foundationdb/flow/genericactors.actor.h

/*
 * genericactors.actor.h
 *
 * This source file is part of the FoundationDB open source project
 *
 * Copyright 2013-2018 Apple Inc. and the FoundationDB project 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.
 */

#pragma once

// When actually compiled (NO_INTELLISENSE), include the generated version of this file.  In intellisense use the source
// version.
#include <utility>
#if defined(NO_INTELLISENSE) && !defined(FLOW_GENERICACTORS_ACTOR_G_H)
#define FLOW_GENERICACTORS_ACTOR_G_H
#include "flow/genericactors.actor.g.h"
#elif !defined(GENERICACTORS_ACTOR_H)
#define GENERICACTORS_ACTOR_H

#include <list>
#include <utility>

#include "flow/flow.h"
#include "flow/Knobs.h"
#include "flow/Util.h"
#include "flow/IndexedSet.h"
#include "flow/actorcompiler.h" // This must be the last #include.

#ifdef _MSC_VER
#pragma warning(disable : 4355) // 'this' : used in base member initializer list
#endif

ACTOR template <class T, class X>
Future<T> traceAfter(Future<T> what, const char* type, const char* key, X value, bool traceErrors = false) {
	try {
		T val = wait(what);
		TraceEvent(type).detail(key, value);
		return val;
	} catch (Error& e) {
		if (traceErrors)
			TraceEvent(type).error(e, true).detail(key, value);
		throw;
	}
}

ACTOR template <class T, class X>
Future<T> traceAfterCall(Future<T> what, const char* type, const char* key, X func, bool traceErrors = false) {
	try {
		state T val = wait(what);
		try {
			TraceEvent(type).detail(key, func(val));
		} catch (Error& e) {
			TraceEvent(SevError, "TraceAfterCallError").error(e);
		}
		return val;
	} catch (Error& e) {
		if (traceErrors)
			TraceEvent(type).error(e, true);
		throw;
	}
}

ACTOR template <class T>
Future<Optional<T>> stopAfter(Future<T> what) {
	state Optional<T> ret = T();
	try {
		T _ = wait(what);
		ret = Optional<T>(_);
	} catch (Error& e) {
		bool ok = e.code() == error_code_please_reboot || e.code() == error_code_please_reboot_delete ||
		          e.code() == error_code_actor_cancelled;
		TraceEvent(ok ? SevInfo : SevError, "StopAfterError").error(e);
		if (!ok) {
			fprintf(stderr, "Fatal Error: %s\n", e.what());
			ret = Optional<T>();
		}
	}
	g_network->stop();
	return ret;
}

template <class T>
T sorted(T range) {
	std::sort(range.begin(), range.end());
	return range;
}

template <class T>
ErrorOr<T> errorOr(T t) {
	return ErrorOr<T>(t);
}

ACTOR template <class T>
Future<ErrorOr<T>> errorOr(Future<T> f) {
	try {
		T t = wait(f);
		return ErrorOr<T>(t);
	} catch (Error& e) {
		return ErrorOr<T>(e);
	}
}

ACTOR template <class T>
Future<T> throwErrorOr(Future<ErrorOr<T>> f) {
	ErrorOr<T> t = wait(f);
	if (t.isError())
		throw t.getError();
	return t.get();
}

ACTOR template <class T>
Future<T> transformErrors(Future<T> f, Error err) {
	try {
		T t = wait(f);
		return t;
	} catch (Error& e) {
		if (e.code() == error_code_actor_cancelled)
			throw e;
		throw err;
	}
}

ACTOR template <class T>
Future<T> transformError(Future<T> f, Error inErr, Error outErr) {
	try {
		T t = wait(f);
		return t;
	} catch (Error& e) {
		if (e.code() == inErr.code())
			throw outErr;
		throw e;
	}
}

// Note that the RequestStream<T> version of forwardPromise doesn't exist, because what to do with errors?

ACTOR template <class T>
void forwardEvent(Event* ev, Future<T> input) {
	try {
		T value = wait(input);
	} catch (Error&) {
	}
	ev->set();
}

ACTOR template <class T>
void forwardEvent(Event* ev, T* t, Error* err, FutureStream<T> input) {
	try {
		T value = waitNext(input);
		*t = std::move(value);
		ev->set();
	} catch (Error& e) {
		*err = e;
		ev->set();
	}
}

ACTOR template <class T>
Future<Void> waitForAllReady(std::vector<Future<T>> results) {
	state int i = 0;
	loop {
		if (i == results.size())
			return Void();
		try {
			wait(success(results[i]));
		} catch (...) {
		}
		i++;
	}
}

ACTOR template <class T>
Future<T> timeout(Future<T> what, double time, T timedoutValue, TaskPriority taskID = TaskPriority::DefaultDelay) {
	Future<Void> end = delay(time, taskID);
	choose {
		when(T t = wait(what)) { return t; }
		when(wait(end)) { return timedoutValue; }
	}
}

ACTOR template <class T>
Future<Optional<T>> timeout(Future<T> what, double time) {
	Future<Void> end = delay(time);
	choose {
		when(T t = wait(what)) { return t; }
		when(wait(end)) { return Optional<T>(); }
	}
}

ACTOR template <class T>
Future<T> timeoutError(Future<T> what, double time, TaskPriority taskID = TaskPriority::DefaultDelay) {
	Future<Void> end = delay(time, taskID);
	choose {
		when(T t = wait(what)) { return t; }
		when(wait(end)) { throw timed_out(); }
	}
}

ACTOR template <class T>
Future<T> delayed(Future<T> what, double time = 0.0, TaskPriority taskID = TaskPriority::DefaultDelay) {
	try {
		state T t = wait(what);
		wait(delay(time, taskID));
		return t;
	} catch (Error& e) {
		state Error err = e;
		wait(delay(time, taskID));
		throw err;
	}
}

ACTOR template <class Func>
Future<Void> recurring(Func what, double interval, TaskPriority taskID = TaskPriority::DefaultDelay) {
	loop choose {
		when(wait(delay(interval, taskID))) { what(); }
	}
}

ACTOR template <class Func>
Future<Void> trigger(Func what, Future<Void> signal) {
	wait(signal);
	what();
	return Void();
}

ACTOR template <class Func>
Future<Void> triggerOnError(Func what, Future<Void> signal) {
	try {
		wait(signal);
	} catch (Error& e) {
		what();
	}

	return Void();
}

// Waits for a future to complete and cannot be cancelled
// Most situations will use the overload below, which does not require a promise
ACTOR template <class T>
void uncancellable(Future<T> what, Promise<T> result) {
	try {
		T val = wait(what);
		result.send(val);
	} catch (Error& e) {
		result.sendError(e);
	}
}

// Waits for a future to complete and cannot be cancelled
ACTOR template <class T>
[[flow_allow_discard]] Future<T> uncancellable(Future<T> what) {
	Promise<T> resultPromise;
	Future<T> result = resultPromise.getFuture();

	uncancellable(what, resultPromise);
	T val = wait(result);

	return val;
}

// Holds onto an object until a future either completes or is cancelled
// Used to prevent the object from being reclaimed
//
// NOTE: the order of the arguments is important. The arguments will be destructed in
// reverse order, and we need the object to be destructed last.
ACTOR template <class T, class X>
Future<T> holdWhile(X object, Future<T> what) {
	T val = wait(what);
	return val;
}

ACTOR template <class T, class X>
Future<Void> holdWhileVoid(X object, Future<T> what) {
	T val = wait(what);
	return Void();
}

