from manim import *


class SineDefinition(Scene):
    def construct(self):
        # 第一部分：标题淡入（2秒）
        title = Text("正弦函数的几何意义", font_size=48, color=BLUE)
        self.play(FadeIn(title, run_time=2))
        self.wait(0.5)
        self.play(FadeOut(title, run_time=0.5))

        # 第二部分：直角三角形展示（5秒）
        # 创建三角形和标签
        triangle = Polygon(ORIGIN, [3, 0, 0], [3, 2, 0], color=WHITE)
        opposite = Line([3, 0, 0], [3, 2, 0], color=GREEN)
        hypotenuse = Line(ORIGIN, [3, 2, 0], color=RED)
        angle_arc = Arc(radius=0.5, start_angle=0, angle=PI / 3.5, color=YELLOW)
        theta = MathTex(r"\theta", color=YELLOW).next_to(angle_arc, DOWN, buff=0.1)

        # 添加标签文本
        opposite_label = Text("对边", color=GREEN).next_to(opposite, RIGHT, buff=0.1)
        hypotenuse_label = Text("斜边", color=RED).next_to(hypotenuse, UP, buff=0.2).shift(LEFT * 0.5)

        # 动画展示
        self.play(Create(triangle), run_time=1)
        self.play(Create(angle_arc), Write(theta), run_time=1)
        self.play(Create(opposite), Write(opposite_label), run_time=1.5)
        self.play(Create(hypotenuse), Write(hypotenuse_label), run_time=1.5)
        self.wait(0.5)

        # 第三部分：单位圆动态演示（8秒）
        # 创建坐标系
        axes = Axes(
            x_range=[-1.5, 1.5],
            y_range=[-1.5, 1.5],
            axis_config={"color": BLUE},
            x_length=5,
            y_length=5
        )
        axes_labels = axes.get_axis_labels(
            x_label=Text("角度 θ", font_size=32),
            y_label=Text("正弦值", font_size=32)
        )

        # 创建单位圆
        unit_circle = Circle(radius=1, color=WHITE)
        radius_vector = Line(ORIGIN, [1, 0, 0], color=RED)

        # 创建正弦曲线坐标系
        sin_axes = Axes(
            x_range=[0, 2 * PI, PI / 2],
            y_range=[-1, 1, 0.5],
            x_length=5,
            y_length=3,
            axis_config={"color": BLUE}
        ).to_edge(RIGHT)
        sin_axes_labels = sin_axes.get_axis_labels(
            x_label=Text("角度 θ", font_size=32),
            y_label=Text("正弦值", font_size=32)
        )

        # 动画转换
        self.play(
            ReplacementTransform(triangle, unit_circle),
            ReplacementTransform(hypotenuse, radius_vector),
            FadeOut(opposite),
            FadeOut(angle_arc),
            FadeOut(theta),
            FadeOut(opposite_label),
            FadeOut(hypotenuse_label),
            run_time=2
        )
        self.play(
            Create(axes),
            Create(sin_axes),
            Write(axes_labels),
            Write(sin_axes_labels),
            run_time=2
        )

        # 动态轨迹
        dot = Dot(color=YELLOW)
        sin_dot = Dot(color=YELLOW)
        trace = TracedPath(dot.get_center, stroke_color=YELLOW, stroke_width=4)

        # 更新函数
        def update_dot(mob, alpha):
            angle = alpha * 2 * PI
            x = np.cos(angle)
            y = np.sin(angle)
            mob.move_to(axes.c2p(x, y))

            sin_x = alpha * 2 * PI
            sin_y = np.sin(angle)
            sin_dot.move_to(sin_axes.c2p(sin_x, sin_y))
            return mob

        # 运行动画
        self.add(trace, dot, sin_dot)
        self.play(
            UpdateFromAlphaFunc(dot, update_dot),
            rate_func=linear,
            run_time=8
        )
        self.remove(trace, dot, sin_dot)

        # 第四部分：总结公式（3秒）
        formula = MathTex(r"\sin\theta = \frac{\text{对边}}{\text{斜边}}", font_size=60)
        formula.set_color_by_tex("对边", GREEN)
        formula.set_color_by_tex("斜边", RED)
        self.play(Write(formula), run_time=2)
        self.wait(1)

        # 末尾静止帧（3秒）
        self.wait(3)


if __name__ == "__main__":
    scene = SineDefinition()
    scene.render()