# /// script
# requires-python = ">=3.11"
# dependencies = ["numpy", "matplotlib"]
# ///

import numpy as np
import matplotlib.pyplot as plt

plt.rcParams["font.sans-serif"] = [
    "WenQuanYi Micro Hei",
    "Noto Sans CJK SC",
    "Microsoft YaHei",
    "DejaVu Sans",
]
plt.rcParams["axes.unicode_minus"] = False

fig, ax = plt.subplots(figsize=(10, 7), dpi=150)

x = np.linspace(-1, 5, 500)
y = -2 * x**2 + 8 * x - 3

ax.plot(x, y, "b-", linewidth=2, label="$y = -2x^2 + 8x - 3$")

vertex_x, vertex_y = 2, 5
ax.scatter(
    [vertex_x],
    [vertex_y],
    color="red",
    s=150,
    zorder=5,
    label=f"顶点 ({vertex_x}, {vertex_y})",
)
ax.annotate(
    f"顶点 ({vertex_x}, {vertex_y})\n最大值: y = {vertex_y}",
    xy=(vertex_x, vertex_y),
    xytext=(vertex_x + 0.8, vertex_y + 1.5),
    fontsize=11,
    ha="left",
    arrowprops=dict(arrowstyle="->", color="red", lw=1.5),
    bbox=dict(boxstyle="round,pad=0.3", facecolor="yellow", alpha=0.7),
)

ax.axhline(y=0, color="gray", linestyle="--", linewidth=1, alpha=0.7)
ax.axvline(x=0, color="gray", linestyle="--", linewidth=1, alpha=0.7)
ax.axvline(
    x=vertex_x,
    color="green",
    linestyle=":",
    linewidth=1.5,
    alpha=0.7,
    label=f"对称轴 x = {vertex_x}",
)

ax.set_xlabel("x", fontsize=12)
ax.set_ylabel("y", fontsize=12)
ax.set_title("二次函数 $y = -2x^2 + 8x - 3$ 的图像", fontsize=14, fontweight="bold")
ax.legend(loc="upper right", fontsize=10)
ax.grid(True, alpha=0.3)

ax.set_xlim(-0.5, 5.5)
ax.set_ylim(-6, 8)

plt.tight_layout()
plt.savefig("figure.png", bbox_inches="tight", dpi=150)
plt.close()
print("图像已保存: figure.png")