using System.Collections.Generic;
using System.Text.RegularExpressions;
using UnityEngine.UI;
using UnityEngine;
using System.Collections;

[AddComponentMenu("UI/Effects/Letter Spacing", 15)]
public class LetterSpacing : BaseMeshEffect
{
    private const string SupportedTagRegexPattersn = @"<b>|</b>|<i>|</i>|<size=.*?>|</size>|<color=.*?>|</color>|<material=.*?>|</material>";
    [SerializeField]
    private bool useRichText;

    [SerializeField]
    private float m_spacing = 0f;

    protected LetterSpacing() { }

#if UNITY_EDITOR
    protected override void OnValidate()
    {
        spacing = m_spacing;
        base.OnValidate();
    }
#endif

    public float spacing
    {
        get { return m_spacing; }
        set
        {
            if (m_spacing == value) return;
            m_spacing = value;
            if (graphic != null) graphic.SetVerticesDirty();
        }
    }

    public override void ModifyMesh(VertexHelper vh)
    {
        if (!this.IsActive())
            return;

        List<UIVertex> list = new List<UIVertex>();
        vh.GetUIVertexStream(list);

        ModifyVertices(list);

        vh.Clear();
        vh.AddUIVertexTriangleStream(list);
    }

    public void ModifyVertices(List<UIVertex> verts)
    {
        if (!IsActive()) return;

        Text text = GetComponent<Text>();

        string str = text.text;

        IList<UILineInfo> lineInfos = text.cachedTextGenerator.lines;
        for (int i = lineInfos.Count - 1; i > 0; i--)
        {
            str = str.Insert(lineInfos[i].startCharIdx, "\n");
            str = str.Remove(lineInfos[i].startCharIdx - 1, 1);
        }

        string[] lines = str.Split('\n');


        if (text == null)
        {
            Debug.LogWarning("LetterSpacing: Missing Text component");
            return;
        }

        Vector3 pos;
        float letterOffset = spacing * (float)text.fontSize / 100f;
        float alignmentFactor = 0;
        int glyphIdx = 0;  // 字符索引从文本开始，包括RichText标记和换行符

        bool isRichText = useRichText && text.supportRichText;
        IEnumerator matchedTagCollection = null; // 当使用RichText时，它将收集所有标签 (index, length, value)
        Match currentMatchedTag = null;

        switch (text.alignment)
        {
            case TextAnchor.LowerLeft:
            case TextAnchor.MiddleLeft:
            case TextAnchor.UpperLeft:
                alignmentFactor = 0f;
                break;

            case TextAnchor.LowerCenter:
            case TextAnchor.MiddleCenter:
            case TextAnchor.UpperCenter:
                alignmentFactor = 0.5f;
                break;

            case TextAnchor.LowerRight:
            case TextAnchor.MiddleRight:
            case TextAnchor.UpperRight:
                alignmentFactor = 1f;
                break;
        }

        for (int lineIdx = 0; lineIdx < lines.Length; lineIdx++)
        {
            string line = lines[lineIdx];
            int lineLength = line.Length;

            if (isRichText)
            {
                matchedTagCollection = GetRegexMatchedTagCollection(line, out lineLength);
                currentMatchedTag = null;
                if (matchedTagCollection.MoveNext())
                {
                    currentMatchedTag = (Match)matchedTagCollection.Current;
                }
            }

            float lineOffset = (lineLength - 1) * letterOffset * alignmentFactor;

            for (int charIdx = 0, actualCharIndex = 0; charIdx < line.Length; charIdx++, actualCharIndex++)
            {
                if (isRichText)
                {
                    if (currentMatchedTag != null && currentMatchedTag.Index == charIdx)
                    {
                        // skip matched RichText tag
                        charIdx += currentMatchedTag.Length - 1;  // -1 because next iteration will increment charIdx
                        actualCharIndex--;                          // tag is not an actual character, cancel counter increment on this iteration
                        glyphIdx += currentMatchedTag.Length;      // glyph index is not incremented in for loop so skip entire length

                        // prepare next tag to detect
                        currentMatchedTag = null;
                        if (matchedTagCollection.MoveNext())
                        {
                            currentMatchedTag = (Match)matchedTagCollection.Current;
                        }

                        continue;
                    }
                }

                int idx1 = glyphIdx * 6 + 0;
                int idx2 = glyphIdx * 6 + 1;
                int idx3 = glyphIdx * 6 + 2;
                int idx4 = glyphIdx * 6 + 3;
                int idx5 = glyphIdx * 6 + 4;
                int idx6 = glyphIdx * 6 + 5;

                // Check for truncated text (doesn't generate verts for all characters)
                if (idx6 > verts.Count - 1) return;

                UIVertex vert1 = verts[idx1];
                UIVertex vert2 = verts[idx2];
                UIVertex vert3 = verts[idx3];
                UIVertex vert4 = verts[idx4];
                UIVertex vert5 = verts[idx5];
                UIVertex vert6 = verts[idx6];

                pos = Vector3.right * (letterOffset * actualCharIndex - lineOffset);

                vert1.position += pos;
                vert2.position += pos;
                vert3.position += pos;
                vert4.position += pos;
                vert5.position += pos;
                vert6.position += pos;

                verts[idx1] = vert1;
                verts[idx2] = vert2;
                verts[idx3] = vert3;
                verts[idx4] = vert4;
                verts[idx5] = vert5;
                verts[idx6] = vert6;

                glyphIdx++;
            }

            // Offset for carriage return character that still generates verts
            glyphIdx++;
        }
    }

    private IEnumerator GetRegexMatchedTagCollection(string line, out int lineLengthWithoutTags)
    {
        MatchCollection matchedTagCollection = Regex.Matches(line, SupportedTagRegexPattersn);
        lineLengthWithoutTags = 0;
        int tagsLength = 0;

        if (matchedTagCollection.Count > 0)
        {
            foreach (Match matchedTag in matchedTagCollection)
            {
                tagsLength += matchedTag.Length;
            }
        }

        lineLengthWithoutTags = line.Length - tagsLength;
        return matchedTagCollection.GetEnumerator();
    }
}