// Assign the future value of what to out
template <class T>
Future<Void> store(T& out, Future<T> what) {
	return map(what, [&out](T const& v) {
		out = v;
		return Void();
	});
}

template <class T>
Future<Void> storeOrThrow(T& out, Future<Optional<T>> what, Error e = key_not_found()) {
	return map(what, [&out, e](Optional<T> const& o) {
		if (!o.present())
			throw e;
		out = o.get();
		return Void();
	});
}

// Waits for a future to be ready, and then applies an asynchronous function to it.
ACTOR template <class T, class F, class U = decltype(std::declval<F>()(std::declval<T>()).getValue())>
Future<U> mapAsync(Future<T> what, F actorFunc) {
	T val = wait(what);
	U ret = wait(actorFunc(val));
	return ret;
}

// maps a vector of futures with an asynchronous function
template <class T, class F>
auto mapAsync(std::vector<Future<T>> const& what, F const& actorFunc) {
	std::vector<std::invoke_result_t<F, T>> ret;
	ret.reserve(what.size());
	for (const auto& f : what)
		ret.push_back(mapAsync(f, actorFunc));
	return ret;
}

// maps a stream with an asynchronous function
ACTOR template <class T, class F, class U = decltype(std::declval<F>()(std::declval<T>()).getValue())>
Future<Void> mapAsync(FutureStream<T> input, F actorFunc, PromiseStream<U> output) {
	state Deque<Future<U>> futures;

	loop {
		try {
			choose {
				when(T nextInput = waitNext(input)) { futures.push_back(actorFunc(nextInput)); }
				when(U nextOutput = wait(futures.size() == 0 ? Never() : futures.front())) {
					output.send(nextOutput);
					futures.pop_front();
				}
			}
		} catch (Error& e) {
			if (e.code() == error_code_end_of_stream) {
				break;
			} else {
				output.sendError(e);
				throw e;
			}
		}
	}

	while (futures.size()) {
		U nextOutput = wait(futures.front());
		output.send(nextOutput);
		futures.pop_front();
	}

	output.sendError(end_of_stream());

	return Void();
}

// Waits for a future to be ready, and then applies a function to it.
ACTOR template <class T, class F>
Future<std::invoke_result_t<F, T>> map(Future<T> what, F func) {
	T val = wait(what);
	return func(val);
}

// maps a vector of futures
template <class T, class F>
auto map(std::vector<Future<T>> const& what, F const& func) {
	std::vector<Future<std::invoke_result_t<F, T>>> ret;
	ret.reserve(what.size());
	for (const auto& f : what)
		ret.push_back(map(f, func));
	return ret;
}

// maps a stream
ACTOR template <class T, class F>
Future<Void> map(FutureStream<T> input, F func, PromiseStream<std::invoke_result_t<F, T>> output) {
	loop {
		try {
			T nextInput = waitNext(input);
			output.send(func(nextInput));
		} catch (Error& e) {
			if (e.code() == error_code_end_of_stream) {
				break;
			} else
				throw;
		}
	}

	output.sendError(end_of_stream());

	return Void();
}

// Returns if the future returns true, otherwise waits forever.
ACTOR Future<Void> returnIfTrue(Future<bool> f);

// Returns if the future, when waited on and then evaluated with the predicate, returns true, otherwise waits forever
template <class T, class F>
Future<Void> returnIfTrue(Future<T> what, F pred) {
	return returnIfTrue(map(what, pred));
}

// filters a stream
ACTOR template <class T, class F>
Future<Void> filter(FutureStream<T> input, F pred, PromiseStream<T> output) {
	loop {
		try {
			T nextInput = waitNext(input);
			if (func(nextInput))
				output.send(nextInput);
		} catch (Error& e) {
			if (e.code() == error_code_end_of_stream) {
				break;
			} else
				throw;
		}
	}

	output.sendError(end_of_stream());

	return Void();
}

// filters a stream asynchronously
ACTOR template <class T, class F>
Future<Void> asyncFilter(FutureStream<T> input, F actorPred, PromiseStream<T> output) {
	state Deque<std::pair<T, Future<bool>>> futures;
	state std::pair<T, Future<bool>> p;

	loop {
		try {
			choose {
				when(T nextInput = waitNext(input)) { futures.emplace_back(nextInput, actorPred(nextInput)); }
				when(bool pass = wait(futures.size() == 0 ? Never() : futures.front().second)) {
					if (pass)
						output.send(futures.front().first);
					futures.pop_front();
				}
			}
		} catch (Error& e) {
			if (e.code() == error_code_end_of_stream) {
				break;
			} else {
				throw e;
			}
		}
	}

	while (futures.size()) {
		p = futures.front();
		bool pass = wait(p.second);
		if (pass)
			output.send(p.first);
		futures.pop_front();
	}

	output.sendError(end_of_stream());

	return Void();
}

template <class T>
struct WorkerCache {
	// SOMEDAY: Would we do better to use "unreliable" (at most once) transport for the initialize requests and get rid
	// of this? It doesn't provide true at most once behavior because things are removed from the cache after they have
	// terminated.
	bool exists(UID id) { return id_interface.count(id) != 0; }
	void set(UID id, const Future<T>& onReady) {
		ASSERT(!exists(id));
		id_interface[id] = onReady;
	}
	Future<T> get(UID id) {
		ASSERT(exists(id));
		return id_interface[id];
	}

	Future<Void> removeOnReady(UID id, Future<Void> const& ready) { return removeOnReady(this, id, ready); }

private:
	ACTOR static Future<Void> removeOnReady(WorkerCache* self, UID id, Future<Void> ready) {
		try {
			wait(ready);
			self->id_interface.erase(id);
			return Void();
		} catch (Error& e) {
			self->id_interface.erase(id);
			throw;
		}
	}

	std::map<UID, Future<T>> id_interface;
};

template <class K, class V>
class AsyncMap : NonCopyable {
public:
	// Represents a complete function from keys to values (K -> V)
	// All values not explicitly inserted map to V()
	// If this isn't appropriate, use V=Optional<X>

	AsyncMap() : defaultValue(), destructing(false) {}

	virtual ~AsyncMap() {
		destructing = true;
		items.clear();
	}

	void set(K const& k, V const& v) {
		auto& i = items[k];
		if (i.value != v)
			setUnconditional(k, v, i);
	}
	void setUnconditional(K const& k, V const& v) { setUnconditional(k, v, items[k]); }
	void triggerAll() {
		std::vector<Promise<Void>> ps;
		for (auto it = items.begin(); it != items.end(); ++it) {
			ps.resize(ps.size() + 1);
			ps.back().swap(it->second.change);
		}
		std::vector<Promise<Void>> noDestroy = ps; // See explanation of noDestroy in setUnconditional()
		for (auto p = ps.begin(); p != ps.end(); ++p)
			p->send(Void());
	}
	void triggerRange(K const& begin, K const& end) {
		std::vector<Promise<Void>> ps;
		for (auto it = items.lower_bound(begin); it != items.end() && it->first < end; ++it) {
			ps.resize(ps.size() + 1);
			ps.back().swap(it->second.change);
		}
		std::vector<Promise<Void>> noDestroy = ps; // See explanation of noDestroy in setUnconditional()
		for (auto p = ps.begin(); p != ps.end(); ++p)
			p->send(Void());
	}
	void trigger(K const& key) {
		if (items.count(key) != 0) {
			auto& i = items[key];
			Promise<Void> trigger;
			i.change.swap(trigger);
			Promise<Void> noDestroy = trigger; // See explanation of noDestroy in setUnconditional()

			if (i.value == defaultValue)
				items.erase(key);

