#!/usr/bin/env python3
"""Validate COLMAP binary sparse models without importing COLMAP or NumPy."""

from __future__ import annotations

import argparse
import struct
from pathlib import Path


CAMERA_MODEL_PARAMETER_COUNTS = {
    0: 3,   # SIMPLE_PINHOLE
    1: 4,   # PINHOLE
    2: 4,   # SIMPLE_RADIAL
    3: 5,   # RADIAL
    4: 8,   # OPENCV
    5: 8,   # OPENCV_FISHEYE
    6: 12,  # FULL_OPENCV
    7: 5,   # FOV
    8: 4,   # SIMPLE_RADIAL_FISHEYE
    9: 5,   # RADIAL_FISHEYE
    10: 12, # THIN_PRISM_FISHEYE
}


def read_exact(handle, byte_count: int) -> bytes:
    data = handle.read(byte_count)
    if len(data) != byte_count:
        raise ValueError(
            f"Unexpected end of file at byte {handle.tell()}: "
            f"wanted {byte_count}, received {len(data)}"
        )
    return data


def unpack(handle, format_string: str):
    value_struct = struct.Struct("<" + format_string)
    return value_struct.unpack(read_exact(handle, value_struct.size))


def skip_exact(handle, byte_count: int, file_size: int) -> None:
    if byte_count < 0 or handle.tell() + byte_count > file_size:
        raise ValueError(f"Invalid block length {byte_count} at byte {handle.tell()}")
    handle.seek(byte_count, 1)


def require_eof(handle, file_size: int) -> None:
    if handle.tell() != file_size:
        raise ValueError(
            f"Parsed {handle.tell()} bytes but file contains {file_size} bytes"
        )


def validate_cameras(model_directory: Path) -> tuple[int, set[int]]:
    model_file = model_directory / "cameras.bin"
    file_size = model_file.stat().st_size
    camera_ids: set[int] = set()

    with model_file.open("rb") as handle:
        (camera_count,) = unpack(handle, "Q")
        for _ in range(camera_count):
            camera_id, model_id, width, height = unpack(handle, "iiQQ")
            if camera_id in camera_ids:
                raise ValueError(f"Duplicate camera ID {camera_id}")
            if model_id not in CAMERA_MODEL_PARAMETER_COUNTS:
                raise ValueError(f"Unsupported camera model ID {model_id}")
            if width <= 0 or height <= 0:
                raise ValueError(f"Invalid camera dimensions {width}x{height}")
            read_exact(handle, 8 * CAMERA_MODEL_PARAMETER_COUNTS[model_id])
            camera_ids.add(camera_id)
        require_eof(handle, file_size)

    return camera_count, camera_ids


def validate_images(model_directory: Path, camera_ids: set[int]) -> int:
    model_file = model_directory / "images.bin"
    file_size = model_file.stat().st_size
    image_ids: set[int] = set()

    with model_file.open("rb") as handle:
        (image_count,) = unpack(handle, "Q")
        for _ in range(image_count):
            image_data = unpack(handle, "idddddddi")
            image_id = image_data[0]
            camera_id = image_data[-1]
            if image_id in image_ids:
                raise ValueError(f"Duplicate image ID {image_id}")
            if camera_id not in camera_ids:
                raise ValueError(f"Image {image_id} references camera {camera_id}")

            name_bytes = bytearray()
            while True:
                character = read_exact(handle, 1)
                if character == b"\x00":
                    break
                name_bytes.extend(character)
            name_bytes.decode("utf-8")

            (point_count,) = unpack(handle, "Q")
            skip_exact(handle, 24 * point_count, file_size)
            image_ids.add(image_id)
        require_eof(handle, file_size)

    return image_count


def validate_points(model_directory: Path) -> int:
    model_file = model_directory / "points3D.bin"
    file_size = model_file.stat().st_size
    point_ids: set[int] = set()

    with model_file.open("rb") as handle:
        (point_count,) = unpack(handle, "Q")
        for _ in range(point_count):
            point_data = unpack(handle, "QdddBBBd")
            point_id = point_data[0]
            if point_id in point_ids:
                raise ValueError(f"Duplicate point ID {point_id}")
            (track_length,) = unpack(handle, "Q")
            skip_exact(handle, 8 * track_length, file_size)
            point_ids.add(point_id)
        require_eof(handle, file_size)

    return point_count


def discover_models(root_directory: Path) -> list[Path]:
    return sorted(
        camera_file.parent
        for camera_file in root_directory.rglob("cameras.bin")
        if (camera_file.parent / "images.bin").is_file()
        and (camera_file.parent / "points3D.bin").is_file()
    )


def main() -> int:
    parser = argparse.ArgumentParser()
    parser.add_argument(
        "root",
        nargs="?",
        type=Path,
        default=Path(__file__).resolve().parent,
        help="Directory containing one or more COLMAP sparse models",
    )
    arguments = parser.parse_args()

    models = discover_models(arguments.root)
    if not models:
        raise SystemExit(f"No complete COLMAP models found below {arguments.root}")

    failures = 0
    for model_directory in models:
        try:
            camera_count, camera_ids = validate_cameras(model_directory)
            image_count = validate_images(model_directory, camera_ids)
            point_count = validate_points(model_directory)
            print(
                f"OK {model_directory}: "
                f"{camera_count} cameras, {image_count} images, {point_count} points"
            )
        except (OSError, UnicodeDecodeError, ValueError, struct.error) as error:
            failures += 1
            print(f"FAILED {model_directory}: {error}")

    print(f"Validated {len(models)} models; failures: {failures}")
    return 1 if failures else 0


if __name__ == "__main__":
    raise SystemExit(main())