#include "BLEConnection.h"

BLEConnection::BLEConnection()
    : pServer(nullptr), pCharacteristic(nullptr),
      pBleCallback(nullptr), pServerCallback(nullptr),
      sendMutex(nullptr),
      queueHead(0), queueTail(0),
      queueMux(portMUX_INITIALIZER_UNLOCKED)
{
}

BLEConnection::~BLEConnection() {
    if (sendMutex) {
        vSemaphoreDelete(sendMutex);
        sendMutex = nullptr;
    }
    delete pBleCallback;
    pBleCallback = nullptr;
    delete pServerCallback;
    pServerCallback = nullptr;
}

void BLEConnection::begin(const std::string& deviceName) {
    if (pServer) return;  // already initialized

    sendMutex = xSemaphoreCreateMutex();

    BLEDevice::init(deviceName);
    pServer = BLEDevice::createServer();

    // Server callbacks: handle connect/disconnect and restart advertising automatically.
    class ServerCallback : public BLEServerCallbacks {
    public:
        BLEConnection* bleCon;
        ServerCallback(BLEConnection* con) : bleCon(con) {}
        void onConnect(BLEServer*) override {
            bleCon->dispatchConnected();
        }
        void onDisconnect(BLEServer*) override {
            // Flush pending data from the disconnected central.
            portENTER_CRITICAL(&bleCon->queueMux);
            bleCon->queueHead = 0;
            bleCon->queueTail = 0;
            portEXIT_CRITICAL(&bleCon->queueMux);

            bleCon->dispatchDisconnected();
            // Restart advertising so a new central can connect.
            BLEDevice::startAdvertising();
        }
    };
    delete pServerCallback;
    pServerCallback = new ServerCallback(this);
    pServer->setCallbacks(pServerCallback);

    BLEService* pService = pServer->createService(BLE_MIDI_SERVICE_UUID);

    // BLE MIDI spec requires READ + NOTIFY + WRITE_NR.
    // The CCCD (0x2902) descriptor is added automatically by the underlying stack
    // (NimBLE in arduino-esp32 3.x; BlueDroid in 2.x) whenever NOTIFY/INDICATE is set,
    // so we no longer add it manually (BLE2902 is deprecated and will be removed).
    pCharacteristic = pService->createCharacteristic(
        BLE_MIDI_CHARACTERISTIC_UUID,
        BLECharacteristic::PROPERTY_READ    |
        BLECharacteristic::PROPERTY_NOTIFY  |
        BLECharacteristic::PROPERTY_WRITE_NR
    );

    // Receive callback: strips the 2-byte BLE MIDI header and enqueues raw MIDI bytes.
    // BLE MIDI packet format: [header][timestamp][midi_bytes...]
    // Processing is deferred to task() — same pattern as USBConnection.
    class BLECallback : public BLECharacteristicCallbacks {
    public:
        BLEConnection* bleCon;
        BLECallback(BLEConnection* con) : bleCon(con) {}
        void onWrite(BLECharacteristic* characteristic) override {
            std::string rxValue = characteristic->getValue();
            size_t len = rxValue.length();
            // Minimum valid BLE MIDI packet: header + timestamp + 1 MIDI byte = 3 bytes
            if (len >= 3) {
                const uint8_t* data = reinterpret_cast<const uint8_t*>(rxValue.c_str());
                // Skip header (byte 0) and timestamp (byte 1); enqueue raw MIDI bytes.
                // Processing happens in task() on the main loop — thread-safe.
                bleCon->enqueueMidiMessage(data + 2, len - 2);
            }
        }
    };
    delete pBleCallback;
    pBleCallback = new BLECallback(this);
    pCharacteristic->setCallbacks(pBleCallback);
    pService->start();

    BLEAdvertising* pAdvertising = BLEDevice::getAdvertising();
    pAdvertising->addServiceUUID(BLE_MIDI_SERVICE_UUID);
    pAdvertising->setScanResponse(false);
    BLEDevice::startAdvertising();
}

void BLEConnection::task() {
    // Drain the ring buffer and dispatch via MIDITransport callbacks.
    processQueue();
}

bool BLEConnection::isConnected() const {
    if (pServer)
        return (pServer->getConnectedCount() > 0);
    return false;
}

// ---------- Ring Buffer ----------
// Same pattern as USBConnection. Spinlock protects cross-task access:
// enqueue() runs in the BLE stack task; dequeue() runs in the main loop.

bool BLEConnection::enqueueMidiMessage(const uint8_t* data, size_t length) {
    portENTER_CRITICAL(&queueMux);
    int next = (queueHead + 1) % QUEUE_SIZE;
    if (next == queueTail) {
        // Queue full — discard to avoid blocking the BLE task.
        portEXIT_CRITICAL(&queueMux);
        return false;
    }
    size_t copyLen = (length > sizeof(bleQueue[0].data)) ? sizeof(bleQueue[0].data) : length;
    memcpy(bleQueue[queueHead].data, data, copyLen);
    bleQueue[queueHead].length = copyLen;
    queueHead = next;
    portEXIT_CRITICAL(&queueMux);
    return true;
}

bool BLEConnection::dequeueMidiMessage(RawBleMessage& msg) {
    portENTER_CRITICAL(&queueMux);
    if (queueTail == queueHead) {
        portEXIT_CRITICAL(&queueMux);
        return false;
    }
    msg = bleQueue[queueTail];
    queueTail = (queueTail + 1) % QUEUE_SIZE;
    portEXIT_CRITICAL(&queueMux);
    return true;
}

void BLEConnection::processQueue() {
    RawBleMessage msg;
    while (dequeueMidiMessage(msg)) {
        dispatchMidiData(msg.data, msg.length);
    }
}

// ---------- BLE MIDI Output ----------

bool BLEConnection::sendMidiMessage(const uint8_t* data, size_t length) {
    if (!pCharacteristic || !sendMutex || length == 0) return false;

    // Build BLE MIDI 1.0 packet before acquiring the mutex.
    //   Byte 0: Header    = 0x80 | ((timestamp_ms >> 7) & 0x3F)
    //   Byte 1: Timestamp = 0x80 | (timestamp_ms & 0x7F)
    //   Byte 2+: MIDI bytes (status + data bytes)
    uint32_t ts = (uint32_t)millis();
    uint8_t header    = 0x80 | ((ts >> 7) & 0x3F);
    uint8_t timestamp = 0x80 | (ts & 0x7F);

    size_t midiLen = (length > 18) ? 18 : length;  // safe limit for default BLE MTU
    uint8_t packet[20];
    packet[0] = header;
    packet[1] = timestamp;
    memcpy(packet + 2, data, midiLen);

    // Check connection inside the mutex to minimize TOCTOU race window.
    if (xSemaphoreTake(sendMutex, pdMS_TO_TICKS(100)) != pdTRUE) return false;

    bool sent = false;
    if (isConnected()) {
        pCharacteristic->setValue(packet, 2 + midiLen);
        pCharacteristic->notify();
        sent = true;
    }

    xSemaphoreGive(sendMutex);
    return sent;
}
