"""Client utilities for interacting with the Ollama API."""

from __future__ import annotations

from typing import Any, Dict, Iterable, Iterator

try:  # pragma: no cover - optional dependency may not be installed in CI
    import ollama
except ImportError:  # pragma: no cover - fallback path for environments without Ollama
    ollama = None  # type: ignore[assignment]


class OllamaClientError(RuntimeError):
    """Base exception raised when Ollama operations fail."""


class OllamaUnavailableError(OllamaClientError):
    """Raised when the Ollama Python SDK is not available."""


class OllamaClient:
    """Thin wrapper around the Ollama Python SDK with graceful degradation."""

    def __init__(self, host: str | None = None) -> None:
        self._host = host
        self._client = None
        self._cached_models: list[str] | None = None

        if ollama is None:
            return

        if host and hasattr(ollama, "Client"):
            self._client = ollama.Client(host=host)  # type: ignore[call-arg]

    # ------------------------------------------------------------------ helpers
    @property
    def is_available(self) -> bool:
        return ollama is not None

    @property
    def default_model(self) -> str | None:
        models = self.list_models()
        return models[0] if models else None

    def list_models(self, force_refresh: bool = False) -> list[str]:
        """Return the available model names, caching the result for quick reuse."""
        if not self.is_available:
            return []

        if self._cached_models is not None and not force_refresh:
            return list(self._cached_models)

        try:
            response = self._call_sdk("list")  # type: ignore[arg-type]
        except OllamaClientError:
            return []

        models: list[str] = []
        for item in response.get("models", []):  # type: ignore[assignment]
            name = item.get("name") or item.get("model")
            if name:
                models.append(name)

        self._cached_models = models
        return list(models)

    # ------------------------------------------------------------------ chat APIs
    def chat(
        self,
        *,
        model: str,
        messages: Iterable[Dict[str, str]],
    ) -> dict[str, str] | None:
        """Execute a blocking chat call against Ollama."""
        if not self.is_available:
            return {
                "role": "assistant",
                "content": "Ollama SDK is not installed; install `ollama` to enable responses.",
            }

        try:
            result = self._call_sdk(
                "chat",
                model=model,
                messages=list(messages),
                stream=False,
            )
        except OllamaClientError as exc:
            return {
                "role": "assistant",
                "content": f"Unable to reach Ollama: {exc}",
            }

        message = result.get("message") if isinstance(result, dict) else None
        if not message:
            return {"role": "assistant", "content": ""}

        role = message.get("role") or "assistant"
        content = message.get("content") or ""
        return {"role": role, "content": content}

    def stream_chat(
        self, *, model: str, messages: Iterable[Dict[str, str]]
    ) -> Iterator[dict[str, Any]]:
        """Placeholder that exposes the streaming API for future UI hooks."""
        if not self.is_available:
            raise OllamaUnavailableError(
                "Streaming requires the Ollama Python SDK to be installed."
            )

        try:
            stream = self._call_sdk(
                "chat",
                model=model,
                messages=list(messages),
                stream=True,
            )
        except OllamaClientError as exc:
            raise OllamaClientError(f"Failed to start streaming chat: {exc}") from exc

        if not hasattr(stream, "__iter__"):
            raise OllamaClientError("Ollama returned a non-iterable stream response.")
        return iter(stream)

    # ------------------------------------------------------------------ internals
    def _call_sdk(self, method: str, *args: Any, **kwargs: Any) -> Any:
        if not self.is_available:
            raise OllamaUnavailableError(
                "Ollama Python SDK is not available in the environment."
            )

        target = self._client if self._client is not None else ollama
        if target is None or not hasattr(target, method):
            raise OllamaClientError(
                f"Ollama SDK does not expose method '{method}'. Install or update the SDK."
            )

        func = getattr(target, method)

        try:
            return func(*args, **kwargs)
        except Exception as exc:  # pragma: no cover - network errors depend on runtime
            raise OllamaClientError(str(exc)) from exc