/*
 * Copyright (C) 2020 Apple Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */

#pragma once

#include "ArgumentCoders.h"
#include "Connection.h"
#include "Decoder.h"
#include "IPCSemaphore.h"
#include "MessageNames.h"
#include "StreamConnectionBuffer.h"
#include "StreamConnectionEncoder.h"
#include <wtf/MonotonicTime.h>
#include <wtf/Threading.h>

namespace WebKit {
namespace IPCTestingAPI {
class JSIPCStreamClientConnection;
}
}

namespace IPC {

// A message stream is a half-duplex two-way stream of messages to a between the client and the
// server.
//
// StreamClientConnection can send messages and receive synchronous replies
// through this message stream or through IPC::Connection.
//
// The server will receive messages in order _for the destination messages_.
// The whole IPC::Connection message order is not preserved.
//
// The StreamClientConnection trusts the StreamServerConnection.
class StreamClientConnection final {
    WTF_MAKE_FAST_ALLOCATED;
    WTF_MAKE_NONCOPYABLE(StreamClientConnection);
public:
    // Creates StreamClientConnection where the out of stream messages and server replies are
    // sent through the passed IPC::Connection. The messages from the server are delivered to
    // the caller through the passed IPC::Connection.
    // Note: This function should be used only in cases where the
    // stream server starts listening to messages with new identifiers on the same thread as
    // in which the server IPC::Connection dispatch messages. At the time of writing,
    // IPC::Connection dispatches messages only in main thread.
    StreamClientConnection(Connection&, size_t bufferSize);

    struct StreamConnectionWithDedicatedConnection {
        std::unique_ptr<StreamClientConnection> streamConnection;
        Attachment connectionIdentifier;
        // FIXME: Once IPC can treat handles as first class objects, add stream buffer as
        // a handle here.
    };

    // Creates StreamClientConnection where the out of stream messages and server replies are
    // sent through a dedidcated, new IPC::Connection. The messages from the server are delivered to
    // the caller through the passed IPC::MessageReceiver.
    // The caller should send StreamConnectionWithDedicatedConnection::connectionIdentifier and
    // StreamClientConnection::streamBuffer() to the server via an existing IPC::Connection.
    static StreamConnectionWithDedicatedConnection createWithDedicatedConnection(MessageReceiver&, size_t bufferSize);

    ~StreamClientConnection();

    StreamConnectionBuffer& streamBuffer() { return m_buffer; }
    void setSemaphores(IPC::Semaphore&& wakeUp, IPC::Semaphore&& clientWait);
    bool hasSemaphores() const { return m_semaphores.has_value(); }

    void setWakeUpMessageHysteresis(unsigned hysteresis)
    {
        ASSERT(!m_remainingMessageCountBeforeSendingWakeUp);
        m_wakeUpMessageHysteresis = hysteresis;
    }
    void sendDeferredWakeUpMessageIfNeeded();

    void open();
    void invalidate();

    template<typename T, typename U> bool send(T&& message, ObjectIdentifier<U> destinationID, Timeout);

    using SendSyncResult = Connection::SendSyncResult;
    template<typename T, typename U>
    SendSyncResult sendSync(T&& message, typename T::Reply&&, ObjectIdentifier<U> destinationID, Timeout);

    template<typename T, typename U>
    bool waitForAndDispatchImmediately(ObjectIdentifier<U> destinationID, Timeout, OptionSet<WaitForOption> = { });

    StreamConnectionBuffer& bufferForTesting();
    Connection& connectionForTesting();

private:
    class DedicatedConnectionClient;
    StreamClientConnection(Ref<Connection>&&, size_t bufferSize, std::unique_ptr<DedicatedConnectionClient>&&);

    struct Span {
        uint8_t* data;
        size_t size;
    };
    static constexpr size_t minimumMessageSize = StreamConnectionEncoder::minimumMessageSize;
    static constexpr size_t messageAlignment = StreamConnectionEncoder::messageAlignment;
    template<typename T>
    bool trySendStream(T& message, Span&);
    template<typename T>
    std::optional<SendSyncResult> trySendSyncStream(T& message, typename T::Reply&, Timeout, Span&);
    bool trySendDestinationIDIfNeeded(uint64_t destinationID, Timeout);
    void sendProcessOutOfStreamMessage(Span&&);

    std::optional<Span> tryAcquire(Timeout);
    std::optional<Span> tryAcquireAll(Timeout);

    enum class WakeUpServer : bool {
        No,
        Yes
    };
    WakeUpServer release(size_t writeSize);
    void wakeUpServer();
    void deferredWakeUpServer();
    void decrementRemainingMessageCountBeforeSendingWakeUp();

