import base64
import os
from dataclasses import dataclass
from pathlib import Path

from .constants import FLAG_OFF, FLAG_ON

ENV_CONFIG_DIR = "CHECKBOT_CONFIG_DIR"
ENV_DB_PATH = "CHECKBOT_DB"
ENV_BIND_HOST = "CHECKBOT_BIND_HOST"
ENV_BIND_PORT = "CHECKBOT_BIND_PORT"
ENV_SECURE_COOKIES = "CHECKBOT_SECURE_COOKIES"
ENV_LOG_LEVEL = "CHECKBOT_LOG_LEVEL"

DEFAULT_CONFIG_DIR = "/etc/checkbot"
DEFAULT_DB_PATH = "/var/lib/checkbot/checkbot.db"
DEFAULT_BIND_HOST = "127.0.0.1"
DEFAULT_BIND_PORT = "8080"
DEFAULT_LOG_LEVEL = "INFO"

MASTER_KEY_FILE = "master.key"
MASTER_KEY_LEN = 32
SESSION_SECRET_FILE = "session.secret"
SESSION_SECRET_MIN_LEN = 32


@dataclass(frozen=True)
class FileConfig:
    config_dir: Path
    db_path: Path
    bind_host: str
    bind_port: int
    secure_cookies: bool = True
    log_level: str = DEFAULT_LOG_LEVEL


def load_file_config() -> FileConfig:
    return FileConfig(
        config_dir=Path(os.environ.get(ENV_CONFIG_DIR, DEFAULT_CONFIG_DIR)),
        db_path=Path(os.environ.get(ENV_DB_PATH, DEFAULT_DB_PATH)),
        bind_host=os.environ.get(ENV_BIND_HOST, DEFAULT_BIND_HOST),
        bind_port=int(os.environ.get(ENV_BIND_PORT, DEFAULT_BIND_PORT)),
        secure_cookies=os.environ.get(ENV_SECURE_COOKIES, FLAG_ON) != FLAG_OFF,
        log_level=os.environ.get(ENV_LOG_LEVEL, DEFAULT_LOG_LEVEL),
    )


def load_master_key(path: Path) -> bytes:
    key = base64.b64decode(path.read_text().strip())
    if len(key) != MASTER_KEY_LEN:
        raise ValueError(f"master key in {path} must be {MASTER_KEY_LEN} bytes")
    return key


def load_session_secret(path: Path) -> str:
    secret = path.read_text().strip()
    if len(secret) < SESSION_SECRET_MIN_LEN:
        raise ValueError(f"session secret in {path} must have at least {SESSION_SECRET_MIN_LEN} characters")
    return secret