namespace QWERTYkez.WordProcessor;

internal static class SimplyReplaceExt
{
    private readonly struct TextNodeInfo(Text text, int startIndex, int length)
    {
        internal readonly Text Text = text;
        internal readonly int StartIndex = startIndex;
        internal readonly int Length = length;
    }

    private sealed class ParagraphStructure(string fullText, SimplyReplaceExt.TextNodeInfo[] textNodes)
    {
        internal readonly string FullText = fullText;
        internal readonly TextNodeInfo[] TextNodes = textNodes;

        internal int FindFirstNodeIndexAtPosition(int position)
        {
            if (position < 0 || position >= FullText.Length)
                return -1;

            int left = 0;
            int right = TextNodes.Length - 1;
            int result = -1;

            while (left <= right)
            {
                int mid = left + ((right - left) >> 1);
                if (TextNodes[mid].StartIndex <= position)
                {
                    result = mid;
                    left = mid + 1;
                }
                else
                {
                    right = mid - 1;
                }
            }

            return result >= 0 && TextNodes[result].StartIndex + TextNodes[result].Length > position
                ? result : -1;
        }
    }

    internal static void Replace(this Body body, string oldValue, string newValue, StringComparison comparisonType)
    {
        if (body is null || string.IsNullOrEmpty(oldValue)) return;

        var paragraphs = body.Elements<Paragraph>();
        foreach (var paragraph in paragraphs)
        {
            paragraph?.SimpleReplace(oldValue, newValue, comparisonType);
        }
    }

    internal static void Replace(this Body body, IEnumerable<KeyValuePair<string, string>> replacements, StringComparison comparisonType)
    {
        if (body is null || replacements is null || replacements.Count() == 0)
            return;

        var paragraphs = body.Elements<Paragraph>();
        foreach (var paragraph in paragraphs)
        {
            paragraph?.Replace(replacements, comparisonType);
        }
    }

    internal static void Replace(this Body body, IEnumerable<KeyValuePair<string, ReplaceItem>> replacements, StringComparison comparisonType)
    {
        if (body is null || replacements is null || replacements.Count() == 0)
            return;

        var paragraphs = body.Elements<Paragraph>();
        foreach (var paragraph in paragraphs)
        {
            paragraph?.Replace(replacements, comparisonType);
        }
    }

    internal static bool SimpleReplace(this Paragraph? paragraph, string oldValue, string newValue, StringComparison comparisonType, bool breakPage = false)
    {
        if (paragraph is null || string.IsNullOrEmpty(oldValue))
            return false;

        var paragraphText = paragraph.InnerText;
        if (string.IsNullOrEmpty(paragraphText))
            return false;

        int matchIndex = paragraphText.IndexOf(oldValue, comparisonType);
        if (matchIndex == -1)
            return false;

        var runs = paragraph.Elements<Run>();
        if (!runs.Any())
            return false;

        var structure = AnalyzeParagraphStructure(runs);
        if (structure.FullText.Length == 0)
            return false;

        int matchEnd = matchIndex + oldValue.Length;
        var nodesToReplace = FindNodesToReplace(structure, matchIndex, matchEnd);
        if (nodesToReplace.Count == 0)
            return false;

        ExecuteReplacement(nodesToReplace, matchIndex, matchEnd, newValue, breakPage);
        return true;
    }

    internal static void Replace(this Paragraph paragraph, IEnumerable<KeyValuePair<string, string>> replacements, StringComparison comparisonType)
    {
        if (paragraph is null || replacements is null || replacements.Count() == 0)
            return;

        var runs = paragraph.Elements<Run>().ToList();
        if (runs.Count == 0)
            return;

        var structure = AnalyzeParagraphStructure(runs);
        if (structure.FullText.Length == 0)
            return;

        // Используем List с предопределенной емкостью
        var replacementsInParagraph = new List<ReplacementInfo>(replacements.Count() * 2);

        // Сначала находим все вхождения
        var fullText = structure.FullText;
        foreach (var kvp in replacements)
        {
            if (string.IsNullOrEmpty(kvp.Key))
                continue;

            int pos = 0;
            while ((pos = fullText.IndexOf(kvp.Key, pos, comparisonType)) != -1)
            {
                replacementsInParagraph.Add(new ReplacementInfo
                {
                    OldValue = kvp.Key,
                    NewValue = kvp.Value ?? string.Empty,
                    Index = pos
                });
                pos += kvp.Key.Length;
            }
        }

        if (replacementsInParagraph.Count == 0)
            return;

        // Сортируем по убыванию позиции
        replacementsInParagraph.Sort((x, y) => y.Index.CompareTo(x.Index));

        // Выполняем замены
        for (int i = 0; i < replacementsInParagraph.Count; i++)
        {
            var replacement = replacementsInParagraph[i];
            int matchIndex = replacement.Index;
            int matchEnd = matchIndex + replacement.OldValue.Length;

            var nodesToReplace = FindNodesToReplace(structure, matchIndex, matchEnd);
            if (nodesToReplace.Count > 0)
            {
                ExecuteReplacement(nodesToReplace, matchIndex, matchEnd, replacement.NewValue);
            }
        }
    }

    internal static void Replace(this Paragraph paragraph, IEnumerable<KeyValuePair<string, ReplaceItem>> replacements, StringComparison comparisonType)
    {
        if (paragraph is null || replacements is null || replacements.Count() == 0)
            return;

        var runs = paragraph.Elements<Run>().ToList();
        if (runs.Count == 0)
            return;

        var structure = AnalyzeParagraphStructure(runs);
        if (structure.FullText.Length == 0)
            return;

