#!/usr/bin/env python3
"""Validate Real4D structure, frame counts, metadata, and image headers."""

from __future__ import annotations

import argparse
import json
import re
import struct
import sys
from pathlib import Path


EXPECTED = {
    "dynerf": {
        "resolution": (1352, 1014),
        "scenes": {
            "coffee_martini": 324,
            "cook_spinach": 441,
            "cut_roasted_beef": 400,
            "flame_salmon": 361,
            "flame_steak": 441,
            "sear_steak": 441,
        },
    },
    "meetroom": {
        "resolution": (1280, 720),
        "scenes": {
            "discussion": 169,
            "stepin": 169,
            "trimming": 169,
            "vrheadset": 169,
        },
    },
}

REQUIRED_CAMERA_FIELDS = {
    "image_name",
    "timestamp",
    "w2c",
    "R",
    "T",
    "FoVx",
    "FoVy",
    "fl_x",
    "fl_y",
    "cx",
    "cy",
    "width",
    "height",
}


def child_dirs(path: Path) -> set[str]:
    return {entry.name for entry in path.iterdir() if entry.is_dir()}


def json_stems(path: Path) -> set[str]:
    return {entry.stem for entry in path.iterdir() if entry.is_file() and entry.suffix == ".json"}


def jpeg_size(path: Path) -> tuple[int, int]:
    with path.open("rb") as handle:
        if handle.read(2) != b"\xff\xd8":
            raise ValueError("missing JPEG SOI marker")
        while True:
            byte = handle.read(1)
            while byte == b"\xff":
                byte = handle.read(1)
            if not byte:
                raise ValueError("JPEG size marker not found")
            marker = byte[0]
            if marker in (0xD8, 0xD9):
                continue
            length_raw = handle.read(2)
            if len(length_raw) != 2:
                raise ValueError("truncated JPEG segment")
            length = struct.unpack(">H", length_raw)[0]
            if marker in {
                0xC0, 0xC1, 0xC2, 0xC3, 0xC5, 0xC6, 0xC7,
                0xC9, 0xCA, 0xCB, 0xCD, 0xCE, 0xCF,
            }:
                data = handle.read(5)
                if len(data) != 5:
                    raise ValueError("truncated JPEG SOF segment")
                height, width = struct.unpack(">HH", data[1:5])
                return width, height
            handle.seek(length - 2, 1)


def png_info(path: Path) -> tuple[int, int, int, int]:
    with path.open("rb") as handle:
        header = handle.read(29)
    if len(header) != 29 or header[:8] != b"\x89PNG\r\n\x1a\n" or header[12:16] != b"IHDR":
        raise ValueError("invalid PNG header")
    width, height, bit_depth, color_type = struct.unpack(">IIBB", header[16:26])
    return width, height, bit_depth, color_type


def shape_ok(value, rows: int, cols: int | None = None) -> bool:
    if not isinstance(value, list) or len(value) != rows:
        return False
    if cols is None:
        return True
    return all(isinstance(row, list) and len(row) == cols for row in value)


def validate_trajectory(
    scene_dir: Path,
    trajectory: str,
    resolution: tuple[int, int],
    errors: list[str],
    warnings: list[str],
) -> None:
    rgb_dir = scene_dir / "images" / trajectory
    depth_dir = scene_dir / "depths" / trajectory
    vis_dir = scene_dir / "depth_vis" / trajectory
    rgb_pattern = re.compile(rf"^{re.escape(trajectory)}_(\d{{6}})\.jpg$")
    depth_pattern = re.compile(
        rf"^{re.escape(trajectory)}_(\d{{6}})\.jpg\.geometric\.png$"
    )

    def numbered_files(path: Path, pattern: re.Pattern[str]) -> tuple[list[Path], list[int]]:
        files = sorted(entry for entry in path.iterdir() if entry.is_file())
        numbers = []
        for entry in files:
            match = pattern.match(entry.name)
            if match:
                numbers.append(int(match.group(1)))
        return files, numbers

    rgb_files, rgb_numbers = numbered_files(rgb_dir, rgb_pattern)
    depth_files, depth_numbers = numbered_files(depth_dir, depth_pattern)
    vis_files = sorted(entry for entry in vis_dir.iterdir() if entry.is_file())

    expected_numbers = list(range(1, 301))
    if len(rgb_files) != 300 or rgb_numbers != expected_numbers:
        errors.append(f"{scene_dir}/{trajectory}: RGB numbering/count is not 000001..000300")
    if len(depth_files) != 300 or depth_numbers != expected_numbers:
        errors.append(f"{scene_dir}/{trajectory}: depth numbering/count is not 000001..000300")
    if len(vis_files) != 300:
        errors.append(f"{scene_dir}/{trajectory}: expected 300 depth previews, found {len(vis_files)}")

    camera_path = scene_dir / "camera_params" / f"{trajectory}.json"
    try:
        with camera_path.open("r", encoding="utf-8") as handle:
            records = json.load(handle)
    except Exception as exc:
        errors.append(f"{camera_path}: cannot parse JSON: {exc}")
        return
    if not isinstance(records, list) or len(records) != 300:
        errors.append(f"{camera_path}: expected a 300-entry list")
        return

