src/dawn/wire/client/EventManager.cpp

// Copyright 2023 The Dawn Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include <unordered_map>
#include <utility>
#include <vector>

#include "dawn/wire/ObjectHandle.h"
#include "dawn/wire/client/Client.h"
#include "dawn/wire/client/EventManager.h"

namespace dawn::wire::client {

// EventManager

EventManager::EventManager(Client* client) : mClient(client) {}

std::pair<FutureID, bool> EventManager::TrackEvent(WGPUCallbackMode mode,
                                                   EventCallback&& callback) {
    FutureID futureID = mNextFutureID++;

    if (mClient->IsDisconnected()) {
        callback(EventCompletionType::Shutdown);
        return {futureID, false};
    }

    mTrackedEvents.Use([&](auto trackedEvents) {
        auto [it, inserted] =
            trackedEvents->emplace(futureID, TrackedEvent(mode, std::move(callback)));
        DAWN_ASSERT(inserted);
    });

    return {futureID, true};
}

void EventManager::ShutDown() {
    // Call any outstanding callbacks before destruction.
    while (true) {
        std::unordered_map<FutureID, TrackedEvent> movedEvents;
        mTrackedEvents.Use([&](auto trackedEvents) { movedEvents = std::move(*trackedEvents); });

        if (movedEvents.empty()) {
            break;
        }

        for (auto& [futureID, trackedEvent] : movedEvents) {
            // Event should be already marked Ready since events are actually driven by
            // RequestTrackers (at the time of this writing), which all shut down before this.
            DAWN_ASSERT(trackedEvent.mReady);
            trackedEvent.mCallback(EventCompletionType::Shutdown);
            trackedEvent.mCallback = nullptr;
        }
    }
}

void EventManager::SetFutureReady(FutureID futureID) {
    DAWN_ASSERT(futureID > 0);
    mTrackedEvents.Use([&](auto trackedEvents) {
        TrackedEvent& trackedEvent = trackedEvents->at(futureID);  // Asserts futureID is in the map
        trackedEvent.mReady = true;
    });
    // TODO(crbug.com/dawn/2059): Handle spontaneous completions.
}

void EventManager::ProcessPollEvents() {
    std::vector<TrackedEvent> eventsToCompleteNow;

    // TODO(crbug.com/dawn/2060): EventManager shouldn't bother to track ProcessEvents-type events
    // until they've completed. We can queue them up when they're received on the wire. (Before that
    // point, the RequestTracker tracks them. If/when we merge this with RequestTracker, then we'll
    // track both here but still don't need to queue them for ProcessEvents until they complete.)
    mTrackedEvents.Use([&](auto trackedEvents) {
        for (auto it = trackedEvents->begin(); it != trackedEvents->end();) {
            TrackedEvent& event = it->second;
            bool shouldRemove = (event.mMode == WGPUCallbackMode_AllowProcessEvents ||
                                 event.mMode == WGPUCallbackMode_AllowSpontaneous) &&
                                event.mReady;
            if (!shouldRemove) {
                ++it;
                continue;
            }

            // mCallback may still be null if it's stale (was already spontaneously completed).
            if (event.mCallback) {
                eventsToCompleteNow.emplace_back(std::move(event));
            }
            it = trackedEvents->erase(it);
        }
    });

    for (TrackedEvent& event : eventsToCompleteNow) {
        DAWN_ASSERT(event.mReady && event.mCallback);
        event.mCallback(EventCompletionType::Ready);
        event.mCallback = nullptr;
    }
}

WGPUWaitStatus EventManager::WaitAny(size_t count, WGPUFutureWaitInfo* infos, uint64_t timeoutNS) {
    // Validate for feature support.
    if (timeoutNS > 0) {
        // Wire doesn't support timedWaitEnable (for now). (There's no UnsupportedCount or
        // UnsupportedMixedSources validation here, because those only apply to timed waits.)
        //
        // TODO(crbug.com/dawn/1987): CreateInstance needs to validate timedWaitEnable was false.
        return WGPUWaitStatus_UnsupportedTimeout;
    }

    if (count == 0) {
        return WGPUWaitStatus_Success;
    }

    std::vector<TrackedEvent> eventsToCompleteNow;
    bool anyCompleted = false;
    const FutureID firstInvalidFutureID = mNextFutureID;
    mTrackedEvents.Use([&](auto trackedEvents) {
        for (size_t i = 0; i < count; ++i) {
            FutureID futureID = infos[i].future.id;
            DAWN_ASSERT(futureID < firstInvalidFutureID);

            auto it = trackedEvents->find(futureID);
            if (it == trackedEvents->end()) {
                infos[i].completed = true;
                anyCompleted = true;
                continue;
            }

            TrackedEvent& event = it->second;
            // Early update .completed, in prep to complete the callback if ready.
            infos[i].completed = event.mReady;
            if (event.mReady) {
                anyCompleted = true;
                if (event.mCallback) {
                    eventsToCompleteNow.emplace_back(std::move(event));
                }
                trackedEvents->erase(it);
            }
        }
    });

    // TODO(crbug.com/dawn/2066): Guarantee the event ordering from the JS spec.
    for (TrackedEvent& event : eventsToCompleteNow) {
        DAWN_ASSERT(event.mReady && event.mCallback);
        // .completed has already been set to true (before the callback, per API contract).
        event.mCallback(EventCompletionType::Ready);
        event.mCallback = nullptr;
    }

    return anyCompleted ? WGPUWaitStatus_Success : WGPUWaitStatus_TimedOut;
}

// EventManager::TrackedEvent

EventManager::TrackedEvent::TrackedEvent(WGPUCallbackMode mode, EventCallback&& callback)
    : mMode(mode), mCallback(callback) {}

EventManager::TrackedEvent::~TrackedEvent() {
    // Make sure we're not dropping a callback on the floor.
    DAWN_ASSERT(!mCallback);
}

}  // namespace dawn::wire::client