#test_time03_pi.py
# copied by D@CC on 2021EMay31
# stop by ^C or Stop/Restart Backend
# tested ok
import asyncio

def foo():                   #single timed operation
    #   loop.stop()          # D@CC this will stop the loop timer. .  eventually
    print("timer went off!")
def fooLoopEnd():            # D@CC
    print("done loop")       # D@CC
def fooTick(nn):
    print(nn[0])  
def countdown(n):            # internal timer loop task; n is the counter of ticks
    if n[0] == 0:
        #loop.stop() # end loop.run_forever()
        ## D@CC commented out the above to make it loop forever
        loop.call_later(4, foo) # call foo() in 4 seconds  #schedule a task
        ## added above by D@CC to (optionally) repeat foo in every loop
        fooLoopEnd()             # added by D@CC event at end of loop
        n[0]=10                  # added by D@CC to loop forever
    else:
        #print(n[0])                      # show each tick  (D@CC:optional)
        fooTick(n)                      #fooTick routine runs once per tick
        n[0] -= 1                        # reduce n each tick

def frange(start=0, stop=None, step=1):  #internal timer range function
    while stop is None or start < stop:
        yield start
        start += step #NOTE: loss of precision over time

def call_every(loop, seconds, func, *args, now=True): #internal timer definition
    def repeat(now=True, times=frange(loop.time() + seconds, None, seconds)):
        if now:
            func(*args)
        loop.call_at(next(times), repeat)
    repeat(now=now)

loop = asyncio.get_event_loop()                    #create timer named loop

loop.call_later(4, foo) # call foo() in 4 seconds  #schedule a task
call_every(loop, 0.5, countdown, [10]) # repeat the call every .5 seconds
#   timerName  DTtick(secs) timer-action (timer-init)
loop.run_forever()                                 # can stop after 1 loop
loop.close()                                       # close the timer
print("done")                                      #inform user
#end test_timer.py
#Source: https://stackoverflow.com/questions/5177439/postponing-functions-in-python/14040516#14040516
#Source: https://docs.python.org/3/library/asyncio.html#:~:text=asyncio%20is%20used%20as%20a,high%2Dlevel%20structured%20network%20code.
#Output
#10
#9
#8
#7
#6
#5
#4
#3
#timer went off!
#2
#1
#done     # D@CC stops here if loop.stop() is not commented out
#         # if no loop.stop ... 10,9,8,7  ..... 3, timer went off, 2, 1, 10, 9 etc
#end test_timer03_pi.py
#/test_time03_pi.py