    Span alignedSpan(size_t offset, size_t limit);
    size_t size(size_t offset, size_t limit);

    size_t wrapOffset(size_t offset) const { return m_buffer.wrapOffset(offset); }
    size_t alignOffset(size_t offset) const { return m_buffer.alignOffset<messageAlignment>(offset, minimumMessageSize); }
    using ClientOffset = StreamConnectionBuffer::ClientOffset;
    Atomic<ClientOffset>& sharedClientOffset() { return m_buffer.clientOffset(); }
    using ClientLimit = StreamConnectionBuffer::ServerOffset;
    Atomic<ClientLimit>& sharedClientLimit() { return m_buffer.serverOffset(); }
    size_t toLimit(ClientLimit) const;
    uint8_t* data() const { return m_buffer.data(); }
    size_t dataSize() const { return m_buffer.dataSize(); }

    Ref<Connection> m_connection;
    std::unique_ptr<DedicatedConnectionClient> m_dedicatedConnectionClient;
    uint64_t m_currentDestinationID { 0 };
    size_t m_clientOffset { 0 };
    StreamConnectionBuffer m_buffer;
    struct Semaphores {
        Semaphore wakeUp;
        Semaphore clientWait;
    };
    std::optional<Semaphores> m_semaphores;
    unsigned m_remainingMessageCountBeforeSendingWakeUp { 0 };
    unsigned m_wakeUpMessageHysteresis { 0 };

    friend class WebKit::IPCTestingAPI::JSIPCStreamClientConnection;
};

template<typename T, typename U>
bool StreamClientConnection::send(T&& message, ObjectIdentifier<U> destinationID, Timeout timeout)
{
    static_assert(!T::isSync, "Message is sync!");
    if (!trySendDestinationIDIfNeeded(destinationID.toUInt64(), timeout))
        return false;
    auto span = tryAcquire(timeout);
    if (!span)
        return false;
    if constexpr(T::isStreamEncodable) {
        if (trySendStream(message, *span))
            return true;
    }
    sendProcessOutOfStreamMessage(WTFMove(*span));
    if (!m_connection->send(WTFMove(message), destinationID, IPC::SendOption::DispatchMessageEvenWhenWaitingForSyncReply))
        return false;
    return true;
}

template<typename T>
bool StreamClientConnection::trySendStream(T& message, Span& span)
{
    StreamConnectionEncoder messageEncoder { T::name(), span.data, span.size };
    if (messageEncoder << message.arguments()) {
        auto wakeupResult = release(messageEncoder.size());
        if (wakeupResult == StreamClientConnection::WakeUpServer::Yes)
            deferredWakeUpServer();
        else
            decrementRemainingMessageCountBeforeSendingWakeUp();
        return true;
    }
    return false;
}

template<typename T, typename U>
StreamClientConnection::SendSyncResult StreamClientConnection::sendSync(T&& message, typename T::Reply&& reply, ObjectIdentifier<U> destinationID, Timeout timeout)
{
    static_assert(T::isSync, "Message is not sync!");
    if (!trySendDestinationIDIfNeeded(destinationID.toUInt64(), timeout))
        return { };
    auto span = tryAcquire(timeout);
    if (!span)
        return { };
    if constexpr(T::isStreamEncodable) {
        auto maybeSendResult = trySendSyncStream(message, reply, timeout, *span);
        if (maybeSendResult)
            return WTFMove(*maybeSendResult);
    }
    sendProcessOutOfStreamMessage(WTFMove(*span));
    return m_connection->sendSync(WTFMove(message), WTFMove(reply), destinationID.toUInt64(), timeout);
}