			trigger.send(Void());
		}
	}
	void clear(K const& k) { set(k, V()); }
	V const& get(K const& k) const {
		auto it = items.find(k);
		if (it != items.end())
			return it->second.value;
		else
			return defaultValue;
	}
	int count(K const& k) const {
		auto it = items.find(k);
		if (it != items.end())
			return 1;
		return 0;
	}
	virtual Future<Void> onChange(K const& k) { // throws broken_promise if this is destroyed
		auto& item = items[k];
		if (item.value == defaultValue)
			return destroyOnCancel(this, k, item.change.getFuture());
		return item.change.getFuture();
	}
	std::vector<K> getKeys() const {
		std::vector<K> keys;
		keys.reserve(items.size());
		for (auto i = items.begin(); i != items.end(); ++i)
			keys.push_back(i->first);
		return keys;
	}
	void resetNoWaiting() {
		for (auto i = items.begin(); i != items.end(); ++i)
			ASSERT(i->second.change.getFuture().getFutureReferenceCount() == 1);
		items.clear();
	}

protected:
	// Invariant: Every item in the map either has value!=defaultValue xor a destroyOnCancel actor waiting on
	// change.getFuture()
	struct P {
		V value;
		Promise<Void> change;
		P() : value() {}
	};
	std::map<K, P> items;
	const V defaultValue;
	bool destructing;

	void setUnconditional(K const& k, V const& v, P& i) {
		Promise<Void> trigger;
		i.change.swap(trigger);
		Promise<Void> noDestroy =
		    trigger; // The send(Void()) or even V::operator= could cause destroyOnCancel,
		             // which could undo the change to i.value here.  Keeping the promise reference count >= 2
		             // prevents destroyOnCancel from erasing anything from the map.
		if (v == defaultValue) {
			items.erase(k);
		} else {
			i.value = v;
		}

		trigger.send(Void());
	}

	ACTOR Future<Void> destroyOnCancel(AsyncMap* self, K key, Future<Void> change) {
		try {
			wait(change);
			return Void();
		} catch (Error& e) {
			if (e.code() == error_code_actor_cancelled && !self->destructing && change.getFutureReferenceCount() == 1 &&
			    change.getPromiseReferenceCount() == 1) {
				if (EXPENSIVE_VALIDATION) {
					auto& p = self->items[key];
					ASSERT(p.change.getFuture() == change);
				}
				self->items.erase(key);
			}
			throw;
		}
	}
};

template <class V>
class ReferencedObject : NonCopyable, public ReferenceCounted<ReferencedObject<V>> {
public:
	ReferencedObject() : value() {}
	ReferencedObject(V const& v) : value(v) {}
	ReferencedObject(V&& v) : value(std::move(v)) {}
	ReferencedObject(ReferencedObject&& r) : value(std::move(r.value)) {}

	void operator=(ReferencedObject&& r) { value = std::move(r.value); }

	V const& get() const { return value; }

	V& mutate() { return value; }

	void set(V const& v) { value = v; }

	void set(V&& v) { value = std::move(v); }

	static Reference<ReferencedObject<V>> from(V const& v) { return makeReference<ReferencedObject<V>>(v); }

	static Reference<ReferencedObject<V>> from(V&& v) { return makeReference<ReferencedObject<V>>(std::move(v)); }

private:
	V value;
};

template <class V>
class AsyncVar : NonCopyable, public ReferenceCounted<AsyncVar<V>> {
public:
	AsyncVar() : value() {}
	AsyncVar(V const& v) : value(v) {}
	AsyncVar(AsyncVar&& av) : value(std::move(av.value)), nextChange(std::move(av.nextChange)) {}
	void operator=(AsyncVar&& av) {
		value = std::move(av.value);
		nextChange = std::move(av.nextChange);
	}

	V const& get() const { return value; }
	Future<Void> onChange() const { return nextChange.getFuture(); }
	void set(V const& v) {
		if (v != value)
			setUnconditional(v);
	}
	void setUnconditional(V const& v) {
		Promise<Void> t;
		this->nextChange.swap(t);
		this->value = v;
		t.send(Void());
	}
	void trigger() {
		Promise<Void> t;
		this->nextChange.swap(t);
		t.send(Void());
	}

private:
	V value;
	Promise<Void> nextChange;
};

class AsyncTrigger : NonCopyable {
public:
	AsyncTrigger() {}
	AsyncTrigger(AsyncTrigger&& at) : v(std::move(at.v)) {}
	void operator=(AsyncTrigger&& at) { v = std::move(at.v); }
	Future<Void> onTrigger() const { return v.onChange(); }
	void trigger() { v.trigger(); }

private:
	AsyncVar<Void> v;
};

// Binds an AsyncTrigger object to an AsyncVar, so when the AsyncVar changes
// the AsyncTrigger is triggered.
ACTOR template <class T>
void forward(Reference<AsyncVar<T> const> from, AsyncTrigger* to) {
	loop {
		wait(from->onChange());
		to->trigger();
	}
}

class Debouncer : NonCopyable {
public:
	explicit Debouncer(double delay) { worker = debounceWorker(this, delay); }
	Debouncer(Debouncer&& at) = default;
	Debouncer& operator=(Debouncer&& at) = default;
	Future<Void> onTrigger() { return output.onChange(); }
	void trigger() { input.setUnconditional(Void()); }

private:
	AsyncVar<Void> input;
	AsyncVar<Void> output;
	Future<Void> worker;

	ACTOR Future<Void> debounceWorker(Debouncer* self, double bounceTime) {
		loop {
			wait(self->input.onChange());
			loop {
				choose {
					when(wait(self->input.onChange())) {}
					when(wait(delay(bounceTime))) { break; }
				}
			}
			self->output.setUnconditional(Void());
		}
	}
};

ACTOR template <class T>
Future<Void> asyncDeserialize(Reference<AsyncVar<Standalone<StringRef>>> input,
                              Reference<AsyncVar<Optional<T>>> output) {
	loop {
		if (input->get().size()) {
			ObjectReader reader(input->get().begin(), IncludeVersion());
			T res;
			reader.deserialize(res);
			output->set(res);
		} else
			output->set(Optional<T>());
		wait(input->onChange());
	}
}

ACTOR template <class V, class T>
void forwardVector(Future<V> values, std::vector<Promise<T>> out) {
	V in = wait(values);
	ASSERT(in.size() == out.size());
	for (int i = 0; i < out.size(); i++)
		out[i].send(in[i]);
}

ACTOR template <class T>
Future<Void> delayedAsyncVar(Reference<AsyncVar<T>> in, Reference<AsyncVar<T>> out, double time) {
	try {
		loop {
			wait(delay(time));
			out->set(in->get());
			wait(in->onChange());
		}
	} catch (Error& e) {
		out->set(in->get());
		throw;
	}
}

ACTOR template <class T>
Future<Void> setAfter(Reference<AsyncVar<T>> var, double time, T val) {
	wait(delay(time));
	var->set(val);
	return Void();
}

ACTOR template <class T>
Future<Void> resetAfter(Reference<AsyncVar<T>> var,
                        double time,
                        T val,
                        int warningLimit = -1,
                        double warningResetDelay = 0,
                        const char* context = nullptr) {
	state bool isEqual = var->get() == val;
	state Future<Void> resetDelay = isEqual ? Never() : delay(time);
	state int resetCount = 0;
	state double lastReset = now();
	loop {
		choose {
			when(wait(resetDelay)) {
				var->set(val);
				if (now() - lastReset > warningResetDelay) {
					resetCount = 0;
				}
				resetCount++;
				if (context && warningLimit >= 0 && resetCount > warningLimit) {
					TraceEvent(SevWarnAlways, context)
					    .detail("ResetCount", resetCount)
					    .detail("LastReset", now() - lastReset);
				}
				lastReset = now();
				isEqual = true;
				resetDelay = Never();
			}
			when(wait(var->onChange())) {}
		}
		if (isEqual && var->get() != val) {
			isEqual = false;
			resetDelay = delay(time);
		}
		if (!isEqual && var->get() == val) {
			isEqual = true;
			resetDelay = Never();
		}
	}
}

