namespace QWERTYkez.WordProcessor;

/// <summary>
/// Выполняет замену всех вхождений ключей из словаря на соответствующие массивы значений.
/// Каждое значение из массива помещается в отдельный параграф, причём первое значение
/// остаётся в текущем параграфе, а последующие создают новые.
/// Текст между вхождениями и после последнего сохраняется в соответствующих параграфах.
/// Поддерживает разрывы страниц и смену ориентации (альбомная/книжная) через <see cref="ReplaceItem.SplitValue"/>.
/// </summary>
internal static class MultiReplaceExt
{
    // ---------- ПУБЛИЧНЫЕ МЕТОДЫ (для Body) ----------

    #region Body.Replace с одним ключом

    internal static void Replace(this Body body, string oldValue, IEnumerable<string> newValues, StringComparison comparisonType)
    {
        if (body is null || string.IsNullOrEmpty(oldValue) || newValues is null) return;
        body.Replace(new Dictionary<string, IEnumerable<string>> { { oldValue, newValues } }, comparisonType);
    }

    internal static void Replace(this Body body, string oldValue, IEnumerable<ReplaceItem> newValues, StringComparison comparisonType)
    {
        if (body is null || string.IsNullOrEmpty(oldValue) || newValues is null) return;
        body.Replace(new Dictionary<string, IEnumerable<ReplaceItem>> { { oldValue, newValues } }, comparisonType);
    }

    #endregion

    #region Body.Replace со словарём массивов

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

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

    private static void ReplaceInBody(
        Body body,
        IEnumerable<KeyValuePair<string, IEnumerable<string>>>? stringReplacements,
        IEnumerable<KeyValuePair<string, IEnumerable<ReplaceItem>>>? itemReplacements,
        StringComparison comparisonType)
    {
        var paragraphs = body.Elements<Paragraph>().ToList();
        for (int i = paragraphs.Count - 1; i >= 0; i--)
        {
            var p = paragraphs[i];
            if (p?.Parent is null) continue;

            var newParas = ProcessMultiReplacements(p, stringReplacements, itemReplacements, comparisonType);
            if (newParas is { Count: > 0 })
                ParagraphReplacer.ReplaceParagraph(p, newParas);
        }
    }

    #endregion

    #region Paragraph.ReplaceWithMultiple (один ключ)

    internal static bool ReplaceWithMultiple(this Paragraph? paragraph, string oldValue, IEnumerable<string> newValues, StringComparison comparisonType)
    {
        if (paragraph?.Parent is null || string.IsNullOrEmpty(oldValue) || newValues is null || !newValues.Any())
            return false;

        var dict = new Dictionary<string, IEnumerable<string>> { { oldValue, newValues } };
        var newParas = ProcessMultiReplacements(paragraph, dict, null, comparisonType);

        if (newParas is { Count: > 0 })
        {
            ParagraphReplacer.ReplaceParagraph(paragraph, newParas);
            return true;
        }
        return false;
    }

    internal static bool ReplaceWithMultiple(this Paragraph? paragraph, string oldValue, IEnumerable<ReplaceItem> newValues, StringComparison comparisonType)
    {
        if (paragraph?.Parent is null || string.IsNullOrEmpty(oldValue) || newValues is null || !newValues.Any())
            return false;

        var dict = new Dictionary<string, IEnumerable<ReplaceItem>> { { oldValue, newValues } };
        var newParas = ProcessMultiReplacements(paragraph, null, dict, comparisonType);

        if (newParas is { Count: > 0 })
        {
            ParagraphReplacer.ReplaceParagraph(paragraph, newParas);
            return true;
        }
        return false;
    }

