#!/usr/bin/env python3

import sys
import json
import datetime
import time

def get_period_index(periods, test_time : datetime.time):
    for i, state in enumerate(periods):
        if i == len(periods) - 1:
            return(i)
        if test_time >= state["timestart"] and test_time < periods[i+1]["timestart"]:
            return(i)

    # Should NOT be reached since last state assumed to last until midnight
    # TODO: Raise exception?
    return None

def simulate(periods, start_time, run_time=90, time_factor=1.0):
    simulation_start_time = time.time()
    
    simulation_start_datetime = datetime.datetime.fromisoformat("1900-01-01 " + start_time.isoformat())

    current_period_index = get_period_index(periods, simulation_start_datetime.time())
    current_state_index = 0

    next_changeover_time = simulation_start_time + (periods[current_period_index]["states"][current_state_index]["duration"] / time_factor)

    print("Starting with simulation time {}".format(simulation_start_datetime.time()))
    print("Initial data: {}".format(periods[current_period_index]["states"][current_state_index]))
    print("Starting simulation of {} second(s) with time factor {}".format(run_time, time_factor))

    while (run_time is None) or (run_time is not None and time.time() < simulation_start_time + run_time):
        now = time.time()

        current_simulation_datetime = simulation_start_datetime + datetime.timedelta(seconds=int((now - simulation_start_time) * time_factor))
        timed_state_index = get_period_index(periods, current_simulation_datetime.time())

        if now >= next_changeover_time:
            timed_state_index = get_period_index(periods, current_simulation_datetime.time())
            if timed_state_index != current_period_index and current_state_index == len(periods[current_period_index]["states"])-1:
                # Safe to change periods
                print()
                print("{} : Changing periods from {} to {}".format(current_simulation_datetime.time(), periods[current_period_index]["name"], periods[timed_state_index]["name"]))
                print("  Old cycle data: {}".format(periods[current_period_index]["states"][current_state_index]))

                current_period_index = timed_state_index
                current_state_index = 0

                print("  New cycle data: {}".format(periods[current_period_index]["states"][current_state_index]))
                print("  Next changeover in {} second(s)".format(periods[current_period_index]["states"][current_state_index]["duration"]))
            else:
                next_cycle_index = (current_state_index + 1) % len(periods[current_period_index]["states"])

                print()
                print("{} : Changing cycle from {} to {}".format(current_simulation_datetime.time(), current_state_index, next_cycle_index))
                if current_period_index != timed_state_index:
                    print("  [state change pending]")
                print("  Old cycle data: {}".format(periods[current_period_index]["states"][current_state_index]))
                print("  New cycle data: {}".format(periods[current_period_index]["states"][next_cycle_index]))
                print("  Next changeover in {} second(s)".format(periods[current_period_index]["states"][next_cycle_index]["duration"]))

                current_state_index = next_cycle_index

            next_changeover_time = next_changeover_time + (periods[current_period_index]["states"][current_state_index]["duration"] / time_factor)
        else:
            print(".", end="")
            sys.stdout.flush()
            
        time.sleep(1.0 / time_factor)


def main():
    periods = json.load(open("periods.json"))

    # Essential due to assumed ordering further below
    periods.sort(key=lambda x : x["timestart"])

    for state in periods:
        time = datetime.time.fromisoformat(state["timestart"])
        print("Name: {}\t\tTime start: {}".format(state["name"], time))
        print("   Number of states: {}".format(len(state["states"])))
        state["timestart"] = datetime.time.fromisoformat(state["timestart"])

    test_times = [
        "00:00:00",
        "07:59:59",
        "08:00:00",
        "09:59:59",
        "10:00:00",
        "16:59:59",
        "17:00:00",
        "18:59:59",
        "19:00:00",
        "23:59:59",
    ]

    for test_time in test_times:
        test_time_obj = datetime.time.fromisoformat(test_time)

        print("Period matching time {} is '{}'".format(test_time, periods[get_period_index(periods, test_time_obj)]["name"]))

    simulate(periods, datetime.time.fromisoformat("07:59"), 60, 4.0)

if __name__ == '__main__':
    main()