from __future__ import annotations

import os
from functools import lru_cache
from pathlib import Path

from pydantic import AliasChoices, Field, field_validator
from pydantic_settings import BaseSettings, SettingsConfigDict


ROOT_DIR = Path(__file__).resolve().parent.parent
CONFIG_DIR = ROOT_DIR / "config"
DATA_DIR = ROOT_DIR / "data"


class Settings(BaseSettings):
    app_name: str = "sub-provider"
    app_env: str = "prod"
    host: str = "0.0.0.0"
    port: int = 18080
    log_level: str = "info"

    public_path: str = Field(default="change-me-random-hash-path")
    public_base_url: str | None = None
    request_timeout_seconds: float = 20.0
    cache_ttl_seconds: int = 900
    bundle_cache_ttl_seconds: int = 600
    max_proxy_name_length: int = 80
    default_user_agent: str = Field(
        default="sub-provider/0.2",
        validation_alias=AliasChoices("UPSTREAM_USER_AGENT", "DEFAULT_USER_AGENT"),
    )

    sources_file: Path = CONFIG_DIR / "sources.yaml"
    conf_base_file: Path = CONFIG_DIR / "conf" / "base.conf"
    conf_profiles_dir: Path = CONFIG_DIR / "conf" / "profiles"
    rules_dir: Path = CONFIG_DIR / "rules"
    bundle_cache_dir: Path = ROOT_DIR / "output" / "bundle-cache"
    fetch_cache_dir: Path = DATA_DIR / "fetch-cache"

    model_config = SettingsConfigDict(
        env_file=ROOT_DIR / ".env",
        env_file_encoding="utf-8",
        extra="ignore",
    )

    @field_validator("default_user_agent", mode="before")
    @classmethod
    def _coalesce_default_user_agent(cls, value: str) -> str:
        if isinstance(value, str) and value.strip():
            return value
        legacy = os.getenv("DEFAULT_USER_AGENT", "").strip()
        if legacy:
            return legacy
        return "sub-provider/0.2"


@lru_cache(maxsize=1)
def get_settings() -> Settings:
    return Settings()