# Copyright The Lightning AI 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.
"""Profiler to check if there are any bottlenecks in your code."""
import logging
import os
from abc import ABC, abstractmethod
from contextlib import contextmanager
from pathlib import Path
from typing import Any, Callable, Dict, Generator, Optional, TextIO, Union

from lightning.fabric.utilities.cloud_io import get_filesystem

log = logging.getLogger(__name__)


class Profiler(ABC):
    """If you wish to write a custom profiler, you should inherit from this class."""

    def __init__(
        self,
        dirpath: Optional[Union[str, Path]] = None,
        filename: Optional[str] = None,
    ) -> None:
        self.dirpath = dirpath
        self.filename = filename

        self._output_file: Optional[TextIO] = None
        self._write_stream: Optional[Callable] = None
        self._local_rank: Optional[int] = None
        self._stage: Optional[str] = None

    @abstractmethod
    def start(self, action_name: str) -> None:
        """Defines how to start recording an action."""

    @abstractmethod
    def stop(self, action_name: str) -> None:
        """Defines how to record the duration once an action is complete."""

    def summary(self) -> str:
        return ""

    @contextmanager
    def profile(self, action_name: str) -> Generator:
        """Yields a context manager to encapsulate the scope of a profiled action.

        Example::

            with self.profile('load training data'):
                # load training data code

        The profiler will start once you've entered the context and will automatically
        stop once you exit the code block.
        """
        try:
            self.start(action_name)
            yield action_name
        finally:
            self.stop(action_name)

    def _rank_zero_info(self, *args: Any, **kwargs: Any) -> None:
        if self._local_rank in (None, 0):
            log.info(*args, **kwargs)

    def _prepare_filename(
        self, action_name: Optional[str] = None, extension: str = ".txt", split_token: str = "-"
    ) -> str:
        args = []
        if self._stage is not None:
            args.append(self._stage)
        if self.filename:
            args.append(self.filename)
        if self._local_rank is not None:
            args.append(str(self._local_rank))
        if action_name is not None:
            args.append(action_name)
        return split_token.join(args) + extension

    def _prepare_streams(self) -> None:
        if self._write_stream is not None:
            return
        if self.filename and self.dirpath:
            filepath = os.path.join(self.dirpath, self._prepare_filename())
            fs = get_filesystem(filepath)
            fs.mkdirs(self.dirpath, exist_ok=True)
            file = fs.open(filepath, "a")
            self._output_file = file
            self._write_stream = file.write
        else:
            self._write_stream = self._rank_zero_info

    def describe(self) -> None:
        """Logs a profile report after the conclusion of run."""
        # users might call `describe` directly as the profilers can be used by themselves.
        # to allow this, we open and close the files within this function by calling `_prepare_streams` and `teardown`
        # manually instead of letting the `Trainer` do it through `setup` and `teardown`
        self._prepare_streams()
        summary = self.summary()
        if summary and self._write_stream is not None:
            self._write_stream(summary)
        if self._output_file is not None:
            self._output_file.flush()
        self.teardown(stage=self._stage)

    def _stats_to_str(self, stats: Dict[str, str]) -> str:
        stage = f"{self._stage.upper()} " if self._stage is not None else ""
        output = [stage + "Profiler Report"]
        for action, value in stats.items():
            header = f"Profile stats for: {action}"
            if self._local_rank is not None:
                header += f" rank: {self._local_rank}"
            output.append(header)
            output.append(value)
        return os.linesep.join(output)

    def setup(self, stage: str, local_rank: Optional[int] = None, log_dir: Optional[str] = None) -> None:
        """Execute arbitrary pre-profiling set-up steps."""
        self._stage = stage
        self._local_rank = local_rank
        self.dirpath = self.dirpath or log_dir

    def teardown(self, stage: Optional[str]) -> None:
        """Execute arbitrary post-profiling tear-down steps.

        Closes the currently open file and stream.
        """
        self._write_stream = None
        if self._output_file is not None:
            self._output_file.close()
            self._output_file = None  # can't pickle TextIOWrapper

    def __del__(self) -> None:
        self.teardown(stage=self._stage)

    @property
    def local_rank(self) -> int:
        return 0 if self._local_rank is None else self._local_rank
