"""ONNX Runtime session management — load-once, reuse-many."""

from __future__ import annotations

import threading
from pathlib import Path
from typing import Dict, Optional

import numpy as np

from config.settings import settings as _default_settings
from cores.embedding.cache import EmbeddingCache


# --------------------------------------------------------------------------- #
# Availability check
# --------------------------------------------------------------------------- #
def is_onnx_available() -> bool:
    """True if onnxruntime is importable."""
    try:
        import onnxruntime  # noqa: F401
        return True
    except ImportError:
        return False


# --------------------------------------------------------------------------- #
# Session cache — one session per model path
# --------------------------------------------------------------------------- #
_session_cache: EmbeddingCache = EmbeddingCache()
_init_lock = threading.Lock()


class ONNXModel:
    """Wrapper around an ONNX inference session.

    Encapsulates the session + input/output name discovery so providers
    don't repeat that boilerplate.
    """

    def __init__(self, session) -> None:
        self._session = session
        self._input_name = session.get_inputs()[0].name
        self._output_names = [o.name for o in session.get_outputs()]

    @property
    def input_name(self) -> str:
        return self._input_name

    @property
    def output_names(self) -> list[str]:
        return list(self._output_names)

    def run(self, input_array: np.ndarray) -> list[np.ndarray]:
        """Run inference.  Returns list of output arrays."""
        return self._session.run(
            self._output_names,
            {self._input_name: input_array},
        )

    def run_single(self, input_array: np.ndarray) -> np.ndarray:
        """Run inference + return only the first output."""
        return self.run(input_array)[0]


def get_session(model_path: Path | str, settings=None) -> ONNXModel:
    """Load (or return cached) ONNXModel for the given model file.

    The session is created ONCE per process and reused.  Thread-safe.

    Args:
        model_path: path to .onnx file
        settings: Settings (uses default singleton if None)

    Returns:
        ONNXModel wrapper
    """
    s = settings or _default_settings
    key = str(model_path)
    return _session_cache.get_or_load(key, lambda: _create_session(model_path, s))


def _create_session(model_path: Path | str, settings) -> ONNXModel:
    """Create a new ONNX Runtime session."""
    import onnxruntime as ort

    path = Path(model_path)
    if not path.exists():
        raise FileNotFoundError(f"ONNX model not found: {path}")

    # CPU-only, limited threads for low-RAM deployments
    opts = ort.SessionOptions()
    opts.intra_op_num_threads = settings.onnx_intra_op_threads
    opts.inter_op_num_threads = 1
    opts.graph_optimization_level = ort.GraphOptimizationLevel.ORT_ENABLE_ALL

    session = ort.InferenceSession(
        str(path),
        sess_options=opts,
        providers=["CPUExecutionProvider"],  # CPU-only by design
    )
    return ONNXModel(session)


def run_inference(model_path: Path | str, input_array: np.ndarray,
                  settings=None) -> list[np.ndarray]:
    """Convenience: load (or get cached) session + run inference."""
    model = get_session(model_path, settings)
    return model.run(input_array)