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class BT_HID_Keyboard
{
public:
    BT_HID_Keyboard(){}

    void inputCallback(const uint8_t* data, uint16_t length)
    {
        if (length >= 5)
        {
            uint8_t pressedButtons[3];
            pressedButtons[0] = data[2];
            pressedButtons[1] = data[3];
            pressedButtons[2] = data[4];

            uint8_t modifier = data[0];
            bool shift = (modifier & 0x22) !=0;

            for (int i=0; i < 3; ++i)
            {
                uint8_t keyCode = pressedButtons[i];
                if (keyCode != 0) // a key is pressed
                {
                    bool found = false;
                    // todo use std lib for search
                    for (int j=0; j < 3; ++j)
                    {
                        if (keyCode == m_pressedButtons[j])
                        {
                            found = true;
                            break;
                        }
                    }

                    if (!found) // not found = new = rising edge
                    {
                        if ( (keyCode >= 0x04) && (keyCode <= 0x1d)) // letter
                        {
                          if (shift)
                          {
                            m_text += char(keyCode - 0x04 + 'A');
                          }
                          else
                          {
                            m_text += char(keyCode - 0x04 + 'a');
                          }
                        }
                        else if(keyCode == 0x28) // return-key
                        {
                            m_text.clear();
                        }
                        else if(keyCode == 0x2A) // backspace
                        {
                            if (!m_text.empty())
                            {
                                m_text.pop_back();
                            }
                        }
                        else if ( (keyCode >= 0x1E) && (keyCode <= 0x27)) // digit
                        {
                            if (!shift)
                            {
                                m_text += (keyCode - 0x1E + 1) % 10 + '0';
                            }
                        }
                        else if(keyCode == 0x2C) // space
                        {
                            m_text += ' ';
                        }
                        //todo add mapping table
                    }
                }
            }

            m_pressedButtons[0] = pressedButtons[0];
            m_pressedButtons[1] = pressedButtons[1];
            m_pressedButtons[2] = pressedButtons[2];
        }
    }

    void printStatus()
    {
        printf("Keyboard: %s\n", m_text.c_str());
    }

private:
    uint8_t m_pressedButtons[3];

    std::string m_text;
};