scripts/generate_path_data.py

"""
Programmatic path tracing data generation.

Generates images with curved lines that connect start/end icons.
The model must trace the line using visual primitives (points).
"""

import argparse
import json
import random
import math
from pathlib import Path
from typing import List, Tuple
import numpy as np
from PIL import Image, ImageDraw


def _de_casteljau(control_points: List[Tuple[float, float]], t: float) -> Tuple[float, float]:
    """Evaluate a Bézier curve at parameter t using De Casteljau's algorithm."""
    pts = list(control_points)
    while len(pts) > 1:
        pts = [
            ((1 - t) * pts[i][0] + t * pts[i + 1][0],
             (1 - t) * pts[i][1] + t * pts[i + 1][1])
            for i in range(len(pts) - 1)
        ]
    return pts[0]


def generate_curve(
    start: Tuple[int, int],
    end: Tuple[int, int],
    num_control_points: int = 3,
    curvature: float = 1.0,
) -> List[Tuple[int, int]]:
    """Generate a smooth curved path from start to end using Bézier curves.

    Per the paper: "We generate images which consist of multiple Bézier curves."
    Uses De Casteljau's algorithm for evaluation.
    """
    # Build control points: start, random intermediates, end
    control_pts = [start]
    for _ in range(num_control_points):
        # Interpolate between start and end, then add random offset for curvature
        frac = random.random()
        base_x = start[0] + frac * (end[0] - start[0])
        base_y = start[1] + frac * (end[1] - start[1])
        offset_x = (random.random() - 0.5) * curvature * 200
        offset_y = (random.random() - 0.5) * curvature * 200
        x = max(0, min(999, int(base_x + offset_x)))
        y = max(0, min(999, int(base_y + offset_y)))
        control_pts.append((x, y))
    control_pts.append(end)

    # Sort intermediate control points by their projection onto start->end axis
    # to avoid self-intersecting curves
    if len(control_pts) > 2:
        dx = end[0] - start[0]
        dy = end[1] - start[1]
        length_sq = dx * dx + dy * dy
        if length_sq > 0:
            intermediates = control_pts[1:-1]
            intermediates.sort(key=lambda p: ((p[0] - start[0]) * dx + (p[1] - start[1]) * dy) / length_sq)
            control_pts = [start] + intermediates + [end]

    # Evaluate Bézier curve at uniform parameter values
    n_segments = 50
    path = []
    for i in range(n_segments + 1):
        t = i / n_segments
        x, y = _de_casteljau(control_pts, t)
        path.append((int(x), int(y)))
    return path


def generate_crossing_lines(
    img_size: int = 800,
    num_lines: int = 3,
    uniform_style: bool = False,
) -> Tuple[Image.Image, List[Tuple[int, int]], str, str]:
    """
    Generate an image with multiple curved Bézier lines crossing each other.

    Args:
        uniform_style: If True, all lines share the same color and stroke width,
            stripping away color-based shortcuts and forcing the model to rely
            solely on curvature continuity at crossings (per paper).

    Returns:
      image, target_path_points, start_label, end_label
    """
    img = Image.new("RGB", (img_size, img_size), "white")
    draw = ImageDraw.Draw(img)

    # Generate background noise
    for _ in range(100):
        x, y = random.randint(0, img_size - 1), random.randint(0, img_size - 1)
        draw.point((x, y), fill=(240, 240, 240))

    lines = []
    labels_pool = ["crown", "octopus", "star", "heart", "diamond", "club", "spade",
                   "moon", "sun", "cloud", "tree", "flower", "fish", "bird"]
    chosen_labels = random.sample(labels_pool, num_lines + 1)

    # Uniform style: same color and width for all lines
    if uniform_style:
        uniform_color = "black"
        uniform_width = 3
    else:
        uniform_color = None
        uniform_width = None

    for i in range(num_lines):
        start = (random.randint(50, img_size - 50), random.randint(50, img_size - 50))
        end = (random.randint(50, img_size - 50), random.randint(50, img_size - 50))
        path = generate_curve(start, end, num_control_points=random.randint(2, 5))
        color = uniform_color if uniform_style else random.choice(
            ["red", "blue", "green", "purple", "orange", "black"])
        width = uniform_width if uniform_style else random.randint(2, 4)
        lines.append({
            "path": path, "color": color, "width": width,
            "start": chosen_labels[i], "end": chosen_labels[i + 1],
        })

