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

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

/** @cond */
namespace juce::universal_midi_packets
{

/** Represents a MIDI message on bytestream transport that happened at a particular time.

    Unlike MidiMessage, BytestreamMidiView is non-owning.
*/
struct BytestreamMidiView
{
    constexpr BytestreamMidiView (Span<const std::byte> bytesIn, double timestampIn)
        : bytes (bytesIn), timestamp (timestampIn) {}

    /** Creates a view over the provided message.

        Note that the argument is a pointer, not a reference, in order to avoid taking a reference
        to a temporary.
    */
    explicit BytestreamMidiView (const MidiMessage* msg)
        : bytes (msg->asSpan()),
          timestamp (msg->getTimeStamp()) {}

    explicit BytestreamMidiView (const MidiMessageMetadata msg)
        : bytes (msg.asSpan()),
          timestamp (msg.samplePosition) {}

    MidiMessage getMessage() const
    {
        return MidiMessage (bytes.data(), (int) bytes.size(), timestamp);
    }

    MidiMessageMetadata getMidiMessageMetadata() const
    {
        return MidiMessageMetadata { reinterpret_cast<const uint8*> (bytes.data()),
                                     (int) bytes.size(),
                                     (int) timestamp };
    }

    Span<const std::byte> bytes;
    double timestamp = 0.0;
};

//==============================================================================
/**
    Functions to assist conversion of UMP messages to/from other formats,
    especially older 'bytestream' formatted MidiMessages.

    @tags{Audio}
*/
struct Conversion
{
    /** Converts 7-bit data (the most significant bit of each byte must be unset) to a series of
        Universal MIDI Packets.
    */
    template <typename PacketCallbackFunction>
    static void umpFrom7BitData (BytesOnGroup msg, PacketCallbackFunction&& callback)
    {
        // If this is hit, non-7-bit data was supplied.
        // Maybe you forgot to trim the leading/trailing bytes that delimit a bytestream SysEx message.
        jassert (std::all_of (msg.bytes.begin(), msg.bytes.end(), [] (std::byte b) { return (b & std::byte { 0x80 }) == std::byte{}; }));

        Factory::splitIntoPackets (msg.bytes, 6, [&] (SysEx7::Kind kind, Span<const std::byte> bytesThisTime)
        {
            const auto packet = Factory::Detail::makeSysEx (msg.group, kind, bytesThisTime);
            const uint32_t paddedPacket[] { packet[0], packet[1], 0, 0 };
            callback (View (paddedPacket));
        });
    }

    /** Converts from a MIDI 1 bytestream to MIDI 1 on Universal MIDI Packets.

        @param bytes    the bytes in a single well-formed bytestream MIDI message
        @param callback a function that accepts a single View argument. This may be called several
                        times for each invocation of toMidi1 if the bytestream message converts
                        to multiple Universal MIDI Packets.
    */
    template <typename PacketCallbackFunction>
    static void toMidi1 (const BytesOnGroup& groupBytes, PacketCallbackFunction&& callback)
    {
        const auto size = groupBytes.bytes.size();

        if (size <= 0)
            return;

        const auto* data = groupBytes.bytes.data();
        const auto firstByte = data[0];

        if (firstByte != std::byte { 0xf0 })
        {
            const auto mask = [size]() -> uint32_t
            {
                switch (size)
                {
                    case 0: return 0xff000000;
                    case 1: return 0xffff0000;
                    case 2: return 0xffffff00;
                    case 3: return 0xffffffff;
                }

                // This function can only handle a single bytestream MIDI message at a time!
                jassertfalse;
                return 0x00000000;
            }();

            const auto extraByte = ((((firstByte & std::byte { 0xf0 }) == std::byte { 0xf0 }) ? std::byte { 0x1 } : std::byte { 0x2 }) << 0x4);
            const std::byte group { (uint8_t) (groupBytes.group & 0xf) };
            const uint32_t packet[] { mask & Utils::bytesToWord (extraByte | group, data[0], data[1], data[2]), 0, 0, 0 };
            callback (View (packet));
            return;
        }

        umpFrom7BitData ({ groupBytes.group, Span (data + 1, size - 2) }, std::forward<PacketCallbackFunction> (callback));
    }

    /** Widens a 7-bit MIDI 1.0 value to a 8-bit MIDI 2.0 value. */
    static uint8_t scaleTo8 (uint8_t word7Bit)
    {
        const auto shifted = (uint8_t) (word7Bit << 0x1);
        const auto repeat = (uint8_t) (word7Bit & 0x3f);
        const auto mask = (uint8_t) (word7Bit <= 0x40 ? 0x0 : 0xff);
        return (uint8_t) (shifted | ((repeat >> 5) & mask));
    }

