import os
import logging
from pathlib import Path
from functools import reduce
from operator import getitem
from datetime import datetime
from logger import setup_logging
from utils import read_json, write_json
import time
import inspect


class ConfigParser:
    def __init__(self, args, options='', timestamp=True, test=False):
        # parse default and custom cli options
        for opt in options:
            args.add_argument(*opt.flags, default=None, type=opt.type)
        args = args.parse_args()

        if args.device:
            os.environ["CUDA_VISIBLE_DEVICES"] = args.device
        if args.resume is None:
            msg_no_cfg = "Configuration file need to be specified. Add '-c config.json', for example."
            assert args.config is not None, msg_no_cfg
            self.cfg_fname = Path(args.config)
            print(self.cfg_fname)
            config = read_json(self.cfg_fname)
            self.resume = None
        else:
            self.resume = Path(args.resume)
            resume_cfg_fname = self.resume.parent / 'config.json'
            config = read_json(resume_cfg_fname)
            if args.config is not None:
                config.update(read_json(Path(args.config)))

        # load config file and apply custom cli options
        self._config = _update_config(config, options, args)

        # set save_dir where trained model and log will be saved.
        save_dir = Path(self.config['trainer']['save_dir'])
        timestamp = datetime.now().strftime(r'%m%d_%H%M%S') if timestamp else ''

        exper_name = self.config['name']
        self._save_dir = save_dir / 'models' / exper_name / timestamp
        self._web_log_dir = save_dir / 'web' / exper_name / timestamp
        self._log_dir = save_dir / 'log' / exper_name / timestamp

        if not test:
            self.save_dir.mkdir(parents=True, exist_ok=True)
            self.log_dir.mkdir(parents=True, exist_ok=True)

        # if set, remove all previous experiments with the current config
        if vars(args).get("purge_exp_dir", False):
            for dirpath in (self._save_dir, self._log_dir, self._web_log_dir):
                config_dir = dirpath.parent
                existing = list(config_dir.glob("*"))
                print(f"purging {len(existing)} directories from config_dir...")
                tic = time.time()
                os.system(f"rm -rf {config_dir}")
                print(f"Finished purge in {time.time() - tic:.3f}s")

        # save updated config file to the checkpoint dir
        if not test:
            write_json(self.config, self.save_dir / 'config.json')

            # configure logging module
            setup_logging(self.log_dir)
            self.log_levels = {
                0: logging.WARNING,
                1: logging.INFO,
                2: logging.DEBUG
            }

    def initialize(self, name, module, *args, index=None, **kwargs):
        """
        finds a function handle with the name given as 'type' in config, and returns the 
        instance initialized with corresponding keyword args given as 'args'.
        """
        if index is None:
            module_name = self[name]['type']
            module_args = dict(self[name]['args'])
            assert all([k not in module_args for k in kwargs]), 'Overwriting kwargs given in config file is not allowed'
            module_args.update(kwargs)
        else:
            module_name = self[name][index]['type']
            module_args = dict(self[name][index]['args'])

        # if parameter not in config subdict, then check if it's in global config.
        signature = inspect.signature(getattr(module, module_name).__init__)
        print(module_name)
        for param in signature.parameters.keys():
            if param not in module_args and param in self.config:
                module_args[param] = self[param]

        return getattr(module, module_name)(*args, **module_args)

    def __getitem__(self, name):
        return self.config[name]

    def get_logger(self, name, verbosity=2):
        msg_verbosity = 'verbosity option {} is invalid. Valid options are {}.'.format(verbosity,
                                                                                       self.log_levels.keys())
        assert verbosity in self.log_levels, msg_verbosity
        logger = logging.getLogger(name)
        logger.setLevel(self.log_levels[verbosity])
        return logger

    # setting read-only attributes
    @property
    def config(self):
        return self._config

    @property
    def save_dir(self):
        return self._save_dir

    @property
    def log_dir(self):
        return self._log_dir


# helper functions used to update config dict with custom cli options
def _update_config(config, options, args):
    for opt in options:
        value = getattr(args, _get_opt_name(opt.flags))
        if value is not None:
            _set_by_path(config, opt.target, value)
    return config


def _get_opt_name(flags):
    for flg in flags:
        if flg.startswith('--'):
            return flg.replace('--', '')
    return flags[0].replace('--', '')


def _set_by_path(tree, keys, value):
    """Set a value in a nested object in tree by sequence of keys."""
    _get_by_path(tree, keys[:-1])[keys[-1]] = value


def _get_by_path(tree, keys):
    """Access a nested object in tree by sequence of keys."""
    return reduce(getitem, keys, tree)
