#!/usr/bin/env python3

import functools
import logging
import os
from inspect import stack
import sys

# This module is commonly used by others in here and should avoid
# taking any unnecessary dependencies back on them.

from argparse_utils import ActionNoYes
import config
import logging_utils

logger = logging.getLogger(__name__)

args = config.add_commandline_args(
    f'Bootstrap ({__file__})',
    'Args related to python program bootstrapper and Swiss army knife')
args.add_argument(
    '--debug_unhandled_exceptions',
    action=ActionNoYes,
    default=False,
    help='Break into pdb on top level unhandled exceptions.'
)
args.add_argument(
    '--show_random_seed',
    action=ActionNoYes,
    default=False,
    help='Should we display (and log.debug) the global random seed?'
)
args.add_argument(
    '--set_random_seed',
    type=int,
    nargs=1,
    default=None,
    metavar='SEED_INT',
    help='Override the global random seed with a particular number.'
)
args.add_argument(
    '--dump_all_objects',
    action=ActionNoYes,
    default=False,
    help='Should we dump the Python import tree before main?'
)
args.add_argument(
    '--audit_import_events',
    action=ActionNoYes,
    default=False,
    help='Should we audit all import events?',
)


original_hook = sys.excepthook


def handle_uncaught_exception(exc_type, exc_value, exc_tb):
    """
    Top-level exception handler for exceptions that make it past any exception
    handlers in the python code being run.  Logs the error and stacktrace then
    maybe attaches a debugger.

    """
    global original_hook
    msg = f'Unhandled top level exception {exc_type}'
    logger.exception(msg)
    print(msg, file=sys.stderr)
    if issubclass(exc_type, KeyboardInterrupt):
        sys.__excepthook__(exc_type, exc_value, exc_tb)
        return
    else:
        if (
                not sys.stderr.isatty() or
                not sys.stdin.isatty()
        ):
            # stdin or stderr is redirected, just do the normal thing
            original_hook(exc_type, exc_value, exc_tb)
        else:
            # a terminal is attached and stderr is not redirected, maybe debug.
            import traceback
            traceback.print_exception(exc_type, exc_value, exc_tb)
            if config.config['debug_unhandled_exceptions']:
                import pdb
                logger.info("Invoking the debugger...")
                pdb.pm()
            else:
                original_hook(exc_type, exc_value, exc_tb)


class ImportInterceptor(object):
    def __init__(self):
        import collect.trie
        self.module_by_filename_cache = {}
        self.repopulate_modules_by_filename()
        self.tree = collect.trie.Trie()
        self.tree_node_by_module = {}

    def repopulate_modules_by_filename(self):
        self.module_by_filename_cache.clear()
        for mod in sys.modules:
            if hasattr(sys.modules[mod], '__file__'):
                fname = getattr(sys.modules[mod], '__file__')
            else:
                fname = 'unknown'
            self.module_by_filename_cache[fname] = mod

    def should_ignore_filename(self, filename: str) -> bool:
        return 'importlib' in filename or 'six.py' in filename

    def find_spec(self, loaded_module, path=None, target=None):
        s = stack()
        for x in range(3, len(s)):
            filename = s[x].filename
            if self.should_ignore_filename(filename):
                continue

            loading_function = s[x].function
            if filename in self.module_by_filename_cache:
                loading_module = self.module_by_filename_cache[filename]
            else:
                self.repopulate_modules_by_filename()
                loading_module = self.module_by_filename_cache.get(filename, 'unknown')

            path = self.tree_node_by_module.get(loading_module, [])
            path.extend([loaded_module])
            self.tree.insert(path)
            self.tree_node_by_module[loading_module] = path

            msg = f'*** Import {loaded_module} from {filename}:{s[x].lineno} in {loading_module}::{loading_function}'
            logger.debug(msg)
            print(msg)
            return
        msg = f'*** Import {loaded_module} from ?????'
        logger.debug(msg)
        print(msg)

    def find_importer(self, module: str):
        if module in self.tree_node_by_module:
            node = self.tree_node_by_module[module]
            return node
        return []


# # TODO: test this with python 3.8+
# def audit_import_events(event, args):
#     if event == 'import':
#         module = args[0]
#         filename = args[1]
#         sys_path = args[2]
#         sys_meta_path = args[3]
#         sys_path_hooks = args[4]
#         logger.debug(msg)
#         print(msg)


