Mirror textbox input winform application

Question

c# winform

iam trying code mirror from textbox1 input like below if user not used bracket like below

textbox1

8-a
4-b
2-c
50-d
100-a

output should be

8-a
4-b
2-c
50-d
100-a
100-a
50-d
2-c
4-b
8-a

Here is my code

        private void button1_Click(object sender, EventArgs e)
        {
            //without bracket mirror working code

            // Get the input from textBox1
            string input = textBox1.Text;

            // Split the input into lines
            string[] lines = input.Split(new[] { Environment.NewLine }, StringSplitOptions.RemoveEmptyEntries);

            // Reverse the lines
            string[] reversedLines = lines.Reverse().ToArray();

            // Append the reversed lines to the original input
            string output = input + Environment.NewLine + string.Join(Environment.NewLine, reversedLines);

            // Set the result back to textBox1
            textBox1.Text = output;

        }

 

but i want to impliment this code if user used bracket like below then output should be mirror with bracket.

textbox1 input

8-a
[4-b
2-c]5
50-d
100-a

output should be

8-a
[4-b
2-c]5
50-d
100-a
100-a
50-d
[2-c
4-b]5
8-a