code/visual_attribute_transfer/spot_the_stroke_diff/creation.py

"""Generate 'Spot the Stroke Diff' visual benchmark dataset.

Two panels are shown side by side. Each panel contains the same set of brush
strokes (B-spline curves) at the same positions, but some strokes in the
right panel have a different shape from the corresponding stroke in the left
panel. Each stroke pair is labelled with an uppercase letter (A, B, C, ...)
placed identically in both panels. The task is to list the letters of the
strokes that differ.

Stroke generation is reused from the sibling ``stroke_gesture_count`` task.
"""
from __future__ import annotations

import argparse
import json
import math
import os
import random
import sys
from pathlib import Path
from typing import Any, Dict, List, Tuple

import matplotlib

matplotlib.use("Agg")
import matplotlib.pyplot as plt
import matplotlib.patches as mpatches
import numpy as np
from tqdm import tqdm

# Reuse stroke generation helpers from stroke_gesture_count.
_SIBLING = Path(__file__).resolve().parent.parent / "stroke_gesture_count"
sys.path.insert(0, str(_SIBLING))
from creation import (  # type: ignore  # noqa: E402
    STROKE_WIDTH,
    _curve_bbox,
    _hausdorff_distance,
    _render_curve_on_ax,
    generate_distractor_stroke,
    generate_template_stroke,
)


# ---------------------------------------------------------------------------
# Constants
# ---------------------------------------------------------------------------

NUM_ITEMS = 14
MIN_DIFFS = 4
MAX_DIFFS = 7

PANEL_W = 900
PANEL_H = 900
PADDING = 20
EDGE_PADDING = 20

HAUSDORFF_THRESH = 8.0
HAUSDORFF_MAX = 18.0

BG_COLOR = "#0a1020"
BORDER_COLOR = "#7aa6ff"
BORDER_WIDTH = 2.0
HIGHLIGHT_COLOR = "#dc1e1e"
LABEL_COLOR = "#cfe0ff"
STROKE_LABEL_COLOR = "#ffd24a"
STROKE_LABEL_OFFSET = 14.0
STROKE_LABEL_FONTSIZE = 14

MARGIN_PX = 60
GAP_PX = 100
LABEL_HEIGHT = 44

QUESTION = (
    "Two panels are shown side by side. Each panel contains the same number "
    "of brush strokes at the same positions. Some strokes in the right panel "
    "have a different shape from the corresponding stroke in the left panel. "
    "Count the number of stroke pairs whose shape differs between the two "
    "panels and report the integer count. "
    "Provide your final answer enclosed in <answer>...</answer> tags."
)


# ---------------------------------------------------------------------------
# Geometry helpers
# ---------------------------------------------------------------------------


def _curve_radius(curve: np.ndarray) -> float:
    """Max distance from origin to any point on a centred curve."""
    return float(np.max(np.sqrt((curve * curve).sum(axis=1))))


def _index_to_letters(idx: int) -> str:
    """Convert 0-based index to uppercase spreadsheet-style label.

    0 -> A, 25 -> Z, 26 -> AA, 27 -> AB, ...
    """
    n = idx
    chars: List[str] = []
    while True:
        chars.append(chr(ord("A") + (n % 26)))
        n = n // 26 - 1
        if n < 0:
            break
    return "".join(reversed(chars))


def _compute_label_positions(
    width: int,
    height: int,
    centers: List[Tuple[float, float]],
    curves: List[np.ndarray],
) -> List[Tuple[float, float]]:
    """For each stroke, generate many candidate label positions and pick
    the one that (a) hugs its own stroke, (b) maximally clears every other
    stroke, and (c) doesn't collide with previously-placed labels.

    Strategy: for ~12 anchor points sampled along each stroke, try both
    perpendicular normals at offsets {12, 18, 24, 30}; plus the two
    endpoint-tangent extensions. Filter by hard clearance gates, then
    score by other-stroke clearance and label-label clearance.

