"""
GPU / provider detection and vision-engine mode selection for CEPHEUS.

CEPHEUS_CLOUD=1 without CEPHEUS_GPU_VISION uses the lightweight stub.
CEPHEUS_GPU_VISION=1 on cloud uses the full vision stack (for Cloud Run + L4).
CEPHEUS_FORCE_FULL_VISION=1 on cloud forces the full vision stack even on CPU.
Local dev (CEPHEUS_CLOUD unset/0) always uses the full vision stack.
"""
from __future__ import annotations

import logging
import os
import threading
from typing import Any

logger = logging.getLogger(__name__)

_warmload_lock = threading.Lock()
_warmload_state: dict[str, Any] = {
    "started": False,
    "complete": False,
    "error": None,
    "result": None,
}


def _env_truthy(name: str) -> bool:
    return os.getenv(name, "").strip().lower() in ("1", "true", "yes")


def use_full_vision_engine() -> bool:
    """Return True when YOLO + InsightFace should load (local or GPU cloud)."""
    if not _env_truthy("CEPHEUS_CLOUD"):
        return True
    return _env_truthy("CEPHEUS_GPU_VISION") or _env_truthy("CEPHEUS_FORCE_FULL_VISION")


def detect_acceleration() -> dict[str, Any]:
    """Probe PyTorch CUDA and ONNX Runtime providers without crashing."""
    info: dict[str, Any] = {
        "cuda_available": False,
        "torch_cuda": False,
        "onnx_providers": [],
        "provider": "cpu",
        "device_name": None,
        "fallback_reason": None,
    }

    try:
        import onnxruntime as ort

        info["onnx_providers"] = list(ort.get_available_providers())
    except Exception as exc:
        logger.debug("ONNX Runtime probe skipped: %s", exc)

    try:
        import torch

        info["torch_cuda"] = bool(torch.cuda.is_available())
        if info["torch_cuda"]:
            info["cuda_available"] = True
            info["provider"] = "cuda"
            try:
                info["device_name"] = torch.cuda.get_device_name(0)
            except Exception:
                info["device_name"] = "cuda:0"
    except ImportError:
        if "CUDAExecutionProvider" in info["onnx_providers"]:
            info["cuda_available"] = True
            info["provider"] = "cuda"
            info["device_name"] = "onnxruntime-cuda"

    if not info["cuda_available"]:
        if _env_truthy("CEPHEUS_FORCE_CPU"):
            info["fallback_reason"] = "CEPHEUS_FORCE_CPU=1"
        elif not info["onnx_providers"]:
            info["fallback_reason"] = "ONNX Runtime unavailable"
        elif "CUDAExecutionProvider" not in info["onnx_providers"] and not info["torch_cuda"]:
            info["fallback_reason"] = (
                "CUDA not available (install torch+cuda or onnxruntime-gpu for GPU inference)"
            )
        else:
            info["fallback_reason"] = "CUDA not available"

    return info


def insightface_ctx_id() -> int:
    """InsightFace ctx_id: 0 = GPU, -1 = CPU."""
    if _env_truthy("CEPHEUS_FORCE_CPU"):
        return -1
    accel = detect_acceleration()
    return 0 if accel["cuda_available"] else -1


def get_warmload_state() -> dict[str, Any]:
    with _warmload_lock:
        return dict(_warmload_state)


def mark_warmload_started() -> bool:
    """Return False if warmload was already started."""
    with _warmload_lock:
        if _warmload_state["started"]:
            return False
        _warmload_state["started"] = True
        return True


def mark_warmload_complete(result: dict[str, Any] | None = None) -> None:
    with _warmload_lock:
        _warmload_state["complete"] = True
        _warmload_state["result"] = result


def mark_warmload_failed(error: str) -> None:
    with _warmload_lock:
        _warmload_state["error"] = error


_face_ready_probe: Any = None


def register_face_ready_probe(probe: Any) -> None:
    """Optional callback from main after VisionEngine init — avoids import cycles."""
    global _face_ready_probe
    _face_ready_probe = probe


def live_status_payload() -> dict[str, str]:
    state = get_warmload_state()
    if state.get("complete"):
        return {"status": "ready", "message": "Instance ready"}
    if _face_ready_probe:
        try:
            if _face_ready_probe():
                return {"status": "ready", "message": "Face engine loaded"}
        except Exception:
            pass
    if state.get("started"):
        return {"status": "warming", "message": "Model warmload in progress"}
    return {"status": "warming", "message": "Instance initialization triggered"}