TextUtils.cs

using System;

namespace NewProject
{
    public static class TextUtils
    {
        public static bool IsNullOrWhiteSpace(string s)
        {
            if (s == null) return true;
            if (s.Length == 0) return true;

            for (int i = 0; i < s.Length; i++)
            {
                char c = s[i];
                if (c != ' ' && c != '\t' && c != '\r' && c != '\n')
                    return false;
            }
            return true;
        }

        public static bool EqualsManual(string a, string b)
        {
            if (a == null || b == null) return false;
            if (a.Length != b.Length) return false;

            for (int i = 0; i < a.Length; i++)
                if (a[i] != b[i]) return false;

            return true;
        }

        public static int FindChar(string text, char target, int startIndex)
        {
            if (text == null) return -1;
            if (startIndex < 0) startIndex = 0;

            for (int i = startIndex; i < text.Length; i++)
                if (text[i] == target) return i;

            return -1;
        }

        public static int FindString(string text, string pattern, int startIndex)
        {
            if (text == null || pattern == null) return -1;
            if (pattern.Length == 0) return startIndex;
            if (startIndex < 0) startIndex = 0;
            if (pattern.Length > text.Length) return -1;

            for (int i = startIndex; i <= text.Length - pattern.Length; i++)
            {
                bool match = true;
                for (int j = 0; j < pattern.Length; j++)
                {
                    if (text[i + j] != pattern[j])
                    {
                        match = false;
                        break;
                    }
                }
                if (match) return i;
            }

            return -1;
        }

        public static bool StartsWithManual(string text, string prefix)
        {
            if (text == null || prefix == null) return false;
            if (prefix.Length > text.Length) return false;

            for (int i = 0; i < prefix.Length; i++)
                if (text[i] != prefix[i]) return false;

            return true;
        }

        public static bool ContainsManual(string text, string value)
        {
            return FindString(text, value, 0) != -1;
        }

        public static string SubstringManual(string text, int start, int length)
        {
            if (text == null) return "";
            if (start < 0) return "";
            if (length < 0) return "";
            if (start + length > text.Length) return "";

            char[] result = new char[length];
            for (int i = 0; i < length; i++)
                result[i] = text[start + i];

            return new string(result);
        }

        public static string SubstringFrom(string text, int start)
        {
            if (text == null) return "";
            if (start < 0 || start > text.Length) return "";
            return SubstringManual(text, start, text.Length - start);
        }

        public static string TrimSpacesAndNulls(string text)
        {
            if (text == null) return "";

            int start = 0;
            int end = text.Length - 1;

            while (start <= end && (text[start] == ' ' || text[start] == '\0'))
                start++;

            while (end >= start && (text[end] == ' ' || text[end] == '\0'))
                end--;

            if (end < start) return "";
            return SubstringManual(text, start, end - start + 1);
        }

        public static string TrimEndSpacesAndNulls(string text)
        {
            if (text == null) return "";
            int end = text.Length - 1;

            while (end >= 0 && (text[end] == ' ' || text[end] == '\0'))
                end--;

            if (end < 0) return "";
            return SubstringManual(text, 0, end + 1);
        }

        public static string ReadUntil(string text, ref int i, char stopChar)
        {
            if (text == null) return "";

            int start = i;
            while (i < text.Length)
            {
                char c = text[i];
                if (c == stopChar || c == ' ')
                    break;
                i++;
            }

            int len = i - start;
            if (len <= 0) return "";
            return SubstringManual(text, start, len);
        }

        public static int ReadIntUntil(string text, ref int i, char stopChar)
        {
            if (text == null) return -1;

            int value = 0;
            bool hasDigit = false;

            while (i < text.Length)
            {
                char c = text[i];
                if (c == stopChar || c == ' ')
                    break;

                if (c < '0' || c > '9') return -1;

                hasDigit = true;
                value = value * 10 + (c - '0');
                i++;
            }

            return hasDigit ? value : -1;
        }

        public static void SkipSpaces(string text, ref int i)
        {
            if (text == null) return;
            while (i < text.Length && text[i] == ' ')
                i++;
        }
    }
}