    All inputs/outputs are in panel-local pixel coordinates (the panel
    being treated as a (width x height) box).
    """
    own_max = 22.0
    other_clearance = 16.0
    label_clearance = 22.0
    label_half_w = 9.0
    label_half_h = 9.0
    offsets = [12.0, 18.0, 24.0, 30.0]
    n_anchors = 12

    shifted_all = [crv + np.array(ctr) for crv, ctr in zip(curves, centers)]

    positions: List[Tuple[float, float]] = []
    placed_label_pts: List[np.ndarray] = []

    for i, sh in enumerate(shifted_all):
        L = len(sh)
        if L < 4:
            positions.append((float(sh[0, 0]), float(sh[0, 1])))
            placed_label_pts.append(np.array(positions[-1]))
            continue

        anchor_idxs = sorted(set(
            [0, L - 1] +
            [int(round(t * (L - 1)))
             for t in np.linspace(0.0, 1.0, n_anchors)]
        ))

        candidates: List[Tuple[float, float, float]] = []
        for idx in anchor_idxs:
            anchor = sh[idx]
            if idx == 0:
                tan = sh[min(L - 1, 5)] - sh[0]
            elif idx == L - 1:
                tan = sh[L - 1] - sh[max(0, L - 6)]
            else:
                lo = max(0, idx - 3)
                hi = min(L - 1, idx + 3)
                tan = sh[hi] - sh[lo]
            n = float(np.linalg.norm(tan))
            if n < 1e-6:
                continue
            t_unit = tan / n
            normal_l = np.array([-t_unit[1], t_unit[0]])
            normal_r = -normal_l
            directions = [normal_l, normal_r]
            if idx == 0:
                directions.append(-t_unit)
            if idx == L - 1:
                directions.append(t_unit)

            for direction in directions:
                for offset in offsets:
                    pos = anchor + direction * offset
                    px, py = float(pos[0]), float(pos[1])
                    if (px - label_half_w < 4 or px + label_half_w > width - 4 or
                        py - label_half_h < 4 or py + label_half_h > height - 4):
                        continue

                    own_d = float("inf")
                    other_d = float("inf")
                    for j, sh_j in enumerate(shifted_all):
                        diffs = sh_j - np.array([px, py])
                        d = float(np.sqrt((diffs * diffs).sum(axis=1)).min())
                        if j == i:
                            if d < own_d:
                                own_d = d
                        else:
                            if d < other_d:
                                other_d = d

                    if own_d > own_max:
                        continue
                    if other_d < other_clearance:
                        continue

                    label_d = float("inf")
                    for lp in placed_label_pts:
                        d = float(np.hypot(px - lp[0], py - lp[1]))
                        if d < label_d:
                            label_d = d
                    if label_d < label_clearance:
                        continue

                    score = other_d + 0.5 * label_d - 0.4 * offset
                    candidates.append((score, px, py))

        if candidates:
            candidates.sort(reverse=True)
            _, px, py = candidates[0]
            best_pos = (px, py)
        else:
            best_pos = None
            for relax in (0.7, 0.5, 0.3):
                clr = other_clearance * relax
                for idx in anchor_idxs:
                    anchor = sh[idx]
                    for direction_sign in (1, -1):
                        if idx == 0:
                            tan = sh[min(L - 1, 5)] - sh[0]
                        elif idx == L - 1:
                            tan = sh[L - 1] - sh[max(0, L - 6)]
                        else:
                            tan = sh[min(L - 1, idx + 3)] - sh[max(0, idx - 3)]
                        n = float(np.linalg.norm(tan)) or 1.0
                        t_unit = tan / n
                        normal = np.array([-t_unit[1] * direction_sign,
                                           t_unit[0] * direction_sign])
                        for offset in offsets:
                            pos = anchor + normal * offset
                            px, py = float(pos[0]), float(pos[1])
                            if (px - label_half_w < 4 or px + label_half_w > width - 4 or
                                py - label_half_h < 4 or py + label_half_h > height - 4):
                                continue
                            other_d = min(
                                float(np.sqrt(((sh_j - np.array([px, py])) ** 2).sum(axis=1)).min())
                                for j, sh_j in enumerate(shifted_all) if j != i
                            )
                            if other_d >= clr:
                                best_pos = (px, py)
                                break
                        if best_pos:
                            break
                    if best_pos:
                        break
                if best_pos:
                    break
            if best_pos is None:
                ep = sh[-1]
                best_pos = (
                    float(np.clip(ep[0] + 16, 4 + label_half_w, width - 4 - label_half_w)),
                    float(np.clip(ep[1], 4 + label_half_h, height - 4 - label_half_h)),
                )

        positions.append(best_pos)
        placed_label_pts.append(np.array(best_pos))

    return positions


# ---------------------------------------------------------------------------
# Stroke sampling / swapping
# ---------------------------------------------------------------------------


def _generate_stroke(rng: random.Random) -> np.ndarray:
    _cp, curve = generate_template_stroke(rng)
    return curve


def _sample_different_stroke(
    rng: random.Random,
    old: np.ndarray,
    old_radius: float,
    max_tries: int = 200,
) -> np.ndarray:
    """Sample a new stroke with Hausdorff distance >= HAUSDORFF_THRESH from
    ``old`` and bounding radius not larger than ``old_radius``."""
    for _ in range(max_tries):
        try:
            _cp, cand = generate_distractor_stroke(
                rng, old, min_hausdorff=HAUSDORFF_THRESH,
                max_hausdorff=HAUSDORFF_MAX,
            )
        except RuntimeError:
            continue
        if _curve_radius(cand) <= old_radius:
            return cand
    raise RuntimeError("Could not sample a sufficiently different stroke.")


