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

"""

Created on Sun Jan  6 14:17:00 2016

@author: kurner

Demonstrates a driver-along-road pattern where the

Driver(road) instance runs to completion when the 

target of 'yield from'.

This is not about interweaving event processing 

asynchonously.  It's about 'yield from' and how 

the iterator pattern lends itself to setting up 

coroutines, wherein a driver (future, task) 

experiences "maturation" (evolving state) based

on traversing a road that keeps continuing where

it left off.

"""

from random import choice

from time import sleep

import sys

def road(co_id):

    """a bumpy road... 

    keeps relinquishing control back to the driver

    """

    drv = yield None

    drv.result = 1

    drv.co_id = co_id

    drv = yield drv

    sleep(0.5)

    drv.result += 1

    drv.name = choice(["Alvin", "Eric", "Gwen"])

    drv = yield drv

    drv.result += 1

    drv.color = choice(["Red", "Purple", "Orange"])

    drv = yield drv

    drv.result += 1

    drv.age = 100

    sleep(0.5)

    return drv  # the driver registers changes made along the way

class Driver:

    """Iterator for driving along a road"""

    

    def __init__(self, r):

        self.g = r        # on your mark...

        self.g.send(None) # get set...

        self.counter = 1

        

    def __iter__(self):

        return self

    def __next__(self): 

        while True:  # go! ...drive to end of road

            try:

                self.counter *= 10

                self = self.g.send(self) # expect delays

            except StopIteration as exc:

                return exc.value         # returned by yield from

   

tasks = [Driver(road(n)) for n in range(4)] # a Driver is instanced per road

def delegator(task):   

    return (yield from task) # delegating to a task (blocking once started)

coroutines = (delegator(x) for x in tasks)  # each based on yield from

print("Non-blocking to here.")

sys.stdout.flush()

 

results = [ ]   

for co in coroutines:

    results.append(co.send(None)) # go! drives each task to completion

for result in results:

    print("Result: {co_id}: {name} {color}".format(**result.__dict__))