#!/usr/bin/env python3
"""Build sample_sheet.png: one row per regime, four evenly spaced frames per row.

Usage: python make_sample_sheet.py [dataset_root]
"""
import csv
import sys
from pathlib import Path

import imageio.v2 as imageio
import numpy as np
from PIL import Image, ImageDraw, ImageFont

REGIME_ORDER = ["train", "val_high_damp", "val_low_damp", "val_large_angle",
                "val_gravity", "val_quad_damping", "val_driven"]
FRAME_FRACTIONS = (0.0, 0.33, 0.66, 1.0)
PAD, LABEL_W, GAP = 8, 210, 4


def main(root="."):
    root = Path(root)
    idx = list(csv.DictReader(open(root / "index.csv")))
    by_regime = {}
    for r in idx:
        by_regime.setdefault(r["regime"], []).append(r)

    try:
        font = ImageFont.truetype("DejaVuSans.ttf", 13)
    except Exception:
        font = ImageFont.load_default()

    rows, size = [], None
    for regime in REGIME_ORDER:
        rows_ = by_regime.get(regime)
        if not rows_:
            continue
        r = rows_[len(rows_) // 3]
        path = root / r["video_path"]
        reader = imageio.get_reader(path)
        frames = [f for f in reader]
        picks = [frames[min(len(frames) - 1, int(f * (len(frames) - 1)))]
                 for f in FRAME_FRACTIONS]
        size = picks[0].shape[0]
        rows.append((regime, r, picks))

    ncol = len(FRAME_FRACTIONS)
    width = LABEL_W + ncol * (size + GAP) + PAD * 2
    height = PAD * 2 + len(rows) * (size + GAP + 22)
    sheet = Image.new("RGB", (width, height), "white")
    draw = ImageDraw.Draw(sheet)

    y = PAD
    for regime, r, picks in rows:
        draw.text((PAD, y), regime, fill="#111", font=font)
        draw.text((PAD, y + 34),
                  f"{r['video_id']}  {size}px",
                  fill="#555", font=font)
        draw.text((PAD, y + 54),
                  f"θ0={float(r['theta0_deg']):+.0f}°  γ={float(r['damping_s_inv']):.2f}",
                  fill="#555", font=font)
        for i, frame in enumerate(picks):
            x = PAD + LABEL_W + i * (size + GAP)
            sheet.paste(Image.fromarray(np.asarray(frame)), (x, y + 22))
        y += size + GAP + 22

    out = root / "sample_sheet.png"
    sheet.save(out)
    print(f"wrote {out} ({sheet.size[0]}x{sheet.size[1]})")


if __name__ == "__main__":
    main(sys.argv[1] if len(sys.argv) > 1 else ".")