        // Используем List с предопределенной емкостью
        var replacementsInParagraph = new List<ReplacementInfo>(replacements.Count() * 2);

        // Сначала находим все вхождения
        var fullText = structure.FullText;
        foreach (var kvp in replacements)
        {
            if (string.IsNullOrEmpty(kvp.Key))
                continue;

            int pos = 0;
            while ((pos = fullText.IndexOf(kvp.Key, pos, comparisonType)) != -1)
            {
                replacementsInParagraph.Add(new ReplacementInfo
                {
                    OldValue = kvp.Key,
                    NewValue = kvp.Value.Text ?? string.Empty,
                    BreakPage = kvp.Value.BreakPage,
                    Index = pos
                });
                pos += kvp.Key.Length;
            }
        }

        if (replacementsInParagraph.Count == 0)
            return;

        // Сортируем по убыванию позиции
        replacementsInParagraph.Sort((x, y) => y.Index.CompareTo(x.Index));

        // Выполняем замены
        for (int i = 0; i < replacementsInParagraph.Count; i++)
        {
            var replacement = replacementsInParagraph[i];
            int matchIndex = replacement.Index;
            int matchEnd = matchIndex + replacement.OldValue.Length;

            var nodesToReplace = FindNodesToReplace(structure, matchIndex, matchEnd);
            if (nodesToReplace.Count > 0)
            {
                ExecuteReplacement(nodesToReplace, matchIndex, matchEnd, replacement.NewValue, replacement.BreakPage);
            }
        }
    }

    private class ReplacementInfo
    {
        internal string OldValue { get; set; } = null!;
        internal string NewValue { get; set; } = null!;
        internal int Index { get; set; }
        internal bool BreakPage { get; set; }
    }

    private static ParagraphStructure AnalyzeParagraphStructure(IEnumerable<Run> runs)
    {
        var textNodesList = new List<TextNodeInfo>(32);
        var sb = new StringBuilder(256);
        int currentIndex = 0;

        foreach (var run in runs)
        {
            var texts = run.Elements<Text>();
            foreach (var text in texts)
            {
                var textValue = text.Text;
                if (string.IsNullOrEmpty(textValue))
                    continue;

                textNodesList.Add(new TextNodeInfo(
                    text,
                    currentIndex,
                    textValue.Length
                ));

                sb.Append(textValue);
                currentIndex += textValue.Length;
            }
        }

        return new ParagraphStructure(sb.ToString(), [.. textNodesList]);
    }

    private static List<TextNodeInfo> FindNodesToReplace(
        ParagraphStructure structure,
        int matchStart,
        int matchEnd)
    {
        var result = new List<TextNodeInfo>(4);
        int firstNodeIndex = structure.FindFirstNodeIndexAtPosition(matchStart);

        if (firstNodeIndex == -1)
            return result;

        var textNodes = structure.TextNodes;
        for (int i = firstNodeIndex; i < textNodes.Length; i++)
        {
            var node = textNodes[i];
            if (node.StartIndex >= matchEnd)
                break;

            if (node.StartIndex + node.Length > matchStart)
            {
                result.Add(node);
            }
        }

        return result;
    }

    private static void ExecuteReplacement(
        List<TextNodeInfo> nodesToReplace,
        int matchStart,
        int matchEnd,
        string newValue,
        bool breakPage = false)
    {
        if (nodesToReplace.Count == 0) return;

        var firstNode = nodesToReplace[0];
        string oldText = firstNode.Text.Text ?? string.Empty;
        int startInFirstNode = matchStart - firstNode.StartIndex;
        int charsToReplaceInFirstNode = Math.Min(
            oldText.Length - startInFirstNode,
            matchEnd - matchStart
        );

        string processedNewValue = ReplaceSpacesWithNonBreaking(newValue);
        firstNode.Text.Text = ReplaceSubstringOptimized(
            oldText,
            startInFirstNode,
            charsToReplaceInFirstNode,
            processedNewValue
        );

        // Очищаем остальные текстовые ноды
        for (int i = 1; i < nodesToReplace.Count; i++)
        {
            nodesToReplace[i].Text.Text = string.Empty;
        }

        if (breakPage)
        {
            if (nodesToReplace[0].Text.Parent is Run run && run.Parent is Paragraph para)
            {
                var breakRun = new Run(new Break() { Type = BreakValues.Page });
                if (run.RunProperties is not null)
                    breakRun.RunProperties = (RunProperties)run.RunProperties.CloneNode(true);
                para.AppendChild(breakRun);
            }
        }
    }

    private static unsafe string ReplaceSpacesWithNonBreaking(string input)
    {
        if (!input.Contains(' '))
            return input;

        fixed (char* pInput = input)
        {
            char* resultPtr = stackalloc char[input.Length];
            for (int i = 0; i < input.Length; i++)
            {
                resultPtr[i] = pInput[i] == ' ' ? '\u00A0' : pInput[i];
            }
            return new string(resultPtr, 0, input.Length);
        }
    }

    private static string ReplaceSubstringOptimized(string original, int start, int length, string replacement)
    {
        if (string.IsNullOrEmpty(original))
            return replacement ?? string.Empty;

        if (start < 0 || start >= original.Length || length <= 0)
            return original;

        if (start == 0 && length == original.Length)
            return replacement;

        int end = Math.Min(start + length, original.Length);

        // Оптимизированная конкатенация
        var sb = new StringBuilder(original.Length - length + replacement.Length);
        if (start > 0)
        {
            sb.Append(original, 0, start);
        }
        sb.Append(replacement);
        if (end < original.Length)
        {
            sb.Append(original, end, original.Length - end);
        }
        return sb.ToString();
    }
}