from typing import NamedTuple, Sequence, List

import numpy as np


class DepthResult(NamedTuple):
    """Result from depth estimation inference."""
    depth_map: np.ndarray  # HxW float32 depth in meters
    focal_length: float    # Estimated focal length in pixels


class DepthEstimator:
    """Base interface for depth estimation models."""

    name: str
    supports_batch: bool = False
    max_batch_size: int = 1

    def predict(self, frame: np.ndarray) -> DepthResult:
        """
        Run depth estimation on a single frame.

        Args:
            frame: Input image as numpy array (HxWxC, BGR format from OpenCV)

        Returns:
            DepthResult with depth_map and focal_length
        """
        raise NotImplementedError

    def predict_batch(self, frames: Sequence[np.ndarray]) -> Sequence[DepthResult]:
        return [self.predict(f) for f in frames]