EDMarketConnector/EDMCLogging.py

"""
Set up required logging for the application.

This module provides for a common logging-powered log facility.
Mostly it implements a logging.Filter() in order to get two extra
members on the logging.LogRecord instance for use in logging.Formatter()
strings.
"""

# So that any warning about accessing a protected member is only in one place.
from sys import _getframe as getframe
import inspect
import logging
import logging.handlers
import pathlib
import tempfile
from os import mkdir
from typing import Tuple

from config import config, appname

# TODO: Tests:
#
#       1. Call from bare function in file.
#       2. Call from `if __name__ == "__main__":` section
#
#       3. Call from 1st level function in 1st level Class in file
#       4. Call from 2nd level function in 1st level Class in file
#       5. Call from 3rd level function in 1st level Class in file
#
#       6. Call from 1st level function in 2nd level Class in file
#       7. Call from 2nd level function in 2nd level Class in file
#       8. Call from 3rd level function in 2nd level Class in file
#
#       9. Call from 1st level function in 3rd level Class in file
#      10. Call from 2nd level function in 3rd level Class in file
#      11. Call from 3rd level function in 3rd level Class in file
#
#      12. Call from 2nd level file, all as above.
#
#      13. Call from *module*
#
#      14. Call from *package*

_default_loglevel = logging.INFO


class Logger:
    """
    Wrapper class for all logging configuration and code.

    Class instantiation requires the 'logger name' and optional loglevel.
    It is intended that this 'logger name' be re-used in all files/modules
    that need to log.

    Users of this class should then call getLogger() to get the
    logging.Logger instance.
    """

    def __init__(self, logger_name: str, loglevel: int = _default_loglevel):
        """
        Set up a `logging.Logger` with our preferred configuration.

        This includes using an EDMCContextFilter to add 'class' and 'qualname'
        expansions for logging.Formatter().
        """
        self.logger = logging.getLogger(logger_name)
        # Configure the logging.Logger
        self.logger.setLevel(loglevel)

        # Set up filter for adding class name
        self.logger_filter = EDMCContextFilter()
        self.logger.addFilter(self.logger_filter)

        ## Our basic channel handling stdout
        self.logger_channel = logging.StreamHandler()
        # Do *NOT* set here, want logger's level to work: self.logger_channel.setLevel(loglevel)

        self.logger_formatter = logging.Formatter('%(asctime)s - %(levelname)s - %(module)s.%(qualname)s:%(lineno)d: %(message)s')  # noqa: E501
        self.logger_formatter.default_time_format = '%Y-%m-%d %H:%M:%S'
        self.logger_formatter.default_msec_format = '%s.%03d'

        self.logger_channel.setFormatter(self.logger_formatter)
        self.logger.addHandler(self.logger_channel)

        ## Rotating Handler in sub-directory
        ## We want the files in %TEMP%\{appname}\ as {logger_name}.log and rotated versions
        ## This is {logger_name} so that EDMC.py logs to a different file.
        logfile_rotating = pathlib.Path(tempfile.gettempdir())
        logfile_rotating = logfile_rotating / f'{appname}'
        try:
            mkdir(logfile_rotating)
        except FileExistsError:
            pass
        logfile_rotating = logfile_rotating / f'{logger_name}.log'

        _MAXBYTES = 1024 * 1024  # 1MiB
        _BACKUPS = 10
        self.logger_channel_rotating = logging.handlers.RotatingFileHandler(logfile_rotating, mode='a', maxBytes=_MAXBYTES, backupCount=_BACKUPS, encoding='utf-8', delay=False)
        # Do *NOT* set here, want logger's level to work: self.logger_channel_rotating.setLevel(loglevel)
        self.logger_channel_rotating.setFormatter(self.logger_formatter)
        self.logger.addHandler(self.logger_channel_rotating)

    def get_logger(self) -> logging.Logger:
        """
        Obtain the self.logger of the class instance.

        Not to be confused with logging.getLogger().
        """
        return self.logger


def get_plugin_logger(name: str, loglevel: int = _default_loglevel) -> logging.Logger:
    """
    Return a logger suitable for a plugin.

    'Found' plugins need their own logger to call out where the logging is
    coming from, but we don't need to set up *everything* for them.

    The name will be '{config.appname}.{plugin.name}', e.g.
    'EDMarketConnector.miggytest'.  This means that any logging sent through
    there *also* goes to the channels defined in the 'EDMarketConnector'
    logger, so we can let that take care of the formatting.

    If we add our own channel then the output gets duplicated (assuming same
    logLevel set).

    However we do need to attach our filter to this still.  That's not at
    the channel level.
    :param name: Name of this Logger.
    :param loglevel: Optional logLevel for this Logger.
    :return: logging.Logger instance, all set up.
    """
    plugin_logger = logging.getLogger(name)
    plugin_logger.setLevel(loglevel)

    plugin_logger.addFilter(EDMCContextFilter())

    return plugin_logger


class EDMCContextFilter(logging.Filter):
    """
    Implements filtering to add extra format specifiers, and tweak others.

    logging.Filter sub-class to place extra attributes of the calling site
    into the record.
    """

    def filter(self, record: logging.LogRecord) -> bool:
        """
        Attempt to set/change fields in the LogRecord.

        1. class = class name(s) of the call site, if applicable
        2. qualname = __qualname__ of the call site.  This simplifies
         logging.Formatter() as you can use just this no matter if there is
         a class involved or not, so you get a nice clean:
             <file/module>.<classA>[.classB....].<function>

        If we fail to be able to properly set either then:

        1. Use print() to alert, to be SURE a message is seen.
        2. But also return strings noting the error, so there'll be
         something in the log output if it happens.

