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

   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
{

enum class SysexExtractorCallbackKind
{
    notSysex,
    ongoingSysex,
    lastSysex,
};

class BytestreamSysexExtractor
{
public:
    void reset()
    {
        state = RunningStatus{};
    }

    template <typename Callback>
    void push (Span<const std::byte> bytes, Callback&& callback)
    {
        for (const auto pair : enumerate (bytes))
        {
            const auto index = pair.index;
            const auto byte = pair.value;

            state = std::invoke ([&]() -> State
            {
                if (auto* inSysex = std::get_if<InSysex> (&state))
                {
                    if (byte == std::byte { 0xf0 })
                    {
                        callback (SysexExtractorCallbackKind::lastSysex,
                                  Span { bytes.data() + index - inSysex->numBytes, inSysex->numBytes });
                        return InSysex { 1 };
                    }

                    if (byte == std::byte { 0xf7 })
                    {
                        callback (SysexExtractorCallbackKind::lastSysex,
                                  Span { bytes.data() + index - inSysex->numBytes, inSysex->numBytes + 1 });
                        return RunningStatus{};
                    }

                    if (isRealtimeMessage (byte))
                    {
                        callback (SysexExtractorCallbackKind::ongoingSysex,
                                  Span { bytes.data() + index - inSysex->numBytes, inSysex->numBytes });
                        callback (SysexExtractorCallbackKind::notSysex,
                                  Span { bytes.data() + index, 1 });
                        return InSysex{};
                    }

                    if (isStatusByte (byte))
                    {
                        callback (SysexExtractorCallbackKind::lastSysex,
                                  Span { bytes.data() + index - inSysex->numBytes, inSysex->numBytes });
                        return RunningStatus { 1, { byte } };
                    }

                    return InSysex { inSysex->numBytes + 1 };
                }

                if (auto* runningStatus = std::get_if<RunningStatus> (&state))
                {
                    if (byte == std::byte { 0xf0 })
                        return InSysex { 1 };

                    const auto nextRunningStatus = std::invoke ([&]
                    {
                        if (isRealtimeMessage (byte))
                        {
                            callback (SysexExtractorCallbackKind::notSysex,
                                      Span { bytes.data() + index, 1 });
                            return *runningStatus;
                        }

                        if (isInitialByte (byte))
                            return RunningStatus{}.withAppendedByte (byte);

                        if (0 < runningStatus->size && runningStatus->size < runningStatus->data.size())
                            return runningStatus->withAppendedByte (byte);

                        // If we get to this branch, we're trying to process a non-status byte
                        // without having seen any previous status byte, so ignore the current byte
                        return RunningStatus{};
                    });

                    if (const auto completeMessage = nextRunningStatus.getCompleteMessage(); ! completeMessage.empty())
                    {
                        callback (SysexExtractorCallbackKind::notSysex,
                                  completeMessage);
                        return RunningStatus{}.withAppendedByte (nextRunningStatus.data[0]);
                    }

                    return nextRunningStatus;
                }

                // Can only happen if the variant is valueless by exception, which indicates a much
                // more severe problem!
                std::terminate();
            });
        }

        if (auto* inSysex = std::get_if<InSysex> (&state))
        {
            callback (SysexExtractorCallbackKind::ongoingSysex,
                      Span { bytes.data() + bytes.size() - inSysex->numBytes, inSysex->numBytes });
            state = InSysex{};
        }
    }

private:
    static bool isRealtimeMessage (std::byte byte)  { return std::byte (0xf8) <= byte && byte <= std::byte (0xfe); }
    static bool isStatusByte      (std::byte byte)  { return std::byte (0x80) <= byte; }
    static bool isInitialByte     (std::byte byte)  { return isStatusByte (byte) && byte != std::byte (0xf7); }

    struct InSysex
    {
        size_t numBytes{};
    };

    struct RunningStatus
    {
        // These constructors are required to work around a bug in GCC 7
        RunningStatus() {}