# ---------------------------------------------------------------------------
# Layout
# ---------------------------------------------------------------------------


def _place_items(
    rng: random.Random,
    radii: List[float],
    max_tries_per_item: int = 5000,
) -> List[Tuple[float, float]]:
    order = sorted(range(len(radii)), key=lambda i: -radii[i])
    centers: List[Tuple[float, float] | None] = [None] * len(radii)

    for i in order:
        r = radii[i]
        placed = False
        for _ in range(max_tries_per_item):
            x = rng.uniform(r + EDGE_PADDING, PANEL_W - r - EDGE_PADDING)
            y = rng.uniform(r + EDGE_PADDING, PANEL_H - r - EDGE_PADDING)
            ok = True
            for j, c in enumerate(centers):
                if c is None or j == i:
                    continue
                min_dist = radii[i] + radii[j] + PADDING
                dx = x - c[0]
                dy = y - c[1]
                if dx * dx + dy * dy < min_dist * min_dist:
                    ok = False
                    break
            if ok:
                centers[i] = (x, y)
                placed = True
                break
        if not placed:
            raise RuntimeError(f"Could not place stroke {i} (r={r:.1f}) without overlap.")
    return [c for c in centers]  # type: ignore[return-value]


# ---------------------------------------------------------------------------
# Sample construction
# ---------------------------------------------------------------------------


def build_sample(
    rng: random.Random,
    num_items: int,
    num_diffs: int,
) -> Tuple[List[Dict[str, Any]], List[Dict[str, Any]]]:
    left_strokes = [_generate_stroke(rng) for _ in range(num_items)]
    radii = [_curve_radius(s) for s in left_strokes]

    right_strokes: List[np.ndarray] = [s.copy() for s in left_strokes]
    changed_idx = rng.sample(range(num_items), num_diffs)
    for i in changed_idx:
        right_strokes[i] = _sample_different_stroke(rng, left_strokes[i], radii[i])

    centers = _place_items(rng, radii)
    changed_set = set(changed_idx)

    # Compute label positions in panel-local coords using the LEFT stroke set
    # as geometry reference. The same (px, py) is used in both panels.
    label_positions = _compute_label_positions(
        PANEL_W, PANEL_H, centers, left_strokes
    )

    items: List[Dict[str, Any]] = []
    for i in range(num_items):
        x, y = centers[i]
        lx, ly = label_positions[i]
        items.append({
            "index": i,
            "label": _index_to_letters(i),
            "x": x,
            "y": y,
            "bounding_radius": radii[i],
            "left_curve": left_strokes[i],
            "right_curve": right_strokes[i],
            "changed": i in changed_set,
            "label_pos": (lx, ly),
        })

    diffs: List[Dict[str, Any]] = [
        {
            "index": i,
            "label": items[i]["label"],
            "x": items[i]["x"],
            "y": items[i]["y"],
            "bounding_radius": items[i]["bounding_radius"],
        }
        for i in sorted(changed_idx)
    ]
    return items, diffs


# ---------------------------------------------------------------------------
# Rendering
# ---------------------------------------------------------------------------


def _panel_origins() -> Tuple[Tuple[float, float], Tuple[float, float]]:
    oy = MARGIN_PX + LABEL_HEIGHT
    ox_left = MARGIN_PX
    ox_right = MARGIN_PX + PANEL_W + GAP_PX
    return (ox_left, oy), (ox_right, oy)


def _canvas_size() -> Tuple[int, int]:
    w = MARGIN_PX + PANEL_W + GAP_PX + PANEL_W + MARGIN_PX
    h = MARGIN_PX + LABEL_HEIGHT + PANEL_H + MARGIN_PX
    return w, h


def _draw_panel(
    ax: plt.Axes,
    items: List[Dict[str, Any]],
    side: str,
    ox: float,
    oy: float,
) -> None:
    key = "left_curve" if side == "left" else "right_curve"
    for it in items:
        center = np.array([ox + it["x"], oy + it["y"]])
        _render_curve_on_ax(ax, it[key], center, color="white", linewidth=STROKE_WIDTH)
    # Letter labels removed: task is now a count, not a label list.