        :param record: The LogRecord we're "filtering"
        :return: bool - Always true in order for this record to be logged.
        """
        (class_name, qualname, module_name) = self.caller_attributes(module_name=getattr(record, 'module'))

        # Only set if we got a useful value
        if module_name:
            setattr(record, 'module', module_name)

        # Only set if not already provided by logging itself
        if getattr(record, 'class', None) is None:
            setattr(record, 'class', class_name)

        # Only set if not already provided by logging itself
        if getattr(record, 'qualname', None) is None:
            setattr(record, 'qualname', qualname)

        return True

    @classmethod  # noqa: CCR001 - this is as refactored as is sensible
    def caller_attributes(cls, module_name: str = '') -> Tuple[str, str, str]:
        """
        Determine extra or changed fields for the caller.

        1. qualname finds the relevant object and its __qualname__
        2. caller_class_names is just the full class names of the calling
         class if relevant.
        3. module is munged if we detect the caller is an EDMC plugin,
         whether internal or found.
        """
        frame = cls.find_caller_frame()

        caller_qualname = caller_class_names = ''
        if frame:
            # <https://stackoverflow.com/questions/2203424/python-how-to-retrieve-class-information-from-a-frame-object#2220759>
            frame_info = inspect.getframeinfo(frame)
            args, _, _, value_dict = inspect.getargvalues(frame)
            if len(args) and args[0] in ('self', 'cls'):
                frame_class = value_dict[args[0]]

                if frame_class:
                    # Find __qualname__ of the caller
                    fn = getattr(frame_class, frame_info.function)
                    if fn and fn.__qualname__:
                        caller_qualname = fn.__qualname__

                    # Find containing class name(s) of caller, if any
                    if frame_class.__class__ and frame_class.__class__.__qualname__:
                        caller_class_names = frame_class.__class__.__qualname__

            # It's a call from the top level module file
            elif frame_info.function == '<module>':
                caller_class_names = '<none>'
                caller_qualname = value_dict['__name__']

            elif frame_info.function != '':
                caller_class_names = '<none>'
                caller_qualname = frame_info.function

            module_name = cls.munge_module_name(frame_info, module_name)

            # https://docs.python.org/3.7/library/inspect.html#the-interpreter-stack
            del frame

        if caller_qualname == '':
            print('ALERT!  Something went wrong with finding caller qualname for logging!')
            caller_qualname = '<ERROR in EDMCLogging.caller_class_and_qualname() for "qualname">'

        if caller_class_names == '':
            print('ALERT!  Something went wrong with finding caller class name(s) for logging!')
            caller_class_names = '<ERROR in EDMCLogging.caller_class_and_qualname() for "class">'

        return caller_class_names, caller_qualname, module_name

    @classmethod
    def find_caller_frame(cls):
        """
        Find the stack frame of the logging caller.

        :returns: 'frame' object such as from sys._getframe()
        """
        # Go up through stack frames until we find the first with a
        # type(f_locals.self) of logging.Logger.  This should be the start
        # of the frames internal to logging.
        frame: 'frame' = getframe(0)
        while frame:
            if isinstance(frame.f_locals.get('self'), logging.Logger):
                frame = frame.f_back  # Want to start on the next frame below
                break
            frame = frame.f_back
        # Now continue up through frames until we find the next one where
        # that is *not* true, as it should be the call site of the logger
        # call
        while frame:
            if not isinstance(frame.f_locals.get('self'), logging.Logger):
                break  # We've found the frame we want
            frame = frame.f_back
        return frame

    @classmethod
    def munge_module_name(cls, frame_info: inspect.Traceback, module_name: str) -> str:
        """
        Adjust module_name based on the file path for the given frame.

        We want to distinguish between other code and both our internal plugins
        and the 'found' ones.

        For internal plugins we want "plugins.<filename>".
        For 'found' plugins we want "<plugins>.<plugin_name>...".

        :param frame_info: The frame_info of the caller.
        :param module_name: The module_name string to munge.
        :return: The munged module_name.
        """
        file_name = pathlib.Path(frame_info.filename).expanduser()
        plugin_dir = pathlib.Path(config.plugin_dir).expanduser()
        internal_plugin_dir = pathlib.Path(config.internal_plugin_dir).expanduser()
        # Find the first parent called 'plugins'
        plugin_top = file_name
        while plugin_top and plugin_top.name != '':
            if plugin_top.parent.name == 'plugins':
                break

            plugin_top = plugin_top.parent

        # Check we didn't walk up to the root/anchor
        if plugin_top.name != '':
            # Check we're still inside config.plugin_dir
            if plugin_top.parent == plugin_dir:
                # In case of deeper callers we need a range of the file_name
                pt_len = len(plugin_top.parts)
                name_path = '.'.join(file_name.parts[(pt_len - 1):-1])
                module_name = f'<plugins>.{name_path}.{module_name}'

            # Check we're still inside the installation folder.
            elif file_name.parent == internal_plugin_dir:
                # Is this a deeper caller ?
                pt_len = len(plugin_top.parts)
                name_path = '.'.join(file_name.parts[(pt_len - 1):-1])

                # Pre-pend 'plugins.<plugin folder>.' to module
                if name_path == '':
                    # No sub-folder involved so module_name is sufficient
                    module_name = f'plugins.{module_name}'

                else:
                    # Sub-folder(s) involved, so include them
                    module_name = f'plugins.{name_path}.{module_name}'

        return module_name