"""Configuration classes and utilities."""
from dataclasses import dataclass, field
from pathlib import Path
from typing import Dict, List, Optional

import toml
import dacite

from flask import current_app


@dataclass
class CoreConfig:
    """Core application configuration."""

    debug: bool = False
    port: int = 5000
    name: str = "Front page"


@dataclass
class OidcConfig:
    """OIDC client configuration."""

    issuer: str
    client_id: str
    client_secret: Optional[str] = None
    client_secret_file: Optional[str] = None
    scopes: List[str] = field(default_factory=list)


@dataclass
class AppConfig:
    """App link configuration."""

    url: str
    name: Optional[str] = None
    image: Optional[str] = None
    description: Optional[str] = None
    groups: List[str] = field(default_factory=list)


@dataclass
class Config:
    """Top-level configuration."""

    core: CoreConfig = field(default_factory=CoreConfig)
    oidc: OidcConfig = field(default_factory=OidcConfig)
    apps: Dict[str, AppConfig] = field(default_factory=dict)


class ConfigError(Exception):
    pass


def _validate(config: Config) -> None:
    oidc = config.oidc
    if oidc.client_secret is None and oidc.client_secret_file is None:
        raise ConfigError(
            "exactly one of oidc.client_secret or oidc.client_secret_file is required"
        )
    if oidc.client_secret is not None and oidc.client_secret_file is not None:
        raise ConfigError(
            "exactly one of oidc.client_secret or oidc.client_secret_file is required"
        )


def load(file: str) -> Config:
    """
    Load the configuration from a `file` path containing a TOML configuration.

    :param file: a file path to a TOML config
    :return: the configuration object
    """
    path = Path(file)
    cfg = dacite.from_dict(data_class=Config, data=toml.load(path))
    _validate(cfg)
    return cfg


def current_config() -> Config:
    """
    Load the configuration from the current Flask app.

    :return: the configuration object
    """
    return current_app.config["user_config"]