from manim import *

def area_rect(mob):
    height = np.linalg.norm(mob.get_right()[1] - mob.get_right()[0])
    width = np.linalg.norm(mob.get_right()[2] - mob.get_right()[1])
    s = height * width
    return s

class GraphAreaPlot(Scene):
    def construct(self):
        ax = Axes(
            x_range=[-3, 3],
            y_range=[-1.5, 1.5],
            x_axis_config={
                "numbers_to_include": [-1, 1],
                "tip_width": 0.15,
                "tip_height": 0.15,
                "tick_size": 0.08
                },
            y_axis_config={
                "tip_width": 0.15,
                "tip_height": 0.15,
                "tick_size": 0.08
                }
        )
        labels = ax.get_axis_labels()
        # график функции
        graph = ax.plot(lambda x: np.cos(x), x_range=[-3, 3], color=BLUE_B)
        # Разбиения
        dx = ValueTracker(0.3)
        riemann_area = always_redraw(lambda:
            ax.get_riemann_rectangles(
                graph,
                x_range=[0, 0.5 * PI],
                dx=dx.get_value(),
                color=TEAL_A,
                fill_opacity=0.9,
                stroke_width=0.2,
                input_sample_type="right"
            )
        )
        # счетчик разбиений
        num = always_redraw(
            lambda: MathTex("n =", str(round(len(riemann_area), 0))
            ).to_edge(UR)
        )
        num[1].add_updater(
            lambda num: num.become(Tex(str(round(len(riemann_area), 0))).next_to(num[0], RIGHT, buff = 0.05)))

        # счетчик площади
        counter = area_rect(mob = riemann_area[0])
        for i in range(len(riemann_area)):
            s = area_rect(mob = riemann_area[i])
            counter += s

        num_S = always_redraw(
            lambda: MathTex(
                "S =",
                str(round(counter, 2)
            )
        ).next_to(num, DOWN, aligned_edge=RIGHT))
        num_S[1].add_updater(
            lambda num: num.become(Tex(str(round(counter, 2))).next_to(num[0], RIGHT, buff = 0.05)))



        self.add(ax, labels)
        self.add(graph, riemann_area, num, num_S)
        self.play(dx.animate.set_value(0.2), run_time = 10)
        self.wait()