"""Environment-backed configuration shared by every service client."""

from __future__ import annotations

import os
from dataclasses import dataclass
from pathlib import Path
from urllib.parse import urlsplit

from dotenv import load_dotenv

from .errors import ConfigurationError


DEFAULT_ENV_FILE = Path(__file__).resolve().parent.parent / ".env"


def _required(name: str) -> str:
    value = os.getenv(name, "").strip()
    if not value:
        raise ConfigurationError(f".env içinde {name} eksik veya boş.")
    if value.lower() == "change-me":
        raise ConfigurationError(f".env içindeki {name} placeholder değeri değiştirilmemiş.")
    return value


def _positive_float(name: str, default: str) -> float:
    raw_value = os.getenv(name, default).strip()
    try:
        value = float(raw_value)
    except ValueError as exc:
        raise ConfigurationError(f"{name} sayısal bir değer olmalıdır.") from exc
    if value <= 0:
        raise ConfigurationError(f"{name} sıfırdan büyük olmalıdır.")
    return value


def _non_negative_int(name: str, default: str) -> int:
    raw_value = os.getenv(name, default).strip()
    try:
        value = int(raw_value)
    except ValueError as exc:
        raise ConfigurationError(f"{name} tam sayı olmalıdır.") from exc
    if value < 0:
        raise ConfigurationError(f"{name} negatif olamaz.")
    return value


def env_bool(name: str, default: bool = False) -> bool:
    raw_value = os.getenv(name)
    if raw_value is None or not raw_value.strip():
        return default
    normalized = raw_value.strip().lower()
    if normalized in {"1", "true", "yes", "on"}:
        return True
    if normalized in {"0", "false", "no", "off"}:
        return False
    raise ConfigurationError(f"{name} true veya false olmalıdır.")


@dataclass(frozen=True)
class Settings:
    env_file: Path
    base_url: str
    hmac_secret: str
    accept_language: str
    timeout_seconds: float
    token_expiry_skew_seconds: int
    max_retries: int
    retry_base_seconds: float

    @classmethod
    def from_env(cls, env_file: Path = DEFAULT_ENV_FILE) -> "Settings":
        env_file = Path(env_file).resolve()
        if not env_file.is_file():
            raise ConfigurationError(f".env dosyası bulunamadı: {env_file}")

        load_dotenv(env_file, override=True)
        environment = _required("IKLIM_API_ENV").lower()
        url_variables = {
            "test": "IKLIM_API_TEST_URL",
            "prod": "IKLIM_API_PROD_URL",
        }
        if environment not in url_variables:
            raise ConfigurationError("IKLIM_API_ENV yalnızca test veya prod olabilir.")

        base_url = _required(url_variables[environment]).rstrip("/")
        parsed_url = urlsplit(base_url)
        if parsed_url.scheme != "https" or not parsed_url.netloc:
            raise ConfigurationError("Seçilen API adresi geçerli bir HTTPS adresi olmalıdır.")

        language = os.getenv("IKLIM_ACCEPT_LANGUAGE", "en").strip().lower() or "en"
        if language not in {"tr", "en"}:
            raise ConfigurationError("IKLIM_ACCEPT_LANGUAGE yalnızca tr veya en olabilir.")

        return cls(
            env_file=env_file,
            base_url=base_url,
            hmac_secret=_required("IKLIM_HMAC_SECRET"),
            accept_language=language,
            timeout_seconds=_positive_float("IKLIM_TIMEOUT_SECONDS", "30"),
            token_expiry_skew_seconds=_non_negative_int(
                "IKLIM_TOKEN_EXPIRY_SKEW_SECONDS", "60"
            ),
            max_retries=_non_negative_int("IKLIM_MAX_RETRIES", "3"),
            retry_base_seconds=_positive_float("IKLIM_RETRY_BASE_SECONDS", "2"),
        )

    def credentials(self) -> tuple[str, str]:
        return _required("IKLIM_USERNAME"), _required("IKLIM_PASSWORD")