#!/usr/bin/python3


import sys, os, struct, subprocess, json, socket


TYPE_MASK = 0x80000000


def parse_block_header(data):
    res = struct.unpack('!I', data)
    size = res[0]
    if size & TYPE_MASK:
        size -= TYPE_MASK
        tp = 'err'
    else:
        tp = 'out'
    return (size, tp)

def recv_block(sock):
    hdr = sock.recv(4)
    if not hdr:
        print('ERROR: header receiving')
        sys.exit(-1)

    size, tp = parse_block_header(hdr)

    res = b''
    received = 0
    while size > 0:
        part = sock.recv(size)
        res += part
        size -= len(part)
    return (res, tp)

def guest_exec(vm_name):
    print('run guest-exec command...')
    cmd = ['virsh',
           'qemu-agent-command',
           vm_name,
           '{"execute":"guest-exec", "arguments":{"path": "bash", "capture-output": "interactive"}}']
    p = subprocess.run(cmd, stdout=subprocess.PIPE)
    response = p.stdout.decode('utf-8')
    print('response: %s' % response.strip())
    response = json.loads(response)['return']
    cid = int(response['cid'])
    port = int(response['port'])
    return (cid, port)

def srv_conn(cid, port):
    sock = socket.socket(socket.AF_VSOCK, socket.SOCK_STREAM)
    print('connect...')
    sock.connect((cid, port))
    print('connected')
    return sock

def main():
    if len(sys.argv) != 2:
        print('Usage:\n\t%s <VM name>' % sys.argv[0])
        return

    vm_name = sys.argv[1]
    cid, port = guest_exec(vm_name)

    sock = srv_conn(cid, port)
    sock.send(b'echo "Hello world!"\n')
    data, tp = recv_block(sock)
    print('Received from %s: "%s"' % (tp, data.decode('utf-8')))

main()