Code file that edits code files from other code files

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using static System.Console;
using static System.IO.File;

namespace FunctionDefinitionCreator
{
    public static class Program
    {
        public static string fileName;
        public static string[] lines;

        public static void Main(string[] args)
        {
            WriteLineWithColor("Please enter the name of the C++ code file to add definitions in non-defined functions to.", ConsoleColor.Yellow);
            ForegroundColor = ConsoleColor.Cyan;
            fileName = ReadLine();
            lines = ReadAllLines(fileName);
            int currentParenthesisIndex = 0;
            bool omitNextParentheses = false, isValidFunction = false;
            for (int i = 0; i < lines.Length; i++)
            {
                string indent = "";
                int indChars = 0;
                while (indChars < lines[i].Length && (lines[i][indChars] == ' ' || lines[i][indChars] == '\t'))
                    indChars++;
                indent = lines[i].Substring(0, indChars);
                for (int j = 0; j < lines[i].Length; j++)
                {
                    if (lines[i][j] == '=' && currentParenthesisIndex == 0) omitNextParentheses = true;
                    else if (lines[i][j] == '(' && !omitNextParentheses) currentParenthesisIndex++;
                    else if (lines[i][j] == ')' && !omitNextParentheses)
                    {
                        currentParenthesisIndex--;
                        omitNextParentheses = false;
                        isValidFunction = !omitNextParentheses && currentParenthesisIndex == 0;
                    }
                    else if (lines[i][j] == ';' && isValidFunction) lines[i] = lines[i].Replace("\n" + indent + "{\n\n" + indent + "}", j, 1);
                }
            }
            WriteAllLines(fileName, lines);
            WriteLineWithColor("\nThe non-defined functions in that C++ file have been successfully defined.", ConsoleColor.Green);
            ReadKey();
        }

        public static void WriteWithColor(string s, ConsoleColor c)
        {
            ForegroundColor = c;
            Write(s);
        }
        public static void WriteLineWithColor(string s, ConsoleColor c)
        {
            ForegroundColor = c;
            WriteLine(s);
        }
    }
    public static class Extensions
    {
        public static int Find(this string s, string match)
        {
            for (int i = 0; i <= s.Length - match.Length; i++)
            {
                string sub = s.Substring(i, match.Length);
                if (sub == match)
                    return i;
            }
            return -1;
        }
        public static int Find(this string s, string match, int occurence)
        {
            int occurences = 0;
            for (int i = 0; i <= s.Length - match.Length; i++)
            {
                string sub = s.Substring(i, match.Length);
                if (sub == match)
                {
                    occurences++;
                    if (occurences == occurence)
                        return i;
                }
            }
            return -1;
        }
        public static int Find(this string s, string match, int start, int end)
        {
            for (int i = start; i <= end - match.Length; i++)
            {
                string sub = s.Substring(i, match.Length);
                if (sub == match)
                    return i;
            }
            return -1;
        }
        public static int GetLastNumber(this string s)
        {
            int n = 0;
            bool isLastNumber = false;
            for (int i = 0; i < s.Length; i++)
            {
                isLastNumber = int.TryParse(s.Substring(i), out n);
                if (isLastNumber)
                    return n;
            }
            throw new ArgumentException("The string has no number in the end.");
        }
        public static int[] FindAll(this string s, string match)
        {
            List<int> indices = new List<int>();
            for (int i = 0; i <= s.Length - match.Length; i++)
            {
                string sub = s.Substring(i, match.Length);
                if (sub == match)
                    indices.Add(i);
            }
            return indices.ToArray();
        }
        public static int[] FindAll(this string s, string match, int start, int end)
        {
            List<int> indices = new List<int>();
            for (int i = start; i <= end - match.Length; i++)
            {
                string sub = s.Substring(i, match.Length);
                if (sub == match)
                    indices.Add(i);
            }
            return indices.ToArray();
        }
        public static string FixBase64String(this string s)
        {
            int lastNumber = 0;
            int lastInvalidCharacter = 0;
            bool continueChecking = true;
            while (continueChecking)
            {
                if (s[s.Length - lastNumber - 1].IsNumber())
                    lastNumber++;
                else if (!s[s.Length - lastNumber - 1].IsBase64Character())
                    lastInvalidCharacter = ++lastNumber;
                else
                    continueChecking = false;
            }
            s = s.Substring(0, s.Length - lastInvalidCharacter);
            while (s.Length % 4 != 0)
                s += "=";
            return s;
        }
        public static string Substring(this string s, string from, string to)
        {
            int startIndex = s.Find(from) + from.Length;
            int endIndex = s.Find(to);
            int length = endIndex - startIndex;
            return s.Substring(startIndex, length);
        }
        public static string RemoveLastNumber(this string s)
        {
            string l = s;
            for (int i = 0; i < s.Length; i++)
            {
                l = s.Substring(i);
                if (int.TryParse(l, out int shit))
                    return s.Substring(0, i);
            }
            return s;
        }
        public static string Replace(this string originalString, string stringToReplaceWith, int startIndex, int length)
        {
            string result = originalString;
            result = result.Remove(startIndex, length);
            result = result.Insert(startIndex, stringToReplaceWith);
            return result;
        }
        public static string ReplaceWholeWord(this string originalString, string oldString, string newString)
        {
            for (int i = originalString.Length - oldString.Length; i >= 0; i--)
            {
                if (originalString.Substring(i, oldString.Length) == oldString)
                    if ((i > 0 ? (!originalString[i - 1].IsLetterOrNumber()) : true) && (i < originalString.Length - oldString.Length ? (!originalString[i + oldString.Length].IsLetterOrNumber()) : true))
                    {
                        originalString = originalString.Replace(newString, i, oldString.Length);
                        i -= oldString.Length;
                    }
            }
            return originalString;
        }
        public static bool ContainsWholeWord(this string s, string match)
        {
            for (int i = s.Length - match.Length; i >= 0; i--)
            {
                if (s.Substring(i, match.Length) == match)
                    if ((i > 0 ? (!s[i - 1].IsLetterOrNumber()) : true) && (i < s.Length - match.Length ? (!s[i + match.Length].IsLetterOrNumber()) : true))
                        return true;
            }
            return false;
        }
        public static bool MatchesStringCaseFree(this string s, string match)
        {
            if (s.Length != match.Length)
                return false;
            for (int i = 0; i < s.Length; i++)
            {
                if (s[i].IsUpperCaseLetter())
                    if (s[i] + 32 != match[i] && s[i] != match[i])
                        return false;
                    else if (s[i].IsLowerCaseLetter())
                        if (s[i] - 32 != match[i] && s[i] != match[i])
                            return false;
            }
            return true;
        }
        public static bool IsBase64Character(this char c)
        {
            return IsNumber(c) || IsLetter(c) || c == '/' || c == '+' || c == '=';
        }
        public static bool IsLetter(this char c) => (c >= 65 && c <= 90 || c >= 97 && c <= 122);
        public static bool IsLowerCaseLetter(this char c) => (c >= 97 && c <= 122);
        public static bool IsNumber(this char c) => (c >= 48 && c <= 57);
        public static bool IsUpperCaseLetter(this char c) => (c >= 65 && c <= 90);
        public static bool IsLetterOrNumber(this char c) => IsLetter(c) || IsNumber(c);