ACTOR template <class T>
Future<Void> setWhenDoneOrError(Future<Void> condition, Reference<AsyncVar<T>> var, T val) {
	try {
		wait(condition);
	} catch (Error& e) {
		if (e.code() == error_code_actor_cancelled)
			throw;
	}
	var->set(val);
	return Void();
}

Future<bool> allTrue(const std::vector<Future<bool>>& all);
Future<Void> anyTrue(std::vector<Reference<AsyncVar<bool>>> const& input, Reference<AsyncVar<bool>> const& output);
Future<Void> cancelOnly(std::vector<Future<Void>> const& futures);
Future<Void> timeoutWarningCollector(FutureStream<Void> const& input,
                                     double const& logDelay,
                                     const char* const& context,
                                     UID const& id);
Future<bool> quorumEqualsTrue(std::vector<Future<bool>> const& futures, int const& required);
Future<Void> lowPriorityDelay(double const& waitTime);

ACTOR template <class T>
Future<Void> streamHelper(PromiseStream<T> output, PromiseStream<Error> errors, Future<T> input) {
	try {
		T value = wait(input);
		output.send(value);
	} catch (Error& e) {
		if (e.code() == error_code_actor_cancelled)
			throw;
		errors.send(e);
	}
	return Void();
}

template <class T>
Future<Void> makeStream(const std::vector<Future<T>>& futures, PromiseStream<T>& stream, PromiseStream<Error>& errors) {
	std::vector<Future<Void>> forwarders;
	forwarders.reserve(futures.size());
	for (int f = 0; f < futures.size(); f++)
		forwarders.push_back(streamHelper(stream, errors, futures[f]));
	return cancelOnly(forwarders);
}

template <class T>
class QuorumCallback;

template <class T>
struct Quorum : SAV<Void> {
	int antiQuorum;
	int count;

	static inline int sizeFor(int count) { return sizeof(Quorum<T>) + sizeof(QuorumCallback<T>) * count; }

	void destroy() override {
		int size = sizeFor(this->count);
		this->~Quorum();
		freeFast(size, this);
	}
	void cancel() override {
		int cancelled_callbacks = 0;
		for (int i = 0; i < count; i++)
			if (callbacks()[i].next) {
				callbacks()[i].remove();
				callbacks()[i].next = 0;
				++cancelled_callbacks;
			}
		if (canBeSet())
			sendError(actor_cancelled());
		for (int i = 0; i < cancelled_callbacks; i++)
			delPromiseRef();
	}
	explicit Quorum(int quorum, int count) : SAV<Void>(1, count), antiQuorum(count - quorum + 1), count(count) {
		if (!quorum)
			this->send(Void());
	}
	void oneSuccess() {
		if (getPromiseReferenceCount() == antiQuorum && canBeSet())
			this->sendAndDelPromiseRef(Void());
		else
			delPromiseRef();
	}
	void oneError(Error err) {
		if (canBeSet())
			this->sendErrorAndDelPromiseRef(err);
		else
			delPromiseRef();
	}

	QuorumCallback<T>* callbacks() { return (QuorumCallback<T>*)(this + 1); }
};

template <class T>
class QuorumCallback : public Callback<T> {
public:
	void fire(const T& value) override {
		Callback<T>::remove();
		Callback<T>::next = 0;
		head->oneSuccess();
	}
	void error(Error error) override {
		Callback<T>::remove();
		Callback<T>::next = 0;
		head->oneError(error);
	}

private:
	template <class U>
	friend Future<Void> quorum(std::vector<Future<U>> const& results, int n);
	Quorum<T>* head;
	QuorumCallback() = default;
	QuorumCallback(Future<T> future, Quorum<T>* head) : head(head) { future.addCallbackAndClear(this); }
};

template <class T>
Future<Void> quorum(std::vector<Future<T>> const& results, int n) {
	ASSERT(n >= 0 && n <= results.size());

	int size = Quorum<T>::sizeFor(results.size());
	Quorum<T>* q = new (allocateFast(size)) Quorum<T>(n, results.size());

	QuorumCallback<T>* nextCallback = q->callbacks();
	for (auto& r : results) {
		if (r.isReady()) {
			new (nextCallback) QuorumCallback<T>();
			nextCallback->next = 0;
			if (r.isError())
				q->oneError(r.getError());
			else
				q->oneSuccess();
		} else
			new (nextCallback) QuorumCallback<T>(r, q);
		++nextCallback;
	}
	return Future<Void>(q);
}

ACTOR template <class T>
Future<Void> smartQuorum(std::vector<Future<T>> results,
                         int required,
                         double extraSeconds,
                         TaskPriority taskID = TaskPriority::DefaultDelay) {
	if (results.empty() && required == 0)
		return Void();
	wait(quorum(results, required));
	choose {
		when(wait(quorum(results, (int)results.size()))) { return Void(); }
		when(wait(delay(extraSeconds, taskID))) { return Void(); }
	}
}

template <class T>
Future<Void> waitForAll(std::vector<Future<T>> const& results) {
	if (results.empty())
		return Void();
	return quorum(results, (int)results.size());
}

template <class T>
Future<Void> waitForAny(std::vector<Future<T>> const& results) {
	if (results.empty())
		return Void();
	return quorum(results, 1);
}

ACTOR Future<bool> shortCircuitAny(std::vector<Future<bool>> f);

ACTOR template <class T>
Future<std::vector<T>> getAll(std::vector<Future<T>> input) {
	if (input.empty())
		return std::vector<T>();
	wait(quorum(input, input.size()));

	std::vector<T> output;
	output.reserve(input.size());
	for (int i = 0; i < input.size(); i++)
		output.push_back(input[i].get());
	return output;
}

ACTOR template <class T>
Future<std::vector<T>> appendAll(std::vector<Future<std::vector<T>>> input) {
	wait(quorum(input, input.size()));

	std::vector<T> output;
	size_t sz = 0;
	for (const auto& f : input) {
		sz += f.get().size();
	}
	output.reserve(sz);

	for (int i = 0; i < input.size(); i++) {
		auto const& r = input[i].get();
		output.insert(output.end(), r.begin(), r.end());
	}
	return output;
}

ACTOR template <class T>
Future<Void> onEqual(Future<T> in, T equalTo) {
	T t = wait(in);
	if (t == equalTo)
		return Void();
	wait(Never()); // never return
	throw internal_error(); // does not happen
}

ACTOR template <class T>
Future<Void> success(Future<T> of) {
	T t = wait(of);
	(void)t;
	return Void();
}

ACTOR template <class T>
Future<Void> ready(Future<T> f) {
	try {
		wait(success(f));
	} catch (...) {
	}
	return Void();
}

ACTOR template <class T>
Future<T> waitAndForward(FutureStream<T> input) {
	T output = waitNext(input);
	return output;
}

ACTOR template <class T>
Future<T> reportErrorsExcept(Future<T> in, const char* context, UID id, std::set<int> const* pExceptErrors) {
	try {
		T t = wait(in);
		return t;
	} catch (Error& e) {
		if (e.code() != error_code_actor_cancelled && (!pExceptErrors || !pExceptErrors->count(e.code())))
			TraceEvent(SevError, context, id).error(e);
		throw;
	}
}

template <class T>
Future<T> reportErrors(Future<T> const& in, const char* context, UID id = UID()) {
	return reportErrorsExcept(in, context, id, nullptr);
}

ACTOR template <class T>
Future<T> require(Future<Optional<T>> in, int errorCode) {
	Optional<T> o = wait(in);
	if (o.present()) {
		return o.get();
	} else {
		throw Error(errorCode);
	}
}

