"""Per-session preview images for the v2 dataset README.

Iterates both source/v1/ and source/v2/ -- v2 includes all v1 sessions plus
the new collection batches -- and writes a side-by-side composite of the
GelSight stitched panorama (left) and the D555 overhead with crop-grid
overlay (right) into previews/v2/<session_id>.png. Incomplete sessions
(missing stitched output or rgb_grid_debug.png) are skipped.

Run after the v1 and v2 croppers (which write rgb_grid_debug.png):
    uv run python scripts/v2/03_make_previews.py
"""

from __future__ import annotations

from pathlib import Path

import cv2
import numpy as np

REPO_ROOT = Path(__file__).resolve().parents[2]
SOURCE_ROOT = REPO_ROOT / "source"
SOURCE_VERSIONS = ("v1", "v2")
PREVIEWS_DIR = REPO_ROOT / "previews" / "v2"

PREVIEW_HEIGHT = 400
GAP_PX = 16
BG = (255, 255, 255)


def _resize_to_height(img: np.ndarray, h: int) -> np.ndarray:
    w = int(round(img.shape[1] * h / img.shape[0]))
    return cv2.resize(img, (w, h), interpolation=cv2.INTER_AREA)


def make_preview(session_dir: Path) -> bool:
    gel_path = session_dir / "gelsight_stitched.png"
    rgb_path = session_dir / "rgb_grid_debug.png"
    if not gel_path.exists() or not rgb_path.exists():
        print(f"  skip {session_dir.name}: missing {gel_path.name if not gel_path.exists() else rgb_path.name}")
        return False
    gel = cv2.imread(str(gel_path))
    rgb = cv2.imread(str(rgb_path))

    gel_r = _resize_to_height(gel, PREVIEW_HEIGHT)
    rgb_r = _resize_to_height(rgb, PREVIEW_HEIGHT)
    total_w = gel_r.shape[1] + GAP_PX + rgb_r.shape[1]
    canvas = np.full((PREVIEW_HEIGHT, total_w, 3), BG, dtype=np.uint8)
    canvas[:, : gel_r.shape[1]] = gel_r
    canvas[:, gel_r.shape[1] + GAP_PX :] = rgb_r

    out_path = PREVIEWS_DIR / f"{session_dir.name}.png"
    cv2.imwrite(str(out_path), canvas)
    print(f"  {out_path.name}: {canvas.shape[1]}x{canvas.shape[0]}")
    return True


def main() -> None:
    PREVIEWS_DIR.mkdir(parents=True, exist_ok=True)
    written = 0
    for version in SOURCE_VERSIONS:
        src = SOURCE_ROOT / version
        if not src.exists():
            continue
        sessions = sorted(p for p in src.iterdir() if p.is_dir())
        print(f"\n== {version} ({len(sessions)} sessions) -> {PREVIEWS_DIR} ==")
        for sess in sessions:
            if make_preview(sess):
                written += 1
    print(f"\nwrote {written} previews to {PREVIEWS_DIR}")


if __name__ == "__main__":
    main()