        public static int[] FindOccurences(this string[] a, string match)
        {
            if (a != null)
            {
                List<int> occurences = new List<int>();
                for (int i = 0; i < a.Length; i++)
                    if (a[i] == match)
                        occurences.Add(i);
                return occurences.ToArray();
            }
            else return new int[0];
        }
        public static string[] Replace(this string[] a, char oldChar, char newChar)
        {
            for (int i = 0; i < a.Length; i++)
                a[i] = a[i].Replace(oldChar, newChar);
            return a;
        }
        public static string[] Replace(this string[] a, string oldString, string newString)
        {
            for (int i = 0; i < a.Length; i++)
                a[i] = a[i].Replace(oldString, newString);
            return a;
        }
        public static string[] ReplaceWholeWord(this string[] a, string oldString, string newString)
        {
            for (int i = 0; i < a.Length; i++)
                a[i] = a[i].ReplaceWholeWord(oldString, newString);
            return a;
        }
        public static string[] RemoveEmptyElements(this string[] a)
        {
            List<string> result = new List<string>();
            for (int i = 0; i < a.Length; i++)
                if (a[i].Length > 0)
                    result.Add(a[i]);
            return result.ToArray();
        }
        public static bool ContainsAtLeast(this string[] a, string match)
        {
            if (a != null)
            {
                for (int i = 0; i < a.Length; i++)
                    if (a[i].Contains(match))
                        return true;
                return false;
            }
            return false;
        }
        public static bool ContainsAtLeastWholeWord(this string[] a, string match)
        {
            if (a != null)
            {
                for (int i = 0; i < a.Length; i++)
                    if (a[i].ContainsWholeWord(match))
                        return true;
                return false;
            }
            return false;
        }
        public static string Combine(this string[] s)
        {
            StringBuilder str = new StringBuilder();
            for (int i = 0; i < s.Length; i++)
                str = str.Append(s[i]);
            return str.ToString();
        }
        public static string Combine(this string[] s, string separator)
        {
            if (s.Length > 0)
            {
                StringBuilder str = new StringBuilder();
                str = str.Append(s[0]);
                for (int i = 1; i < s.Length; i++)
                    str = str.Append(separator + s[i]);
                return str.ToString();
            }
            else return "";
        }
        public static string[,] Split(this string[] s, char separator)
        {
            List<string[]> separated = new List<string[]>();
            for (int i = 0; i < s.Length; i++)
                separated.Add(s[i].Split(separator));
            return separated.ToTwoDimensionalArray();
        }

        public static T[] GetInnerArray<T>(this T[,] ar, int innerArrayIndex)
        {
            T[] innerAr = new T[ar.GetLength(1)];
            for (int i = 0; i < innerAr.Length; i++)
                innerAr[i] = ar[innerArrayIndex, i];
            return innerAr;
        }
        public static int[] GetLengths<T>(this List<T[]> l)
        {
            int[] lengths = new int[l.Count];
            for (int i = 0; i < l.Count; i++)
                lengths[i] = l[i].Length;
            return lengths;
        }
        public static int[] GetLengths(this int[,] ar)
        {
            int[] lengths = new int[ar.Length];
            for (int i = 0; i < ar.Length; i++)
                lengths[i] = ar.GetInnerArray(i).Length;
            return lengths;
        }
        public static int[] GetLengths(this string[,] ar)
        {
            int[] lengths = new int[ar.GetLength(0)];
            for (int i = 0; i < lengths.Length; i++)
                lengths[i] = ar.GetInnerArray(i).Length;
            return lengths;
        }

        public static T[,] ToTwoDimensionalArray<T>(this List<T[]> l)
        {
            T[,] ar = new T[l.Count, l.GetLengths().Max()];
            for (int i = 0; i < l.Count; i++)
                for (int j = 0; j < l[i].Length; j++)
                    ar[i, j] = l[i][j];
            return ar;
        }
    }
}