from functools import lru_cache

from pydantic import Field
from pydantic_settings import BaseSettings, SettingsConfigDict


class Settings(BaseSettings):
    model_config = SettingsConfigDict(env_prefix="MONITOR_", case_sensitive=False)

    host: str = "0.0.0.0"
    port: int = Field(8000, ge=1, le=65535)
    log_level: str = "INFO"
    default_timeout_seconds: float = Field(5.0, gt=0, le=30)
    max_timeout_seconds: float = Field(15.0, gt=0, le=60)
    max_redirects: int = Field(3, ge=0, le=10)
    allowed_ports: str = "80,443"

    @property
    def allowed_port_set(self) -> frozenset[int]:
        try:
            ports = frozenset(int(value.strip()) for value in self.allowed_ports.split(","))
        except ValueError as exc:
            raise ValueError("MONITOR_ALLOWED_PORTS must be comma-separated integers") from exc
        if not ports or any(port < 1 or port > 65535 for port in ports):
            raise ValueError("MONITOR_ALLOWED_PORTS contains an invalid port")
        return ports


@lru_cache
def get_settings() -> Settings:
    settings = Settings()
    settings.allowed_port_set
    if settings.default_timeout_seconds > settings.max_timeout_seconds:
        raise ValueError("default timeout cannot exceed maximum timeout")
    return settings