ACTOR template <class T>
Future<T> waitForFirst(std::vector<Future<T>> items) {
	state PromiseStream<T> resultStream;
	state PromiseStream<Error> errorStream;

	state Future<Void> forCancellation = makeStream(items, resultStream, errorStream);

	state FutureStream<T> resultFutureStream = resultStream.getFuture();
	state FutureStream<Error> errorFutureStream = errorStream.getFuture();

	choose {
		when(T val = waitNext(resultFutureStream)) {
			forCancellation = Future<Void>();
			return val;
		}
		when(Error e = waitNext(errorFutureStream)) {
			forCancellation = Future<Void>();
			throw e;
		}
	}
}

ACTOR template <class T>
Future<T> tag(Future<Void> future, T what) {
	wait(future);
	return what;
}

ACTOR template <class T>
Future<Void> tag(Future<Void> future, T what, PromiseStream<T> stream) {
	wait(future);
	stream.send(what);
	return Void();
}

ACTOR template <class T>
Future<T> tagError(Future<Void> future, Error e) {
	wait(future);
	throw e;
}

// If the future is ready, yields and returns. Otherwise, returns when future is set.
template <class T>
Future<T> orYield(Future<T> f) {
	if (f.isReady()) {
		if (f.isError())
			return tagError<T>(yield(), f.getError());
		else
			return tag(yield(), f.get());
	} else
		return f;
}

Future<Void> orYield(Future<Void> f);

ACTOR template <class T>
Future<T> chooseActor(Future<T> lhs, Future<T> rhs) {
	choose {
		when(T t = wait(lhs)) { return t; }
		when(T t = wait(rhs)) { return t; }
	}
}

// set && set -> set
// error && x -> error
// all others -> unset
inline Future<Void> operator&&(Future<Void> const& lhs, Future<Void> const& rhs) {
	if (lhs.isReady()) {
		if (lhs.isError())
			return lhs;
		else
			return rhs;
	}
	if (rhs.isReady()) {
		if (rhs.isError())
			return rhs;
		else
			return lhs;
	}

	return waitForAll(std::vector<Future<Void>>{ lhs, rhs });
}

// error || unset -> error
// unset || unset -> unset
// all others -> set
inline Future<Void> operator||(Future<Void> const& lhs, Future<Void> const& rhs) {
	if (lhs.isReady()) {
		if (lhs.isError())
			return lhs;
		if (rhs.isReady())
			return rhs;
		return lhs;
	}

	return chooseActor(lhs, rhs);
}

ACTOR template <class T>
Future<T> brokenPromiseToNever(Future<T> in) {
	try {
		T t = wait(in);
		return t;
	} catch (Error& e) {
		if (e.code() != error_code_broken_promise)
			throw;
		wait(Never()); // never return
		throw internal_error(); // does not happen
	}
}

ACTOR template <class T>
Future<T> brokenPromiseToMaybeDelivered(Future<T> in) {
	try {
		T t = wait(in);
		return t;
	} catch (Error& e) {
		if (e.code() == error_code_broken_promise) {
			throw request_maybe_delivered();
		}
		throw;
	}
}

ACTOR template <class T>
void tagAndForward(Promise<T>* pOutputPromise, T value, Future<Void> signal) {
	state Promise<T> out(std::move(*pOutputPromise));
	wait(signal);
	out.send(value);
}

ACTOR template <class T>
void tagAndForward(PromiseStream<T>* pOutput, T value, Future<Void> signal) {
	wait(signal);
	pOutput->send(value);
}

ACTOR template <class T>
void tagAndForwardError(Promise<T>* pOutputPromise, Error value, Future<Void> signal) {
	state Promise<T> out(std::move(*pOutputPromise));
	wait(signal);
	out.sendError(value);
}

ACTOR template <class T>
void tagAndForwardError(PromiseStream<T>* pOutput, Error value, Future<Void> signal) {
	wait(signal);
	pOutput->sendError(value);
}

ACTOR template <class T>
Future<T> waitOrError(Future<T> f, Future<Void> errorSignal) {
	choose {
		when(T val = wait(f)) { return val; }
		when(wait(errorSignal)) {
			ASSERT(false);
			throw internal_error();
		}
	}
}

// A low-overhead FIFO mutex made with no internal queue structure (no list, deque, vector, etc)
// The lock is implemented as a Promise<Void>, which is returned to callers in a convenient wrapper
// called Lock.
//
// Usage:
//   Lock lock = wait(mutex.take());
//   lock.release();  // Next waiter will get the lock, OR
//   lock.error(e);   // Next waiter will get e, future waiters will see broken_promise
//   lock = Lock();   // Or let Lock and any copies go out of scope.  All waiters will see broken_promise.
struct FlowMutex {
	FlowMutex() { lastPromise.send(Void()); }

	bool available() { return lastPromise.isSet(); }

	struct Lock {
		void release() { promise.send(Void()); }

		void error(Error e = broken_promise()) { promise.sendError(e); }

		// This is exposed in case the caller wants to use/copy it directly
		Promise<Void> promise;
	};

	Future<Lock> take() {
		Lock newLock;
		Future<Lock> f = lastPromise.isSet() ? newLock : tag(lastPromise.getFuture(), newLock);
		lastPromise = newLock.promise;
		return f;
	}

private:
	Promise<Void> lastPromise;
};

ACTOR template <class T, class V>
Future<T> forwardErrors(Future<T> f, PromiseStream<V> output) {
	try {
		T val = wait(f);
		return val;
	} catch (Error& e) {
		output.sendError(e);
		throw;
	}
}

struct FlowLock : NonCopyable, public ReferenceCounted<FlowLock> {
	// FlowLock implements a nonblocking critical section: there can be only a limited number of clients executing code
	// between wait(take()) and release(). Not thread safe. take() returns only when the number of holders of the lock
	// is fewer than the number of permits, and release() makes the caller no longer a holder of the lock. release()
	// only runs waiting take()rs after the caller wait()s

	struct Releaser : NonCopyable {
		FlowLock* lock;
		int remaining;
		Releaser() : lock(0), remaining(0) {}
		Releaser(FlowLock& lock, int64_t amount = 1) : lock(&lock), remaining(amount) {}
		Releaser(Releaser&& r) noexcept : lock(r.lock), remaining(r.remaining) { r.remaining = 0; }
		void operator=(Releaser&& r) {
			if (remaining)
				lock->release(remaining);
			lock = r.lock;
			remaining = r.remaining;
			r.remaining = 0;
		}

		void release(int64_t amount = -1) {
			if (amount == -1 || amount > remaining)
				amount = remaining;

			if (remaining)
				lock->release(amount);
			remaining -= amount;
		}

		~Releaser() {
			if (remaining)
				lock->release(remaining);
		}
	};

	FlowLock() : permits(1), active(0) {}
	explicit FlowLock(int64_t permits) : permits(permits), active(0) {}

	Future<Void> take(TaskPriority taskID = TaskPriority::DefaultYield, int64_t amount = 1) {
		if (active + amount <= permits || active == 0) {
			active += amount;
			return safeYieldActor(this, taskID, amount);
		}
		return takeActor(this, taskID, amount);
	}
	void release(int64_t amount = 1) {
		ASSERT((active > 0 || amount == 0) && active - amount >= 0);
		active -= amount;

		while (!takers.empty()) {
			if (active + takers.begin()->second <= permits || active == 0) {
				std::pair<Promise<Void>, int64_t> next = std::move(*takers.begin());
				active += next.second;
				takers.pop_front();
				next.first.send(Void());
			} else {
				break;
			}
		}
	}

