"""
滑块轨迹生成工具

生成模拟人类操作的滑块拖拽轨迹。
"""

import math
import random


def generate_slide_track(
    distance: int,
    duration: float = 1.0,
    seed: int | None = None,
) -> list[dict]:
    """
    生成滑块拖拽轨迹。

    使用贝塞尔曲线 ease-out 加速减速，末尾带微小过冲回退。
    y 轴 ±1~3px 随机抖动，时间间隔不均匀。

    Args:
        distance: 滑动距离 (像素)
        duration: 总时长 (秒)
        seed:     随机种子

    Returns:
        [{"x": float, "y": float, "t": float}, ...]
    """
    rng = random.Random(seed)

    if distance <= 0:
        return [{"x": 0.0, "y": 0.0, "t": 0.0}]

    track = []
    # 采样点数
    num_points = rng.randint(30, 60)
    total_ms = duration * 1000

    # 生成不均匀时间点
    raw_times = sorted([rng.random() for _ in range(num_points - 2)])
    times = [0.0] + raw_times + [1.0]

    # 过冲距离
    overshoot = rng.uniform(2, 6)
    overshoot_start = 0.85  # 85% 时到达目标 + 过冲

    for t_norm in times:
        t_ms = round(t_norm * total_ms, 1)

        if t_norm <= overshoot_start:
            # ease-out: 快速启动，缓慢减速
            progress = t_norm / overshoot_start
            eased = 1 - (1 - progress) ** 3  # cubic ease-out
            x = eased * (distance + overshoot)
        else:
            # 过冲回退段
            retract_progress = (t_norm - overshoot_start) / (1 - overshoot_start)
            eased_retract = retract_progress ** 2  # ease-in 回退
            x = (distance + overshoot) - overshoot * eased_retract

        # y 轴随机抖动
        y_jitter = rng.uniform(-3, 3) if t_norm > 0.05 else 0.0

        track.append({
            "x": round(x, 1),
            "y": round(y_jitter, 1),
            "t": t_ms,
        })

    # 确保最后一个点精确到达目标
    track[-1]["x"] = float(distance)
    track[-1]["y"] = round(rng.uniform(-0.5, 0.5), 1)

    return track