#!/usr/bin/env python3

from __future__ import annotations
from collections.abc import Mapping
import concurrent.futures as fut
import time
from typing import Callable, List, TypeVar

# This module is commonly used by others in here and should avoid
# taking any unnecessary dependencies back on them.
from deferred_operand import DeferredOperand
import id_generator

T = TypeVar('T')


def wait_any(futures: List[SmartFuture], *, callback: Callable = None):
    finished: Mapping[int, bool] = {}
    x = 0
    while True:
        future = futures[x]
        if not finished.get(future.get_id(), False):
            if future.is_ready():
                finished[future.get_id()] = True
                yield future
            else:
                if callback is not None:
                    callback()
                time.sleep(0.1)
        x += 1
        if x >= len(futures):
            x = 0
        if len(finished) == len(futures):
            if callback is not None:
                callback()
            return


def wait_all(futures: List[SmartFuture]) -> None:
    done_set = set()
    while len(done_set) < len(futures):
        for future in futures:
            i = future.get_id()
            if i not in done_set and future.wrapped_future.done():
                done_set.add(i)
            time.sleep(0.1)


class SmartFuture(DeferredOperand):
    """This is a SmartFuture, a class that wraps a normal Future and can
    then be used, mostly, like a normal (non-Future) identifier.

    Using a FutureWrapper in expressions will block and wait until
    the result of the deferred operation is known.
    """

    def __init__(self, wrapped_future: fut.Future) -> None:
        self.wrapped_future = wrapped_future
        self.id = id_generator.get("smart_future_id")

    def get_id(self) -> int:
        return self.id

    def is_ready(self) -> bool:
        return self.wrapped_future.done()

    # You shouldn't have to call this; instead, have a look at defining a
    # method on DeferredOperand base class.
    def _resolve(self, *, timeout=None) -> T:
        return self.wrapped_future.result(timeout)