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import time, os, logging
from . import Logger
from . import Pcap


DEFAULT_CAPTURE_FILE_DIR = Logger.DEFAULT_LOG_FILE_DIR
DEFAULT_CAPTURE_FILE_NAME = "capture.pcap"


def get_capture_file_path(capture_file_path=None):
    default_path = os.path.join(DEFAULT_CAPTURE_FILE_DIR, DEFAULT_CAPTURE_FILE_NAME)
    if capture_file_path is None:
        return default_path
    if os.path.splitext(capture_file_path)[1] != ".pcap":
        return default_path
    return os.path.abspath(capture_file_path)


class CaptureFileHandler:
    def __init__(self, capture_file_path=None, clear=False):
        filename = get_capture_file_path(capture_file_path)
        if not os.path.isdir(os.path.dirname(filename)):
            os.makedirs(os.path.dirname(filename))
        self.filename = filename
        self.backupFilename = self.filename + ".1"
        if not os.path.isfile(self.filename):
            self.startNewFile()
        elif os.path.getsize(self.filename) > 20000000:
            self.doRollover()
        if clear:
            # clear file
            self.startNewFile()

    def startNewFile(self):
        with open(self.filename, "wb") as f:
            f.write(Pcap.get_global_header())

    def doRollover(self):
        try:
            os.remove(self.backupFilename)
        except:
            logging.exception("capture file rollover remove backup failed")
        try:
            os.rename(self.filename, self.backupFilename)
            self.startNewFile()
        except:
            logging.exception("capture file rollover failed")

    def writePacket(self, packet):
        with open(self.filename, "ab") as f:
            packet = Pcap.create_packet(
                bytes([packet.boardId] + packet.getList()), packet.time
            )
            f.write(packet)