using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;

namespace Test_SearchAndFind
{
    /// <summary>
    /// Searches the specified string in a text
    /// </summary>
    class Search
    {
        public void StartSearch(string text, string searchString, bool noCaseSensitve, bool onlyFullWord)
        {
            Text = text;
            SearchString = searchString;
            NoCaseSensitve = noCaseSensitve;
            OnlyFullWord = onlyFullWord;

            SearchEntities();
            if (!Error)
            {
                CurrentCursorPosition = AllPositions[0];
                Index = 0;
            }
            else
            {
                //Suchstring wurde nicht gefunden
                throw new StringNotMatchException();
            }
        }

        private string Text { set; get; }
        private string SearchString { set; get; }
        private bool NoCaseSensitve { set; get; }
        private bool OnlyFullWord { set; get; }
        public int Index { private set; get; }
        /// <summary>
        /// Contains the current cursor position
        /// </summary>
        public int CurrentCursorPosition { private set; get; }
        /// <summary>
        /// Contains a list with all found positions
        /// </summary>
        public List<int> AllPositions { private set; get; }
        /// <summary>
        /// Is true if an error has occurred
        /// </summary>
        public bool Error { private set; get; }

        private void SearchEntities()
        {
            Error = false;

            string text = Text;
            string searchString = SearchString;

            if (NoCaseSensitve)
            {
                //Groß-/Kleinschreibung ignorieren
                text = text.ToLower();
                searchString = searchString.ToLower();
            }

            if (!String.IsNullOrEmpty(searchString) && text.Contains(searchString))
            {
                AllPositions = Positions(text, searchString);
            }
            else
            {
                Error = true;
            }
        }

        private List<int> Positions(string text, string searchString)
        {
            List<int> positions = new List<int>();

            if (String.IsNullOrEmpty(text) || String.IsNullOrEmpty(searchString))
            {
                return positions;
            }

            int position = 0;
            int currentPos = 0;

            while (text.Contains(searchString))
            {
                if (OnlyFullWord)
                {
                    //Nur ganzes Wort suchen
                    currentPos = IndexOfWord(text, searchString);
                }
                else
                {
                    //Suchstring suchen
                    currentPos = text.IndexOf(searchString);
                }

                position += currentPos;
                positions.Add(position);
                position += searchString.Length;

                text = text.Remove(0, currentPos + searchString.Length);
            }

            return positions;
        }

        private Regex myRegex;

        private int IndexOfWord(string myString, string myWord)
        {
            myRegex = new Regex("\\b" + Regex.Escape(myWord) + "\\b", RegexOptions.Compiled);

            Match mtch = myRegex.Match(myString);

            if (mtch.Success)
                return mtch.Index;
            else
                return -1;
        }

        /// <summary>
        /// Jumps to the next occurrence position
        /// </summary>
        public void NextPosition()
        {
            if (Index + 1 < AllPositions.Count)
            {
                Index++;
            }
            else
            {
                Index = 0;
            }
            CurrentCursorPosition = AllPositions[Index];
        }

        /// <summary>
        /// Jumps to previous occurrence position
        /// </summary>
        public void PreviousPosition()
        {
            if (Index > 0)
            {
                Index--;
            }
            else
            {
                Index = AllPositions.Count - 1;
            }
            CurrentCursorPosition = AllPositions[Index];
        }
    }

    #region Exceptions
    public class StringNotMatchException : Exception
    {
        public StringNotMatchException() { }

        public StringNotMatchException(string message)
            : base(message) { }

        public StringNotMatchException(string message, Exception inner)
            : base(message, inner) { }
    }
    #endregion
}