using System.IO;
using System.Text.Json;
using DocumentFormat.OpenXml;
using DocumentFormat.OpenXml.Packaging;
using DocumentFormat.OpenXml.Spreadsheet;

namespace AxCopilot.Services.Agent;

/// <summary>
/// Excel (.xlsx) 문서를 생성하는 내장 스킬.
/// 셀 서식(색상/테두리/볼드), 수식, 열 너비, 셀 병합, 틀 고정, 테마, 숫자 형식, 멀티시트, 정렬 등을 지원합니다.
/// </summary>
public class ExcelSkill : IAgentTool
{
    public string Name => "excel_create";
    public string Description => "Create a styled Excel (.xlsx) file. " +
        "Supports: header styling (bold white text on colored background), " +
        "striped rows, column auto-width, formulas (=SUM, =AVERAGE, etc), " +
        "cell merge, freeze panes (freeze header row), number formatting, " +
        "themes (professional/modern/dark/minimal), column alignments, executive summary sheets, and multi-sheet workbooks. " +
        "Inline icons: use {icon:name} in cell text (e.g. '{icon:checkmark} 완료', '{icon:warning} 주의'). " +
        "170+ built-in icons: checkmark, warning, star, rocket, chart_up, chart_down, etc.";

    public ToolParameterSchema Parameters => new()
    {
        Properties = new()
        {
            ["path"] = new() { Type = "string", Description = "Output file path (.xlsx). Relative to work folder." },
            ["sheet_name"] = new() { Type = "string", Description = "Sheet name. Default: 'Sheet1'." },
            ["headers"] = new() { Type = "array", Description = "Column headers as JSON array of strings.", Items = new() { Type = "string" } },
            ["rows"] = new() { Type = "array", Description = "Data rows as JSON array of arrays. Use string starting with '=' for formulas (e.g. '=SUM(A2:A10)').", Items = new() { Type = "array", Items = new() { Type = "string" } } },
            ["style"] = new() { Type = "string", Description = "Table style: 'styled' (colored header, striped rows, borders) or 'plain'. Default: 'styled'" },
            ["theme"] = new() { Type = "string", Description = "Color theme: 'professional' (blue), 'modern' (green), 'dark' (slate), 'minimal' (gray). Default: 'professional'." },
            ["col_widths"] = new() { Type = "array", Description = "Column widths as JSON array of numbers (in characters). e.g. [15, 10, 20]. Auto-fit if omitted.", Items = new() { Type = "number" } },
            ["freeze_header"] = new() { Type = "boolean", Description = "Freeze the header row. Default: true for styled." },
            ["merges"] = new() { Type = "array", Description = "Cell merge ranges. e.g. [\"A1:C1\", \"D5:D8\"]", Items = new() { Type = "string" } },
            ["summary_row"] = new() { Type = "object", Description = "Auto-generate summary row. {\"label\": \"합계\", \"columns\": {\"B\": \"SUM\", \"C\": \"AVERAGE\"}}. Adds formulas at bottom." },
            ["summary_sheet"] = new()
            {
                Type = "object",
                Description = "Optional executive summary sheet inserted before detail sheets. " +
                    "Example: {\"name\":\"Summary\",\"title\":\"2026 운영 리뷰\",\"subtitle\":\"핵심 KPI와 후속 과제\",\"kpis\":[{\"label\":\"Revenue\",\"value\":\"12%\",\"trend\":\"YoY\",\"note\":\"Strong\"}],\"highlights\":[\"핵심 인사이트 1\",\"핵심 인사이트 2\"],\"actions\":[\"즉시 과제 1\",\"즉시 과제 2\"]}"
            },
            ["number_formats"] = new() { Type = "array", Description = "Number format per column index. Supported: 'currency' (#,##0\"원\"), 'percent' (0.00%), 'decimal' (#,##0.00), 'integer' (#,##0), 'date' (yyyy-mm-dd), or any custom Excel format string. e.g. [\"text\",\"integer\",\"currency\",\"percent\"]", Items = new() { Type = "string" } },
            ["data_validations"] = new() { Type = "array", Description = "Validation rules such as [{\"range\":\"E2:E100\",\"type\":\"list\",\"formula1\":\"\\\"Open,In Progress,Done\\\"\",\"allow_blank\":true,\"prompt\":\"Select status\"}].", Items = new() { Type = "object" } },
            ["conditional_formats"] = new() { Type = "array", Description = "Conditional formatting rules such as [{\"range\":\"C2:C20\",\"type\":\"color_scale\",\"low\":\"FEE2E2\",\"mid\":\"FEF3C7\",\"high\":\"DCFCE7\"},{\"range\":\"D2:D20\",\"type\":\"data_bar\",\"color\":\"2563EB\"}].", Items = new() { Type = "object" } },
            ["col_alignments"] = new() { Type = "array", Description = "Horizontal alignment per column: 'left', 'center', 'right'. Headers always center-aligned.", Items = new() { Type = "string" } },
            ["sheets"] = new() { Type = "array", Description = "Multi-sheet mode: array of sheet objects [{name, headers, rows, style?, theme?, col_widths?, freeze_header?, number_formats?, col_alignments?, merges?, summary_row?, data_validations?, conditional_formats?}]. When present, overrides top-level headers/rows/sheet_name.", Items = new() { Type = "object" } },
        },
        Required = []
    };

