// Copyright 2018 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "third_party/blink/renderer/modules/xr/xr_space.h"

#include <algorithm>
#include <array>
#include <cmath>

#include "third_party/blink/renderer/modules/event_target_modules.h"
#include "third_party/blink/renderer/modules/xr/xr_input_source.h"
#include "third_party/blink/renderer/modules/xr/xr_pose.h"
#include "third_party/blink/renderer/modules/xr/xr_rigid_transform.h"
#include "third_party/blink/renderer/modules/xr/xr_session.h"

namespace blink {

XRSpace::XRSpace(XRSession* session) : session_(session) {}

XRSpace::~XRSpace() = default;

std::optional<gfx::Transform> XRSpace::NativeFromViewer(
    const std::optional<gfx::Transform>& mojo_from_viewer) const {
  if (!mojo_from_viewer)
    return std::nullopt;

  std::optional<gfx::Transform> native_from_mojo = NativeFromMojo();
  if (!native_from_mojo)
    return std::nullopt;

  native_from_mojo->PreConcat(*mojo_from_viewer);

  // This is now native_from_viewer
  return native_from_mojo;
}

gfx::Transform XRSpace::NativeFromOffsetMatrix() const {
  gfx::Transform identity;
  return identity;
}

gfx::Transform XRSpace::OffsetFromNativeMatrix() const {
  gfx::Transform identity;
  return identity;
}

std::optional<gfx::Transform> XRSpace::MojoFromOffsetMatrix() const {
  auto maybe_mojo_from_native = MojoFromNative();
  if (!maybe_mojo_from_native) {
    return std::nullopt;
  }

  // Modifies maybe_mojo_from_native - it becomes mojo_from_offset_matrix.
  // Saves a heap allocation since there is no need to create a new unique_ptr.
  maybe_mojo_from_native->PreConcat(NativeFromOffsetMatrix());
  return maybe_mojo_from_native;
}

std::optional<gfx::Transform> XRSpace::NativeFromMojo() const {
  std::optional<gfx::Transform> mojo_from_native = MojoFromNative();
  if (!mojo_from_native)
    return std::nullopt;

  return mojo_from_native->GetCheckedInverse();
}

bool XRSpace::EmulatedPosition() const {
  return session()->EmulatedPosition();
}

XRPose* XRSpace::getPose(const XRSpace* other_space) const {
  DVLOG(2) << __func__ << ": ToString()=" << ToString()
           << ", other_space->ToString()=" << other_space->ToString();

  // Named mojo_from_offset because that is what we will leave it as, though it
  // starts mojo_from_native.
  std::optional<gfx::Transform> mojo_from_offset = MojoFromNative();
  if (!mojo_from_offset) {
    DVLOG(2) << __func__ << ": MojoFromNative() is not set";
    return nullptr;
  }

  // Add any origin offset now.
  mojo_from_offset->PreConcat(NativeFromOffsetMatrix());

  std::optional<gfx::Transform> other_from_mojo = other_space->NativeFromMojo();
  if (!other_from_mojo) {
    DVLOG(2) << __func__ << ": other_space->NativeFromMojo() is not set";
    return nullptr;
  }

  // Add any origin offset from the other space now.
  gfx::Transform other_offset_from_mojo =
      other_space->OffsetFromNativeMatrix() * other_from_mojo.value();

  // TODO(crbug.com/969133): Update how EmulatedPosition is determined here once
  // spec issue https://github.com/immersive-web/webxr/issues/534 has been
  // resolved.
  gfx::Transform other_offset_from_offset =
      other_offset_from_mojo * mojo_from_offset.value();

  return MakeGarbageCollected<XRPose>(
      other_offset_from_offset,
      EmulatedPosition() || other_space->EmulatedPosition());
}

std::optional<gfx::Transform> XRSpace::OffsetFromViewer() const {
  std::optional<gfx::Transform> native_from_viewer =
      NativeFromViewer(session()->GetMojoFrom(
          device::mojom::blink::XRReferenceSpaceType::kViewer));

  if (!native_from_viewer) {
    return std::nullopt;
  }

  return OffsetFromNativeMatrix() * *native_from_viewer;
}

ExecutionContext* XRSpace::GetExecutionContext() const {
  return session()->GetExecutionContext();
}

const AtomicString& XRSpace::InterfaceName() const {
  return event_target_names::kXRSpace;
}

void XRSpace::Trace(Visitor* visitor) const {
  visitor->Trace(session_);
  ScriptWrappable::Trace(visitor);
  EventTarget::Trace(visitor);
}

}  // namespace blink