#!/usr/bin/env python3

"""
MIT License

Permission is hereby granted, free of charge, to any person obtaining a copy 
in the Software without restriction, including without limitation the rights 
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell 
copies of the Software, and to permit persons to whom the Software is 
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in 
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR 
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, 
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE 
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER 
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, 
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN 
THE SOFTWARE.


This example sends one message at start and then echos
the received CAN messages back.
"""

from __future__ import print_function

import can
from time import sleep

def send_first_msg():
    # Using specific bus can0 with 125kbit baud rate on bus type socketcan 
    bus = can.interface.Bus(bustype='socketcan', channel='can0', bitrate=125000)
    # Create the a message to be sent out at the start of the program
    msg = can.Message(arbitration_id=0x234, data=[0xDE, 0xAD, 0xBE, 0xEF], is_extended_id=False)

    try:
        # Send the message
        bus.send(msg)
        print("First message sent on {}".format(bus.channel_info))
    except can.CanError:
        print("First message NOT sent")

def do_echo():
    # Using specific bus can0 with 125kbit baud rate on bus type socketcan 
    bus = can.interface.Bus(bustype='socketcan', channel='can0', bitrate=125000)

    while True:
        try:
            # Wait indefinitely for a CAN message to arrive 
            message = bus.recv()
            # Print error message if something went wrong
            if message is None:
                print("Error: No message received, but receive aborted!")
            else:
                # Print the received message to the console
                print("Message: ")
                print(message)
                
            # Now echo the received message back
            try:
                # Change the message ID before sending the message
                message.arbitration_id = 0x321
                bus.send(message)
                print("Echo message sent on {}".format(bus.channel_info))
            except can.CanError:
                print("Echo message NOT sent!")
        except:
            pass
        # Short wait, then loop back to receiving messages
        sleep(0.5)

if __name__ == '__main__':
    # Send one message at the start of the program
    send_first_msg()
    # Loop indefinitely echoing received CAN messages
    do_echo()