"""Environment + provider configuration.

Single source of truth for which LLM provider/model to use and for
constructing the underlying SDK client. Fails fast with a clear message
when the required API key is missing.
"""

from __future__ import annotations

import os

from dotenv import load_dotenv

load_dotenv()

PROVIDER = os.getenv("LLM_PROVIDER", "anthropic").strip().lower()

_SUPPORTED = {"anthropic", "openai", "gemini"}
_DEFAULT_MODELS = {
    "anthropic": "claude-sonnet-4-6",
    "openai": "gpt-4o",
    "gemini": "gemini-2.5-flash",
}
# Gemini's OpenAI-compatible surface — lets us reuse the OpenAI client/code path.
_GEMINI_BASE_URL = "https://generativelanguage.googleapis.com/v1beta/openai/"

# Use the explicit MODEL if set, else a sensible per-provider default.
MODEL = (os.getenv("MODEL") or _DEFAULT_MODELS.get(PROVIDER, "claude-sonnet-4-6")).strip()


class ConfigError(RuntimeError):
    """Raised when configuration is incomplete or invalid."""


def _require_key(name: str) -> str:
    key = os.getenv(name, "").strip()
    if not key:
        raise ConfigError(
            f"{name} is not set. Copy .env.example to .env and add your key "
            f"(LLM_PROVIDER={PROVIDER})."
        )
    return key


def get_llm_client():
    """Return an SDK client for the configured provider.

    The returned object is the raw provider SDK client. Callers should use
    ``src.utils.complete`` rather than calling the client directly so that
    provider differences stay in one place.
    """
    if PROVIDER == "anthropic":
        import anthropic

        return anthropic.Anthropic(api_key=_require_key("ANTHROPIC_API_KEY"))

    if PROVIDER == "openai":
        from openai import OpenAI

        return OpenAI(api_key=_require_key("OPENAI_API_KEY"))

    if PROVIDER == "gemini":
        from openai import OpenAI

        # GEMINI_API_KEY preferred; GOOGLE_API_KEY accepted as a fallback.
        key = os.getenv("GEMINI_API_KEY", "").strip() or os.getenv(
            "GOOGLE_API_KEY", ""
        ).strip()
        if not key:
            raise ConfigError(
                "GEMINI_API_KEY is not set. Add it to .env (LLM_PROVIDER=gemini)."
            )
        return OpenAI(api_key=key, base_url=_GEMINI_BASE_URL)

    raise ConfigError(
        f"Unsupported LLM_PROVIDER={PROVIDER!r}. Supported: {sorted(_SUPPORTED)}."
    )