    /** Widens a 7-bit MIDI 1.0 value to a 16-bit MIDI 2.0 value. */
    static uint16_t scaleTo16 (uint8_t word7Bit)
    {
        const auto shifted = (uint16_t) (word7Bit << 0x9);
        const auto repeat = (uint16_t) (word7Bit & 0x3f);
        const auto mask = (uint16_t) (word7Bit <= 0x40 ? 0x0 : 0xffff);
        return (uint16_t) (shifted | (((repeat << 3) | (repeat >> 3)) & mask));
    }

    /** Widens a 14-bit MIDI 1.0 value to a 16-bit MIDI 2.0 value. */
    static uint16_t scaleTo16 (uint16_t word14Bit)
    {
        const auto shifted = (uint16_t) (word14Bit << 0x2);
        const auto repeat = (uint16_t) (word14Bit & 0x1fff);
        const auto mask = (uint16_t) (word14Bit <= 0x2000 ? 0x0 : 0xffff);
        return (uint16_t) (shifted | ((repeat >> 11) & mask));
    }

    /** Widens a 7-bit MIDI 1.0 value to a 32-bit MIDI 2.0 value. */
    static uint32_t scaleTo32 (uint8_t word7Bit)
    {
        const auto shifted = (uint32_t) (word7Bit << 0x19);
        const auto repeat = (uint32_t) (word7Bit & 0x3f);
        const auto mask = (uint32_t) (word7Bit <= 0x40 ? 0x0 : 0xffffffff);
        return (uint32_t) (shifted | (((repeat << 19)
                                     | (repeat << 13)
                                     | (repeat << 7)
                                     | (repeat << 1)
                                     | (repeat >> 5)) & mask));
    }

    /** Widens a 14-bit MIDI 1.0 value to a 32-bit MIDI 2.0 value. */
    static uint32_t scaleTo32 (uint16_t word14Bit)
    {
        const auto shifted = (uint32_t) (word14Bit << 0x12);
        const auto repeat = (uint32_t) (word14Bit & 0x1fff);
        const auto mask = (uint32_t) (word14Bit <= 0x2000 ? 0x0 : 0xffffffff);
        return (uint32_t) (shifted | (((repeat << 5) | (repeat >> 8)) & mask));
    }

    /** Narrows a 16-bit MIDI 2.0 value to a 7-bit MIDI 1.0 value. */
    static uint8_t scaleTo7 (uint8_t word8Bit) { return (uint8_t) (word8Bit >> 1); }

    /** Narrows a 16-bit MIDI 2.0 value to a 7-bit MIDI 1.0 value. */
    static uint8_t scaleTo7 (uint16_t word16Bit) { return (uint8_t) (word16Bit >> 9); }

    /** Narrows a 32-bit MIDI 2.0 value to a 7-bit MIDI 1.0 value. */
    static uint8_t scaleTo7 (uint32_t word32Bit) { return (uint8_t) (word32Bit >> 25); }

    /** Narrows a 32-bit MIDI 2.0 value to a 14-bit MIDI 1.0 value. */
    static uint16_t scaleTo14 (uint16_t word16Bit) { return (uint16_t) (word16Bit >> 2); }

    /** Narrows a 32-bit MIDI 2.0 value to a 14-bit MIDI 1.0 value. */
    static uint16_t scaleTo14 (uint32_t word32Bit) { return (uint16_t) (word32Bit >> 18); }

    /** Converts UMP messages which may include MIDI 2.0 channel voice messages into
        equivalent MIDI 1.0 messages (still in UMP format).

        `callback` is a function that accepts a single View argument and will be
        called with each converted packet.

        Note that not all MIDI 2.0 messages have MIDI 1.0 equivalents, so such
        messages will be ignored.
    */
    template <typename Callback>
    static void midi2ToMidi1DefaultTranslation (const View& v, Callback&& callback)
    {
        const auto firstWord = v[0];

        if (Utils::getMessageType (firstWord) != Utils::MessageKind::channelVoice2)
        {
            callback (v);
            return;
        }

        const auto status = Utils::getStatus (firstWord);
        const auto typeAndGroup = ((std::byte { 0x2 } << 0x4) | std::byte { Utils::getGroup (firstWord) });

        switch ((uint8_t) status)
        {
            case 0x8:   // note off
            case 0x9:   // note on
            case 0xa:   // poly pressure
            case 0xb:   // control change
            {
                const auto statusAndChannel = std::byte ((firstWord >> 0x10) & 0xff);
                const auto byte2 = std::byte ((firstWord >> 0x08) & 0xff);
                const auto byte3 = std::byte { scaleTo7 (v[1]) };