    // ═══════════════════════════════════════════════════
    //  Theme definitions
    // ═══════════════════════════════════════════════════

    private record ThemeColors(string HeaderBg, string HeaderFg, string StripeBg);

    private static ThemeColors GetTheme(string? theme) => theme?.ToLower() switch
    {
        "modern" => new("FF065F46", "FFFFFFFF", "FFF0FDF4"),
        "dark"   => new("FF1E293B", "FFFFFFFF", "FFF1F5F9"),
        "minimal"=> new("FF374151", "FFFFFFFF", "FFF9FAFB"),
        _        => new("FF1F4E79", "FFFFFFFF", "FFF2F7FC"), // professional (default)
    };

    // ═══════════════════════════════════════════════════
    //  Number format resolution
    // ═══════════════════════════════════════════════════

    // Returns (isBuiltIn, numFmtId, formatString)
    // Built-in IDs we use: 0=General, 164+ = custom
    private static (bool isBuiltIn, uint numFmtId, string? formatCode) ResolveNumberFormat(string? fmt)
    {
        if (string.IsNullOrEmpty(fmt) || fmt == "text")
            return (true, 0, null); // General / no special format

        return fmt.ToLower() switch
        {
            "percent"  => (true, 10, null),    // 0.00%  (built-in id 10)
            "decimal"  => (true, 4, null),     // #,##0.00 (built-in id 4)
            "integer"  => (true, 3, null),     // #,##0 (built-in id 3)
            "date"     => (true, 14, null),    // m/d/yyyy (built-in id 14)
            "currency" => (false, 0, "#,##0\"원\""),  // custom
            _ => (false, 0, fmt),               // user-supplied custom string
        };
    }

    // ═══════════════════════════════════════════════════
    //  Execute
    // ═══════════════════════════════════════════════════

    public async Task<ToolResult> ExecuteAsync(JsonElement args, AgentContext context, CancellationToken ct)
    {
        // path 미제공 시 title 또는 sheet_name에서 자동 생성
        string path;
        if (args.SafeTryGetProperty("path", out var pathEl) && pathEl.ValueKind == JsonValueKind.String
            && !string.IsNullOrWhiteSpace(pathEl.SafeGetString()))
        {
            path = pathEl.SafeGetString()!;
        }
        else
        {
            var hint = (args.SafeTryGetProperty("title", out var tEl) ? tEl.SafeGetString() : null)
                    ?? (args.SafeTryGetProperty("sheet_name", out var snEl) ? snEl.SafeGetString() : null)
                    ?? "workbook";
            var safe = System.Text.RegularExpressions.Regex.Replace(hint, @"[\\/:*?""<>|]", "_").Trim().TrimEnd('.');
            if (safe.Length > 60) safe = safe[..60].TrimEnd();
            path = (string.IsNullOrWhiteSpace(safe) ? "workbook" : safe) + ".xlsx";
        }

        var fullPath = FileReadTool.ResolvePath(path, context.WorkFolder);
        if (context.ActiveTab == "Cowork") fullPath = AgentContext.EnsureTimestampedPath(fullPath);
        if (!fullPath.EndsWith(".xlsx", StringComparison.OrdinalIgnoreCase))
            fullPath += ".xlsx";

        if (!context.IsPathAllowed(fullPath))
            return ToolResult.Fail($"경로 접근 차단: {fullPath}");

        if (!await context.CheckWritePermissionAsync(Name, fullPath))
            return ToolResult.Fail($"쓰기 권한 거부: {fullPath}");

        try
        {
            var dir = Path.GetDirectoryName(fullPath);
            if (!string.IsNullOrEmpty(dir)) Directory.CreateDirectory(dir);

            var hasSummarySheet = args.SafeTryGetProperty("summary_sheet", out var summarySheet)
                && summarySheet.ValueKind == JsonValueKind.Object;

            // Determine if we are in multi-sheet mode
            var multiSheetMode = args.SafeTryGetProperty("sheets", out var sheetsArr)
                && sheetsArr.ValueKind == JsonValueKind.Array
                && sheetsArr.GetArrayLength() > 0;

            if (multiSheetMode)
                return GenerateMultiSheetWorkbook(args, sheetsArr, fullPath, hasSummarySheet ? summarySheet : default);
            else if (hasSummarySheet)
                return GenerateSingleSheetWorkbookWithSummary(args, summarySheet, fullPath);
            else
                return GenerateSingleSheetWorkbook(args, fullPath);
        }
        catch (Exception ex)
        {
            return ToolResult.Fail($"Excel 생성 실패: {ex.Message}");
        }
    }

    // ═══════════════════════════════════════════════════
    //  Single-sheet workbook (backward-compatible path)
    // ═══════════════════════════════════════════════════

    private static ToolResult GenerateSingleSheetWorkbook(JsonElement args, string fullPath)
    {
        if (!args.SafeTryGetProperty("headers", out var headers) || headers.ValueKind != JsonValueKind.Array)
            return ToolResult.Fail("필수 파라미터 누락: 'headers'");
        if (!args.SafeTryGetProperty("rows", out var rows) || rows.ValueKind != JsonValueKind.Array)
            return ToolResult.Fail("필수 파라미터 누락: 'rows'");

        var sheetName   = args.SafeTryGetProperty("sheet_name", out var sn)  ? sn.SafeGetString()  ?? "Sheet1"    : "Sheet1";
        var tableStyle  = args.SafeTryGetProperty("style", out var st)       ? st.SafeGetString()  ?? "styled"    : "styled";
        var themeName   = args.SafeTryGetProperty("theme", out var th)       ? th.SafeGetString()                 : null;
        var isStyled    = tableStyle != "plain";
        var freezeHeader= args.SafeTryGetProperty("freeze_header", out var fh) ? fh.GetBoolean() : isStyled;

        var theme       = GetTheme(themeName);
        var numFmts     = ParseNumberFormats(args, "number_formats");
        var alignments  = ParseAlignments(args, "col_alignments");