	Future<Void> releaseWhen(Future<Void> const& signal, int amount = 1) {
		return releaseWhenActor(this, signal, amount);
	}

	// returns when any permits are available, having taken as many as possible up to the given amount, and modifies
	// amount to the number of permits taken
	Future<Void> takeUpTo(int64_t& amount) { return takeMoreActor(this, &amount); }

	int64_t available() const { return permits - active; }
	int64_t activePermits() const { return active; }
	int waiters() const { return takers.size(); }

	// Try to send error to all current and future waiters
	// Only works if broken_on_destruct.canBeSet()
	void kill(Error e = broken_promise()) {
		if (broken_on_destruct.canBeSet()) {
			auto local = broken_on_destruct;
			// It could be the case that calling broken_on_destruct destroys this FlowLock
			local.sendError(e);
		}
	}

private:
	std::list<std::pair<Promise<Void>, int64_t>> takers;
	const int64_t permits;
	int64_t active;
	Promise<Void> broken_on_destruct;

	ACTOR static Future<Void> takeActor(FlowLock* lock, TaskPriority taskID, int64_t amount) {
		state std::list<std::pair<Promise<Void>, int64_t>>::iterator it =
		    lock->takers.emplace(lock->takers.end(), Promise<Void>(), amount);

		try {
			wait(it->first.getFuture());
		} catch (Error& e) {
			if (e.code() == error_code_actor_cancelled) {
				lock->takers.erase(it);
				lock->release(0);
			}
			throw;
		}
		try {
			double duration = BUGGIFY_WITH_PROB(.001)
			                      ? deterministicRandom()->random01() * FLOW_KNOBS->BUGGIFY_FLOW_LOCK_RELEASE_DELAY
			                      : 0.0;
			choose {
				when(wait(delay(duration, taskID))) {
				} // So release()ing the lock doesn't cause arbitrary code to run on the stack
				when(wait(lock->broken_on_destruct.getFuture())) {}
			}
			return Void();
		} catch (...) {
			TEST(true); // If we get cancelled here, we are holding the lock but the caller doesn't know, so release it
			lock->release(amount);
			throw;
		}
	}

	ACTOR static Future<Void> takeMoreActor(FlowLock* lock, int64_t* amount) {
		wait(lock->take());
		int64_t extra = std::min(lock->available(), *amount - 1);
		lock->active += extra;
		*amount = 1 + extra;
		return Void();
	}

	ACTOR static Future<Void> safeYieldActor(FlowLock* lock, TaskPriority taskID, int64_t amount) {
		try {
			choose {
				when(wait(yield(taskID))) {}
				when(wait(lock->broken_on_destruct.getFuture())) {}
			}
			return Void();
		} catch (Error& e) {
			lock->release(amount);
			throw;
		}
	}

	ACTOR static Future<Void> releaseWhenActor(FlowLock* self, Future<Void> signal, int64_t amount) {
		wait(signal);
		self->release(amount);
		return Void();
	}
};

struct NotifiedInt {
	NotifiedInt(int64_t val = 0) : val(val) {}

	Future<Void> whenAtLeast(int64_t limit) {
		if (val >= limit)
			return Void();
		Promise<Void> p;
		waiting.emplace(limit, p);
		return p.getFuture();
	}

	int64_t get() const { return val; }

	void set(int64_t v) {
		ASSERT(v >= val);
		if (v != val) {
			val = v;

			std::vector<Promise<Void>> toSend;
			while (waiting.size() && v >= waiting.top().first) {
				Promise<Void> p = std::move(waiting.top().second);
				waiting.pop();
				toSend.push_back(p);
			}
			for (auto& p : toSend) {
				p.send(Void());
			}
		}
	}

	void operator=(int64_t v) { set(v); }

	NotifiedInt(NotifiedInt&& r) noexcept : waiting(std::move(r.waiting)), val(r.val) {}
	void operator=(NotifiedInt&& r) noexcept {
		waiting = std::move(r.waiting);
		val = r.val;
	}

private:
	typedef std::pair<int64_t, Promise<Void>> Item;
	struct ItemCompare {
		bool operator()(const Item& a, const Item& b) { return a.first > b.first; }
	};
	std::priority_queue<Item, std::vector<Item>, ItemCompare> waiting;
	int64_t val;
};

struct BoundedFlowLock : NonCopyable, public ReferenceCounted<BoundedFlowLock> {
	// BoundedFlowLock is different from a FlowLock in that it has a bound on how many locks can be taken from the
	// oldest outstanding lock. For instance, with a FlowLock that has two permits, if one permit is taken but never
	// released, the other permit can be reused an unlimited amount of times, but with a BoundedFlowLock, it can only be
	// reused a fixed number of times.

	struct Releaser : NonCopyable {
		BoundedFlowLock* lock;
		int64_t permitNumber;
		Releaser() : lock(nullptr), permitNumber(0) {}
		Releaser(BoundedFlowLock* lock, int64_t permitNumber) : lock(lock), permitNumber(permitNumber) {}
		Releaser(Releaser&& r) noexcept : lock(r.lock), permitNumber(r.permitNumber) { r.permitNumber = 0; }
		void operator=(Releaser&& r) {
			if (permitNumber)
				lock->release(permitNumber);
			lock = r.lock;
			permitNumber = r.permitNumber;
			r.permitNumber = 0;
		}

		void release() {
			if (permitNumber) {
				lock->release(permitNumber);
			}
			permitNumber = 0;
		}

		~Releaser() {
			if (permitNumber)
				lock->release(permitNumber);
		}
	};

	BoundedFlowLock() : minOutstanding(0), nextPermitNumber(0), unrestrictedPermits(1), boundedPermits(0) {}
	explicit BoundedFlowLock(int64_t unrestrictedPermits, int64_t boundedPermits)
	  : minOutstanding(0), nextPermitNumber(0), unrestrictedPermits(unrestrictedPermits),
	    boundedPermits(boundedPermits) {}

	Future<int64_t> take() { return takeActor(this); }
	void release(int64_t permitNumber) {
		outstanding.erase(permitNumber);
		updateMinOutstanding();
	}

private:
	IndexedSet<int64_t, int64_t> outstanding;
	NotifiedInt minOutstanding;
	int64_t nextPermitNumber;
	const int64_t unrestrictedPermits;
	const int64_t boundedPermits;

	void updateMinOutstanding() {
		auto it = outstanding.index(unrestrictedPermits - 1);
		if (it == outstanding.end()) {
			minOutstanding.set(nextPermitNumber);
		} else {
			minOutstanding.set(*it);
		}
	}

	ACTOR static Future<int64_t> takeActor(BoundedFlowLock* lock) {
		state int64_t permitNumber = ++lock->nextPermitNumber;
		lock->outstanding.insert(permitNumber, 1);
		lock->updateMinOutstanding();
		wait(lock->minOutstanding.whenAtLeast(std::max<int64_t>(0, permitNumber - lock->boundedPermits)));
		return permitNumber;
	}
};

ACTOR template <class T>
Future<Void> yieldPromiseStream(FutureStream<T> input,
                                PromiseStream<T> output,
                                TaskPriority taskID = TaskPriority::DefaultYield) {
	loop {
		T f = waitNext(input);
		output.send(f);
		wait(yield(taskID));
	}
}

struct YieldedFutureActor : SAV<Void>, ActorCallback<YieldedFutureActor, 1, Void>, FastAllocated<YieldedFutureActor> {
	Error in_error_state;

	typedef ActorCallback<YieldedFutureActor, 1, Void> CB1;

	using FastAllocated<YieldedFutureActor>::operator new;
	using FastAllocated<YieldedFutureActor>::operator delete;

