# -*- coding: utf-8 -*-
#

import os
import select
import socket
import struct
import time

# From /usr/include/linux/icmp.h; your milage may vary.
ICMP_ECHO_REQUEST = 8  # Seems to be the same on Solaris.


def checksum(source_string):
    """
    I'm not too confident that this is right but testing seems
    to suggest that it gives the same answers as in_cksum in ping.c
    """
    sum = 0
    count_to = int((len(source_string) / 2) * 2)
    for count in range(0, count_to, 2):
        this = source_string[count + 1] * 256 + source_string[count]
        sum = sum + this
        sum = sum & 0xffffffff  # Necessary?

    if count_to < len(source_string):
        sum = sum + ord(source_string[len(source_string) - 1])
        sum = sum & 0xffffffff  # Necessary?

    sum = (sum >> 16) + (sum & 0xffff)
    sum = sum + (sum >> 16)
    answer = ~sum
    answer = answer & 0xffff

    # Swap bytes. Bugger me if I know why.
    answer = answer >> 8 | (answer << 8 & 0xff00)

    return answer


def receive_one_ping(my_socket, id, timeout):
    """
    Receive the ping from the socket.
    """
    time_left = timeout
    while True:
        started_select = time.time()
        what_ready = select.select([my_socket], [], [], time_left)
        how_long_in_select = time.time() - started_select
        if not what_ready[0]:  # Timeout
            return

        time_received = time.time()
        received_packet, addr = my_socket.recvfrom(1024)
        icmpHeader = received_packet[20:28]
        type, code, checksum, packet_id, sequence = struct.unpack("bbHHh", icmpHeader)
        if packet_id == id:
            bytes = struct.calcsize("d")
            time_sent = struct.unpack("d", received_packet[28: 28 + bytes])[0]
            return time_received - time_sent

        time_left = time_left - how_long_in_select
        if time_left <= 0:
            return


def send_one_ping(my_socket, dest_addr, id, psize):
    """
    Send one ping to the given >dest_addr<.
    """
    dest_addr = socket.gethostbyname(dest_addr)

    # Remove header size from packet size
    # psize = psize - 8
    # laixintao edit:
    # Do not need to remove header here. From BSD ping man:
    #     The default is 56, which translates into 64 ICMP data
    #     bytes when combined with the 8 bytes of ICMP header data.

    # Header is type (8), code (8), checksum (16), id (16), sequence (16)
    my_checksum = 0

    # Make a dummy heder with a 0 checksum.
    header = struct.pack("bbHHh", ICMP_ECHO_REQUEST, 0, my_checksum, id, 1)
    bytes = struct.calcsize("d")
    data = (psize - bytes) * b"Q"
    data = struct.pack("d", time.time()) + data

    # Calculate the checksum on the data and the dummy header.
    my_checksum = checksum(header + data)

    # Now that we have the right checksum, we put that in. It's just easier
    # to make up a new header than to stuff it into the dummy.
    header = struct.pack(
        "bbHHh", ICMP_ECHO_REQUEST, 0, socket.htons(my_checksum), id, 1
    )
    packet = header + data
    my_socket.sendto(packet, (dest_addr, 1))  # Don't know about the 1


def ping(dest_addr, timeout, psize, flag=0):
    """
    Returns either the delay (in seconds) or none on timeout.
    """
    icmp = socket.getprotobyname("icmp")
    try:
        if os.getuid() != 0:
            my_socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM, icmp)
        else:
            my_socket = socket.socket(socket.AF_INET, socket.SOCK_RAW, icmp)
    except socket.error as e:
        if e.errno == 1:
            # Operation not permitted
            msg = str(e)
            raise socket.error(msg)
        raise  # raise the original error

    process_pre = os.getpid() & 0xFF00
    flag = flag & 0x00FF
    my_id = process_pre | flag

    send_one_ping(my_socket, dest_addr, my_id, psize)
    delay = receive_one_ping(my_socket, my_id, timeout)

    my_socket.close()
    return delay


def verbose_ping(dest_addr, timeout=2, count=5, psize=64):
    """
    Send `count' ping with `psize' size to `dest_addr' with
    the given `timeout' and display the result.
    """
    for i in range(count):
        print("ping %s with ..." % dest_addr, end="")
        try:
            delay = ping(dest_addr, timeout, psize)
        except socket.gaierror as e:
            print("failed. (socket error: '%s')" % str(e))
            break

        if delay is None:
            print("failed. (timeout within %ssec.)" % timeout)
        else:
            delay = delay * 1000
            print("get ping in %0.4fms" % delay)
    print()


if __name__ == "__main__":
    verbose_ping("google.com")
    verbose_ping("192.168.4.1")
    verbose_ping("www.baidu.com")
    verbose_ping("sssssss")