/*
  ==============================================================================

   This file is part of the JUCE framework.
   Copyright (c) Raw Material Software Limited

   JUCE is an open source framework subject to commercial or open source
   licensing.

   By downloading, installing, or using the JUCE framework, or combining the
   JUCE framework with any other source code, object code, content or any other
   copyrightable work, you agree to the terms of the JUCE End User Licence
   Agreement, and all incorporated terms including the JUCE Privacy Policy and
   the JUCE Website Terms of Service, as applicable, which will bind you. If you
   do not agree to the terms of these agreements, we will not license the JUCE
   framework to you, and you must discontinue the installation or download
   process and cease use of the JUCE framework.

   JUCE End User Licence Agreement: https://juce.com/legal/juce-8-licence/
   JUCE Privacy Policy: https://juce.com/juce-privacy-policy
   JUCE Website Terms of Service: https://juce.com/juce-website-terms-of-service/

   Or:

   You may also use this code under the terms of the AGPLv3:
   https://www.gnu.org/licenses/agpl-3.0.en.html

   THE JUCE FRAMEWORK IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL
   WARRANTIES, WHETHER EXPRESSED OR IMPLIED, INCLUDING WARRANTY OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, ARE DISCLAIMED.

  ==============================================================================
*/

namespace juce::midi_ci
{

class PropertyHost::Visitor : public detail::MessageTypeUtils::MessageVisitor
{
public:
    Visitor (PropertyHost* h, ResponderOutput* o, bool* b)
        : host (h), output (o), handled (b) {}

    void visit (const Message::PropertyExchangeCapabilities& body)  const override { visitImpl (body); }
    void visit (const Message::PropertyGetData& body)               const override { visitImpl (body); }
    void visit (const Message::PropertySetData& body)               const override { visitImpl (body); }
    void visit (const Message::PropertySubscribe& body)             const override { visitImpl (body); }
    using MessageVisitor::visit;

private:
    template <typename Body>
    void visitImpl (const Body& body) const { *handled = messageReceived (body); }

    bool messageReceived (const Message::PropertyExchangeCapabilities&) const
    {
        detail::MessageTypeUtils::send (*output, Message::PropertyExchangeCapabilitiesResponse { std::byte { host->delegate.getNumSimultaneousRequestsSupported() },
                                                                                                 {},
                                                                                                 {} });
        return true;
    }

    bool messageReceived (const Message::PropertyGetData& data) const
    {
        // This should always be a single message, so no need to accumulate chunks
        const auto reply = host->delegate.propertyGetDataRequested (output->getIncomingHeader().source,
                                                                    PropertyRequestHeader::parseCondensed (Encodings::jsonFrom7BitText (data.header)));

        const auto encoded = Encodings::tryEncode (reply.body, reply.header.mutualEncoding);

        if (! encoded.has_value())
        {
            // If this is hit, the data that was supplied isn't valid for the encoding that was specified
            jassertfalse;
            return false;
        }

        detail::PropertyHostUtils::send (*output,
                                         output->getIncomingGroup(),
                                         detail::MessageMeta::Meta<Message::PropertyGetDataResponse>::subID2,
                                         output->getIncomingHeader().source,
                                         data.requestID,
                                         Encodings::jsonTo7BitText (reply.header.toVarCondensed()),
                                         *encoded,
                                         host->cacheProvider.getMaxSysexSizeForMuid (output->getIncomingHeader().source));

        return true;
    }

    bool messageReceived (const Message::PropertySetData& data) const
    {
        auto* caches = host->cacheProvider.getCacheForMuidAsResponder (output->getIncomingHeader().source);

        if (caches == nullptr)
            return false;

        const auto source = output->getIncomingHeader().source;
        const auto dest = output->getIncomingHeader().destination;
        const auto group = output->getIncomingGroup();
        const auto request = RequestID::create (data.requestID);

        if (! request.has_value())
            return false;

        caches->primeCache (host->delegate.getNumSimultaneousRequestsSupported(), [hostPtr = host, source, dest, group, request] (const PropertyExchangeResult& result)
        {
            const auto send = [&] (const PropertyReplyHeader& header)
            {
                detail::MessageTypeUtils::send (hostPtr->output,
                                                group,
                                                Message::Header { ChannelInGroup::wholeBlock,
                                                                  detail::MessageMeta::Meta<Message::PropertySetDataResponse>::subID2,
                                                                  detail::MessageMeta::implementationVersion,
                                                                  dest,
                                                                  source },
                                                Message::PropertySetDataResponse { { request->asByte(), Encodings::jsonTo7BitText (header.toVarCondensed()) } });
            };