        // Collect custom number formats for stylesheet
        var customFmts  = CollectCustomFormats(numFmts);

        using var spreadsheet = SpreadsheetDocument.Create(fullPath, SpreadsheetDocumentType.Workbook);
        var workbookPart = spreadsheet.AddWorkbookPart();
        workbookPart.Workbook = new Workbook();

        var stylesPart = workbookPart.AddNewPart<WorkbookStylesPart>();
        stylesPart.Stylesheet = CreateStylesheet(isStyled, theme, customFmts, numFmts, alignments);
        stylesPart.Stylesheet.Save();

        var worksheetPart = workbookPart.AddNewPart<WorksheetPart>();
        worksheetPart.Worksheet = new Worksheet();

        var colCount = headers.GetArrayLength();

        var summaryArg = args.SafeTryGetProperty("summary_row", out var sumEl) ? sumEl : default;
        var mergesArg  = args.SafeTryGetProperty("merges", out var mergeEl)    ? mergeEl : default;
        var validationsArg = args.SafeTryGetProperty("data_validations", out var validationsEl) ? validationsEl : default;
        var conditionalFormatsArg = args.SafeTryGetProperty("conditional_formats", out var conditionalFormatsEl) ? conditionalFormatsEl : default;

        var (rowCount, validationCount, conditionalFormattingCount) = WriteSheetContent(worksheetPart, args, sheetName, headers, rows,
            isStyled, freezeHeader, theme, numFmts, alignments, customFmts,
            summaryArg, mergesArg, validationsArg, conditionalFormatsArg, colCount);

        var wbSheets = workbookPart.Workbook.AppendChild(new Sheets());
        wbSheets.Append(new Sheet
        {
            Id = workbookPart.GetIdOfPart(worksheetPart),
            SheetId = 1,
            Name = sheetName,
        });

        workbookPart.Workbook.Save();
        var features = BuildFeatureList(isStyled, freezeHeader,
            mergesArg.ValueKind == JsonValueKind.Array,
            summaryArg.ValueKind == JsonValueKind.Object,
            numFmts.Count > 0, alignments.Count > 0, themeName);

        var review = ArtifactQualityReviewService.ReviewWorkbook(new WorkbookReviewInput(
            sheetName,
            1,
            1,
            rowCount,
            CountFormulaCells(rows),
            0,
            validationCount,
            conditionalFormattingCount,
            false,
            false,
            summaryArg.ValueKind == JsonValueKind.Object));
        features += $"\n{review.ToToolSummary()}";

        return ToolResult.Ok(
            $"Excel 파일 생성 완료: {fullPath}\n시트: {sheetName}, 열: {colCount}, 행: {rowCount}{features}",
            fullPath);
    }

    // ═══════════════════════════════════════════════════
    //  Multi-sheet workbook
    // ═══════════════════════════════════════════════════

    private static ToolResult GenerateSingleSheetWorkbookWithSummary(JsonElement args, JsonElement summarySheet, string fullPath)
    {
        if (!args.SafeTryGetProperty("headers", out var headers) || headers.ValueKind != JsonValueKind.Array)
            return ToolResult.Fail("?꾩닔 ?뚮씪誘명꽣 ?꾨씫: 'headers'");
        if (!args.SafeTryGetProperty("rows", out var rows) || rows.ValueKind != JsonValueKind.Array)
            return ToolResult.Fail("?꾩닔 ?뚮씪誘명꽣 ?꾨씫: 'rows'");

        var sheetName = args.SafeTryGetProperty("sheet_name", out var sn) ? sn.SafeGetString() ?? "Sheet1" : "Sheet1";
        var tableStyle = args.SafeTryGetProperty("style", out var st) ? st.SafeGetString() ?? "styled" : "styled";
        var themeName = args.SafeTryGetProperty("theme", out var th) ? th.SafeGetString() : null;
        var isStyled = tableStyle != "plain";
        var freezeHeader = args.SafeTryGetProperty("freeze_header", out var fh) ? fh.GetBoolean() : isStyled;

        var theme = GetTheme(themeName);
        var numFmts = ParseNumberFormats(args, "number_formats");
        var alignments = ParseAlignments(args, "col_alignments");
        var customFmts = CollectCustomFormats(numFmts);

        using var spreadsheet = SpreadsheetDocument.Create(fullPath, SpreadsheetDocumentType.Workbook);
        var workbookPart = spreadsheet.AddWorkbookPart();
        workbookPart.Workbook = new Workbook();

        var stylesPart = workbookPart.AddNewPart<WorkbookStylesPart>();
        stylesPart.Stylesheet = CreateStylesheet(true, theme, customFmts, numFmts, alignments);
        stylesPart.Stylesheet.Save();

