# Copyright 2022-2023 ETSI TeraFlowSDN - TFS OSG (https://tfs.etsi.org/)
#
# 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 concurrent.futures, graphlib, random, threading, time
from typing import Any, Dict, Optional

class _Task:
    def __init__(self, name : str) -> None:
        self._name = name

    @property
    def name(self): return self._name

    def execute(self) -> None:
        delay = 1 # random.uniform(1, 5)
        print(time.time(), 'task', self._name, 'waiting', delay)
        time.sleep(delay)

class ConcurrentTaskExecutor:
    def __init__(self, max_workers: Optional[int] = None, thread_name_prefix: str = '') -> None:
        self._max_workers = max_workers
        self._thread_name_prefix = thread_name_prefix
        self._tasks : Dict[str, _Task] = dict()
        self._dag = graphlib.TopologicalSorter()
        self._lock = threading.Lock()
        self._changed = threading.Event()
    
    def add_task(self, task: _Task, *predecessors : str) -> None:
        self._tasks[task.name] = task
        if len(predecessors) > 0: self.add_predecessors(task.name, *predecessors)

    def add_predecessors(self, task_name : str, *predecessors : str) -> None:
        self._dag.add(task_name, *predecessors)

    def run_task(self, task : _Task) -> None:
        print(time.time(), 'task', task.name, 'started')
        task.execute()
        print(time.time(), 'task', task.name, 'completed')
        with self._lock:
            self._dag.done(task.name)
        self._changed.set()

    def execute(self) -> None:
        self._dag.prepare()
        self._changed.set()

        tpe_settings = dict(max_workers=self._max_workers, thread_name_prefix=self._thread_name_prefix)
        with concurrent.futures.ThreadPoolExecutor(**tpe_settings) as executor:
            while self._changed.wait():
                with self._lock:
                    if not self._dag.is_active(): break
                self._changed.clear()
                with self._lock:
                    tasks = self._dag.get_ready()
                print(time.time(), 'triggering tasks', tasks)
                for task in tasks:
                    executor.submit(self.run_task, task)
        

cte = ConcurrentTaskExecutor()

cte.add_task(_Task('svc:pkt1:planned'), 'svc:root:planned')
cte.add_task(_Task('svc:pkt2:planned'), 'svc:root:planned')
cte.add_task(_Task('svc:opt1:planned'), 'svc:pkt1:planned')
cte.add_task(_Task('svc:opt2:planned'), 'svc:pkt2:planned')
cte.add_task(_Task('con:opt1:config'), 'svc:opt1:planned')
cte.add_task(_Task('con:opt2:config'), 'svc:opt2:planned')
cte.add_task(_Task('svc:opt1:active'), 'svc:opt1:planned', 'con:opt1:config')
cte.add_task(_Task('svc:opt2:active'), 'svc:opt2:planned', 'con:opt2:config')
cte.add_task(_Task('con:pkt1:config'), 'svc:pkt1:planned', 'svc:opt1:active')
cte.add_task(_Task('con:pkt2:config'), 'svc:pkt2:planned', 'svc:opt2:active')
cte.add_task(_Task('svc:pkt1:active'), 'svc:pkt1:planned', 'con:pkt1:config')
cte.add_task(_Task('svc:pkt2:active'), 'svc:pkt2:planned', 'con:pkt2:config')
cte.add_task(_Task('svc:root:active'), 'svc:pkt1:active', 'svc:pkt2:active')

print(time.time(), 'started')
cte.execute()
print(time.time(), 'completed')