def _render(
    out_path: Path,
    items: List[Dict[str, Any]],
    diffs: List[Dict[str, Any]] | None = None,
) -> None:
    w, h = _canvas_size()
    dpi = 100
    fig, ax = plt.subplots(1, 1, figsize=(w / dpi, h / dpi), dpi=dpi)
    ax.set_xlim(0, w)
    ax.set_ylim(h, 0)
    ax.set_aspect("equal")
    ax.axis("off")
    fig.patch.set_facecolor(BG_COLOR)
    ax.set_facecolor(BG_COLOR)

    (ox_left, oy), (ox_right, _) = _panel_origins()

    for ox in (ox_left, ox_right):
        border = mpatches.Rectangle(
            (ox, oy), PANEL_W, PANEL_H,
            facecolor="none", edgecolor=BORDER_COLOR,
            linewidth=BORDER_WIDTH, zorder=1,
        )
        ax.add_patch(border)

    _draw_panel(ax, items, "left", ox_left, oy)
    _draw_panel(ax, items, "right", ox_right, oy)

    ax.text(
        ox_left + PANEL_W / 2, MARGIN_PX + LABEL_HEIGHT * 0.5,
        "Left", ha="center", va="center",
        fontsize=16, fontweight="bold", color=LABEL_COLOR,
    )
    ax.text(
        ox_right + PANEL_W / 2, MARGIN_PX + LABEL_HEIGHT * 0.5,
        "Right", ha="center", va="center",
        fontsize=16, fontweight="bold", color=LABEL_COLOR,
    )

    if diffs:
        for diff in diffs:
            hl_r = diff["bounding_radius"] + 14
            for ox in (ox_left, ox_right):
                cx = ox + diff["x"]
                cy = oy + diff["y"]
                ring = mpatches.Circle(
                    (cx, cy), hl_r,
                    facecolor="none", edgecolor=HIGHLIGHT_COLOR,
                    linewidth=2.5, zorder=10,
                )
                ax.add_patch(ring)

    fig.savefig(out_path, facecolor=BG_COLOR)
    plt.close(fig)


def render_pair(out_path: Path, items: List[Dict[str, Any]]) -> None:
    _render(out_path, items)


def render_answer(
    out_path: Path,
    items: List[Dict[str, Any]],
    diffs: List[Dict[str, Any]],
) -> None:
    _render(out_path, items, diffs)


# ---------------------------------------------------------------------------
# Annotation
# ---------------------------------------------------------------------------


def _answer_string(diffs: List[Dict[str, Any]]) -> str:
    return str(len(diffs))


def build_annotation(
    image_name: str,
    items: List[Dict[str, Any]],
    diffs: List[Dict[str, Any]],
) -> Dict[str, Any]:
    return {
        "image": image_name,
        "num_items": len(items),
        "num_differences": len(diffs),
        "differences": diffs,
        "question": QUESTION,
        "answer": _answer_string(diffs),
    }


# ---------------------------------------------------------------------------
# Dataset generation
# ---------------------------------------------------------------------------


def generate_dataset(
    rng: random.Random,
    count: int,
    output_dir: Path,
    num_items: int = NUM_ITEMS,
    min_diffs: int = MIN_DIFFS,
    max_diffs: int = MAX_DIFFS,
) -> None:
    images_dir = output_dir / "images"
    answers_dir = output_dir / "answers"
    images_dir.mkdir(parents=True, exist_ok=True)
    answers_dir.mkdir(parents=True, exist_ok=True)

    annotations: List[Dict[str, Any]] = []
    data_items: List[Dict[str, Any]] = []

    if count > 1:
        forced = [int(round(min_diffs + i * (max_diffs - min_diffs) / (count - 1))) for i in range(count)]
    else:
        forced = [min_diffs]
    print(f"forced stroke diff counts: {forced}")

    for idx in tqdm(range(count), desc="Generating stroke diff pairs"):
        num_diffs = forced[idx]
        for _ in range(30):
            try:
                items, diffs = build_sample(rng, num_items, num_diffs)
                break
            except RuntimeError:
                continue
        else:
            raise RuntimeError(f"Failed to build sample {idx} after many retries")

        image_name = f"stroke_diff_{idx:05d}.png"
        img_path = images_dir / image_name
        ans_path = answers_dir / image_name