        var wbSheets = workbookPart.Workbook.AppendChild(new Sheets());

        var summaryName = summarySheet.SafeTryGetProperty("name", out var summaryNameEl)
            ? summaryNameEl.SafeGetString() ?? "Summary"
            : "Summary";
        var summaryPart = workbookPart.AddNewPart<WorksheetPart>();
        WriteExecutiveSummarySheet(summaryPart, summarySheet, [sheetName]);
        wbSheets.Append(new Sheet
        {
            Id = workbookPart.GetIdOfPart(summaryPart),
            SheetId = 1,
            Name = summaryName,
        });

        var worksheetPart = workbookPart.AddNewPart<WorksheetPart>();
        worksheetPart.Worksheet = new Worksheet();

        var colCount = headers.GetArrayLength();
        var summaryArg = args.SafeTryGetProperty("summary_row", out var sumEl) ? sumEl : default;
        var mergesArg = args.SafeTryGetProperty("merges", out var mergeEl) ? mergeEl : default;
        var validationsArg = args.SafeTryGetProperty("data_validations", out var validationsEl) ? validationsEl : default;
        var conditionalFormatsArg = args.SafeTryGetProperty("conditional_formats", out var conditionalFormatsEl) ? conditionalFormatsEl : default;
        var (rowCount, validationCount, conditionalFormattingCount) = WriteSheetContent(worksheetPart, args, sheetName, headers, rows,
            isStyled, freezeHeader, theme, numFmts, alignments, customFmts,
            summaryArg, mergesArg, validationsArg, conditionalFormatsArg, colCount);

        wbSheets.Append(new Sheet
        {
            Id = workbookPart.GetIdOfPart(worksheetPart),
            SheetId = 2,
            Name = sheetName,
        });

        workbookPart.Workbook.Save();

        var features = BuildFeatureList(isStyled, freezeHeader,
            mergesArg.ValueKind == JsonValueKind.Array,
            summaryArg.ValueKind == JsonValueKind.Object,
            numFmts.Count > 0, alignments.Count > 0, themeName);
        var review = ArtifactQualityReviewService.ReviewWorkbook(new WorkbookReviewInput(
            summaryName,
            2,
            1,
            rowCount,
            CountFormulaCells(rows),
            1,
            validationCount,
            conditionalFormattingCount,
            true,
            HasSummaryItems(summarySheet, "highlights"),
            HasSummaryItems(summarySheet, "actions")));
        features += $"\n{review.ToToolSummary()}";

        return ToolResult.Ok(
            $"Excel ?뚯씪 ?앹꽦 ?꾨즺: {fullPath}\n?쒗듃: {summaryName}, {sheetName}, ?? {colCount}, ?? {rowCount}{features} [?붿빟 ?쒗듃]",
            fullPath);
    }

    private static ToolResult GenerateMultiSheetWorkbook(JsonElement args, JsonElement sheetsArr, string fullPath, JsonElement summarySheet)
    {
        using var spreadsheet = SpreadsheetDocument.Create(fullPath, SpreadsheetDocumentType.Workbook);
        var workbookPart = spreadsheet.AddWorkbookPart();
        workbookPart.Workbook = new Workbook();

        // Build a combined set of custom formats and alignments across all sheets for the stylesheet.
        // We create one shared stylesheet (using the first sheet's theme if not overridden).
        var allNumFmts   = new List<string?>();
        var allAligns    = new List<string?>();
        foreach (var sheetDef in sheetsArr.EnumerateArray())
        {
            var nf = ParseNumberFormats(sheetDef, "number_formats");
            var al = ParseAlignments(sheetDef, "col_alignments");
            allNumFmts.AddRange(nf);
            allAligns.AddRange(al);
        }

        // Use first sheet's theme for the shared stylesheet
        var firstThemeName = sheetsArr[0].SafeTryGetProperty("theme", out var ft) ? ft.SafeGetString() : null;
        var firstTheme     = GetTheme(firstThemeName);

        var combinedCustomFmts = CollectCustomFormats(allNumFmts);

        var stylesPart = workbookPart.AddNewPart<WorkbookStylesPart>();
        stylesPart.Stylesheet = CreateStylesheet(true, firstTheme, combinedCustomFmts, allNumFmts, allAligns);
        stylesPart.Stylesheet.Save();

        var wbSheets = workbookPart.Workbook.AppendChild(new Sheets());

        uint sheetId = 1;
        var totalSheets = 0;
        var totalRows = 0;
        var totalFormulaCount = 0;
        var totalValidationCount = 0;
        var totalConditionalFormattingCount = 0;
        var detailSheetNames = new List<string>();

        foreach (var sheetDef in sheetsArr.EnumerateArray())
        {
            var detailSheetName = sheetDef.SafeTryGetProperty("name", out var nameEl)
                ? nameEl.SafeGetString() ?? $"Sheet{detailSheetNames.Count + 1}"
                : $"Sheet{detailSheetNames.Count + 1}";
            detailSheetNames.Add(detailSheetName);
        }

        if (summarySheet.ValueKind == JsonValueKind.Object)
        {
            var summaryName = summarySheet.SafeTryGetProperty("name", out var summaryNameEl)
                ? summaryNameEl.SafeGetString() ?? "Summary"
                : "Summary";
            var summaryPart = workbookPart.AddNewPart<WorksheetPart>();
            WriteExecutiveSummarySheet(summaryPart, summarySheet, detailSheetNames);
            wbSheets.Append(new Sheet
            {
                Id = workbookPart.GetIdOfPart(summaryPart),
                SheetId = sheetId++,
                Name = summaryName,
            });
        }

