using System.Globalization;

public class Program
{
    private static void Main()
    {
        double[] inputArray = ReadData(@"..\..\..\..\TestData\input_data.txt");
        Console.WriteLine($"Input data: [{string.Join("; ", inputArray)}]");

        var outputData = ArrayProc(inputArray);
        WriteToFile(outputData!, "output_data_csharp.txt");

        var minValue = SearchMinValue(outputData!);
        Console.WriteLine($"Output data: [{(outputData != null ? string.Join(" ; ", outputData) : "null")}]");

        WriteToFile(minValue!, "min_value_csharp.txt");
        Console.WriteLine($"Min value: {minValue.ToString()}");
    }

    private static void WriteToFile(double[] data, string filename)
    {
        if (data == null) return;

        using (StreamWriter sw = new StreamWriter(filename))
        {
            foreach (var value in data) sw.WriteLine(value.ToString(CultureInfo.InvariantCulture));
        }
    }

    private static void WriteToFile(double? data, string filename)
    {
        if (data == null) return;

        File.WriteAllText(filename, data.Value.ToString(CultureInfo.InvariantCulture) + Environment.NewLine);
    }

    public static double[] ReadData(string txtFile)
    {
        string[] lines = File.ReadAllLines(txtFile);

        if (lines.Length == 0 || lines[0] == "None")
            return new double[0];

        double[] data = new double[lines.Length];
        for (int i = 0; i < lines.Length; i++)
        {
            data[i] = double.Parse(lines[i], CultureInfo.InvariantCulture);
        }
        return data;
    }

    public static double? SearchMinValue(double[] inputData)
    {
        if (inputData == null) return null;
        if (inputData.Length == 0) return null;

        var minValue = inputData[0];
        int i = 1;
        while (i < inputData.Length)
        {
            if (inputData[i] < minValue)
                minValue = inputData[i];
            i++;
        }
        return minValue;
    }

    public static double[]? ArrayProc(double[] inputData)
    {
        double[] outputArray;
        int pairs = 0;
        int n = inputData.Length - 1;

        int i = 0;
        while (i <= n / 2)
        {
            if (i + 8 <= n)
                pairs++;
            i++;
        }

        if (pairs == 0)
            return new double[0];

        outputArray = new double[pairs];

        int j = 0;
        i = 8;
        while (j < outputArray.Length)
        {
            outputArray[j] = inputData[i] * inputData[i - 8];
            j++;
            i++;
        }

        if (outputArray.Length % 2 != 0)
        {
            int centralIdx = outputArray.Length / 2;
            double centralItem = outputArray[centralIdx];
            outputArray[centralIdx] = centralItem * centralItem;
        }

        return outputArray;
    }
}