# Copyright The PyTorch Lightning team.
#
# 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 os
import socket

from pytorch_lightning import _logger as log
from pytorch_lightning.plugins.environments import ClusterEnvironment


class LSFEnvironment(ClusterEnvironment):
    """
    An environment for running on clusters managed by the LSF resource manager.

    It is expected that any execution using this ClusterEnvironment was executed
    using the Job Step Manager i.e. ``jsrun``.

    This plugin expects the following environment variables.

    LSB_JOBID:
        The LSF assigned job ID

    LSB_HOSTS:
        The hosts used in the job. This string is expected to have the format "batch <rank_0_host> ...."

    JSM_NAMESPACE_LOCAL_RANK:
        The node local rank for the task. This environment variable is set by jsrun

    JSM_NAMESPACE_SIZE:
        The world size for the task. This environment variable is set by jsrun
    """

    def __init__(self):
        self._master_address = self._get_master_address()
        self._master_port = self._get_master_port()
        log.debug(f"MASTER_ADDR: {self._master_address}")
        log.debug(f"MASTER_PORT: {self._master_port}")

    @staticmethod
    def is_using_lsf() -> bool:
        """ Returns ``True`` if the current process was launched using the jsrun command. """
        required_env_vars = (
            "LSB_JOBID",
            "LSB_HOSTS",
            "JSM_NAMESPACE_LOCAL_RANK",
            "JSM_NAMESPACE_SIZE",
        )
        return all(v in os.environ for v in required_env_vars)

    def creates_children(self) -> bool:
        return True

    def master_address(self):
        """ The master address is read from a list of hosts contained in the environment variable `LSB_HOSTS`. """
        return self._master_address

    def master_port(self):
        """ THe master port gets calculated from the LSF job ID. """
        return self._master_port

    def world_size(self):
        """ The world size is read from the environment variable `JSM_NAMESPACE_SIZE`. """
        var = "JSM_NAMESPACE_SIZE"
        world_size = os.environ.get(var)
        if world_size is None:
            raise ValueError(
                f"Cannot determine world size from environment variable {var}."
                " Make sure you run your executable with `jsrun`"
            )
        return int(world_size)

    def set_world_size(self, size: int) -> None:
        log.debug("LSFEnvironment.set_world_size was called, but setting world size is not allowed. Ignored.")

    def global_rank(self):
        """ The world size is read from the environment variable `JSM_NAMESPACE_RANK`. """
        var = "JSM_NAMESPACE_RANK"
        global_rank = os.environ.get(var)
        if global_rank is None:
            raise ValueError(
                f"Cannot determine global rank from environment variable {var}."
                " Make sure you run your executable with `jsrun`"
            )
        return int(global_rank)

    def set_global_rank(self, rank: int) -> None:
        log.debug("LSFEnvironment.set_global_rank was called, but setting global rank is not allowed. Ignored.")

    def local_rank(self):
        """ The local rank is read from the environment variable `JSM_NAMESPACE_LOCAL_RANK`. """
        var = "JSM_NAMESPACE_LOCAL_RANK"
        local_rank = os.environ.get(var)
        if local_rank is None:
            raise ValueError(
                f"Cannot determine local rank from environment variable {var}."
                " Make sure you run your executable with `jsrun`"
            )
        return int(local_rank)

    def node_rank(self):
        """
        The node rank is determined by the position of the current hostname in the list of hosts stored in
        the environment variable `LSB_HOSTS`.
        """
        hosts = self._read_hosts()
        count = {}
        for host in hosts:
            if "batch" in host or "login" in host:
                continue
            if host not in count:
                count[host] = len(count)
        return count[socket.gethostname()]

    @staticmethod
    def _read_hosts():
        hosts = os.environ.get("LSB_HOSTS")
        if not hosts:
            raise ValueError("Could not find hosts in environment variable LSB_HOSTS")
        hosts = hosts.split()
        if len(hosts) < 2:
            raise ValueError(
                "Cannot parse hosts from LSB_HOSTS environment variable."
                " Expected format: \"batch <rank_0_host> ...\""
            )
        return hosts

    def _get_master_address(self):
        hosts = self._read_hosts()
        return hosts[1]

    @staticmethod
    def _get_master_port():
        """
        A helper function for accessing the master port.
        Uses the LSF job ID so all ranks can compute the master port.
        """
        # check for user-specified master port
        port = os.environ.get("MASTER_PORT")
        if not port:
            jobid = os.environ.get("LSB_JOBID")
            if not jobid:
                raise ValueError("Could not find job id in environment variable LSB_JOBID")
            port = int(jobid)
            # all ports should be in the 10k+ range
            port = int(port) % 1000 + 10000
            log.debug(f"calculated LSF master port: {port}")
        else:
            log.debug(f"using externally specified master port: {port}")
        return int(port)