    timestamps = []
    image_names = set()
    for index, record in enumerate(records):
        missing = REQUIRED_CAMERA_FIELDS - set(record)
        if missing:
            errors.append(f"{camera_path}[{index}]: missing fields {sorted(missing)}")
            break
        timestamps.append(record["timestamp"])
        image_names.add(record["image_name"])
        if (record["width"], record["height"]) != resolution:
            errors.append(f"{camera_path}[{index}]: unexpected resolution")
            break
        if not shape_ok(record["w2c"], 4, 4):
            errors.append(f"{camera_path}[{index}]: w2c must be 4x4")
            break
        if not shape_ok(record["R"], 3, 3) or not shape_ok(record["T"], 3):
            errors.append(f"{camera_path}[{index}]: invalid R or T shape")
            break
    if any(b <= a for a, b in zip(timestamps, timestamps[1:])):
        errors.append(f"{camera_path}: timestamps are not strictly increasing")
    if len(image_names) == 1:
        warnings.append(f"{camera_path}: image_name is a constant source-camera identifier")

    if rgb_files:
        try:
            if jpeg_size(rgb_files[0]) != resolution:
                errors.append(f"{rgb_files[0]}: unexpected JPEG resolution")
        except Exception as exc:
            errors.append(f"{rgb_files[0]}: {exc}")
    if depth_files:
        try:
            width, height, bit_depth, color_type = png_info(depth_files[0])
            if (width, height) != resolution or bit_depth != 16 or color_type != 0:
                errors.append(
                    f"{depth_files[0]}: expected {resolution[0]}x{resolution[1]} "
                    "16-bit grayscale PNG"
                )
        except Exception as exc:
            errors.append(f"{depth_files[0]}: {exc}")


def main() -> int:
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument("root", type=Path, help="Real4D dataset root")
    parser.add_argument(
        "--full",
        action="store_true",
        help="scan all 3,084 trajectories; default samples three per scene",
    )
    args = parser.parse_args()
    root = args.root.resolve()
    errors: list[str] = []
    warnings: list[str] = []
    total_trajectories = 0

    for subset, subset_spec in EXPECTED.items():
        subset_dir = root / subset
        expected_scenes = set(subset_spec["scenes"])
        if not subset_dir.is_dir():
            errors.append(f"missing subset directory: {subset_dir}")
            continue
        actual_scenes = child_dirs(subset_dir)
        if actual_scenes != expected_scenes:
            errors.append(
                f"{subset}: scene mismatch; expected {sorted(expected_scenes)}, "
                f"found {sorted(actual_scenes)}"
            )

        for scene, expected_count in subset_spec["scenes"].items():
            scene_dir = subset_dir / scene
            required_dirs = ("images", "depths", "depth_vis", "camera_params", "video")
            missing_dirs = [name for name in required_dirs if not (scene_dir / name).is_dir()]
            if missing_dirs:
                errors.append(f"{scene_dir}: missing directories {missing_dirs}")
                continue

            image_trajectories = child_dirs(scene_dir / "images")
            depth_trajectories = child_dirs(scene_dir / "depths")
            vis_trajectories = child_dirs(scene_dir / "depth_vis")
            camera_trajectories = json_stems(scene_dir / "camera_params")
            total_trajectories += len(image_trajectories)

            if len(image_trajectories) != expected_count:
                errors.append(
                    f"{scene_dir}: expected {expected_count} trajectories, "
                    f"found {len(image_trajectories)}"
                )
            for label, values in (
                ("depths", depth_trajectories),
                ("depth_vis", vis_trajectories),
                ("camera_params", camera_trajectories),
            ):
                if values != image_trajectories:
                    errors.append(f"{scene_dir}: {label} trajectory set differs from images")

            videos = {entry.name for entry in (scene_dir / "video").iterdir() if entry.is_file()}
            missing_videos = [
                filename
                for trajectory in image_trajectories
                for filename in (f"{trajectory}_rgb.mp4", f"{trajectory}_depth.mp4")
                if filename not in videos
            ]
            if missing_videos:
                errors.append(
                    f"{scene_dir}: missing {len(missing_videos)} release preview videos; "
                    f"first={missing_videos[0]}"
                )

            ordered = sorted(image_trajectories)
            selected = ordered if args.full else sorted({ordered[0], ordered[len(ordered) // 2], ordered[-1]})
            for trajectory in selected:
                validate_trajectory(
                    scene_dir,
                    trajectory,
                    subset_spec["resolution"],
                    errors,
                    warnings,
                )
            print(
                f"checked {subset}/{scene}: {len(image_trajectories)} trajectories "
                f"({len(selected)} deeply scanned)"
            )

    if total_trajectories != 3084:
        errors.append(f"expected 3,084 total trajectories, found {total_trajectories}")

    if warnings:
        print(f"\nNotes ({len(warnings)}):")
        limit = len(warnings) if not args.full else min(10, len(warnings))
        for warning in warnings[:limit]:
            print(f"  - {warning}")
        if len(warnings) > limit:
            print(f"  - ... {len(warnings) - limit} identical notes omitted")

    if errors:
        print(f"\nFAILED with {len(errors)} error(s):", file=sys.stderr)
        for error in errors:
            print(f"  - {error}", file=sys.stderr)
        return 1

    mode = "full" if args.full else "quick"
    print(f"\nPASS: {mode} validation; {total_trajectories:,} trajectories found.")
    return 0


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