            const auto sendStatus = [&] (int status, StringRef message)
            {
                PropertyReplyHeader header;
                header.status = status;
                header.message = message;
                send (header);
            };

            if (const auto error = result.getError())
            {
                switch (*error)
                {
                    case PropertyExchangeResult::Error::tooManyTransactions:
                        sendStatus (343, TRANS ("The device has initiated too many simultaneous requests"));
                        break;

                    case PropertyExchangeResult::Error::partial:
                        sendStatus (400, TRANS ("Request was incomplete"));
                        break;

                    case PropertyExchangeResult::Error::notify:
                        break;
                }

                return;
            }

            send (hostPtr->delegate.propertySetDataRequested (source, { result.getHeaderAsRequestHeader(), result.getBody() }));
        }, *request);

        caches->addChunk (*request, data);

        return true;
    }

    bool messageReceived (const Message::PropertySubscribe& data) const
    {
        auto* caches = host->cacheProvider.getCacheForMuidAsResponder (output->getIncomingHeader().source);

        if (caches == nullptr)
            return false;

        if (data.header.empty() || data.thisChunkNum != 1 || data.totalNumChunks != 1)
            return false;

        const auto subHeader = PropertySubscriptionHeader::parseCondensed (Encodings::jsonFrom7BitText (data.header));
        const auto tryNotifyInitiator = subHeader.command == PropertySubscriptionCommand::start
                                        || subHeader.command == PropertySubscriptionCommand::end;

        if (! tryNotifyInitiator)
            return false;

        const auto source = output->getIncomingHeader().source;

        const auto sendResponse = [&] (const PropertyReplyHeader& header)
        {
            detail::PropertyHostUtils::send (*output,
                                             output->getIncomingGroup(),
                                             detail::MessageMeta::Meta<Message::PropertySubscribeResponse>::subID2,
                                             source,
                                             data.requestID,
                                             Encodings::jsonTo7BitText (header.toVarCondensed()),
                                             {},
                                             host->cacheProvider.getMaxSysexSizeForMuid (source));
        };

        if (subHeader.command == PropertySubscriptionCommand::start)
        {
            if (host->delegate.subscriptionStartRequested (source, subHeader))
            {
                auto& currentSubscribeIds = host->registry[source];
                const auto newToken = findUnusedSubscribeId (currentSubscribeIds);
                [[maybe_unused]] const auto pair = currentSubscribeIds.emplace (newToken, subHeader.resource);
                jassert (pair.second);
                const auto subscribeId = subscribeIdFromUid (newToken);
                host->delegate.subscriptionDidStart (source, subscribeId, subHeader);

                PropertyReplyHeader header;
                header.extended["subscribeId"] = subscribeId;
                sendResponse (header);
            }
            else
            {
                PropertyReplyHeader header;
                header.status = 405;
                sendResponse (header);
            }

            return true;
        }

        if (subHeader.command == PropertySubscriptionCommand::end)
        {
            const auto token = uidFromSubscribeId (subHeader.subscribeId);
            auto& currentSubscribeIds = host->registry[source];
            const auto iter = currentSubscribeIds.find (token);

            if (iter != currentSubscribeIds.end())
            {
                host->delegate.subscriptionWillEnd (source, { subHeader.subscribeId, iter->second });
                currentSubscribeIds.erase (iter);

                sendResponse ({});
                return true;
            }

            return false;
        }

        return false;
    }

    PropertyHost* host = nullptr;
    ResponderOutput* output = nullptr;
    bool* handled = nullptr;
};

//==============================================================================
std::set<Subscription> PropertyHost::findSubscriptionsForDevice (MUID device) const
{
    const auto iter = registry.find (device);

    if (iter == registry.end())
        return {};

    std::set<Subscription> result;

    for (const auto& [subId, resource] : iter->second)
    {
        [[maybe_unused]] const auto pair = result.insert ({ subscribeIdFromUid (subId), resource });
        jassert (pair.second);
    }

    return result;
}

int PropertyHost::countOngoingTransactions() const
{
    const auto muids = cacheProvider.getDiscoveredMuids();

    return std::accumulate (muids.begin(), muids.end(), 0, [&] (auto acc, const auto& m)
    {
        if (auto* cache = cacheProvider.getCacheForMuidAsResponder (m))
            return acc + cache->countOngoingTransactions();