                // If this is a note-on, and the scaled byte is 0,
                // the scaled velocity should be 1 instead of 0
                const auto needsCorrection = status == std::byte { 0x9 } && byte3 == std::byte { 0 };
                const auto correctedByte = needsCorrection ? std::byte { 1 } : byte3;

                const auto shouldIgnore = status == std::byte { 0xb } && [&]
                {
                    switch (uint8_t (byte2))
                    {
                        case 0:
                        case 6:
                        case 32:
                        case 38:
                        case 98:
                        case 99:
                        case 100:
                        case 101:
                            return true;
                    }

                    return false;
                }();

                if (shouldIgnore)
                    return;

                const PacketX1 packet { Utils::bytesToWord (typeAndGroup,
                                                            statusAndChannel,
                                                            byte2,
                                                            correctedByte) };
                callback (View (packet.data()));
                return;
            }

            case 0xd: // channel pressure
            {
                const auto statusAndChannel = std::byte ((firstWord >> 0x10) & 0xff);
                const auto byte2 = std::byte { scaleTo7 (v[1]) };

                const PacketX1 packet { Utils::bytesToWord (typeAndGroup,
                                                            statusAndChannel,
                                                            byte2,
                                                            std::byte { 0 }) };
                callback (View (packet.data()));
                return;
            }

            case 0x2:   // rpn
            case 0x3:   // nrpn
            {
                const auto ccX = status == std::byte { 0x2 } ? std::byte { 101 } : std::byte { 99 };
                const auto ccY = status == std::byte { 0x2 } ? std::byte { 100 } : std::byte { 98 };
                const auto statusAndChannel = std::byte ((0xb << 0x4) | Utils::getChannel (firstWord));
                const auto data = scaleTo14 (v[1]);

                const PacketX1 packets[]
                {
                    PacketX1 { Utils::bytesToWord (typeAndGroup, statusAndChannel, ccX,              std::byte ((firstWord >> 0x8) & 0x7f)) },
                    PacketX1 { Utils::bytesToWord (typeAndGroup, statusAndChannel, ccY,              std::byte ((firstWord >> 0x0) & 0x7f)) },
                    PacketX1 { Utils::bytesToWord (typeAndGroup, statusAndChannel, std::byte { 6 },  std::byte ((data >> 0x7) & 0x7f)) },
                    PacketX1 { Utils::bytesToWord (typeAndGroup, statusAndChannel, std::byte { 38 }, std::byte ((data >> 0x0) & 0x7f)) },
                };

                for (const auto& packet : packets)
                    callback (View (packet.data()));

                return;
            }

            case 0xc: // program change / bank select
            {
                if (firstWord & 1)
                {
                    const auto statusAndChannel = std::byte ((0xb << 0x4) | Utils::getChannel (firstWord));
                    const auto secondWord = v[1];

                    const PacketX1 packets[]
                    {
                        PacketX1 { Utils::bytesToWord (typeAndGroup, statusAndChannel, std::byte { 0 },  std::byte ((secondWord >> 0x8) & 0x7f)) },
                        PacketX1 { Utils::bytesToWord (typeAndGroup, statusAndChannel, std::byte { 32 }, std::byte ((secondWord >> 0x0) & 0x7f)) },
                    };

                    for (const auto& packet : packets)
                        callback (View (packet.data()));
                }

                const auto statusAndChannel = std::byte ((0xc << 0x4) | Utils::getChannel (firstWord));
                const PacketX1 packet { Utils::bytesToWord (typeAndGroup,
                                                            statusAndChannel,
                                                            std::byte ((v[1] >> 0x18) & 0x7f),
                                                            std::byte { 0 }) };
                callback (View (packet.data()));
                return;
            }

            case 0xe: // pitch bend
            {
                const auto data = scaleTo14 (v[1]);
                const auto statusAndChannel = std::byte ((firstWord >> 0x10) & 0xff);
                const PacketX1 packet { Utils::bytesToWord (typeAndGroup,
                                                            statusAndChannel,
                                                            std::byte (data & 0x7f),
                                                            std::byte ((data >> 7) & 0x7f)) };
                callback (View (packet.data()));
                return;
            }

            default: // other message types do not translate
                return;
        }
    }
};

} // namespace juce::universal_midi_packets
/** @endcond */
