using System;
using System.Drawing;
using System.Linq;
using System.Windows.Forms;

namespace DiffComparison
{
    public partial class MainForm : Form
    {
        public MainForm()
        {
            InitializeComponent();
            panelOverview.Paint += PanelOverview_Paint;
            rtbLeft.SelectionChanged += RtbLeft_SelectionChanged;
            rtbRight.SelectionChanged += RtbRight_SelectionChanged;
        }

        private void btnCompare_Click(object sender, EventArgs e)
        {
            CompareTexts();
        }

        private void CompareTexts()
        {
            string[] leftLines = rtbLeft.Lines;
            string[] rightLines = rtbRight.Lines;

            rtbLeft.Clear();
            rtbRight.Clear();

            for (int i = 0; i < Math.Max(leftLines.Length, rightLines.Length); i++)
            {
                if (i < leftLines.Length)
                {
                    rtbLeft.AppendText(leftLines[i] + Environment.NewLine);
                    if (i < rightLines.Length && leftLines[i] != rightLines[i])
                    {
                        rtbLeft.SelectionStart = rtbLeft.GetFirstCharIndexFromLine(i);
                        rtbLeft.SelectionLength = leftLines[i].Length;
                        rtbLeft.SelectionBackColor = Color.Pink;
                    }
                }

                if (i < rightLines.Length)
                {
                    rtbRight.AppendText(rightLines[i] + Environment.NewLine);
                    if (i < leftLines.Length && leftLines[i] != rightLines[i])
                    {
                        rtbRight.SelectionStart = rtbRight.GetFirstCharIndexFromLine(i);
                        rtbRight.SelectionLength = rightLines[i].Length;
                        rtbRight.SelectionBackColor = Color.Pink;
                    }
                }
            }

            panelOverview.Invalidate(); // 重新繪製概覽面板
        }

        private void PanelOverview_Paint(object sender, PaintEventArgs e)
        {
            Graphics g = e.Graphics;
            int lineHeight = rtbLeft.Font.Height;
            int leftLineCount = rtbLeft.Lines.Length;
            int rightLineCount = rtbRight.Lines.Length;
            int maxLines = Math.Max(leftLineCount, rightLineCount);

            for (int i = 0; i < maxLines; i++)
            {
                if (i < leftLineCount && i < rightLineCount && rtbLeft.Lines[i] != rtbRight.Lines[i])
                {
                    int y = i * lineHeight;
                    g.FillRectangle(Brushes.Red, new Rectangle(0, y, panelOverview.Width, lineHeight));
                }
            }
        }

        private void RtbLeft_SelectionChanged(object sender, EventArgs e)
        {
            ScrollToCorrespondingLine(rtbLeft);
        }

        private void RtbRight_SelectionChanged(object sender, EventArgs e)
        {
            ScrollToCorrespondingLine(rtbRight);
        }

        private void ScrollToCorrespondingLine(RichTextBox rtb)
        {
            int lineIndex = rtb.GetLineFromCharIndex(rtb.SelectionStart);
            rtb.ScrollToCaret(); // 滾動到當前選擇行
            panelOverview.Invalidate(); // 重新繪製概覽面板
        }
    }
}