        foreach (var sheetDef in sheetsArr.EnumerateArray())
        {
            var sheetName    = sheetDef.SafeTryGetProperty("name", out var snEl)  ? snEl.SafeGetString() ?? $"Sheet{sheetId}"  : $"Sheet{sheetId}";
            var tableStyle   = sheetDef.SafeTryGetProperty("style", out var stEl) ? stEl.SafeGetString() ?? "styled"           : "styled";
            var themeName    = sheetDef.SafeTryGetProperty("theme", out var thEl) ? thEl.SafeGetString()                        : firstThemeName;
            var isStyled     = tableStyle != "plain";
            var freezeHeader = sheetDef.SafeTryGetProperty("freeze_header", out var fhEl) ? fhEl.GetBoolean() : isStyled;
            var theme        = GetTheme(themeName);
            var numFmts      = ParseNumberFormats(sheetDef, "number_formats");
            var alignments   = ParseAlignments(sheetDef, "col_alignments");

            if (!sheetDef.SafeTryGetProperty("headers", out var headers) || headers.ValueKind != JsonValueKind.Array) continue;
            if (!sheetDef.SafeTryGetProperty("rows",    out var rows)    || rows.ValueKind    != JsonValueKind.Array) continue;

            var colCount   = headers.GetArrayLength();
            var summaryArg = sheetDef.SafeTryGetProperty("summary_row", out var sumEl) ? sumEl : default;
            var mergesArg  = sheetDef.SafeTryGetProperty("merges", out var mergeEl)    ? mergeEl : default;
            var validationsArg = sheetDef.SafeTryGetProperty("data_validations", out var validationsEl) ? validationsEl : default;
            var conditionalFormatsArg = sheetDef.SafeTryGetProperty("conditional_formats", out var conditionalFormatsEl) ? conditionalFormatsEl : default;

            var worksheetPart = workbookPart.AddNewPart<WorksheetPart>();
            worksheetPart.Worksheet = new Worksheet();

            var (rowCount, validationCount, conditionalFormattingCount) = WriteSheetContent(worksheetPart, sheetDef, sheetName, headers, rows,
                isStyled, freezeHeader, theme, numFmts, alignments, combinedCustomFmts,
                summaryArg, mergesArg, validationsArg, conditionalFormatsArg, colCount);

            wbSheets.Append(new Sheet
            {
                Id = workbookPart.GetIdOfPart(worksheetPart),
                SheetId = sheetId,
                Name = sheetName,
            });

            sheetId++;
            totalSheets++;
            totalRows += rowCount;
            totalFormulaCount += CountFormulaCells(rows);
            totalValidationCount += validationCount;
            totalConditionalFormattingCount += conditionalFormattingCount;
        }

        workbookPart.Workbook.Save();
        var review = ArtifactQualityReviewService.ReviewWorkbook(new WorkbookReviewInput(
            fullPath,
            totalSheets + (summarySheet.ValueKind == JsonValueKind.Object ? 1 : 0),
            totalSheets,
            totalRows,
            totalFormulaCount,
            summarySheet.ValueKind == JsonValueKind.Object ? detailSheetNames.Count : 0,
            totalValidationCount,
            totalConditionalFormattingCount,
            summarySheet.ValueKind == JsonValueKind.Object,
            HasSummaryItems(summarySheet, "highlights"),
            HasSummaryItems(summarySheet, "actions")));
        return ToolResult.Ok(
            $"Excel 파일 생성 완료: {fullPath}\n시트: {totalSheets}개, 총 데이터 행: {totalRows}\n{review.ToToolSummary()}",
            fullPath);
    }

    // ═══════════════════════════════════════════════════
    //  Core sheet writer (shared by single + multi)
    // ═══════════════════════════════════════════════════

    private static void WriteExecutiveSummarySheet(WorksheetPart worksheetPart, JsonElement summarySheet, IReadOnlyList<string> detailSheetNames)
    {
        worksheetPart.Worksheet = new Worksheet();

        var columns = new Columns(
            new Column { Min = 1, Max = 1, Width = 22, CustomWidth = true },
            new Column { Min = 2, Max = 2, Width = 18, CustomWidth = true },
            new Column { Min = 3, Max = 3, Width = 18, CustomWidth = true },
            new Column { Min = 4, Max = 4, Width = 28, CustomWidth = true },
            new Column { Min = 5, Max = 5, Width = 18, CustomWidth = true },
            new Column { Min = 6, Max = 6, Width = 30, CustomWidth = true });
        worksheetPart.Worksheet.Append(columns);

        var sheetData = new SheetData();
        worksheetPart.Worksheet.Append(sheetData);

        var merges = new MergeCells();
        var hyperlinks = new Hyperlinks();
        uint rowIndex = 1;

        var title = summarySheet.SafeTryGetProperty("title", out var titleEl)
            ? titleEl.SafeGetString() ?? "Executive Summary"
            : "Executive Summary";
        var subtitle = summarySheet.SafeTryGetProperty("subtitle", out var subtitleEl)
            ? subtitleEl.SafeGetString() ?? ""
            : "";

