from    sys         import  argv,  executable
from    os          import  environ, getcwd, sep as psep
from    os.path     import  dirname, abspath, join as joinpath, \
                            expanduser, splitdrive, isfile

from    time    import sleep

from    copy                            import deepcopy

from    apscheduler.triggers.cron       import CronTrigger
from    apscheduler.triggers.interval   import IntervalTrigger

import  logging
import  pprint

from    zasd.logging    import *
from    zasd.util       import *

#
# Constants

CONFIG_BASENAME = 'zasd.conf.py'
CONFIG_FILENAMES = [CONFIG_BASENAME, '.' + CONFIG_BASENAME]

# Default configuration
DEFAULT_CONFIG = {
    'zfs_path':         '/usr/local/bin/zfs',
    'fswatch_path':     '/usr/local/bin/fswatch',
    
    'tab_size':         2,

    'log_level':        logging.INFO,
    'log_format':       '%(asctime)s %(name)s [%(levelname)-8s]: %(message)s',
    'log_date_format':  '%a, %d %b %Y, %H:%M:%S',
   
    'separator':        ':',
    'destroy_trigger':  CronTrigger.from_crontab('* * * * *'),
    
    # Defaults will take a snapshot every 12 hours
    # and keep them for a week, so if the config file
    # should disappear for some reason, there will
    # at least be _some_ recoverable snapshots
    'defaults': {
        'disabled':     False,
        'filesystems':  ['tank'],
        'recursive':    True,
        'tag':          'zasd',
        'trigger':      IntervalTrigger(hours=12),
        'priority':     1,
        'keep':         14
    },

    'schedules': [{}]
}

# Load configuration
def load_config():
    global logger

    if len(argv) > 1:
        # Configuration pathname given as first argument
        if isfile(argv[1]):
            config_pathname = argv[1]
        else:
            logger.warning('Could not find configuration file %s', argv[1])
            return _warn_load_default()
    else:
        # No configuration pathname given; attempt to find it:
     
        # Get root of system partition
        sys_root_path = environ.get('SystemDrive', splitdrive(executable)[0] + psep)

        # Get system configuration directory
        sys_conf_path = joinpath(*ifenv('SystemRoot',
            lambda path:    [path,          'System32', 'drivers', 'etc'],
            lambda:         [sys_root_path, 'etc']))
        
        # Get user home directory
        user_home_path = expanduser('~')
       
        # Get path of this Python file
        if '__file__' in globals():
            script_path = dirname(abspath(__file__))
        else:
            script_path = dirname(abspath(argv[0]))
 
        # Build list of configuration file pathnames to search
        config_paths = uniq([
            getcwd(),
            user_home_path,
            joinpath(user_home_path, '.config'),
            joinpath(user_home_path, '.local', 'share'),
            sys_conf_path,
            script_path])
        config_pathnames = list(joinpath(p, f) for p in config_paths for f in CONFIG_FILENAMES)

        # Attempt to find a config file
        config_pathname = find_file(config_pathnames)

        if config_pathname is None:
            logger.warning('Unable to find a config file at:')
            for pathname in config_pathnames:
                logger.warning('  ' + pathname)

            return _warn_load_default()

    with open(config_pathname, 'rt', encoding='utf-8') as f:
        config_source = f.read()

    # Create configuration file scopes

    global_scope = dict(
            CRITICAL    = logging.CRITICAL,
            ERROR       = logging.ERROR,
            WARNING     = logging.WARNING,
            INFO        = logging.INFO,
            DEBUG       = logging.DEBUG,
            NOTSET      = logging.NOTSET,

            crontab     = CronTrigger.from_crontab,
            cron        = CronTrigger.from_crontab,
            
            interval    = IntervalTrigger,
            every       = IntervalTrigger)

    local_scope = dict()

    # Execute configuration file
    exec(config_source, global_scope, local_scope)

    # Merge configuration with default configuration
    config = merge_configs(DEFAULT_CONFIG, local_scope)
    
    logger.debug('Loaded configuration')
    
    if config['log_level'] <= logging.DEBUG:
        logger.debug('')
        for line in pprint.pformat(config).split('\n'):
            logging.debug(config['tab_size'] * ' ' + line)
        logger.debug('')

    return config

def _warn_load_default():
    global DEFAULT_CONFIG

    logger.warning('')
    logger.warning('Waiting 10 seconds before loading default configuration...')
    logger.warning('')
    sleep(10)
    logger.warning('Loading default configuration')
    logger.warning('')
    return deepcopy(DEFAULT_CONFIG)

def merge_configs(base, diff, path=[]):
    base = base if len(path) == 0 else deepcopy(base)
    for key, value in diff.items():
        if not key in base:
            base[key] = value
        elif not isinstance(value, type(base[key])):
            logger.error('Cannot merge diff type %s with base %s type at %s.%s',
                    type(value), type(base[key]), '.'.join(path), key)
            return None
        elif isinstance(value, dict):
            merged = merge_configs(base[key], value, path + [key])
            if merged is None:
                return None
            base[key] = merged
        else:
            base[key] = value
    return base