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"""Run box-prompted segmentation with EfficientSAM-S and ONNX Runtime."""

import argparse
import json
from pathlib import Path

import numpy as np
import onnxruntime as ort
from PIL import Image, ImageDraw


MODEL_DIR = Path(__file__).resolve().parent
MODEL_PATH = MODEL_DIR / "efficient_sam_s_graviton_onnx_optimized.onnx"
SAMPLE_IMAGE_PATH = MODEL_DIR / "sample_input.jpg"

INPUT_SIZE = 1024
SAMPLE_BOX_PROMPT = [410, 510, 600, 830]
EXECUTION_PROVIDER = "CPUExecutionProvider"


def required_file(path: Path) -> Path:
    if not path.is_file():
        raise FileNotFoundError(f"required model file not found: {path}")
    return path


def load_model() -> ort.InferenceSession:
    available = ort.get_available_providers()
    if EXECUTION_PROVIDER not in available:
        raise RuntimeError(
            f"{EXECUTION_PROVIDER} is unavailable; available providers: {', '.join(available)}"
        )
    session = ort.InferenceSession(str(required_file(MODEL_PATH)), providers=[EXECUTION_PROVIDER])
    input_names = [node.name for node in session.get_inputs()]
    if input_names != ["image", "point_coords", "point_labels"]:
        raise RuntimeError(f"unexpected model inputs: {input_names}")
    return session


def resize_bilinear(image: np.ndarray, size: int) -> np.ndarray:
    """Resize an HWC float image with half-pixel centres and no antialiasing."""
    height, width = image.shape[:2]

    def axis(source: int) -> tuple[np.ndarray, np.ndarray, np.ndarray]:
        coords = (np.arange(size, dtype=np.float64) + 0.5) * (source / size) - 0.5
        coords = np.clip(coords, 0.0, source - 1)
        low = np.floor(coords).astype(np.int64)
        high = np.minimum(low + 1, source - 1)
        return low, high, (coords - low).astype(np.float32)

    y0, y1, wy = axis(height)
    x0, x1, wx = axis(width)
    wy = wy[:, None, None]
    wx = wx[None, :, None]
    top = image[y0][:, x0] * (1 - wx) + image[y0][:, x1] * wx
    bottom = image[y1][:, x0] * (1 - wx) + image[y1][:, x1] * wx
    return top * (1 - wy) + bottom * wy


def preprocess(image_path: Path) -> np.ndarray:
    with Image.open(required_file(image_path)) as image:
        pixels = np.asarray(image.convert("RGB"), dtype=np.float32) / 255.0
    resized = resize_bilinear(pixels, INPUT_SIZE)
    return np.ascontiguousarray(resized.transpose(2, 0, 1)[None], dtype=np.float32)


def make_box_prompt(box: list[int]) -> tuple[np.ndarray, np.ndarray]:
    x1, y1, x2, y2 = box
    point_coords = np.array([[[[x1, y1], [x2, y2]]]], dtype=np.float32)
    point_labels = np.array([[[2, 3]]], dtype=np.float32)
    return point_coords, point_labels


def validate_box(box: list[int]) -> list[int]:
    x1, y1, x2, y2 = box
    if not (0 <= x1 < x2 <= INPUT_SIZE and 0 <= y1 < y2 <= INPUT_SIZE):
        raise ValueError(
            f"box must satisfy 0 <= x1 < x2 <= {INPUT_SIZE} and "
            f"0 <= y1 < y2 <= {INPUT_SIZE}; received {box}"
        )
    return box


def postprocess(raw_output: np.ndarray, box: list[int]) -> tuple[np.ndarray, dict[str, object]]:
    if tuple(raw_output.shape) != (1, INPUT_SIZE, INPUT_SIZE):
        raise ValueError(
            f"expected output shape (1, {INPUT_SIZE}, {INPUT_SIZE}), "
            f"found {tuple(raw_output.shape)}"
        )
    if not np.isfinite(raw_output).all():
        raise ValueError("model output contains non-finite mask values")

    mask = (raw_output[0] > 0.5).astype(np.uint8)
    pixel_count = int(mask.sum())
    total_pixels = int(mask.size)
    result = {
        "pixel_count": pixel_count,
        "total_pixels": total_pixels,
        "coverage_pct": round(100.0 * pixel_count / total_pixels, 2),
        "box_prompt": box,
    }
    return mask, result


def create_overlay(mask: np.ndarray, image_path: Path, box: list[int]) -> Image.Image:
    with Image.open(required_file(image_path)) as image:
        source = image.convert("RGB")

    source_width, source_height = source.size
    source_mask = Image.fromarray(mask * 255).resize(
        source.size,
        resample=Image.Resampling.NEAREST,
    )
    source_mask_array = np.asarray(source_mask, dtype=np.uint8) > 0

    mask_rgba = np.zeros((source_height, source_width, 4), dtype=np.uint8)
    mask_rgba[source_mask_array] = [0, 200, 0, 200]
    overlay = Image.fromarray(mask_rgba)
    composited = Image.alpha_composite(source.convert("RGBA"), overlay).convert("RGB")

    x1, y1, x2, y2 = box
    scaled_box = [
        round(x1 * source_width / INPUT_SIZE),
        round(y1 * source_height / INPUT_SIZE),
        round(x2 * source_width / INPUT_SIZE),
        round(y2 * source_height / INPUT_SIZE),
    ]
    draw = ImageDraw.Draw(composited)
    draw.rectangle(scaled_box, outline=(255, 0, 0), width=3)
    return composited


def parse_args() -> argparse.Namespace:
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument(
        "--image",
        type=Path,
        default=SAMPLE_IMAGE_PATH,
        help="input image (default: sample_input.jpg)",
    )
    parser.add_argument(
        "--box",
        nargs=4,
        type=int,
        metavar=("X1", "Y1", "X2", "Y2"),
        default=SAMPLE_BOX_PROMPT,
        help="box prompt in resized 1024x1024 coordinates (default: sample box)",
    )
    parser.add_argument("--output-dir", type=Path, help="optional output directory")
    return parser.parse_args()


def main() -> None:
    args = parse_args()
    image_path = required_file(args.image)
    box = validate_box(args.box)
    image_tensor = preprocess(image_path)
    point_coords, point_labels = make_box_prompt(box)
    session = load_model()
    raw_output = session.run(
        None,
        {"image": image_tensor, "point_coords": point_coords, "point_labels": point_labels},
    )[0]
    mask, result = postprocess(raw_output, box)

    print(f"Input: {image_path.name}; tensor shape: {tuple(image_tensor.shape)}")
    print(f"Box prompt: {box}")
    print(
        f"Segmented pixels: {result['pixel_count']:,} / {result['total_pixels']:,} "
        f"({result['coverage_pct']:.2f}%)"
    )

    if args.output_dir is not None:
        args.output_dir.mkdir(parents=True, exist_ok=True)
        overlay_path = args.output_dir / "sample_output.png"
        result_path = args.output_dir / "segmentation.json"
        create_overlay(mask, image_path, box).save(overlay_path)
        result_path.write_text(json.dumps(result, indent=2) + "\n", encoding="utf-8")
        print(f"Saved: {overlay_path}")
        print(f"Saved: {result_path}")


if __name__ == "__main__":
    main()