    #endregion

    #region ProcessParagraphWithAllReplacements (для обратной совместимости)

    internal static List<Paragraph>? ProcessParagraphWithAllReplacements(
        Paragraph paragraph,
        IEnumerable<KeyValuePair<string, IEnumerable<string>>> replacements,
        StringComparison comparisonType)
        => ProcessMultiReplacements(paragraph, replacements, null, comparisonType);

    internal static List<Paragraph>? ProcessParagraphWithAllReplacements(
        Paragraph paragraph,
        IEnumerable<KeyValuePair<string, IEnumerable<ReplaceItem>>> replacements,
        StringComparison comparisonType)
        => ProcessMultiReplacements(paragraph, null, replacements, comparisonType);

    internal static List<Paragraph>? ProcessParagraphWithAllReplacements(
        Paragraph paragraph,
        IEnumerable<KeyValuePair<string, string>> replacements,
        StringComparison comparisonType)
    {
        var dict = replacements
            .Where(kvp => !string.IsNullOrEmpty(kvp.Key))
            .ToDictionary(kvp => kvp.Key, kvp => (IEnumerable<string>)[kvp.Value]);

        return ProcessMultiReplacements(paragraph, dict, null, comparisonType);
    }

    #endregion

    // ---------- ВНУТРЕННЯЯ РЕАЛИЗАЦИЯ ----------

    private class MatchDefinition(string key, IEnumerable<ReplaceItem> values)
    {
        public string Key { get; } = key;
        public IEnumerable<ReplaceItem> Values { get; } = values;
    }

    private class Match
    {
        public MatchDefinition Definition { get; init; } = null!;
        public int Start { get; init; }
        public int End { get; init; }
    }

    private class RunSegment(Run run, string text, int start, int end)
    {
        public Run Run { get; } = run;
        public string Text { get; } = text;
        public int Start { get; } = start;
        public int End { get; } = end;
    }

    private class ParagraphStructure(string fullText, List<RunSegment> segments)
    {
        public string FullText { get; } = fullText;
        public List<RunSegment> Segments { get; } = segments;
    }

    private static ParagraphStructure AnalyzeParagraphStructure(List<Run> runs)
    {
        var segments = new List<RunSegment>(runs.Count);
        var sb = new StringBuilder();
        int pos = 0;

        foreach (var run in runs)
        {
            string text = GetRunText(run);
            if (string.IsNullOrEmpty(text)) continue;

            segments.Add(new RunSegment(run, text, pos, pos + text.Length));
            sb.Append(text);
            pos += text.Length;
        }
        return new ParagraphStructure(sb.ToString(), segments);
    }

    private static string GetRunText(Run run)
    {
        var sb = new StringBuilder();
        foreach (var text in run.Elements<Text>())
            sb.Append(text.Text);
        return sb.ToString();
    }

    /// <summary>Клонирует параграф, удаляя все SectionProperties и PageBreakBefore.</summary>
    private static Paragraph CloneParagraphWithoutSection(Paragraph original)
    {
        var newPara = new Paragraph();
        if (original.ParagraphProperties is null) return newPara;

        var newProps = new ParagraphProperties();
        foreach (var child in original.ParagraphProperties.ChildElements)
        {
            if (child is not SectionProperties and not PageBreakBefore)
                newProps.AppendChild(child.CloneNode(true));
        }

        if (newProps.HasChildren)
            newPara.ParagraphProperties = newProps;

        return newPara;
    }

    private static Paragraph? BuildRemainderParagraph(Paragraph original, ParagraphStructure structure, int position)
    {
        if (position >= structure.FullText.Length) return null;

        var newPara = CloneParagraphWithoutSection(original);
        foreach (var seg in structure.Segments)
        {
            if (seg.End <= position) continue;

            if (seg.Start >= position)
            {
                newPara.AppendChild(seg.Run.CloneNode(true));
            }
            else
            {
                var runClone = (Run)seg.Run.CloneNode(true);
                runClone.RemoveAllChildren<Text>(); // Упрощенная очистка

                int offset = position - seg.Start;
                runClone.AppendChild(new Text(seg.Text.Substring(offset)));
                newPara.AppendChild(runClone);
            }
        }

