import hmac
from hashlib import sha1
import ctypes


def generatePublicSharingKey(appID, appCertificate, channelName, unixTs, randomInt, uid, expiredTs):
    return generateDynamicKey(appID, appCertificate, channelName, unixTs, randomInt, uid, expiredTs, "APSS")


def generateRecordingKey(appID, appCertificate, channelName, unixTs, randomInt, uid, expiredTs):
    return generateDynamicKey(appID, appCertificate, channelName, unixTs, randomInt, uid, expiredTs, "ARS")


def generateMediaChannelKey(appID, appCertificate, channelName, unixTs, randomInt, uid, expiredTs):
    return generateDynamicKey(appID, appCertificate, channelName, unixTs, randomInt, uid, expiredTs, "ACS")


def generateDynamicKey(appID, appCertificate, channelName, unixTs, randomInt, uid, expiredTs, servicetype):
    uid = ctypes.c_uint(uid).value
    randomInt = ctypes.c_uint(randomInt).value
    key = "\x00" * (32 - len(appID)) + appID
    signature = generateSignature(appID, appCertificate, channelName, unixTs, randomInt, uid, expiredTs, servicetype)
    version = '{0:0>3}'.format(4)
    ret = version + str(signature) + \
          appID + \
          '{0:0>10}'.format(unixTs) + \
          "%.8x" % (int(randomInt) & 0xFFFFFFFF) + \
          '{:0>10}'.format(expiredTs)
    return ret


def generateSignature(appID, appCertificate, channelName, unixTs, randomInt, uid, expiredTs, servicetype):
    key = "\x00" * (32 - len(appID)) + appID
    content = servicetype + key + \
              '{:0>10}'.format(unixTs) + \
              "%.8x" % (int(randomInt) & 0xFFFFFFFF) + \
              str(channelName) + \
              '{:0>10}'.format(uid) + \
              '{:0>10}'.format(expiredTs)
    signature = hmac.new(appCertificate, content, sha1).hexdigest()
    return signature