// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.
use crate::ops::*;
use crate::OpResult;
use crate::PromiseId;
use anyhow::Error;
use futures::future::Either;
use futures::future::Future;
use futures::future::FutureExt;
use futures::task::noop_waker_ref;
use std::cell::RefCell;
use std::future::ready;
use std::option::Option;
use std::task::Context;
use std::task::Poll;

#[inline]
pub fn queue_fast_async_op<R: serde::Serialize + 'static>(
  ctx: &OpCtx,
  promise_id: PromiseId,
  op: impl Future<Output = Result<R, Error>> + 'static,
) {
  let get_class = {
    let state = RefCell::borrow(&ctx.state);
    state.tracker.track_async(ctx.id);
    state.get_error_class_fn
  };
  let fut = op.map(|result| crate::_ops::to_op_result(get_class, result));
  // SAFETY: this is guaranteed to be running on a current-thread executor
  ctx.context_state.borrow_mut().pending_ops.spawn(unsafe {
    crate::task::MaskFutureAsSend::new(OpCall::new(ctx, promise_id, fut))
  });
}

#[inline]
pub fn map_async_op1<R: serde::Serialize + 'static>(
  ctx: &OpCtx,
  op: impl Future<Output = Result<R, Error>> + 'static,
) -> impl Future<Output = OpResult> {
  let get_class = {
    let state = RefCell::borrow(&ctx.state);
    state.tracker.track_async(ctx.id);
    state.get_error_class_fn
  };

  op.map(|res| crate::_ops::to_op_result(get_class, res))
}

#[inline]
pub fn map_async_op2<R: serde::Serialize + 'static>(
  ctx: &OpCtx,
  op: impl Future<Output = R> + 'static,
) -> impl Future<Output = OpResult> {
  let state = RefCell::borrow(&ctx.state);
  state.tracker.track_async(ctx.id);

  op.map(|res| OpResult::Ok(res.into()))
}

#[inline]
pub fn map_async_op3<R: serde::Serialize + 'static>(
  ctx: &OpCtx,
  op: Result<impl Future<Output = Result<R, Error>> + 'static, Error>,
) -> impl Future<Output = OpResult> {
  let get_class = {
    let state = RefCell::borrow(&ctx.state);
    state.tracker.track_async(ctx.id);
    state.get_error_class_fn
  };

  match op {
    Err(err) => {
      Either::Left(ready(OpResult::Err(OpError::new(get_class, err))))
    }
    Ok(fut) => {
      Either::Right(fut.map(|res| crate::_ops::to_op_result(get_class, res)))
    }
  }
}

#[inline]
pub fn map_async_op4<R: serde::Serialize + 'static>(
  ctx: &OpCtx,
  op: Result<impl Future<Output = R> + 'static, Error>,
) -> impl Future<Output = OpResult> {
  let get_class = {
    let state = RefCell::borrow(&ctx.state);
    state.tracker.track_async(ctx.id);
    state.get_error_class_fn
  };

  match op {
    Err(err) => {
      Either::Left(ready(OpResult::Err(OpError::new(get_class, err))))
    }
    Ok(fut) => Either::Right(fut.map(|r| OpResult::Ok(r.into()))),
  }
}

pub fn queue_async_op<'s>(
  ctx: &OpCtx,
  scope: &'s mut v8::HandleScope,
  deferred: bool,
  promise_id: PromiseId,
  op: impl Future<Output = OpResult> + 'static,
) -> Option<v8::Local<'s, v8::Value>> {
  // An op's realm (as given by `OpCtx::realm_idx`) must match the realm in
  // which it is invoked. Otherwise, we might have cross-realm object exposure.
  // deno_core doesn't currently support such exposure, even though embedders
  // can cause them, so we panic in debug mode (since the check is expensive).
  // TODO(mmastrac): Restore this
  // debug_assert_eq!(
  //   runtime_state.borrow().context(ctx.realm_idx as usize, scope),
  //   Some(scope.get_current_context())
  // );

  let id = ctx.id;

  // TODO(mmastrac): We have to poll every future here because that assumption is baked into a large number
  // of ops. If we can figure out a way around this, we can remove this call to boxed_local and save a malloc per future.
  let mut pinned = op.map(move |res| (promise_id, id, res)).boxed_local();

  match pinned.poll_unpin(&mut Context::from_waker(noop_waker_ref())) {
    Poll::Pending => {}
    Poll::Ready(mut res) => {
      if deferred {
        ctx
          .context_state
          .borrow_mut()
          .pending_ops
          // SAFETY: this is guaranteed to be running on a current-thread executor
          .spawn(unsafe { crate::task::MaskFutureAsSend::new(ready(res)) });
        return None;
      } else {
        ctx.state.borrow_mut().tracker.track_async_completed(ctx.id);
        return Some(res.2.to_v8(scope).unwrap());
      }
    }
  }

  ctx
    .context_state
    .borrow_mut()
    .pending_ops
    // SAFETY: this is guaranteed to be running on a current-thread executor
    .spawn(unsafe { crate::task::MaskFutureAsSend::new(pinned) });
  None
}