        AppendMergedTextRow(sheetData, merges, rowIndex++, "A", "F", title, 1);
        if (!string.IsNullOrWhiteSpace(subtitle))
            AppendMergedTextRow(sheetData, merges, rowIndex++, "A", "F", subtitle, 3);

        rowIndex++;

        if (summarySheet.SafeTryGetProperty("kpis", out var kpis) && kpis.ValueKind == JsonValueKind.Array && kpis.GetArrayLength() > 0)
        {
            AppendMergedTextRow(sheetData, merges, rowIndex++, "A", "F", "Key KPIs", 1);
            var headerRow = new Row { RowIndex = rowIndex++ };
            headerRow.Append(CreateSummaryCell("A", headerRow.RowIndex!.Value, "Metric", 1));
            headerRow.Append(CreateSummaryCell("B", headerRow.RowIndex!.Value, "Value", 1));
            headerRow.Append(CreateSummaryCell("C", headerRow.RowIndex!.Value, "Trend", 1));
            headerRow.Append(CreateSummaryCell("D", headerRow.RowIndex!.Value, "Note", 1));
            sheetData.Append(headerRow);

            var kpiIndex = 0;
            foreach (var kpi in kpis.EnumerateArray())
            {
                var styleIndex = kpiIndex % 2 == 0 ? (uint)0 : (uint)2;
                var row = new Row { RowIndex = rowIndex++ };
                row.Append(CreateSummaryCell("A", row.RowIndex!.Value, kpi.SafeTryGetProperty("label", out var labelEl) ? labelEl.SafeGetString() ?? "" : "", styleIndex));
                row.Append(CreateSummaryCell("B", row.RowIndex!.Value, kpi.SafeTryGetProperty("value", out var valueEl) ? valueEl.SafeGetString() ?? "" : "", styleIndex));
                row.Append(CreateSummaryCell("C", row.RowIndex!.Value, kpi.SafeTryGetProperty("trend", out var trendEl) ? trendEl.SafeGetString() ?? "" : "", styleIndex));
                row.Append(CreateSummaryCell("D", row.RowIndex!.Value, kpi.SafeTryGetProperty("note", out var noteEl) ? noteEl.SafeGetString() ?? "" : "", styleIndex));
                sheetData.Append(row);
                kpiIndex++;
            }

            rowIndex++;
        }

        AppendSummaryTextSection(summarySheet, "highlights", "Key Highlights", sheetData, merges, ref rowIndex);
        AppendSummaryTextSection(summarySheet, "actions", "Next Actions", sheetData, merges, ref rowIndex);

        if (detailSheetNames.Count > 0)
        {
            AppendMergedTextRow(sheetData, merges, rowIndex++, "A", "F", "Detail Sheets", 1);
            foreach (var detailSheetName in detailSheetNames)
                AppendMergedTextRow(sheetData, merges, rowIndex++, "A", "F", $"• {detailSheetName}", 0);
        }

        if (detailSheetNames.Count > 0)
        {
            var hyperlinkStartRow = rowIndex - (uint)detailSheetNames.Count;
            for (var i = 0; i < detailSheetNames.Count; i++)
            {
                hyperlinks.Append(new Hyperlink
                {
                    Reference = $"A{hyperlinkStartRow + (uint)i}",
                    Location = $"'{detailSheetNames[i]}'!A1",
                    Display = detailSheetNames[i]
                });
            }
        }

        if (merges.HasChildren)
            worksheetPart.Worksheet.InsertAfter(merges, sheetData);
        if (hyperlinks.HasChildren)
        {
            var anchor = merges.HasChildren ? (OpenXmlElement)merges : sheetData;
            worksheetPart.Worksheet.InsertAfter(hyperlinks, anchor);
        }
    }

    private static void AppendSummaryTextSection(JsonElement summarySheet, string key, string heading, SheetData sheetData, MergeCells merges, ref uint rowIndex)
    {
        if (!summarySheet.SafeTryGetProperty(key, out var items) || items.ValueKind != JsonValueKind.Array || items.GetArrayLength() == 0)
            return;

        AppendMergedTextRow(sheetData, merges, rowIndex++, "A", "F", heading, 1);
        foreach (var item in items.EnumerateArray())
            AppendMergedTextRow(sheetData, merges, rowIndex++, "A", "F", $"• {item.SafeGetString() ?? ""}", 0);
        rowIndex++;
    }

    private static void AppendMergedTextRow(SheetData sheetData, MergeCells merges, uint rowIndex, string startColumn, string endColumn, string text, uint styleIndex)
    {
        var row = new Row { RowIndex = rowIndex };
        row.Append(CreateSummaryCell(startColumn, rowIndex, text, styleIndex));
        sheetData.Append(row);
        merges.Append(new MergeCell { Reference = $"{startColumn}{rowIndex}:{endColumn}{rowIndex}" });
    }

    private static Cell CreateSummaryCell(string column, uint rowIndex, string text, uint styleIndex)
    {
        return new Cell
        {
            CellReference = $"{column}{rowIndex}",
            DataType = CellValues.String,
            CellValue = new CellValue(text),
            StyleIndex = styleIndex,
        };
    }

    private static (int RowCount, int ValidationCount, int ConditionalFormattingCount) WriteSheetContent(
        WorksheetPart worksheetPart,
        JsonElement args,
        string sheetName,
        JsonElement headers,
        JsonElement rows,
        bool isStyled,
        bool freezeHeader,
        ThemeColors theme,
        List<string?> numFmts,
        List<string?> alignments,
        List<(string code, uint id)> customFmtRegistry,
        JsonElement summaryArg,
        JsonElement mergesArg,
        JsonElement validationsArg,
        JsonElement conditionalFormatsArg,
        int colCount)
    {
        // Column widths
        var columns = CreateColumns(args, colCount);
        if (columns != null)
            worksheetPart.Worksheet.Append(columns);

        var sheetData = new SheetData();
        worksheetPart.Worksheet.Append(sheetData);