	YieldedFutureActor(Future<Void>&& f) : SAV<Void>(1, 1), in_error_state(Error::fromCode(UNSET_ERROR_CODE)) {
		f.addYieldedCallbackAndClear(static_cast<ActorCallback<YieldedFutureActor, 1, Void>*>(this));
	}

	void cancel() override {
		if (!SAV<Void>::canBeSet())
			return; // Cancel could be invoked *by* a callback within finish().  Otherwise it's guaranteed that we are
			        // waiting either on the original future or on a delay().
		ActorCallback<YieldedFutureActor, 1, Void>::remove();
		SAV<Void>::sendErrorAndDelPromiseRef(actor_cancelled());
	}

	void destroy() override { delete this; }

#ifdef ENABLE_SAMPLING
	LineageReference* lineageAddr() { return currentLineage; }
#endif

	void a_callback_fire(ActorCallback<YieldedFutureActor, 1, Void>*, Void) {
		if (int16_t(in_error_state.code()) == UNSET_ERROR_CODE) {
			in_error_state = Error::fromCode(SET_ERROR_CODE);
			if (check_yield())
				doYield();
			else
				finish();
		} else {
			// We hit this case when and only when the delay() created by a previous doYield() fires.  Then we want to
			// get at least one task done, regardless of what check_yield() would say.
			finish();
		}
	}
	void a_callback_error(ActorCallback<YieldedFutureActor, 1, Void>*, Error const& err) {
		ASSERT(int16_t(in_error_state.code()) == UNSET_ERROR_CODE);
		in_error_state = err;
		if (check_yield())
			doYield();
		else
			finish();
	}
	void finish() {
		ActorCallback<YieldedFutureActor, 1, Void>::remove();
		if (int16_t(in_error_state.code()) == SET_ERROR_CODE)
			SAV<Void>::sendAndDelPromiseRef(Void());
		else
			SAV<Void>::sendErrorAndDelPromiseRef(in_error_state);
	}
	void doYield() {
		// Since we are being fired, we are the first callback in the ring, and `prev` is the source future
		Callback<Void>* source = CB1::prev;
		ASSERT(source->next == static_cast<CB1*>(this));

		// Remove the source future from the ring.  All the remaining callbacks in the ring should be yielded, since
		// yielded callbacks are installed at the end
		CB1::prev = source->prev;
		CB1::prev->next = static_cast<CB1*>(this);

		// The source future's ring is now empty, since we have removed all the callbacks
		source->next = source->prev = source;
		source->unwait();

		// Link all the callbacks, including this one, into the ring of a delay future so that after a short time they
		// will be fired again
		delay(0, g_network->getCurrentTask()).addCallbackChainAndClear(static_cast<CB1*>(this));
	}
};

inline Future<Void> yieldedFuture(Future<Void> f) {
	if (f.isReady())
		return yield();
	else
		return Future<Void>(new YieldedFutureActor(std::move(f)));
}

// An AsyncMap that uses a yieldedFuture in its onChange method.
template <class K, class V>
class YieldedAsyncMap : public AsyncMap<K, V> {
public:
	Future<Void> onChange(K const& k) override { // throws broken_promise if this is destroyed
		auto& item = AsyncMap<K, V>::items[k];
		if (item.value == AsyncMap<K, V>::defaultValue)
			return destroyOnCancelYield(this, k, item.change.getFuture());
		return yieldedFuture(item.change.getFuture());
	}

	ACTOR static Future<Void> destroyOnCancelYield(YieldedAsyncMap* self, K key, Future<Void> change) {
		try {
			wait(yieldedFuture(change));
			return Void();
		} catch (Error& e) {
			if (e.code() == error_code_actor_cancelled && !self->destructing && change.getFutureReferenceCount() == 1 &&
			    change.getPromiseReferenceCount() == 1) {
				if (EXPENSIVE_VALIDATION) {
					auto& p = self->items[key];
					ASSERT(p.change.getFuture() == change);
				}
				self->items.erase(key);
			}
			throw;
		}
	}
};

ACTOR template <class T>
Future<T> delayActionJittered(Future<T> what, double time) {
	wait(delayJittered(time));
	T t = wait(what);
	return t;
}

class AndFuture {
public:
	AndFuture() {}

	AndFuture(AndFuture const& f) { futures = f.futures; }

	AndFuture(AndFuture&& f) noexcept { futures = std::move(f.futures); }

	AndFuture(Future<Void> const& f) { futures.push_back(f); }

	AndFuture(Error const& e) { futures.push_back(e); }

	operator Future<Void>() { return getFuture(); }

	void operator=(AndFuture const& f) { futures = f.futures; }

	void operator=(AndFuture&& f) noexcept { futures = std::move(f.futures); }

	void operator=(Future<Void> const& f) { futures.push_back(f); }

	void operator=(Error const& e) { futures.push_back(e); }

	Future<Void> getFuture() {
		if (futures.empty())
			return Void();

		if (futures.size() == 1)
			return futures[0];

		Future<Void> f = waitForAll(futures);
		futures = std::vector<Future<Void>>{ f };
		return f;
	}

	bool isReady() {
		for (int i = futures.size() - 1; i >= 0; --i) {
			if (!futures[i].isReady()) {
				return false;
			} else if (!futures[i].isError()) {
				swapAndPop(&futures, i);
			}
		}
		return true;
	}

	bool isError() {
		for (int i = 0; i < futures.size(); i++)
			if (futures[i].isError())
				return true;
		return false;
	}

	void cleanup() {
		for (int i = 0; i < futures.size(); i++) {
			if (futures[i].isReady() && !futures[i].isError()) {
				swapAndPop(&futures, i--);
			}
		}
	}

	void add(Future<Void> const& f) {
		if (!f.isReady() || f.isError())
			futures.push_back(f);
	}

	void add(AndFuture f) { add(f.getFuture()); }

private:
	std::vector<Future<Void>> futures;
};

// Performs an unordered merge of a and b.
ACTOR template <class T>
Future<Void> unorderedMergeStreams(FutureStream<T> a, FutureStream<T> b, PromiseStream<T> output) {
	state Future<T> aFuture = waitAndForward(a);
	state Future<T> bFuture = waitAndForward(b);
	state bool aOpen = true;
	state bool bOpen = true;

	loop {
		try {
			choose {
				when(T val = wait(aFuture)) {
					output.send(val);
					aFuture = waitAndForward(a);
				}
				when(T val = wait(bFuture)) {
					output.send(val);
					bFuture = waitAndForward(b);
				}
			}
		} catch (Error& e) {
			if (e.code() != error_code_end_of_stream) {
				output.sendError(e);
				break;
			}

