import hashlib
import secrets

from pathlib import Path

import bottle

from appdirs import AppDirs

import zerobin
from zerobin import default_settings


from runpy import run_path


class SettingsValidationError(Exception):
    pass


class SettingsContainer(object):
    """
        Singleton containing the settings for the whole app
    """

    _instance = None

    def __new__(cls, *args, **kwargs):

        if not cls._instance:
            cls._instance = super(SettingsContainer, cls).__new__(cls, *args, **kwargs)
            cls._instance.update_with_module(default_settings)
        return cls._instance

    def update_with_dict(self, mapping):
        """
            Update settings with values from the given mapping object.
            (Taking only variable with uppercased name)
        """
        for name, value in mapping.items():
            if name.isupper():
                setattr(self, name, value)
        return self

    def update_with_module(self, module):
        """
            Update settings with values from the given module.
            Uses update_with_dict() behind the scenes.
        """
        return self.update_with_dict(module.__dict__)

    @classmethod
    def from_module(cls, module):
        """
            Create an instance of SettingsContainer with values based
            on the one in the passed module.
        """
        params = cls()
        params.update_with_module(module)
        return params

    def update_with_file(self, filepath):
        """
            Update settings with values from the given module file.
            Uses update_with_dict() behind the scenes.
        """
        params = run_path(str(filepath))
        return self.update_with_dict(params)


settings = SettingsContainer()


def ensure_app_context(data_dir=None, config_dir=None):
    """ Ensure all the variable things we generate are available.

        This will make sure we have:

        - a var dir
        - a content dir
        - a secret key
        - an admin URL

        This function is idempotent if nothing touch the files it created.
    """

    app_dirs = AppDirs("0bin", "tygs")

    settings.DATA_DIR = Path(data_dir or app_dirs.user_data_dir).expanduser()
    settings.DATA_DIR.mkdir(exist_ok=True, parents=True)

    settings.CONFIG_DIR = Path(config_dir or app_dirs.user_config_dir).expanduser()
    settings.CONFIG_DIR.mkdir(exist_ok=True, parents=True)

    settings.STATIC_FILES_ROOT = zerobin.ROOT_DIR / "static"

    settings.PASTE_FILES_ROOT = settings.DATA_DIR / "pastes"
    settings.PASTE_FILES_ROOT.mkdir(exist_ok=True)

    settings.SESSIONS_DIR = settings.DATA_DIR / "sessions"
    settings.SESSIONS_DIR.mkdir(exist_ok=True)

    bottle.TEMPLATE_PATH.insert(0, zerobin.ROOT_DIR / "views")

    CUSTOM_VIEWS_DIR = settings.CONFIG_DIR / "custom_views"
    CUSTOM_VIEWS_DIR.mkdir(exist_ok=True)

    bottle.TEMPLATE_PATH.insert(0, CUSTOM_VIEWS_DIR)

    bottle.BaseRequest.MEMFILE_MAX = settings.MAX_SIZE + (1024 * 100)

    secret_key_file = settings.CONFIG_DIR / "secret_key"
    if not secret_key_file.is_file():
        secret_key_file.write_text(secrets.token_urlsafe(64))
    settings.SECRET_KEY = secret_key_file.read_text()

    admin_password_file = settings.CONFIG_DIR / "admin_password"
    if not secret_key_file.is_file():
        admin_password_file.write_text(
            "No password set. Use the set_admin_passord command. Don't write this file by hand."
        )
    settings.ADMIN_PASSWORD_FILE = admin_password_file

    payload = ("admin" + settings.SECRET_KEY).encode("ascii")
    settings.ADMIN_URL = "/admin/" + hashlib.sha256(payload).hexdigest() + "/"

    settings_file = settings.CONFIG_DIR / "settings.py"
    if not settings_file.is_file():
        default_config = (zerobin.ROOT_DIR / "default_settings.py").read_text()
        settings_file.write_text(default_config)

    settings.update_with_file(settings_file)


def hash_password(password):
    return hashlib.scrypt(
        password.encode("utf8"),
        salt=settings.SECRET_KEY.encode("ascii"),
        n=16384,
        r=8,
        p=1,
        dklen=32,
    )


def check_password(password):
    try:
        return settings.ADMIN_PASSWORD_FILE.read_bytes() == hash_password(password)
    except (FileNotFoundError, AttributeError):
        return False