        // Header row
        var headerRow = new Row { RowIndex = 1 };
        for (int ci = 0; ci < colCount; ci++)
        {
            var h = headers.EnumerateArray().ElementAtOrDefault(ci);
            var cellRef = GetCellReference(ci, 0);
            var cell = new Cell
            {
                CellReference = cellRef,
                DataType = CellValues.String,
                CellValue = new CellValue(h.ValueKind != JsonValueKind.Undefined ? h.SafeGetString() ?? "" : ""),
                StyleIndex = isStyled ? (uint)1 : 0,
            };
            headerRow.Append(cell);
        }
        sheetData.Append(headerRow);

        // Data rows
        int rowCount = 0;
        uint rowNum = 2;
        foreach (var row in rows.EnumerateArray())
        {
            var dataRow = new Row { RowIndex = rowNum };
            int ci = 0;
            foreach (var cellVal in row.EnumerateArray())
            {
                var cellRef = GetCellReference(ci, (int)rowNum - 1);
                var cell = new Cell { CellReference = cellRef };

                // Determine style index
                cell.StyleIndex = ResolveDataStyleIndex(
                    ci, rowCount, isStyled, numFmts, alignments, customFmtRegistry);

                var strVal = cellVal.ToString();

                // {icon:name} 인라인 아이콘 → 유니코드 심볼로 치환
                if (strVal.Contains("{icon:"))
                    strVal = ResolveInlineIcons(strVal);

                if (strVal.StartsWith('='))
                {
                    cell.CellFormula = new CellFormula(strVal);
                    cell.DataType = null;
                }
                else if (cellVal.ValueKind == JsonValueKind.Number && !strVal.Contains("{icon:"))
                {
                    cell.DataType = CellValues.Number;
                    cell.CellValue = new CellValue(cellVal.GetDouble().ToString());
                }
                else
                {
                    cell.DataType = CellValues.String;
                    cell.CellValue = new CellValue(strVal);
                }

                dataRow.Append(cell);
                ci++;
            }
            sheetData.Append(dataRow);
            rowCount++;
            rowNum++;
        }

        // Summary row
        if (summaryArg.ValueKind == JsonValueKind.Object)
            AddSummaryRow(sheetData, summaryArg, rowNum, colCount, rowCount, isStyled);

        // Cell merges
        MergeCells? mergeCellsSection = null;
        if (mergesArg.ValueKind == JsonValueKind.Array)
        {
            mergeCellsSection = new MergeCells();
            foreach (var merge in mergesArg.EnumerateArray())
            {
                var range = merge.SafeGetString();
                if (!string.IsNullOrEmpty(range))
                    mergeCellsSection.Append(new MergeCell { Reference = range });
            }
            if (mergeCellsSection.HasChildren)
                worksheetPart.Worksheet.InsertAfter(mergeCellsSection, sheetData);
        }

        var validationCount = AddDataValidations(worksheetPart, sheetData, mergeCellsSection, validationsArg);
        var conditionalFormattingCount = AddConditionalFormats(worksheetPart, mergeCellsSection, conditionalFormatsArg);

        // Freeze header
        if (freezeHeader)
        {
            var sheetViews = new SheetViews(new SheetView(
                new Pane
                {
                    VerticalSplit = 1,
                    TopLeftCell = "A2",
                    ActivePane = PaneValues.BottomLeft,
                    State = PaneStateValues.Frozen
                },
                new Selection
                {
                    Pane = PaneValues.BottomLeft,
                    ActiveCell = "A2",
                    SequenceOfReferences = new ListValue<StringValue> { InnerText = "A2" }
                })
            { TabSelected = true, WorkbookViewId = 0 });

            var insertBefore = (OpenXmlElement?)worksheetPart.Worksheet.GetFirstChild<Columns>()
                ?? worksheetPart.Worksheet.GetFirstChild<SheetData>();
            worksheetPart.Worksheet.InsertBefore(sheetViews, insertBefore);
        }

        return (rowCount, validationCount, conditionalFormattingCount);
    }

    private static int AddDataValidations(WorksheetPart worksheetPart, SheetData sheetData, MergeCells? mergeCells, JsonElement validationsArg)
    {
        if (validationsArg.ValueKind != JsonValueKind.Array || validationsArg.GetArrayLength() == 0)
            return 0;

        var dataValidations = new DataValidations();
        var count = 0;

        foreach (var rule in validationsArg.EnumerateArray())
        {
            var range = rule.SafeTryGetProperty("range", out var rangeEl) ? rangeEl.SafeGetString() : null;
            var typeText = rule.SafeTryGetProperty("type", out var typeEl) ? typeEl.SafeGetString() : null;
            var formula1 = rule.SafeTryGetProperty("formula1", out var formulaEl) ? formulaEl.SafeGetString() : null;
            if (string.IsNullOrWhiteSpace(range) || string.IsNullOrWhiteSpace(typeText) || string.IsNullOrWhiteSpace(formula1))
                continue;

