#include <GLFW/glfw3.h>
#include <iostream>
#include <cmath>

void setPixel(int x, int y)
{
    float pixel_x = float(x)/1000.0;
    float pixel_y = float(y)/1000.0;

    glBegin(GL_POINTS);
    glVertex2f(pixel_x, pixel_y);
    glEnd();
    glFlush();

}

void drawBresenhamLine(int x1, int y1, int x2, int y2)
{
    /*
    В переменных x и y хранятся текущие значения координаты точки
    dx , dy - разница по иксу и по игрику
    d = (dy * 2) - dx
    d1 = dy * 2
    d2 = (dy - dx) * 2
    */
    int x, y, dx = x2 - x1, dy = y2 - y1;
    int d = (dy * 2) - dx, d1 = dy * 2, d2 = (dy - dx) * 2;
    x = x1, y = y1;
    setPixel(x1, y1);
    setPixel(x2, y2);
    x2--;
    while (x < x2)
    {
        x++;
        if (d < 0) d += d1;
        else
        {
            y++;
            d += d2;
        }
        setPixel(x, -y);

    }
}

void drawLine(int x1, int y1, int x2, int y2) {
    const int deltaX = abs(x2 - x1);
    const int deltaY = abs(y2 - y1);
    const int signX = x1 < x2 ? 1 : -1;
    const int signY = y1 < y2 ? 1 : -1;
    //
    int error = deltaX - deltaY;
    //
    setPixel(x2, y2);
    while (x1 != x2 || y1 != y2)
    {
        setPixel(x1, y1);
        const int error2 = error * 2;
        //
        if (error2 > -deltaY)
        {
            error -= deltaY;
            x1 += signX;
        }
        if (error2 < deltaX)
        {
            error += deltaX;
            y1 += signY;
        }
    }

}


void drawCircle(int x0, int y0, int radius) {
    int x = 0;
    int y = radius;
    int delta = 1 - 2 * radius;
    int error = 0;
    while (y >= 0) {
        //setPixel(x0 + x, y0 + y); //1-2
        setPixel(x0 + x, y0 - y); // 7-8
        //setPixel(x0 - x, y0 + y); // 3-4
        //setPixel(x0 - x, y0 - y); // 5-6
        error = 2 * (delta + y) - 1;
        if (delta < 0 && error <= 0) {
            ++x;
            delta += 2 * x + 1;
            continue;
        }
        error = 2 * (delta - x) - 1;
        if (delta > 0 && error > 0) {
            --y;
            delta += 1 - 2 * y;
            continue;
        }
        ++x;
        delta += 2 * (x - y);
        --y;
    }
}


int main(void)
{
    GLFWwindow* window;

    if (!glfwInit())
        return -1;

    window = glfwCreateWindow(1000, 1000, "Hello World", NULL, NULL);
    if (!window)
    {
        glfwTerminate();
        return -1;
    }

    glfwMakeContextCurrent(window);

    while (!glfwWindowShouldClose(window))
    {
        //drawBresenhamLine(0, 0, 1000, 1000);
        drawLine(0, 0, 500, -1000);

        drawCircle(0, 0, 500);
        //glClear(GL_COLOR_BUFFER_BIT);

        glfwSwapBuffers(window);

        glfwPollEvents();
    }

    glfwTerminate();
    return 0;
}