        render_pair(img_path, items)
        render_answer(ans_path, items, diffs)

        rel_image = f"images/{image_name}"
        annotations.append(build_annotation(rel_image, items, diffs))
        data_items.append({
            "image": rel_image,
            "question": QUESTION,
            "answer": _answer_string(diffs),
        })

    with (output_dir / "annotations.jsonl").open("w", encoding="utf-8") as fh:
        for rec in annotations:
            fh.write(json.dumps(rec) + "\n")

    data_json = {
        "task": "spot_the_stroke_diff",
        "category": "visual_attribute_transfer",
        "count": len(data_items),
        "items": data_items,
    }
    with (output_dir / "data.json").open("w", encoding="utf-8") as fh:
        json.dump(data_json, fh, indent=2)
        fh.write("\n")


# ---------------------------------------------------------------------------
# CLI
# ---------------------------------------------------------------------------


def parse_args() -> argparse.Namespace:
    p = argparse.ArgumentParser(
        description="Generate 'Spot the Stroke Diff' visual benchmark dataset."
    )
    p.add_argument("--output-root", type=Path, default=".")
    p.add_argument("--count", type=int, default=20)
    p.add_argument("--seed", type=int, default=42)
    p.add_argument("--difficulty", type=int, default=5,
                   help="Integer difficulty >=0; scales diff count and stroke subtlety.")
    p.add_argument("--workers", type=int, default=8)
    return p.parse_args()


def main() -> None:
    args = parse_args()
    rng = random.Random(args.seed)
    d = max(0, int(args.difficulty))

    N_d = 10 + 2 * d
    N_0 = 10
    s = math.sqrt(max(1.0, N_d / N_0))
    global PANEL_W, PANEL_H
    PANEL_W = int(round(PANEL_W * s))
    PANEL_H = int(round(PANEL_H * s))

    global HAUSDORFF_THRESH, HAUSDORFF_MAX
    HAUSDORFF_THRESH = max(8.0, 12.0 - 0.4 * d)
    HAUSDORFF_MAX = max(HAUSDORFF_THRESH + 10.0, 40.0 - 1.0 * d)

    stroke_count = 10 + 2 * d
    min_diffs = 5
    max_diffs = 5 + 2 * d

    sys.path.insert(0, str(Path(__file__).resolve().parents[3]))
    from _sample_pool import parallel_sample_records  # noqa: E402

    # Force evenly-spaced num_diffs across [min_diffs, max_diffs].
    if args.count > 1:
        forced_targets = [
            int(round(min_diffs + i * (max_diffs - min_diffs) / (args.count - 1)))
            for i in range(args.count)
        ]
    else:
        forced_targets = [min_diffs]
    print(f"forced stroke_diff num_diffs: {forced_targets}")

    output_dir = args.output_root
    images_dir = output_dir / "images"
    answers_dir = output_dir / "answers"
    images_dir.mkdir(parents=True, exist_ok=True)
    answers_dir.mkdir(parents=True, exist_ok=True)

    raw = []
    for ti, tgt in enumerate(forced_targets):
        def _attempt(rng, _tgt=tgt):
            try:
                items, diffs = build_sample(rng, stroke_count, _tgt)
                if len(diffs) != _tgt:
                    return None
                return (items, diffs)
            except RuntimeError:
                return None
        sub = parallel_sample_records(
            _attempt, count=1, workers=args.workers,
            seed_base=args.seed + ti * 977,
        )
        raw.extend(sub)

    annotations = []
    data_items = []
    for idx, (items, diffs) in enumerate(raw):
        image_name = f"stroke_diff_{idx:05d}.png"
        img_path = images_dir / image_name
        ans_path = answers_dir / image_name
        render_pair(img_path, items)
        render_answer(ans_path, items, diffs)
        rel_image = f"images/{image_name}"
        annotations.append(build_annotation(rel_image, items, diffs))
        data_items.append({
            "image": rel_image, "question": QUESTION,
            "answer": _answer_string(diffs),
        })

    with (output_dir / "annotations.jsonl").open("w", encoding="utf-8") as fh:
        for rec in annotations:
            fh.write(json.dumps(rec) + "\n")
    (output_dir / "data.json").write_text(json.dumps({
        "task": "spot_the_stroke_diff",
        "category": "visual_attribute_transfer",
        "count": len(data_items),
        "items": data_items,
    }, indent=2))
    print(f"Saved {len(data_items)} image pairs to {output_dir} (workers={args.workers})")


if __name__ == "__main__":
    main()