        // Удаляем пустые Run-ы без вложений
        newPara.Elements<Run>().Where(r => !r.HasChildren).ToList().ForEach(r => r.Remove());

        return !newPara.Elements<Run>().Any() && newPara.ParagraphProperties is null ? null : newPara;
    }

    private static void InsertFormattedRun(Paragraph para, ReplaceItem item, ParagraphStructure structure, int position)
    {
        var seg = structure.Segments.FirstOrDefault(s => position >= s.Start && position < s.End);
        if (seg is null) return;

        var textRun = new Run();
        if (seg.Run.RunProperties is not null)
            textRun.RunProperties = (RunProperties)seg.Run.RunProperties.CloneNode(true);

        textRun.AppendChild(new Text(item.Text ?? string.Empty));
        para.AppendChild(textRun);
    }

    /// <summary>
    /// Добавляет SectionProperties к параграфу. Все значения (PageSize, PageMargin) берутся из документа.
    /// </summary>
    private static void AddSectionProperties(Paragraph para, PageBreakType splitValue, bool addPageSize, SectionProperties? sourceSection, SectionProperties? portraitSection)
    {
        if (para is null) return;

        // Удаляем существующие секции и разрывы
        if (para.ParagraphProperties is not null)
        {
            para.ParagraphProperties.RemoveAllChildren<SectionProperties>();
            para.ParagraphProperties.RemoveAllChildren<PageBreakBefore>();
        }

        para.ParagraphProperties ??= new ParagraphProperties();
        var sectionProps = new SectionProperties();

        // Добавляем PageSize
        var sizeSource = addPageSize ? sourceSection : portraitSection;
        var sourcePageSize = sizeSource?.GetFirstChild<PageSize>()
                          ?? portraitSection?.GetFirstChild<PageSize>()
                          ?? sourceSection?.GetFirstChild<PageSize>();

        if (sourcePageSize is not null)
        {
            var pageSizeClone = (PageSize)sourcePageSize.CloneNode(true);
            bool sourceIsLandscape = pageSizeClone.Orient?.Value == PageOrientationValues.Landscape ||
                                     pageSizeClone.Width?.Value > pageSizeClone.Height?.Value;
            bool targetIsLandscape = addPageSize && splitValue == PageBreakType.NewLandscapeSection;

            if (targetIsLandscape && !sourceIsLandscape)
            {
                pageSizeClone.SwapValues();
                pageSizeClone.Orient = PageOrientationValues.Landscape;
            }
            else if (!targetIsLandscape && sourceIsLandscape)
            {
                pageSizeClone.SwapValues();
                pageSizeClone.Orient = addPageSize ? PageOrientationValues.Portrait : null;
            }
            else
            {
                pageSizeClone.Orient = targetIsLandscape ? PageOrientationValues.Landscape : (addPageSize ? PageOrientationValues.Portrait : null);
            }
            sectionProps.AppendChild(pageSizeClone);
        }

        // Копируем PageMargin
        PageMargin? marginToUse = null;
        if (addPageSize)
        {
            var sourceMargin = sourceSection?.GetFirstChild<PageMargin>() ?? portraitSection?.GetFirstChild<PageMargin>();
            if (sourceMargin is not null)
            {
                var marginClone = (PageMargin)sourceMargin.CloneNode(true);
                var sourceIsLndscape = sourceSection?.GetFirstChild<PageSize>()?.Orient?.Value == PageOrientationValues.Landscape ||
                                       sourceSection?.GetFirstChild<PageSize>()?.Width?.Value > sourceSection?.GetFirstChild<PageSize>()?.Height?.Value;

                if ((splitValue == PageBreakType.NewLandscapeSection && !sourceIsLndscape) ||
                    (splitValue == PageBreakType.NewPortraitSection && sourceIsLndscape))
                {
                    marginClone.SwapBottomRight();
                }
                marginToUse = marginClone;
            }
        }
        else if (portraitSection?.GetFirstChild<PageMargin>() is { } portraitMargin)
        {
            marginToUse = (PageMargin)portraitMargin.CloneNode(true);
        }

        if (marginToUse is not null)
            sectionProps.AppendChild(marginToUse);

        sectionProps.AppendChild(new SectionType { Val = SectionMarkValues.NextPage });
        para.ParagraphProperties.AppendChild(sectionProps);
    }

