#!/usr/bin/env python3

# Copyright (c) Facebook, Inc. and its affiliates.
# All rights reserved.
#
# This source code is licensed under the BSD-style license found in the
# LICENSE file in the root directory of this source tree.

import datetime
import logging
from typing import Tuple, cast, Optional

# pyre-ignore[21]: Could not find name `Store` in `torch.distributed`.
from torch.distributed import Store, TCPStore, PrefixStore
from torch.distributed.elastic.rendezvous import RendezvousHandler, RendezvousParameters
from torch.distributed.elastic.rendezvous.utils import parse_rendezvous_endpoint

log = logging.getLogger(__name__)

_default_timeout_seconds = 600


class StaticTCPRendezvous(RendezvousHandler):
    """
    Static rendezvous that is a wrapper around the TCPStore.

    Creates TCPStore based on the input parameters with the
    listener on the agent with group_rank=0
    """

    def __init__(
        self,
        master_addr: str,
        master_port: int,
        rank: int,
        world_size: int,
        run_id: str,
        timeout: int,
    ):
        self.master_addr = master_addr
        self.master_port = master_port
        self.rank = rank
        self.world_size = world_size
        self.run_id = run_id
        self.timeout = datetime.timedelta(seconds=timeout)
        self._store: Optional[Store] = None

    def get_backend(self) -> str:
        return "static"

    def next_rendezvous(self) -> Tuple[Store, int, int]:
        log.info("Creating TCPStore as the c10d::Store implementation")
        if not self._store:
            is_master = self.rank == 0
            self._store = TCPStore(  # type: ignore[call-arg]
                self.master_addr,
                self.master_port,
                self.world_size,
                is_master,
                self.timeout,
                multi_tenant=True,
            )
        store = PrefixStore(self.run_id, self._store)
        return store, self.rank, self.world_size

    def is_closed(self):
        return False

    def set_closed(self):
        pass

    def num_nodes_waiting(self):
        return 0

    def get_run_id(self) -> str:
        return self.run_id

    def shutdown(self) -> bool:
        return True


def create_rdzv_handler(params: RendezvousParameters) -> RendezvousHandler:
    if "rank" not in params.config:
        raise ValueError(
            "rank is absent in RendezvousParameters."
            "Try add --node-rank to the cmd request"
        )
    endpoint = params.endpoint.strip()
    if not endpoint:
        raise ValueError(
            "endpoint is absent in RendezvousParameters"
            "Try add --master-port and --master-addr to the cmd request"
        )
    master_addr, master_port = parse_rendezvous_endpoint(endpoint, -1)
    if master_port == -1:
        raise ValueError(
            f"Port is absent in endpoint: {endpoint}. Try launching with --master-port"
        )
    world_size = params.max_nodes
    rank = cast(int, params.config.get("rank"))
    run_id = params.run_id
    if "timeout" in params.config:
        timeout = int(params.config["timeout"])
    else:
        timeout = _default_timeout_seconds
    return StaticTCPRendezvous(
        master_addr, master_port, rank, world_size, run_id, timeout
    )
