class Counter:
    def __init__(self, stream_id, line_orientation, metrics):
        self.in_count = 0
        self.out_count = 0
        self.track_memory = {}
        self.line_orientation = line_orientation
        self.metrics = metrics
        self.stream_id = stream_id

    def update(self, tracks, line_position):
        for track in tracks:
            track_id = track.id
            x, y, w, h = track.bbox

            if self.line_orientation == "horizontal":
                center = int(y + h / 2)
            elif self.line_orientation == "vertical":
                center = int(x + w / 2)
            else:
                raise NotImplementedError(
                    f"Line orientation {self.line_orientation} is invalid!"
                )

            if track_id not in self.track_memory:
                self.track_memory[track_id] = [center, False]
                continue

            prev = self.track_memory[track_id][0]
            self.track_memory[track_id][0] = center

            if self.track_memory[track_id][1]:
                continue

            if prev < line_position <= center:
                self.in_count += 1
                self.metrics["people_in"].labels(stream=self.stream_id).inc()
                self.track_memory[track_id][1] = True
            elif prev > line_position >= center:
                self.out_count += 1
                self.metrics["people_out"].labels(stream=self.stream_id).inc()
                self.track_memory[track_id][1] = True