#   Copyright 2018 WebAssembly Community Group participants
#
#   Licensed under the Apache License, Version 2.0 (the "License");
#   you may not use this file except in compliance with the License.
#   You may obtain a copy of the License at
#
#       http://www.apache.org/licenses/LICENSE-2.0
#
#   Unless required by applicable law or agreed to in writing, software
#   distributed under the License is distributed on an "AS IS" BASIS,
#   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
#   See the License for the specific language governing permissions and
#   limitations under the License.

import multiprocessing
import sys
import queue


def g_testing_thread(test_function, work_queue, result_queue):
    for test in iter(lambda: get_from_queue(work_queue), None):
        result = None
        try:
            result = test_function(test)
        except Exception as e:
            print("Something went wrong", e, file=sys.stderr)
            raise
        result_queue.put(result)


class ParallelRunner(object):
    def __init__(self):
        self.processes = None
        self.result_queue = None

    def map(self, test_function, inputs):
        test_queue = self.create_test_queue(inputs)
        self.init_processes(test_function, test_queue)
        results = self.collect_results()
        return results

    def create_test_queue(self, inputs):
        test_queue = multiprocessing.Queue()
        for test in inputs:
            test_queue.put(test)
        return test_queue

    def init_processes(self, test_function, test_queue):
        self.processes = []
        self.result_queue = multiprocessing.Queue()
        for x in range(multiprocessing.cpu_count()):
            p = multiprocessing.Process(target=g_testing_thread,
                                        args=(test_function, test_queue,
                                              self.result_queue))
            p.start()
            self.processes.append(p)

    def collect_results(self):
        buffered_results = []
        num = 0
        while len(self.processes):
            res = get_from_queue(self.result_queue)
            if res is not None:
                num += 1
                # Print periodically to assure the bot monitor that we are
                # still alive
                if num % 10 == 0:
                    print('Got test results:', num)
                buffered_results.append(res)
            else:
                self.clear_finished_processes()
        return buffered_results

    def clear_finished_processes(self):
        self.processes = [p for p in self.processes if p.is_alive()]


def get_from_queue(q):
    try:
        return q.get(True, 0.1)
    except queue.Empty:
        pass
    return None