        RunningStatus (uint8_t sizeIn, std::array<std::byte, 3> dataIn)
            : size (sizeIn), data (dataIn) {}

        uint8_t size{};
        std::array<std::byte, 3> data{};

        Span<const std::byte> getCompleteMessage() const
        {
            if (size == 0)
                return {};

            const auto expectedSize = MidiMessage::getMessageLengthFromFirstByte ((uint8_t) data[0]);
            return Span { data.data(), size == expectedSize ? size : (size_t) 0 };
        }

        void appendByte (std::byte x)
        {
            jassert (size < data.size());
            data[size++] = x;
        }

        RunningStatus withAppendedByte (std::byte x) const
        {
            auto result = *this;
            result.appendByte (x);
            return result;
        }
    };

    using State = std::variant<RunningStatus, InSysex>;
    State state;
};

//==============================================================================
/**
    Helper class that takes chunks of incoming midi bytes, packages them into
    messages, and dispatches them to a midi callback.

    @tags{Audio}
*/
class MidiDataConcatenator
{
public:
    MidiDataConcatenator (int initialBufferSize)
    {
        pendingSysexData.reserve ((size_t) initialBufferSize);
    }

    MidiDataConcatenator (MidiDataConcatenator&&) noexcept = default;
    MidiDataConcatenator& operator= (MidiDataConcatenator&&) noexcept = default;

    void reset()
    {
        extractor.reset();
        pendingSysexData.clear();
        pendingSysexTime = 0;
    }

    template <typename UserDataType, typename CallbackType>
    void pushMidiData (Span<const std::byte> bytes,
                       double time,
                       UserDataType* input,
                       CallbackType& callback)
    {
        extractor.push (bytes, [&] (SysexExtractorCallbackKind kind, Span<const std::byte> bytesThisTime)
        {
            switch (kind)
            {
                case SysexExtractorCallbackKind::notSysex:
                    callback.handleIncomingMidiMessage (input,
                                                        MidiMessage (bytesThisTime.data(),
                                                                     (int) bytesThisTime.size(),
                                                                     time));
                    return;

                case SysexExtractorCallbackKind::ongoingSysex:
                {
                    if (pendingSysexData.empty())
                        pendingSysexTime = time;

                    pendingSysexData.insert (pendingSysexData.end(), bytesThisTime.begin(), bytesThisTime.end());
                    return;
                }

                case SysexExtractorCallbackKind::lastSysex:
                {
                    pendingSysexData.insert (pendingSysexData.end(), bytesThisTime.begin(), bytesThisTime.end());

                    if (pendingSysexData.empty())
                    {
                        jassertfalse;
                        return;
                    }

                    if (pendingSysexData.back() == std::byte { 0xf7 })
                    {
                        callback.handleIncomingMidiMessage (input,
                                                            MidiMessage (pendingSysexData.data(),
                                                                         (int) pendingSysexData.size(),
                                                                         pendingSysexTime));
                    }
                    else
                    {
                        callback.handlePartialSysexMessage (input,
                                                            unalignedPointerCast<const uint8*> (pendingSysexData.data()),
                                                            (int) pendingSysexData.size(),
                                                            pendingSysexTime);
                    }

                    pendingSysexData.clear();

                    return;
                }
            }
        });
    }

    template <typename UserDataType, typename CallbackType>
    void pushMidiData (const void* inputData,
                       int numBytes,
                       double time,
                       UserDataType* input,
                       CallbackType& callback)
    {
        pushMidiData ({ static_cast<const std::byte*> (inputData), (size_t) numBytes }, time, input, callback);
    }

private:
    BytestreamSysexExtractor extractor;
    std::vector<std::byte> pendingSysexData;
    double pendingSysexTime = 0;

    JUCE_DECLARE_NON_COPYABLE (MidiDataConcatenator)
};

} // namespace juce