    /// <summary>Основной алгоритм множественной замены с поддержкой разрывов и смены ориентации.</summary>
    private static List<Paragraph>? ProcessMultiReplacements(
        Paragraph original,
        IEnumerable<KeyValuePair<string, IEnumerable<string>>>? stringReplacements,
        IEnumerable<KeyValuePair<string, IEnumerable<ReplaceItem>>>? itemReplacements,
        StringComparison comparisonType)
    {
        var definitions = new List<MatchDefinition>();

        if (stringReplacements is not null)
        {
            definitions.AddRange(stringReplacements
                .Where(kvp => !string.IsNullOrEmpty(kvp.Key) && kvp.Value != null && kvp.Value.Any())
                .Select(kvp => new MatchDefinition(kvp.Key, kvp.Value.Select(v => new ReplaceItem(v, PageBreakType.None)))));
        }

        if (itemReplacements is not null)
        {
            definitions.AddRange(itemReplacements
                .Where(kvp => !string.IsNullOrEmpty(kvp.Key) && kvp.Value != null && kvp.Value.Any())
                .Select(kvp => new MatchDefinition(kvp.Key, kvp.Value)));
        }

        if (definitions.Count == 0) return null;

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

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

        var matches = new List<Match>();
        foreach (var def in definitions)
        {
            int pos = 0;
            while ((pos = fullText.IndexOf(def.Key, pos, comparisonType)) != -1)
            {
                matches.Add(new Match { Definition = def, Start = pos, End = pos + def.Key.Length });
                pos += def.Key.Length;
            }
        }

        if (matches.Count == 0) return null;
        matches.Sort((a, b) => a.Start.CompareTo(b.Start));

        var body = original.Ancestors<Body>().FirstOrDefault();
        var sourceSection = original.ParagraphProperties?.GetFirstChild<SectionProperties>()?.CloneNode(true) as SectionProperties
                            ?? body?.Elements<SectionProperties>().LastOrDefault()?.CloneNode(true) as SectionProperties
                            ?? new SectionProperties();

        var portraitSection = body?.Elements<SectionProperties>().FirstOrDefault()?.CloneNode(true) as SectionProperties
                              ?? new SectionProperties();

        var resultParas = new List<Paragraph>();
        Paragraph? currentPara = null;
        int currentPos = 0;
        bool sectionChangeInsideGroup = false;
        PageBreakType? lastOrientation = null;

        foreach (var match in matches)
        {
            if (currentPos < match.Start)
            {
                var beforePara = CloneParagraphWithoutSection(original);
                foreach (var seg in structure.Segments)
                {
                    if (seg.End <= currentPos) continue;
                    if (seg.Start >= match.Start) break;

                    if (seg.Start >= currentPos && seg.End <= match.Start)
                    {
                        beforePara.AppendChild(seg.Run.CloneNode(true));
                    }
                    else if (seg.Start < match.Start && seg.End > currentPos)
                    {
                        int startOffset = Math.Max(0, currentPos - seg.Start);
                        int endOffset = Math.Min(seg.Text.Length, match.Start - seg.Start);

                        var runClone = (Run)seg.Run.CloneNode(true);
                        runClone.RemoveAllChildren<Text>();
                        runClone.AppendChild(new Text(seg.Text.Substring(startOffset, endOffset - startOffset)));
                        beforePara.AppendChild(runClone);
                    }
                }
                if (beforePara.Elements<Run>().Any())
                {
                    resultParas.Add(beforePara);
                    currentPara = beforePara;
                }
            }

            var values = match.Definition.Values.ToList();
            if (values.Count == 0) continue;

            for (int vIdx = 0; vIdx < values.Count; vIdx++)
            {
                var item = values[vIdx];
                currentPara = CloneParagraphWithoutSection(original);
                resultParas.Add(currentPara);

