import logging
import logging.config
import os
import re
import string
import warnings
from functools import partial
from pathlib import Path
from typing import Optional

import yaml

from prefect.settings import (
    PREFECT_LOGGING_EXTRA_LOGGERS,
    PREFECT_LOGGING_SETTINGS_PATH,
    SETTING_VARIABLES,
)
from prefect.utilities.collections import dict_to_flatdict, flatdict_to_dict

# This path will be used if `PREFECT_LOGGING_SETTINGS_PATH` is null
DEFAULT_LOGGING_SETTINGS_PATH = Path(__file__).parent / "logging.yml"

# Stores the configuration used to setup logging in this Python process
PROCESS_LOGGING_CONFIG: dict = None

# Regex call to replace non-alphanumeric characters to '_' to create a valid env var
to_envvar = partial(re.sub, re.compile(r"[^0-9a-zA-Z]+"), "_")


def load_logging_config(path: Path) -> dict:
    """
    Loads logging configuration from a path allowing override from the environment
    """
    template = string.Template(path.read_text())
    with warnings.catch_warnings():
        warnings.filterwarnings("ignore", category=DeprecationWarning)
        config = yaml.safe_load(
            # Substitute settings into the template in format $SETTING / ${SETTING}
            template.substitute(
                {
                    setting.name: str(setting.value())
                    for setting in SETTING_VARIABLES.values()
                }
            )
        )

    # Load overrides from the environment
    flat_config = dict_to_flatdict(config)

    for key_tup, val in flat_config.items():
        env_val = os.environ.get(
            # Generate a valid environment variable with nesting indicated with '_'
            to_envvar("PREFECT_LOGGING_" + "_".join(key_tup)).upper()
        )
        if env_val:
            val = env_val

        # reassign the updated value
        flat_config[key_tup] = val

    return flatdict_to_dict(flat_config)


def setup_logging(incremental: Optional[bool] = None) -> dict:
    """
    Sets up logging.

    Returns the config used.
    """
    global PROCESS_LOGGING_CONFIG

    # If the user has specified a logging path and it exists we will ignore the
    # default entirely rather than dealing with complex merging
    config = load_logging_config(
        (
            PREFECT_LOGGING_SETTINGS_PATH.value()
            if PREFECT_LOGGING_SETTINGS_PATH.value().exists()
            else DEFAULT_LOGGING_SETTINGS_PATH
        )
    )

    incremental = (
        incremental if incremental is not None else bool(PROCESS_LOGGING_CONFIG)
    )

    # Perform an incremental update if setup has already been run
    config.setdefault("incremental", incremental)

    try:
        logging.config.dictConfig(config)
    except ValueError:
        if incremental:
            setup_logging(incremental=False)

    # Copy configuration of the 'prefect.extra' logger to the extra loggers
    extra_config = logging.getLogger("prefect.extra")

    for logger_name in PREFECT_LOGGING_EXTRA_LOGGERS.value():
        logger = logging.getLogger(logger_name)
        for handler in extra_config.handlers:
            if not config["incremental"]:
                logger.addHandler(handler)
            if logger.level == logging.NOTSET:
                logger.setLevel(extra_config.level)
            logger.propagate = extra_config.propagate

    PROCESS_LOGGING_CONFIG = config

    return config