        return acc;
    });
}

bool PropertyHost::tryRespond (ResponderOutput& responderOutput, const Message::Parsed& message)
{
    bool result = false;
    detail::MessageTypeUtils::visit (message, Visitor { this, &responderOutput, &result });
    return result;
}

std::optional<RequestKey> PropertyHost::sendSubscriptionUpdate (MUID device,
                                                                const PropertySubscriptionHeader& header,
                                                                Span<const std::byte> body,
                                                                std::function<void (const PropertyExchangeResult&)> cb)
{
    const auto deviceIter = registry.find (device);

    if (deviceIter == registry.end())
    {
        // That device doesn't have any active subscriptions
        jassertfalse;
        return {};
    }

    const auto uid = uidFromSubscribeId (header.subscribeId);
    const auto subIter = deviceIter->second.find (uid);

    if (subIter == deviceIter->second.end())
    {
        // That subscribeId isn't currently in use by that device
        jassertfalse;
        return {};
    }

    const auto resource = subIter->second;

    if (header.resource != resource)
    {
        // That subscribeId corresponds to a different resource
        jassertfalse;
        return {};
    }

    if (header.command == PropertySubscriptionCommand::start)
    {
        // This function is intended to update ongoing subscriptions. To start a new subscription,
        // use CIDevice.
        jassertfalse;
        return {};
    }

    auto* caches = cacheProvider.getCacheForMuidAsInitiator (device);

    if (caches == nullptr)
        return {};

    auto wrappedCallback = [&]() -> std::function<void (const PropertyExchangeResult&)>
    {
        if (header.command != PropertySubscriptionCommand::end)
            return cb;

        return [this, device, uid, resource, cb] (const PropertyExchangeResult& result)
        {
            if (! result.getError().has_value())
            {
                delegate.subscriptionWillEnd (device, { subscribeIdFromUid (uid), resource });
                registry[device].erase (uid);
            }

            NullCheckedInvocation::invoke (cb, result);
        };
    }();

    const auto encoded = Encodings::tryEncode (body, header.mutualEncoding);

    if (! encoded.has_value())
    {
        // The data could not be encoded successfully
        jassertfalse;
        return {};
    }

    const auto primed = caches->primeCache (delegate.getNumSimultaneousRequestsSupported(),
                                            std::move (wrappedCallback));

    if (! primed.has_value())
        return {};

    const auto id = caches->getRequestIdForToken (*primed);

    if (! id.has_value())
        return {};

    detail::PropertyHostUtils::send (output,
                                     functionBlock.firstGroup,
                                     detail::MessageMeta::Meta<Message::PropertySubscribe>::subID2,
                                     device,
                                     id->asByte(),
                                     Encodings::jsonTo7BitText (header.toVarCondensed()),
                                     *encoded,
                                     cacheProvider.getMaxSysexSizeForMuid (device));

    return RequestKey { device, *primed };
}

void PropertyHost::terminateSubscription (MUID device, const String& subscribeId)
{
    const auto deviceIter = registry.find (device);

    if (deviceIter == registry.end())
    {
        // That device doesn't have any active subscriptions
        jassertfalse;
        return;
    }

    const auto uid = uidFromSubscribeId (subscribeId);
    const auto subIter = deviceIter->second.find (uid);

    if (subIter == deviceIter->second.end())
    {
        // That subscribeId isn't currently in use by that device
        jassertfalse;
        return;
    }

    PropertySubscriptionHeader header;
    header.command = PropertySubscriptionCommand::end;
    header.subscribeId = subscribeId;
    header.resource = subIter->second;

    sendSubscriptionUpdate (device, header, {}, nullptr);
}

PropertyHost::SubscriptionToken PropertyHost::uidFromSubscribeId (String id)
{
    try
    {
        // from_chars would be better once we no longer need to support older macOS
        return { (size_t) std::stoull (id.toStdString(), {}, 36) };
    }
    catch (...) {}

    jassertfalse;
    return {};
}

String PropertyHost::subscribeIdFromUid (SubscriptionToken uid)
{
    const auto str = std::to_string (uid.uid);
    jassert (str.size() <= 8);
    return str;
}

PropertyHost::SubscriptionToken PropertyHost::findUnusedSubscribeId (const std::map<SubscriptionToken, String>& used)
{
    return ! used.empty() ? SubscriptionToken { std::prev (used.end())->first.uid + 1 } : SubscriptionToken { 0 };
}

} // namespace juce::midi_ci