template<typename T, typename U>
bool StreamClientConnection::waitForAndDispatchImmediately(ObjectIdentifier<U> destinationID, Timeout timeout, OptionSet<WaitForOption> waitForOptions)
{
    return m_connection->waitForAndDispatchImmediately<T>(destinationID, timeout, waitForOptions);
}

template<typename T>
std::optional<StreamClientConnection::SendSyncResult> StreamClientConnection::trySendSyncStream(T& message, typename T::Reply& reply, Timeout timeout, Span& span)
{
    // In this function, SendSyncResult { } means error happened and caller should stop processing.
    // std::nullopt means we couldn't send through the stream, so try sending out of stream.
    auto syncRequestID = m_connection->makeSyncRequestID();
    if (!m_connection->pushPendingSyncRequestID(syncRequestID))
        return SendSyncResult { };

    auto result = [&]() -> std::optional<SendSyncResult> {
        StreamConnectionEncoder messageEncoder { T::name(), span.data, span.size };
        if (!(messageEncoder << syncRequestID << message.arguments()))
            return std::nullopt;
        auto wakeupResult = release(messageEncoder.size());

        if (wakeupResult == StreamClientConnection::WakeUpServer::Yes)
            wakeUpServer();
        else
            sendDeferredWakeUpMessageIfNeeded();
        if constexpr(T::isReplyStreamEncodable) {
            auto replySpan = tryAcquireAll(timeout);
            if (!replySpan)
                return SendSyncResult { };
            auto decoder = std::unique_ptr<Decoder> { new Decoder(replySpan->data, replySpan->size, m_currentDestinationID) };
            if (decoder->messageName() != MessageName::ProcessOutOfStreamMessage) {
                ASSERT(decoder->messageName() == MessageName::SyncMessageReply);
                return decoder;
            }
        } else
            m_clientOffset = 0;
        return m_connection->waitForSyncReply(syncRequestID, T::name(), timeout, { });
    }();
    m_connection->popPendingSyncRequestID(syncRequestID);
    if (result && *result) {
        auto& decoder = **result;
        std::optional<typename T::ReplyArguments> replyArguments;
        decoder >> replyArguments;
        if (!replyArguments)
            return SendSyncResult { };
        moveTuple(WTFMove(*replyArguments), reply);
    }
    return result;
}

inline bool StreamClientConnection::trySendDestinationIDIfNeeded(uint64_t destinationID, Timeout timeout)
{
    if (destinationID == m_currentDestinationID)
        return true;
    auto span = tryAcquire(timeout);
    if (!span)
        return false;
    StreamConnectionEncoder encoder { MessageName::SetStreamDestinationID, span->data, span->size };
    if (!(encoder << destinationID)) {
        ASSERT_NOT_REACHED(); // Size of the minimum allocation is incorrect. Likely an alignment issue.
        return false;
    }
    auto wakeupResult = release(encoder.size());
    if (wakeupResult == StreamClientConnection::WakeUpServer::Yes)
        wakeUpServer();
    m_currentDestinationID = destinationID;
    return true;
}

inline void StreamClientConnection::sendProcessOutOfStreamMessage(Span&& span)
{
    StreamConnectionEncoder encoder { MessageName::ProcessOutOfStreamMessage, span.data, span.size };
    // Not notifying on wake up since the out-of-stream message will do that.
    auto result = release(encoder.size());
    UNUSED_VARIABLE(result);
}
inline std::optional<StreamClientConnection::Span> StreamClientConnection::tryAcquire(Timeout timeout)
{
    ClientLimit clientLimit = sharedClientLimit().load(std::memory_order_acquire);
    // This would mean we try to send messages after a timeout. It is a programming error.
    // Since the value is trusted, we only assert.
    ASSERT(clientLimit != ClientLimit::clientIsWaitingTag);

