using System;
using System.Collections.Generic;
using System.Globalization;

namespace JD.UserControls.QuickOpenDialogs
{
    /// <summary>
    /// Allows to search using default search patterns (contains words in order, ...).
    /// </summary>
    public class TextQuery
    {
        private readonly string m_text;
        private readonly string[] m_words;

        public TextQuery(string text)
        {
            m_text = text ?? string.Empty;
            m_words = m_text.Split(new[] { ' ' }, StringSplitOptions.RemoveEmptyEntries);
        }

        /// <summary>
        /// Returns the length of the original search
        /// </summary>
        public int TextLength
        {
            get { return m_text.Length; }
        }

        /// <summary>
        /// Returns the number of word in the query
        /// </summary>
        public IReadOnlyList<string> Words
        {
            get { return m_words; }
        }

        /// <summary>
        /// The original unformatted text of the query.
        /// </summary>
        public string OriginalText
        {
            get { return m_text; }
        }

        /// <summary>
        /// Checks the text for a match.
        /// </summary>
        public MatchResult Matches(string text)
        {
            if (string.IsNullOrEmpty(text))
            {
                return MatchResult.Invalid;
            }

            int index = 0;
            int score = -1;

            for (int i = 0; i < m_words.Length; ++i)
            {
                if (index >= text.Length)
                {
                    return MatchResult.Invalid;
                }

                index = CultureInfo.InvariantCulture.CompareInfo.IndexOf(text, m_words[i], CompareOptions.IgnoreNonSpace | CompareOptions.IgnoreCase);
                if (index == -1)
                {
                    return MatchResult.Invalid;
                }

                CheckPreviousSeparator(text, index, ref score);

                index += m_words[i].Length;

                CheckNextSeparator(text, index, ref score);
            }

            return new MatchResult(score);
        }

        private static void CheckPreviousSeparator(string text, int index, ref int score)
        {
            if (index == 0)
            {
                score -= 4;
            }
            else if (IsSeparator(text[index - 1]))
            {
                score -= 2;
            }
        }

        private static void CheckNextSeparator(string text, int index, ref int score)
        {
            if (index >= text.Length || IsSeparator(text[index]))
            {
                score -= 1;
            }
        }

        private static bool IsSeparator(char c)
        {
            return char.IsWhiteSpace(c) || c == '.' || c == '\\';
        }

        public struct MatchResult : IComparable<MatchResult>
        {
            public static readonly MatchResult Invalid = new MatchResult();

            private readonly int m_score;

            public MatchResult(int score)
            {
                m_score = score;
            }

            public bool IsMatch
            {
                get { return m_score != 0; }
            }

            public int CompareTo(MatchResult other)
            {
                return m_score.CompareTo(other.m_score);
            }
        }
    }
}