"""Load immutable runtime settings from environment variables.

Settings are created once by the application factory and passed to services.
"""

from functools import lru_cache

from pydantic import Field
from pydantic_settings import BaseSettings, SettingsConfigDict

APP_VERSION = "2.0.0"


class Settings(BaseSettings):
    """Environment-backed application configuration."""

    model_config = SettingsConfigDict(
        env_prefix="",
        case_sensitive=False,
        extra="ignore",
    )

    app_password: str | None = None
    app_secret_key: str = Field(min_length=1)
    data_root: str = "/data/loop_logger"
    env: str = "prod"
    app_name: str = "Habit Journal"

    openrouter_api_key: str | None = None
    openrouter_model: str = "openrouter/free"
    openrouter_base_url: str = "https://openrouter.ai/api/v1"
    coach_timeout_sec: float = 25
    coach_temperature: float = 0.3
    coach_max_tokens: int = 400
    coach_history_k: int = 10
    coach_trace_limit: int = 200

    min_stats_n: int = 5
    stats_shrink_k: float = 3
    match_alpha: float = 0.5
    session_max_age_sec: int = 604800
    debug_include_full_brief: bool = False
    login_rate_limit: int = 10
    login_rate_window_sec: int = 900
    max_body_bytes: int = 65536

    agent_token: str | None = None
    reschedule_min_gap_min: int = 90
    schedule_day_start: str = "06:00"
    schedule_day_end: str = "23:00"
    schedule_timezone: str = "Africa/Dar_es_Salaam"
    schedule_max_blocks: int = 20

    @property
    def is_prod(self) -> bool:
        """Return whether production-only security behavior is enabled."""

        return self.env.lower() == "prod"


@lru_cache
def get_settings() -> Settings:
    """Read and cache environment settings."""

    return Settings()