    # Draw all lines
    for line in lines:
        pts = line["path"]
        # Scale to image size
        img_pts = [(int(x / 999 * img_size), int(y / 999 * img_size)) for x, y in pts]
        draw.line(img_pts, fill=line["color"], width=line["width"])

    # Pick one line as target
    target = random.choice(lines)
    # Draw start/end icons as simple text markers
    sx, sy = target["path"][0]
    ex, ey = target["path"][-1]
    sx_img = int(sx / 999 * img_size)
    sy_img = int(sy / 999 * img_size)
    ex_img = int(ex / 999 * img_size)
    ey_img = int(ey / 999 * img_size)
    draw.text((sx_img - 10, sy_img - 10), target["start"][:2].upper(), fill="black")
    draw.text((ex_img - 10, ey_img - 10), target["end"][:2].upper(), fill="black")

    return img, target["path"], target["start"], target["end"]


def generate_path_thinking(path: List[Tuple[int, int]], start_label: str, end_label: str) -> str:
    """Generate thinking content with point visual primitives tracing the path."""
    lines = []
    sx, sy = path[0]
    ex, ey = path[-1]
    lines.append(f"I find the starting point you mentioned, it's located here: <|point|>[[{sx},{sy}]]<|/point|>.")
    lines.append("Following this line, the visual path I observe is:")
    # Sample points adaptively: fewer for straight segments, more for curves
    sampled = [path[0]]
    for i in range(1, len(path)):
        prev = sampled[-1]
        curr = path[i]
        dist = math.hypot(curr[0] - prev[0], curr[1] - prev[1])
        # Adaptive sampling: if distance > threshold, add point
        if dist > 20 or i == len(path) - 1:
            sampled.append(curr)

    pt_str = ",".join(f"[{x},{y}]" for x, y in sampled)
    lines.append(f"<|point|>[{pt_str}]<|/point|>")
    lines.append(f"Following this path, it connects to: <|point|>[[{ex},{ey}]]<|/point|>.")
    return "\n".join(lines)


def main():
    parser = argparse.ArgumentParser()
    parser.add_argument("--output_dir", type=str, default="data/sft/path")
    parser.add_argument("--num_samples", type=int, default=1000)
    parser.add_argument("--min_lines", type=int, default=2)
    parser.add_argument("--max_lines", type=int, default=5)
    parser.add_argument("--seed", type=int, default=42)
    args = parser.parse_args()

    random.seed(args.seed)
    np.random.seed(args.seed)

    out_dir = Path(args.output_dir)
    out_dir.mkdir(parents=True, exist_ok=True)
    img_dir = out_dir / "images"
    img_dir.mkdir(exist_ok=True)

    records = []
    for i in range(args.num_samples):
        num_lines = random.randint(args.min_lines, args.max_lines)
        # 30% of samples use uniform style (per paper: forces curvature-based reasoning)
        use_uniform = random.random() < 0.3
        img, path, start_label, end_label = generate_crossing_lines(
            num_lines=num_lines, uniform_style=use_uniform)
        img_path = img_dir / f"path_{i:06d}.png"
        img.save(img_path)

        thinking = generate_path_thinking(path, start_label, end_label)
        question = f"Where does the {start_label} icon connect to? Put the destination icon name in \\boxed{{}}."
        answer = f"\\boxed{{{end_label}}}"

        records.append({
            "image": str(img_path.relative_to(out_dir)),
            "question": question,
            "thinking": thinking,
            "start_label": start_label,
            "end_label": end_label,
            "answer": answer,
        })

    with open(out_dir / "path_data.jsonl", "w") as f:
        for rec in records:
            f.write(json.dumps(rec, ensure_ascii=False) + "\n")

    print(f"Generated {args.num_samples} path tracing samples in {out_dir}")


if __name__ == "__main__":
    main()