be safe from wgpu
  let slice = unsafe {
    std::slice::from_raw_parts_mut(slice_pointer, range_size as usize)
  };
  buf.copy_from_slice(slice);

  let rid = state
    .resource_table
    .add(WebGpuBufferMapped(slice_pointer, range_size as usize));

  Ok(WebGpuResult::rid(rid))
}

#[op2]
#[serde]
pub fn op_webgpu_buffer_unmap(
  state: &mut OpState,
  #[smi] buffer_rid: ResourceId,
  #[smi] mapped_rid: ResourceId,
  #[buffer] buf: Option<&[u8]>,
) -> Result<WebGpuResult, AnyError> {
  let mapped_resource = state
    .resource_table
    .take::<WebGpuBufferMapped>(mapped_rid)?;
  let instance = state.borrow::<super::Instance>();
  let buffer_resource = state.resource_table.get::<WebGpuBuffer>(buffer_rid)?;
  let buffer = buffer_resource.1;

  if let Some(buf) = buf {
    // SAFETY: guarantee to be safe from wgpu
    let slice = unsafe {
      std::slice::from_raw_parts_mut(mapped_resource.0, mapped_resource.1)
    };
    slice.copy_from_slice(buf);
  }

  gfx_ok!(buffer => instance.buffer_unmap(buffer))
}