# Audit import events?  Note: this runs early in the lifetime of the
# process (assuming that import bootstrap happens early); config has
# (probably) not yet been loaded or parsed the commandline.  Also,
# some things have probably already been imported while we weren't
# watching so this information may be incomplete.
#
# Also note: move bootstrap up in the global import list to catch
# more import events and have a more complete record.
import_interceptor = None
for arg in sys.argv:
    if arg == '--audit_import_events':
        import_interceptor = ImportInterceptor()
        sys.meta_path = [import_interceptor] + sys.meta_path
        # if not hasattr(sys, 'frozen'):
        #     if (
        #             sys.version_info[0] == 3
        #             and sys.version_info[1] >= 8
        #     ):
        #         sys.addaudithook(audit_import_events)


def dump_all_objects() -> None:
    global import_interceptor
    messages = {}
    all_modules = sys.modules
    for obj in object.__subclasses__():
        if not hasattr(obj, '__name__'):
            continue
        klass = obj.__name__
        if not hasattr(obj, '__module__'):
            continue
        class_mod_name = obj.__module__
        if class_mod_name in all_modules:
            mod = all_modules[class_mod_name]
            if not hasattr(mod, '__name__'):
                mod_name = class_mod_name
            else:
                mod_name = mod.__name__
            if hasattr(mod, '__file__'):
                mod_file = mod.__file__
            else:
                mod_file = 'unknown'
            if import_interceptor is not None:
                import_path = import_interceptor.find_importer(mod_name)
            else:
                import_path = 'unknown'
            msg = f'{class_mod_name}::{klass} ({mod_file})'
            if import_path != 'unknown' and len(import_path) > 0:
                msg += f' imported by {import_path}'
            messages[f'{class_mod_name}::{klass}'] = msg
    for x in sorted(messages.keys()):
        logger.debug(messages[x])
        print(messages[x])


def initialize(entry_point):
    """
    Remember to initialize config, initialize logging, set/log a random
    seed, etc... before running main.

    """
    @functools.wraps(entry_point)
    def initialize_wrapper(*args, **kwargs):
        # Hook top level unhandled exceptions, maybe invoke debugger.
        if sys.excepthook == sys.__excepthook__:
            sys.excepthook = handle_uncaught_exception

        # Try to figure out the name of the program entry point.  Then
        # parse configuration (based on cmdline flags, environment vars
        # etc...)
        if (
                '__globals__' in entry_point.__dict__ and
                '__file__' in entry_point.__globals__
        ):
            config.parse(entry_point.__globals__['__file__'])
        else:
            config.parse(None)

        # Initialize logging... and log some remembered messages from
        # config module.
        logging_utils.initialize_logging(logging.getLogger())
        config.late_logging()

        # Allow programs that don't bother to override the random seed
        # to be replayed via the commandline.
        import random
        random_seed = config.config['set_random_seed']
        if random_seed is not None:
            random_seed = random_seed[0]
        else:
            random_seed = int.from_bytes(os.urandom(4), 'little')

        if config.config['show_random_seed']:
            msg = f'Global random seed is: {random_seed}'
            logger.debug(msg)
            print(msg)
        random.seed(random_seed)

        # Do it, invoke the user's code.  Pay attention to how long it takes.
        logger.debug(f'Starting {entry_point.__name__} (program entry point)')
        ret = None
        import stopwatch
        with stopwatch.Timer() as t:
            ret = entry_point(*args, **kwargs)
        logger.debug(
            f'{entry_point.__name__} (program entry point) returned {ret}.'
        )

        if config.config['dump_all_objects']:
            dump_all_objects()

        if config.config['audit_import_events']:
            global import_interceptor
            if import_interceptor is not None:
                print(import_interceptor.tree)

        walltime = t()
        (utime, stime, cutime, cstime, elapsed_time) = os.times()
        logger.debug('\n'
                     f'user: {utime}s\n'
                     f'system: {stime}s\n'
                     f'child user: {cutime}s\n'
                     f'child system: {cstime}s\n'
                     f'machine uptime: {elapsed_time}s\n'
                     f'walltime: {walltime}s')

        # If it doesn't return cleanly, call attention to the return value.
        if ret is not None and ret != 0:
            logger.error(f'Exit {ret}')
        else:
            logger.debug(f'Exit {ret}')
        sys.exit(ret)
    return initialize_wrapper