                InsertFormattedRun(currentPara, item, structure, match.Start);

                if (item.SplitValue is PageBreakType.NewLandscapeSection or PageBreakType.NewPortraitSection)
                {
                    bool addPageSize = vIdx != 0;
                    var orientation = vIdx != 0 ? PageBreakType.NewLandscapeSection : item.SplitValue;

                    AddSectionProperties(currentPara, orientation, addPageSize, sourceSection, portraitSection);
                    lastOrientation = item.SplitValue;
                    sectionChangeInsideGroup = true;
                }
                else if (item.SplitValue == PageBreakType.PageBreak)
                {
                    var seg = structure.Segments.FirstOrDefault(s => match.Start >= s.Start && match.Start < s.End);
                    var breakRun = new Run(new Break { Type = BreakValues.Page });
                    if (seg?.Run.RunProperties is not null)
                        breakRun.RunProperties = (RunProperties)seg.Run.RunProperties.CloneNode(true);
                    currentPara.AppendChild(breakRun);
                }
            }

            if (sectionChangeInsideGroup && lastOrientation.HasValue && currentPara?.ParagraphProperties?.GetFirstChild<SectionProperties>() is null)
            {
                AddSectionProperties(currentPara!, lastOrientation.Value, lastOrientation.Value == PageBreakType.NewLandscapeSection, sourceSection, portraitSection);
            }

            if (body is not null && sourceSection.GetFirstChild<PageSize>() is { } sourcePageSize)
            {
                bool sourceIsLandscape = sourcePageSize.Orient?.Value == PageOrientationValues.Landscape || sourcePageSize.Width?.Value > sourcePageSize.Height?.Value;
                bool lastIsPortrait = lastOrientation == PageBreakType.NewPortraitSection;

                if (sourceIsLandscape && sectionChangeInsideGroup && lastIsPortrait && !body.Elements<SectionProperties>().Any(s => s.GetFirstChild<PageSize>()?.Orient?.Value == PageOrientationValues.Landscape))
                {
                    var bodySection = new SectionProperties();
                    var pageSizeClone = (PageSize)sourcePageSize.CloneNode(true);

                    if (pageSizeClone.Orient?.Value != PageOrientationValues.Landscape)
                    {
                        pageSizeClone.SwapValues();
                        pageSizeClone.Orient = PageOrientationValues.Landscape;
                    }
                    bodySection.AppendChild(pageSizeClone);

                    if (sourceSection.GetFirstChild<PageMargin>() is { } sourceMargin)
                    {
                        var marginClone = (PageMargin)sourceMargin.CloneNode(true);
                        if (sourceSection.GetFirstChild<PageSize>()?.Orient?.Value != PageOrientationValues.Landscape)
                        {
                            marginClone.SwapBottomRight();
                        }
                        bodySection.AppendChild(marginClone);
                    }
                    bodySection.AppendChild(new SectionType { Val = SectionMarkValues.NextPage });
                    body.AppendChild(bodySection);
                }
            }
            currentPos = match.End;
        }

        if (currentPos < fullText.Length && BuildRemainderParagraph(original, structure, currentPos) is { } remainderPara)
        {
            if (sectionChangeInsideGroup && lastOrientation.HasValue)
            {
                remainderPara.InsertAt(new Run(new Break { Type = BreakValues.Page }), 0);
                AddSectionProperties(remainderPara, lastOrientation.Value, lastOrientation.Value == PageBreakType.NewLandscapeSection, sourceSection, portraitSection);
            }
            resultParas.Add(remainderPara);
        }

        resultParas.RemoveAll(p => !p.Elements<Run>().Any() && p.ParagraphProperties is null);
        return resultParas.Count > 0 ? resultParas : null;
    }
}