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

// Text2 extends the Text component in Unity UI.
// It makes hyphens and soft hyphens work.
// Inserting soft hyphens in text can be tricky and confusing, given they are invisible,
// so you can instead also insert Hyphenation Point characters, which will be replaced by soft hyphens:
// https://www.compart.com/en/unicode/U+2027
public class Text2 : Text {

    const char shyChar = '\u00AD';
    const string shy = "\u00AD";
    const string shySpace = "\u00AD ";
    const char zwnjChar = '\u200C';
    const string zwnj = "\u200C";
    const string zwnjSpace = "\u200C ";

    int LastIndexOfInSubString (string input, int start, int length, string value) {
        int pos = input.Substring (start, length).LastIndexOf (value);
        if (pos < 0)
            return pos;
        return pos + start;
    }

    int GetLineEndCharacterIndex (string text, int line) {
        int index = line == cachedTextGenerator.lineCount - 1 ?
                text.Length :
                cachedTextGenerator.lines[line + 1].startCharIdx;
        if (text[index - 1] == '\n')
            index--;
        if (text[index - 1] == ' ')
            index--;
        if (text[index - 1] == shyChar)
            index--;
        if (text[index - 1] == zwnjChar)
            index--;
        return index;
    }

    readonly UIVertex[] m_TempVerts = new UIVertex[4];
    protected override void OnPopulateMesh (VertexHelper toFill) {
        if (font == null)
            return;

        // We don't care if we the font Texture changes while we are doing our Update.
        // The end result of cachedTextGenerator will be valid for this instance.
        // Otherwise we can get issues like Case 619238.
        m_DisableFontTextureRebuiltCallback = true;

        Vector2 extents = rectTransform.rect.size;

        string text2 = text;

        if (this.horizontalOverflow == HorizontalWrapMode.Overflow) {
            // Remove Hyphenation Point characters.
            text2 = text2.Replace ("\u2027", string.Empty);
            // Remove soft hyphens since Unity otherwise renders them.
            text2 = text2.Replace (shy, string.Empty);

            var settings = GetGenerationSettings (extents);
            cachedTextGenerator.PopulateWithErrors (text2, settings, gameObject);
        }
        else {
            // Replace Hyphenation Point characters with soft hyphens.
            text2 = text2.Replace ("\u2027", shy);
            // Add spaces after soft hyphens.
            text2 = text2.Replace (shy, shySpace);
            // Add zero-width non-joiner characters and spaces after hyphens.
            text2 = text2.Replace ("-", "-" + zwnjSpace);

            var settings = GetGenerationSettings (extents);
            cachedTextGenerator.PopulateWithErrors (text2, settings, gameObject);

            int fixLine = 0;
            while (fixLine < cachedTextGenerator.lineCount) {

                var line = cachedTextGenerator.lines[fixLine];
                int charA = line.startCharIdx;
                int charB = GetLineEndCharacterIndex (text2, fixLine);

                // Remove soft hyphen and space combos from current line.
                int lengthBefore = text2.Length;
                text2 =
                    text2.Substring (0, charA) +
                    text2.Substring (charA, charB - charA).Replace (shySpace, "").Replace (zwnjSpace, "") +
                    text2.Substring (charB);

                // If anything was removed, handle the same line again.
                if (text2.Length != lengthBefore) {
                    cachedTextGenerator.PopulateWithErrors (text2, settings, gameObject);
                    continue;
                }

                // If nothing changed, check if there is room for adding one last bit
                // to this line by removing the hyphen at the end of the line.
                bool notLastLine = (fixLine < cachedTextGenerator.lineCount - 1);
                if (notLastLine && (text2[charB] == shyChar || text2[charB] == zwnjChar)) {
                    // Remove hyphen and space combo at end of line.
                    string text3 = text2.Substring (0, charB) + text2.Substring (charB + 2);
                    cachedTextGenerator.PopulateWithErrors (text3, settings, gameObject);

                    if (fixLine == cachedTextGenerator.lineCount - 1) {
                        // We managed to fit the text on one less line, so clearly
                        // we did manage to add more text tot his line.
                        text2 = text3;
                    }
                    else {
                        int newLineIndex = cachedTextGenerator.lines[fixLine + 1].startCharIdx;
                        int newCharB = GetLineEndCharacterIndex (text3, fixLine);
                        // If we managed to add more to this line
                        // AND the last character of the line without space and hyphens is smaller
                        // than the actual last character (meaning we didn't cut a word improperly)
                        // then accept this modification.
                        if (newCharB >= charB && (newCharB < newLineIndex || text3[newCharB] == '-'))
                            text2 = text3;

                        // Otherwise just proceed to next line.
                        // We need to first set the text generator back to using the unmodified string.
                        else
                            cachedTextGenerator.PopulateWithErrors (text2, settings, gameObject);
                    }
                }

                fixLine++;
            }

            {
                // Remove the zero-width non-joiner characters we added
                // since Unity actually does render them.
                int lengthBefore = text2.Length;
                text2 = text2.Replace ("-" + zwnj, "-");
                if (text2.Length < lengthBefore)
                    cachedTextGenerator.PopulateWithErrors (text2, settings, gameObject);
            }
        }

        // The rest of the code is unmodified from the Text class.

        // Apply the offset to the vertices
        IList<UIVertex> verts = cachedTextGenerator.verts;
        float unitsPerPixel = 1 / pixelsPerUnit;
        int vertCount = verts.Count;

        // We have no verts to process just return (case 1037923)
        if (vertCount <= 0) {
            toFill.Clear ();
            return;
        }

        Vector2 roundingOffset = new Vector2 (verts[0].position.x, verts[0].position.y) * unitsPerPixel;
        roundingOffset = PixelAdjustPoint (roundingOffset) - roundingOffset;
        toFill.Clear ();
        if (roundingOffset != Vector2.zero) {
            for (int i = 0; i < vertCount; ++i) {
                int tempVertsIndex = i & 3;
                m_TempVerts[tempVertsIndex] = verts[i];
                m_TempVerts[tempVertsIndex].position *= unitsPerPixel;
                m_TempVerts[tempVertsIndex].position.x += roundingOffset.x;
                m_TempVerts[tempVertsIndex].position.y += roundingOffset.y;
                if (tempVertsIndex == 3)
                    toFill.AddUIVertexQuad (m_TempVerts);
            }
        }
        else {
            for (int i = 0; i < vertCount; ++i) {
                int tempVertsIndex = i & 3;
                m_TempVerts[tempVertsIndex] = verts[i];
                m_TempVerts[tempVertsIndex].position *= unitsPerPixel;
                if (tempVertsIndex == 3)
                    toFill.AddUIVertexQuad (m_TempVerts);
            }
        }

        m_DisableFontTextureRebuiltCallback = false;
    }
}