type Frame struct {
    frameId   int
    data      []byte
    untouched bool
}

type CircularBuffer struct {
    maxLen int
    buffer []Frame
    head   int
    tail   int
}

type CircularBufferAPI interface {
    IsEmpty() bool
    IsFull()
    Enqueue(Frame)
    Dequeue()
    Front() Frame
    Show() []Frame
}

func CBInit(maxLen int) *CircularBuffer {
    return &CircularBuffer{
        maxLen: maxLen,
        buffer: make([]Frame, maxLen),
        head:   0,
        tail:   0,
    }
}

func (cb *CircularBuffer) IsEmpty() bool {
    return cb.head == cb.tail
}

func (cb *CircularBuffer) IsFull() bool {
    return cb.tail == (cb.head-1)%cb.maxLen
}

func (cb *CircularBuffer) Enqueue(frame Frame) Frame {
    if !cb.IsFull() {
        item := cb.buffer[cb.tail]
        cb.buffer[cb.tail] = frame
        cb.tail = (cb.tail + 1) % cb.maxLen
        return item
    }
    return Frame{}
}

func (cb *CircularBuffer) Dequeue() Frame {
    if !cb.IsEmpty() {
        item := cb.buffer[cb.head]
        hollowFrame := Frame{frameId: 0, data: []byte{}}
        cb.buffer[cb.head] = hollowFrame
        cb.head = (cb.head + 1) % cb.maxLen
        return item
    }
    return Frame{}
}

func (cb *CircularBuffer) Front() Frame {
    return cb.buffer[cb.head]
}

func (cb *CircularBuffer) Show() []Frame {
    return cb.buffer
}