# Copyright (C) 2012 Canonical Ltd.
# Copyright (C) 2012 Hewlett-Packard Development Company, L.P.
# Copyright (C) 2012 Yahoo! Inc.
#
# Author: Scott Moser <scott.moser@canonical.com>
# Author: Juerg Haefliger <juerg.haefliger@hp.com>
# Author: Joshua Harlow <harlowja@yahoo-inc.com>
#
# This file is part of cloud-init. See LICENSE file for license information.

import collections.abc  # pylint: disable=import-error
import copy
import io
import logging
import logging.config
import logging.handlers
import os
import sys
import time
from collections import defaultdict
from contextlib import suppress
from typing import DefaultDict

DEFAULT_LOG_FORMAT = "%(asctime)s - %(filename)s[%(levelname)s]: %(message)s"
DEPRECATED = 35
TRACE = logging.DEBUG - 5


class CustomLoggerType(logging.Logger):
    """A hack to get mypy to stop complaining about custom logging methods.

    When using deprecated or trace logging, rather than:
        LOG = logging.getLogger(__name__)
    Instead do:
        LOG = cast(CustomLoggerType, logging.getLogger(__name__))
    """

    def trace(self, *args, **kwargs):
        pass

    def deprecated(self, *args, **kwargs):
        pass


def setup_basic_logging(level=logging.DEBUG, formatter=None):
    formatter = formatter or logging.Formatter(DEFAULT_LOG_FORMAT)
    root = logging.getLogger()
    console = logging.StreamHandler(sys.stderr)
    console.setFormatter(formatter)
    console.setLevel(level)
    root.addHandler(console)
    root.setLevel(level)


def flush_loggers(root):
    if not root:
        return
    for h in root.handlers:
        if isinstance(h, (logging.StreamHandler)):
            with suppress(IOError):
                h.flush()
    flush_loggers(root.parent)


def define_extra_loggers() -> None:
    """Add DEPRECATED and TRACE log levels to the logging module."""

    def new_logger(level):
        def log_at_level(self, message, *args, **kwargs):
            if self.isEnabledFor(level):
                self._log(level, message, args, **kwargs)

        return log_at_level

    logging.addLevelName(DEPRECATED, "DEPRECATED")
    logging.addLevelName(TRACE, "TRACE")
    setattr(logging.Logger, "deprecated", new_logger(DEPRECATED))
    setattr(logging.Logger, "trace", new_logger(TRACE))


def setup_logging(cfg=None):
    # See if the config provides any logging conf...
    if not cfg:
        cfg = {}

    root_logger = logging.getLogger()
    exporter = LogExporter()
    exporter.setLevel(logging.WARN)

    log_cfgs = []
    log_cfg = cfg.get("logcfg")
    if log_cfg and isinstance(log_cfg, str):
        # If there is a 'logcfg' entry in the config,
        # respect it, it is the old keyname
        log_cfgs.append(str(log_cfg))
    elif "log_cfgs" in cfg:
        for a_cfg in cfg["log_cfgs"]:
            if isinstance(a_cfg, str):
                log_cfgs.append(a_cfg)
            elif isinstance(a_cfg, (collections.abc.Iterable)):
                cfg_str = [str(c) for c in a_cfg]
                log_cfgs.append("\n".join(cfg_str))
            else:
                log_cfgs.append(str(a_cfg))

    # See if any of them actually load...
    am_tried = 0

    # log_cfg may contain either a filepath to a file containing a logger
    # configuration, or a string containing a logger configuration
    # https://docs.python.org/3/library/logging.config.html#logging-config-fileformat
    for log_cfg in log_cfgs:
        # The default configuration includes an attempt at using /dev/log,
        # followed up by writing to a file. /dev/log will not exist in
        # very early boot, so an exception on that is expected.
        with suppress(FileNotFoundError):
            am_tried += 1

            # If the value is not a filename, assume that it is a config.
            if not (log_cfg.startswith("/") and os.path.isfile(log_cfg)):
                log_cfg = io.StringIO(log_cfg)

            # Attempt to load its config.
            logging.config.fileConfig(log_cfg)

            # Configure warning exporter after loading logging configuration
            root_logger.addHandler(exporter)

            # Use the first valid configuration.
            return

    # Configure warning exporter for basic logging
    root_logger.addHandler(exporter)

    # If it didn't work, at least setup a basic logger (if desired)
    basic_enabled = cfg.get("log_basic", True)

    sys.stderr.write(
        "WARN: no logging configured! (tried %s configs)\n" % (am_tried)
    )
    if basic_enabled:
        sys.stderr.write("Setting up basic logging...\n")
        setup_basic_logging()


class LogExporter(logging.StreamHandler):
    holder: DefaultDict[str, list] = defaultdict(list)

    def emit(self, record: logging.LogRecord):
        self.holder[record.levelname].append(record.getMessage())

    def export_logs(self):
        return copy.deepcopy(self.holder)

    def clean_logs(self):
        self.holder = defaultdict(list)

    def flush(self):
        pass


def reset_logging():
    """Remove all current handlers and unset log level."""
    log = logging.getLogger()
    handlers = list(log.handlers)
    for h in handlers:
        h.flush()
        h.close()
        log.removeHandler(h)
    log.setLevel(logging.NOTSET)


def setup_backup_logging():
    """In the event that internal logging exception occurs and logging is not
    possible for some reason, make a desperate final attempt to log to stderr
    which may ease debugging.
    """
    fallback_handler = logging.StreamHandler(sys.stderr)
    setattr(fallback_handler, "handleError", lambda record: None)
    fallback_handler.setFormatter(
        logging.Formatter(
            "FALLBACK: %(asctime)s - %(filename)s[%(levelname)s]: %(message)s"
        )
    )

    def handleError(self, record):
        """A closure that emits logs on stderr when other methods fail"""
        with suppress(IOError):
            fallback_handler.handle(record)
            fallback_handler.flush()

    setattr(logging.Handler, "handleError", handleError)


class CloudInitLogRecord(logging.LogRecord):
    """reporting the filename as __init__.py isn't very useful in logs

    if the filename is __init__.py, use the parent directory as the filename
    """

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        if "__init__.py" == self.filename:
            self.filename = os.path.basename(os.path.dirname(self.pathname))


def configure_root_logger():
    """Customize the root logger for cloud-init"""

    # Always format logging timestamps as UTC time
    logging.Formatter.converter = time.gmtime
    define_extra_loggers()
    setup_backup_logging()
    reset_logging()

    # add handler only to the root logger
    handler = LogExporter()
    handler.setLevel(logging.WARN)
    logging.getLogger().addHandler(handler)

    # LogRecord allows us to report more useful information than __init__.py
    logging.setLogRecordFactory(CloudInitLogRecord)