"""Runtime configuration for the GLM API and local processing pipeline."""

from __future__ import annotations

import os
from dataclasses import dataclass


def _get_bool(name: str, default: bool) -> bool:
    """Read a strict boolean environment variable with a safe default."""

    raw_value = os.getenv(name)
    if raw_value is None:
        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 ValueError(f"{name} must be a boolean value, got {raw_value!r}")


def _get_int(name: str, default: int, minimum: int = 1) -> int:
    """Read and validate an integer environment variable."""

    value = int(os.getenv(name, str(default)))
    if value < minimum:
        raise ValueError(f"{name} must be at least {minimum}, got {value}")
    return value


def _get_float(name: str, default: float, minimum: float = 0.0) -> float:
    """Read and validate a floating-point environment variable."""

    value = float(os.getenv(name, str(default)))
    if value < minimum:
        raise ValueError(f"{name} must be at least {minimum}, got {value}")
    return value


@dataclass(frozen=True)
class Settings:
    """Immutable settings used by API clients and command-line workflows."""

    api_key: str
    api_base: str = "https://llm-api.cowin.run"
    api_path: str = "/v1/chat/completions"
    model: str = "glm-5.2"
    timeout_seconds: float = 300.0
    max_retries: int = 5
    max_tokens: int = 8192
    temperature: float = 0.0
    reasoning_effort: str = "high"
    thinking_enabled: bool = True

    @property
    def endpoint(self) -> str:
        """Return the normalized absolute chat-completions URL."""

        base = self.api_base.rstrip("/")
        path = self.api_path if self.api_path.startswith("/") else f"/{self.api_path}"
        return f"{base}{path}"

    @classmethod
    def from_env(cls, *, require_api_key: bool = True) -> Settings:
        """Construct settings from environment variables.

        The API key is intentionally loaded only from ``GLM_API_KEY``. The
        project never reads a committed configuration file containing a key.
        """

        api_key = os.getenv("GLM_API_KEY", "").strip()
        if require_api_key and not api_key:
            raise ValueError("GLM_API_KEY is required but was not set")

        reasoning_effort = os.getenv("GLM_REASONING_EFFORT", "high").strip().lower()
        if reasoning_effort not in {"low", "medium", "high", "max"}:
            raise ValueError(
                "GLM_REASONING_EFFORT must be one of: low, medium, high, max"
            )

        return cls(
            api_key=api_key,
            api_base=os.getenv("GLM_API_BASE", "https://llm-api.cowin.run"),
            api_path=os.getenv("GLM_API_PATH", "/v1/chat/completions"),
            model=os.getenv("GLM_MODEL", "glm-5.2"),
            timeout_seconds=_get_float("GLM_TIMEOUT_SECONDS", 300.0, 1.0),
            max_retries=_get_int("GLM_MAX_RETRIES", 5, 0),
            max_tokens=_get_int("GLM_MAX_TOKENS", 8192, 1),
            temperature=_get_float("GLM_TEMPERATURE", 0.0, 0.0),
            reasoning_effort=reasoning_effort,
            thinking_enabled=_get_bool("GLM_THINKING_ENABLED", True),
        )