"""
Parse YAML config file & update JupyterHub config.

Config should never append or mutate, only set. Functions here could
be called many times per lifetime of a jupyterhub.

Traitlets that modify the startup of JupyterHub should not be here.
FIXME: A strong feeling that JSON Schema should be involved somehow.
"""

import os
import sys

from .config import CONFIG_FILE, STATE_DIR
from .yaml import yaml

# Default configuration for tljh
# User provided config is merged into this
default = {
    'base_url': '/',
    'auth': {
        'type': 'firstuseauthenticator.FirstUseAuthenticator',
        'FirstUseAuthenticator': {
            'create_users': False
        }
    },
    'users': {
        'allowed': [],
        'banned': [],
        'admin': [],
        'extra_user_groups': {}
    },
    'limits': {
        'memory': None,
        'cpu': None,
    },
    'http': {
        'port': 80,
    },
    'https': {
        'enabled': False,
        'port': 443,
        'tls': {
            'cert': '',
            'key': '',
        },
        'letsencrypt': {
            'email': '',
            'domains': [],
        },
    },
    'traefik_api': {
        'ip': "127.0.0.1",
        'port': 8099,
        'username': 'api_admin',
        'password': '',
    },
    'user_environment': {
        'default_app': 'classic',
    },
    'services': {
        'cull': {
            'enabled': True,
            'timeout': 600,
            'every': 60,
            'concurrency': 5,
            'users': False,
            'max_age': 0
        },
        'configurator': {
            'enabled': False
        }
    }
}


def load_config(config_file=CONFIG_FILE):
    """Load the current config as a dictionary

    merges overrides from config.yaml with default config
    """
    if os.path.exists(config_file):
        with open(config_file) as f:
            config_overrides = yaml.load(f)
    else:
        config_overrides = {}

    secrets = load_secrets()
    config = _merge_dictionaries(dict(default), secrets)
    config = _merge_dictionaries(config, config_overrides)
    return config


def apply_config(config_overrides, c):
    """
    Merge config_overrides with config defaults & apply to JupyterHub config c
    """
    tljh_config = _merge_dictionaries(dict(default), config_overrides)

    update_base_url(c, tljh_config)
    update_auth(c, tljh_config)
    update_userlists(c, tljh_config)
    update_usergroups(c, tljh_config)
    update_limits(c, tljh_config)
    update_user_environment(c, tljh_config)
    update_user_account_config(c, tljh_config)
    update_traefik_api(c, tljh_config)
    update_services(c, tljh_config)


def set_if_not_none(parent, key, value):
    """
    Set attribute 'key' on parent if value is not None
    """
    if value is not None:
        setattr(parent, key, value)


def load_traefik_api_credentials():
    """Load traefik api secret from a file"""
    proxy_secret_path = os.path.join(STATE_DIR, 'traefik-api.secret')
    if not os.path.exists(proxy_secret_path):
        return {}
    with open(proxy_secret_path) as f:
        password = f.read()
    return {
        'traefik_api': {
            'password': password,
        }
    }


def load_secrets():
    """Load any secret values stored on disk

    Returns dict to be merged into config during load
    """
    config = {}
    config = _merge_dictionaries(config, load_traefik_api_credentials())
    return config


def update_base_url(c, config):
    """
    Update base_url of JupyterHub through tljh config
    """
    c.JupyterHub.base_url = config['base_url']


def update_auth(c, config):
    """
    Set auth related configuration from YAML config file.

    As an example, this function should update the following TLJH auth
    configuration:

    ```yaml
    auth:
      type: oauthenticator.github.GitHubOAuthenticator
      GitHubOAuthenticator:
        client_id: "..."
        client_secret: "..."
        oauth_callback_url: "..."
      ArbitraryClass:
        arbitrary_key: "..."
        arbitrary_key_with_none_value:
    ```

    by applying the following configuration:

    ```python
    c.JupyterHub.authenticator_class = "oauthenticator.github.GitHubOAuthenticator"
    c.GitHubOAuthenticator.client_id = "..."
    c.GitHubOAuthenticator.client_secret = "..."
    c.GitHubOAuthenticator.oauth_callback_url = "..."
    c.ArbitraryClass.arbitrary_key = "..."
    ```

