import base64
import binascii
from functools import lru_cache

from pydantic_settings import BaseSettings, SettingsConfigDict


class Settings(BaseSettings):
    model_config = SettingsConfigDict(extra="ignore")

    environment: str = "development"
    database_url: str = "postgresql+psycopg://fin:fin@localhost:5432/fin"
    redis_url: str = "redis://localhost:6379/0"
    admin_bootstrap_token: str = ""

    imports_kek_b64: str = ""
    blob_dir: str = "./var/blobs"
    s3_endpoint_url: str = ""
    s3_region: str = "us-east-1"
    s3_access_key_id: str = ""
    s3_secret_access_key: str = ""
    s3_bucket_statements: str = "finance-statements"
    smtp_host: str = ""
    smtp_port: int = 1025
    smtp_use_tls: bool = False
    smtp_from: str = "no-reply@finance.local"
    public_base_url: str = "http://localhost:8080"

    session_cookie_name: str = "fin_session"
    csrf_cookie_name: str = "csrf_token"
    cookie_secure: bool = True
    session_ttl_days: int = 14
    invite_ttl_days: int = 7
    reset_ttl_hours: int = 4

    max_upload_bytes: int = 20 * 1024 * 1024
    max_xlsx_rows: int = 10_000
    max_pdf_pages: int = 200
    max_archive_uncompressed_bytes: int = 64 * 1024 * 1024

    deletion_window_days: int = 30

    celery_task_always_eager: bool = False
    celery_broker_url: str = ""

    default_locale: str = "ru"
    default_timezone: str = "Europe/Moscow"

    @property
    def broker_url(self) -> str:
        return self.celery_broker_url or self.redis_url

    @property
    def kek(self) -> bytes:
        if not self.imports_kek_b64:
            raise RuntimeError("IMPORTS_KEK_B64 must be configured (base64-encoded 32-byte KEK)")
        try:
            raw = base64.b64decode(self.imports_kek_b64, validate=True)
        except (binascii.Error, ValueError) as exc:
            raise RuntimeError("IMPORTS_KEK_B64 is not valid base64") from exc
        if len(raw) != 32:
            raise RuntimeError("IMPORTS_KEK_B64 must decode to exactly 32 bytes")
        return raw


@lru_cache
def get_settings() -> Settings:
    return Settings()