using System;
using System.Collections.Generic;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace LR2
{
    class SeidelMethod
    {
        PictureBox pictureBox;
        RichTextBox richTextBox;
        Graphics g;
        float scale = 35;

        public SeidelMethod(PictureBox pictureBox, RichTextBox richTextBox, float scale = 35)
        {
            this.scale = scale;
            this.pictureBox = pictureBox;
            this.richTextBox = richTextBox;
            if (pictureBox != null)
            {
                g = pictureBox.CreateGraphics();
                g.TranslateTransform(pictureBox.Width / 2, pictureBox.Height / 2);
                g.Clear(Color.White);
                g.DrawLine(Pens.Black, 0, -200, 0, 200);
                g.DrawLine(Pens.Black, -200, 0, 200, 0);
                drawGraphic();
            }
        }

        public void solve(double eps, PointF startPoint)
        {
            richTextBox.Text = string.Empty;
            double x1_start = startPoint.X;
            double x2_start = startPoint.Y;

            double curX1 = 1e9;
            double curX2 = 1e9;

            double nextX1 = x1_start;
            double nextX2 = x2_start;

            richTextBox.Text += "x(k1) = " + nextX1.ToString() + ";\nx(k2) = " + nextX2 + ";\n\n";
            int nIter = 0;
            while (Math.Max(Math.Abs(nextX1 - curX1), Math.Abs(nextX2 - curX2)) > eps)
            {
                curX1 = nextX1;
                curX2 = nextX2;
                nextX1 = (1 - curX2 * curX2) / 2;
                nextX2 = -1 * (nextX1 * nextX1) - 1; //Если просто МПИ, то curX1 (только предыдущая итерация)

                if (nIter > 50 || Math.Abs(nextX1) > 1e6 || Math.Abs(nextX2) > 1e6)
                {
                    MessageBox.Show("Метод Зейделя не сходится");
                    return;
                }

                g.DrawLine(Pens.Black, (float)(scale * curX1), (float)(-scale * curX2), (float)(nextX1 * scale), (float)(-nextX2 * scale));
                g.FillEllipse(Brushes.Red, (float)(nextX1 * scale - 2), (float)(-nextX2 * scale - 2), 4, 4);
                richTextBox.Text += "x(k1) = " + nextX1.ToString() + ";\nx(k2) = " + nextX2 + ";\n\n";
                ++nIter;
            }

            g.FillEllipse(Brushes.Blue, (float)(x1_start * scale - 3), (float)(-x2_start * scale - 3), 6, 6);
            g.FillEllipse(Brushes.Green, (float)(nextX1 * scale - 3), (float)(-nextX2 * scale - 3), 6, 6);
        }

        private bool isEqualNull(double x)
        {
            return Math.Abs(x) <= 1e-8;
        }

        private void drawGraphic()
        {
            float x, y1, y2, _y2;
            for (x = -4; x < 4; x += (float)0.01)
            {
                y1 = -1 - x * x;
                y2 = (float)Math.Sqrt((1.0 - 2 * (double)x));
                _y2 = -(float)Math.Sqrt((1.0 - 2 * (double)x));
                g.FillEllipse(Brushes.Blue, (float)(x * scale - 1), (float)(-y1 * scale - 1), 2, 2);
                g.FillEllipse(Brushes.Cyan, (float)(x * scale - 1), (float)(-y2 * scale - 1), 2, 2);
                g.FillEllipse(Brushes.Cyan, (float)(x * scale - 1), (float)(-_y2 * scale - 1), 2, 2);
            }
        }
    }
}