			ASSERT(!aFuture.isError() || !bFuture.isError() || aFuture.getError().code() == bFuture.getError().code());

			if (aFuture.isError()) {
				aFuture = Never();
				aOpen = false;
			}
			if (bFuture.isError()) {
				bFuture = Never();
				bOpen = false;
			}

			if (!aOpen && !bOpen) {
				output.sendError(e);
				break;
			}
		}
	}

	return Void();
}

// Returns the ordered merge of a and b, assuming that a and b are both already ordered (prefer a over b if keys are
// equal). T must be a class that implements compare()
ACTOR template <class T>
Future<Void> orderedMergeStreams(FutureStream<T> a, FutureStream<T> b, PromiseStream<T> output) {
	state Optional<T> savedKVa;
	state bool aOpen;
	state Optional<T> savedKVb;
	state bool bOpen;

	aOpen = bOpen = true;

	loop {
		if (aOpen && !savedKVa.present()) {
			try {
				T KVa = waitNext(a);
				savedKVa = Optional<T>(KVa);
			} catch (Error& e) {
				if (e.code() == error_code_end_of_stream) {
					aOpen = false;
					if (!bOpen) {
						output.sendError(e);
					}
				} else {
					output.sendError(e);
					break;
				}
			}
		}
		if (bOpen && !savedKVb.present()) {
			try {
				T KVb = waitNext(b);
				savedKVb = Optional<T>(KVb);
			} catch (Error& e) {
				if (e.code() == error_code_end_of_stream) {
					bOpen = false;
					if (!aOpen) {
						output.sendError(e);
					}
				} else {
					output.sendError(e);
					break;
				}
			}
		}

		if (!aOpen) {
			output.send(savedKVb.get());
			savedKVb = Optional<T>();
		} else if (!bOpen) {
			output.send(savedKVa.get());
			savedKVa = Optional<T>();
		} else {
			int cmp = savedKVa.get().compare(savedKVb.get());

			if (cmp == 0) {
				// prefer a
				output.send(savedKVa.get());
				savedKVa = Optional<T>();
				savedKVb = Optional<T>();
			} else if (cmp < 0) {
				output.send(savedKVa.get());
				savedKVa = Optional<T>();
			} else {
				output.send(savedKVb.get());
				savedKVb = Optional<T>();
			}
		}
	}

	return Void();
}

ACTOR template <class T>
Future<Void> timeReply(Future<T> replyToTime, PromiseStream<double> timeOutput) {
	state double startTime = now();
	try {
		T _ = wait(replyToTime);
		wait(delay(0));
		timeOutput.send(now() - startTime);
	} catch (Error& e) {
		// Ignore broken promises.  They typically occur during shutdown and our callers don't want to have to create
		// brokenPromiseToNever actors to ignore them.  For what it's worth we are breaking timeOutput to pass the pain
		// along.
		if (e.code() != error_code_broken_promise)
			throw;
	}
	return Void();
}

ACTOR template <class T>
Future<T> forward(Future<T> from, Promise<T> to) {
	try {
		T res = wait(from);
		to.send(res);
		return res;
	} catch (Error& e) {
		if (e.code() != error_code_actor_cancelled) {
			to.sendError(e);
		}
		throw e;
	}
}

// Monad

ACTOR template <class Fun, class T>
Future<decltype(std::declval<Fun>()(std::declval<T>()))> fmap(Fun fun, Future<T> f) {
	T val = wait(f);
	return fun(val);
}

ACTOR template <class T, class Fun>
Future<decltype(std::declval<Fun>()(std::declval<T>()).getValue())> runAfter(Future<T> lhs, Fun rhs) {
	T val1 = wait(lhs);
	decltype(std::declval<Fun>()(std::declval<T>()).getValue()) res = wait(rhs(val1));
	return res;
}

ACTOR template <class T, class U>
Future<U> runAfter(Future<T> lhs, Future<U> rhs) {
	T val1 = wait(lhs);
	U res = wait(rhs);
	return res;
}

template <class T, class Fun>
auto operator>>=(Future<T> lhs, Fun&& rhs) -> Future<decltype(rhs(std::declval<T>()))> {
	return runAfter(lhs, std::forward<Fun>(rhs));
}

template <class T, class U>
Future<U> operator>>(Future<T> const& lhs, Future<U> const& rhs) {
	return runAfter(lhs, rhs);
}

/*
 * IAsyncListener is similar to AsyncVar, but it decouples the input and output, so the translation unit
 * responsible for handling the output does not need to have knowledge of how the output is generated
 */
template <class Output>
class IAsyncListener : public ReferenceCounted<IAsyncListener<Output>> {
public:
	virtual ~IAsyncListener() = default;
	virtual Output const& get() const = 0;
	virtual Future<Void> onChange() const = 0;
	template <class Input, class F>
	static Reference<IAsyncListener> create(Reference<AsyncVar<Input> const> const& input, F const& f);
	template <class Input, class F>
	static Reference<IAsyncListener> create(Reference<AsyncVar<Input>> const& input, F const& f);
	static Reference<IAsyncListener> create(Reference<AsyncVar<Output>> const& output);
};

namespace IAsyncListenerImpl {

template <class Input, class Output, class F>
class AsyncListener final : public IAsyncListener<Output> {
	// Order matters here, output must outlive monitorActor
	AsyncVar<Output> output;
	Future<Void> monitorActor;
	ACTOR static Future<Void> monitor(Reference<AsyncVar<Input> const> input, AsyncVar<Output>* output, F f) {
		loop {
			wait(input->onChange());
			output->set(f(input->get()));
		}
	}

public:
	AsyncListener(Reference<AsyncVar<Input> const> const& input, F const& f)
	  : output(f(input->get())), monitorActor(monitor(input, &output, f)) {}
	Output const& get() const override { return output.get(); }
	Future<Void> onChange() const override { return output.onChange(); }
};

} // namespace IAsyncListenerImpl

template <class Output>
template <class Input, class F>
Reference<IAsyncListener<Output>> IAsyncListener<Output>::create(Reference<AsyncVar<Input> const> const& input,
                                                                 F const& f) {
	return makeReference<IAsyncListenerImpl::AsyncListener<Input, Output, F>>(input, f);
}

template <class Output>
template <class Input, class F>
Reference<IAsyncListener<Output>> IAsyncListener<Output>::create(Reference<AsyncVar<Input>> const& input, F const& f) {
	return create(Reference<AsyncVar<Input> const>(input), f);
}

template <class Output>
Reference<IAsyncListener<Output>> IAsyncListener<Output>::create(Reference<AsyncVar<Output>> const& input) {
	auto identity = [](const auto& x) { return x; };
	return makeReference<IAsyncListenerImpl::AsyncListener<Output, Output, decltype(identity)>>(input, identity);
}

// A weak reference type to wrap a future Reference<T> object.
// Once the future is complete, this object holds a pointer to the referenced object but does
// not contribute to its reference count.
//
// WARNING: this class will not be aware when the underlying object is destroyed. It is up to the
// user to make sure that an UnsafeWeakFutureReference is discarded at the same time the object is.
template <class T>
class UnsafeWeakFutureReference {
public:
	UnsafeWeakFutureReference() {}
	UnsafeWeakFutureReference(Future<Reference<T>> future) : data(new UnsafeWeakFutureReferenceData(future)) {}

	// Returns a future to obtain a normal reference handle
	// If the future is ready, this creates a Reference<T> to wrap the object
	Future<Reference<T>> get() {
		if (!data) {
			return Reference<T>();
		} else if (data->ptr.present()) {
			return Reference<T>::addRef(data->ptr.get());
		} else {
			return data->future;
		}
	}

	// Returns the raw pointer, if the object is ready
	// Note: this should be used with care, as this pointer is not counted as a reference to the object and
	// it could be deleted if all normal references are destroyed.
	Optional<T*> getPtrIfReady() { return data->ptr; }

private:
	// A class to hold the state for an UnsafeWeakFutureReference
	struct UnsafeWeakFutureReferenceData : public ReferenceCounted<UnsafeWeakFutureReferenceData>, NonCopyable {
		Optional<T*> ptr;
		Future<Reference<T>> future;
		Future<Void> moveResultFuture;

		UnsafeWeakFutureReferenceData(Future<Reference<T>> future) : future(future) {
			moveResultFuture = moveResult(this);
		}

		// Waits for the future to complete and then stores the pointer in local storage
		// When this completes, we will no longer be counted toward the reference count of the object
		ACTOR Future<Void> moveResult(UnsafeWeakFutureReferenceData* self) {
			Reference<T> result = wait(self->future);
			self->ptr = result.getPtr();
			self->future = Future<Reference<T>>();
			return Void();
		}
	};

	Reference<UnsafeWeakFutureReferenceData> data;
};

#include "flow/unactorcompiler.h"

#endif