    Note that "auth.type" and "auth.ArbitraryClass.arbitrary_key_with_none_value"
    are treated a bit differently. auth.type will always map to
    c.JupyterHub.authenticator_class and any configured value being None won't
    be set.
    """
    tljh_auth_config = config['auth']

    c.JupyterHub.authenticator_class = tljh_auth_config['type']

    for auth_key, auth_value in tljh_auth_config.items():
        if not (auth_key[0] == auth_key[0].upper() and isinstance(auth_value, dict)):
            if auth_key == 'type':
                continue
            raise ValueError(f"Error: auth.{auth_key} was ignored, it didn't look like a valid configuration")
        class_name = auth_key
        class_config_to_set = auth_value
        class_config = c[class_name]
        for config_name, config_value in class_config_to_set.items():
            set_if_not_none(class_config, config_name, config_value)


def update_userlists(c, config):
    """
    Set user whitelists & admin lists
    """
    users = config['users']

    c.Authenticator.allowed_users = set(users['allowed'])
    c.Authenticator.blocked_users = set(users['banned'])
    c.Authenticator.admin_users = set(users['admin'])


def update_usergroups(c, config):
    """
    Set user groups
    """
    users = config['users']
    c.UserCreatingSpawner.user_groups = users['extra_user_groups']


def update_limits(c, config):
    """
    Set user server limits
    """
    limits = config['limits']

    c.Spawner.mem_limit = limits['memory']
    c.Spawner.cpu_limit = limits['cpu']


def update_user_environment(c, config):
    """
    Set user environment configuration
    """
    user_env = config['user_environment']

    # Set default application users are launched into
    if user_env['default_app'] == 'jupyterlab':
        c.Spawner.default_url = '/lab'
    elif user_env['default_app'] == 'nteract':
        c.Spawner.default_url = '/nteract'


def update_user_account_config(c, config):
    c.SystemdSpawner.username_template = 'jupyter-{USERNAME}'


def update_traefik_api(c, config):
    """
    Set traefik api endpoint credentials
    """
    c.TraefikTomlProxy.traefik_api_username = config['traefik_api']['username']
    c.TraefikTomlProxy.traefik_api_password = config['traefik_api']['password']


def set_cull_idle_service(config):
    """
    Set Idle Culler service
    """
    cull_cmd = [
        sys.executable, '-m', 'jupyterhub_idle_culler'
    ]
    cull_config = config['services']['cull']
    print()

    cull_cmd += ['--timeout=%d' % cull_config['timeout']]
    cull_cmd += ['--cull-every=%d' % cull_config['every']]
    cull_cmd += ['--concurrency=%d' % cull_config['concurrency']]
    cull_cmd += ['--max-age=%d' % cull_config['max_age']]
    if cull_config['users']:
        cull_cmd += ['--cull-users']

    cull_service = {
        'name': 'cull-idle',
        'admin': True,
        'command': cull_cmd,
    }

    return cull_service


def set_configurator(config):
    """
    Set the JupyterHub Configurator service
    """
    HERE = os.path.abspath(os.path.dirname(__file__))
    configurator_cmd = [
        sys.executable, "-m", "jupyterhub_configurator.app",
        f"--Configurator.config_file={HERE}/jupyterhub_configurator_config.py"
    ]
    configurator_service = {
        'name': 'configurator',
        'url': 'http://127.0.0.1:10101',
        'command': configurator_cmd,
    }

    return configurator_service


def update_services(c, config):
    c.JupyterHub.services = []

    if config['services']['cull']['enabled']:
        c.JupyterHub.services.append(set_cull_idle_service(config))
    if config['services']['configurator']['enabled']:
        c.JupyterHub.services.append(set_configurator(config))


def _merge_dictionaries(a, b, path=None, update=True):
    """
    Merge two dictionaries recursively.

    From https://stackoverflow.com/a/7205107
    """
    if path is None:
        path = []
    for key in b:
        if key in a:
            if isinstance(a[key], dict) and isinstance(b[key], dict):
                _merge_dictionaries(a[key], b[key], path + [str(key)])
            elif a[key] == b[key]:
                pass  # same leaf value
            elif update:
                a[key] = b[key]
            else:
                raise Exception('Conflict at %s' % '.'.join(path + [str(key)]))
        else:
            a[key] = b[key]
    return a