    for (;;) {
        if (clientLimit != ClientLimit::clientIsWaitingTag) {
            auto result = alignedSpan(m_clientOffset, toLimit(clientLimit));
            if (result.size >= minimumMessageSize)
                return result;
        }
        if (timeout.didTimeOut())
            break;
        ClientLimit oldClientLimit = sharedClientLimit().compareExchangeStrong(clientLimit, ClientLimit::clientIsWaitingTag, std::memory_order_acq_rel, std::memory_order_acq_rel);
        if (clientLimit == oldClientLimit) {
            if (!m_semaphores || !m_semaphores->clientWait.waitFor(timeout))
                return std::nullopt;
            clientLimit = sharedClientLimit().load(std::memory_order_acquire);
        } else
            clientLimit = oldClientLimit;
        // The alignedSpan uses the minimumMessageSize to calculate the next beginning position in the buffer,
        // and not the size. The size might be more or less what is needed, depending on where the reader is.
        // If there is no capacity for minimum message size, wait until more is available.
        // In the case where clientOffset < clientLimit we can arrive to a situation where
        // 0 < result.size < minimumMessageSize.
    }
    return std::nullopt;
}

inline std::optional<StreamClientConnection::Span> StreamClientConnection::tryAcquireAll(Timeout timeout)
{
    // This would mean we try to send messages after a timeout. It is a programming error.
    // Since the value is trusted, we only assert.
    ASSERT(sharedClientLimit().load(std::memory_order_acquire) != ClientLimit::clientIsWaitingTag);

    // The server acknowledges that sync message has been processed by setting clientOffset == clientLimit == 0.
    // Wait for this condition, or then the condition where server says that it started to sleep after setting that condition.
    // The wait sequence involves two variables, so form a transaction by setting clientLimit == clientIsWaitingTag.
    // The transaction is cancelled if the server has already set clientOffset == clientLimit == 0, otherwise it commits.
    // If the transaction commits, server is guaranteed to signal.

    for (;;) {
        ClientLimit clientLimit = sharedClientLimit().exchange(ClientLimit::clientIsWaitingTag, std::memory_order_acq_rel);
        ClientOffset clientOffset = sharedClientOffset().load(std::memory_order_acquire);
        if (!clientLimit && (clientOffset == ClientOffset::serverIsSleepingTag || !clientOffset))
            break;

        if (!m_semaphores || !m_semaphores->clientWait.waitFor(timeout))
            return std::nullopt;
        if (timeout.didTimeOut())
            return std::nullopt;
    }
    // In case the transaction was cancelled, undo the transaction marker.
    sharedClientLimit().store(static_cast<ClientLimit>(0), std::memory_order_release);
    m_clientOffset = 0;
    return alignedSpan(m_clientOffset, 0);
}

inline StreamClientConnection::WakeUpServer StreamClientConnection::release(size_t size)
{
    size = std::max(size, minimumMessageSize);
    m_clientOffset = wrapOffset(alignOffset(m_clientOffset) + size);
    ASSERT(m_clientOffset < dataSize());
    // If the server wrote over the clientOffset with serverIsSleepingTag, we know it is sleeping.
    ClientOffset oldClientOffset = sharedClientOffset().exchange(static_cast<ClientOffset>(m_clientOffset), std::memory_order_acq_rel);
    if (oldClientOffset == ClientOffset::serverIsSleepingTag)
        return WakeUpServer::Yes;
    ASSERT(!(oldClientOffset & ClientOffset::serverIsSleepingTag));
    return WakeUpServer::No;
}

inline StreamClientConnection::Span StreamClientConnection::alignedSpan(size_t offset, size_t limit)
{
    ASSERT(offset < dataSize());
    ASSERT(limit < dataSize());
    size_t aligned = alignOffset(offset);
    size_t resultSize = 0;
    if (offset < limit) {
        if (aligned >= offset && aligned < limit)
            resultSize = size(aligned, limit);
    } else {
        if (aligned >= offset || aligned < limit)
            resultSize = size(aligned, limit);
    }
    return { data() + aligned, resultSize };
}

inline size_t StreamClientConnection::size(size_t offset, size_t limit)
{
    if (!limit)
        return dataSize() - 1 - offset;
    if (limit <= offset)
        return dataSize() - offset;
    return limit - offset - 1;
}

inline size_t StreamClientConnection::toLimit(ClientLimit clientLimit) const
{
    ASSERT(!(clientLimit & ClientLimit::clientIsWaitingTag));
    ASSERT(static_cast<size_t>(clientLimit) <= dataSize() - 1);
    return static_cast<size_t>(clientLimit);
}

}