            var validation = new DataValidation
            {
                Type = ResolveValidationType(typeText),
                AllowBlank = !(rule.SafeTryGetProperty("allow_blank", out var allowBlankEl) && allowBlankEl.ValueKind == JsonValueKind.False),
                ShowInputMessage = rule.SafeTryGetProperty("prompt", out _),
                SequenceOfReferences = new ListValue<StringValue> { InnerText = range }
            };

            if (rule.SafeTryGetProperty("prompt", out var promptEl) && !string.IsNullOrWhiteSpace(promptEl.SafeGetString()))
            {
                validation.PromptTitle = "Input";
                validation.Prompt = promptEl.SafeGetString();
            }

            validation.Append(new Formula1(formula1));
            dataValidations.Append(validation);
            count++;
        }

        if (count == 0)
            return 0;

        dataValidations.Count = (uint)count;
        var anchor = (OpenXmlElement?)mergeCells ?? sheetData;
        worksheetPart.Worksheet.InsertAfter(dataValidations, anchor);
        return count;
    }

    private static int AddConditionalFormats(WorksheetPart worksheetPart, MergeCells? mergeCells, JsonElement conditionalFormatsArg)
    {
        if (conditionalFormatsArg.ValueKind != JsonValueKind.Array || conditionalFormatsArg.GetArrayLength() == 0)
            return 0;

        var insertedCount = 0;
        OpenXmlElement anchor = mergeCells is not null
            ? mergeCells
            : worksheetPart.Worksheet.Elements<SheetData>().First();

        foreach (var rule in conditionalFormatsArg.EnumerateArray())
        {
            var range = rule.SafeTryGetProperty("range", out var rangeEl) ? rangeEl.SafeGetString() : null;
            var type = rule.SafeTryGetProperty("type", out var typeEl) ? typeEl.SafeGetString()?.Trim().ToLowerInvariant() : null;
            if (string.IsNullOrWhiteSpace(range) || string.IsNullOrWhiteSpace(type))
                continue;

            ConditionalFormatting? conditionalFormatting = type switch
            {
                "color_scale" => BuildColorScaleConditionalFormatting(range, rule, (uint)(insertedCount + 1)),
                "data_bar" => BuildDataBarConditionalFormatting(range, rule, (uint)(insertedCount + 1)),
                _ => null,
            };

            if (conditionalFormatting == null)
                continue;

            worksheetPart.Worksheet.InsertAfter(conditionalFormatting, anchor);
            anchor = conditionalFormatting;
            insertedCount++;
        }

        return insertedCount;
    }

    private static ConditionalFormatting? BuildColorScaleConditionalFormatting(string range, JsonElement rule, uint priority)
    {
        var low = rule.SafeTryGetProperty("low", out var lowEl) ? NormalizeHex(lowEl.SafeGetString(), "FEE2E2") : "FEE2E2";
        var mid = rule.SafeTryGetProperty("mid", out var midEl) ? NormalizeHex(midEl.SafeGetString(), "FEF3C7") : "FEF3C7";
        var high = rule.SafeTryGetProperty("high", out var highEl) ? NormalizeHex(highEl.SafeGetString(), "DCFCE7") : "DCFCE7";

        var ruleElement = new ConditionalFormattingRule
        {
            Type = ConditionalFormatValues.ColorScale,
            Priority = (int)priority,
        };
        ruleElement.Append(new ColorScale(
            new ConditionalFormatValueObject { Type = ConditionalFormatValueObjectValues.Min },
            new ConditionalFormatValueObject { Type = ConditionalFormatValueObjectValues.Percentile, Val = "50" },
            new ConditionalFormatValueObject { Type = ConditionalFormatValueObjectValues.Max },
            new Color { Rgb = low },
            new Color { Rgb = mid },
            new Color { Rgb = high }));

        return new ConditionalFormatting(ruleElement)
        {
            SequenceOfReferences = new ListValue<StringValue> { InnerText = range }
        };
    }

    private static ConditionalFormatting? BuildDataBarConditionalFormatting(string range, JsonElement rule, uint priority)
    {
        var color = rule.SafeTryGetProperty("color", out var colorEl) ? NormalizeHex(colorEl.SafeGetString(), "2563EB") : "2563EB";

        var ruleElement = new ConditionalFormattingRule
        {
            Type = ConditionalFormatValues.DataBar,
            Priority = (int)priority,
        };
        ruleElement.Append(new DataBar(
            new ConditionalFormatValueObject { Type = ConditionalFormatValueObjectValues.Min },
            new ConditionalFormatValueObject { Type = ConditionalFormatValueObjectValues.Max },
            new Color { Rgb = color }));

        return new ConditionalFormatting(ruleElement)
        {
            SequenceOfReferences = new ListValue<StringValue> { InnerText = range }
        };
    }

    private static string NormalizeHex(string? color, string fallback)
    {
        var value = string.IsNullOrWhiteSpace(color) ? fallback : color.Trim().TrimStart('#');
        return value.Length switch
        {
            6 => "FF" + value.ToUpperInvariant(),
            8 => value.ToUpperInvariant(),
            _ => fallback,
        };
    }

    private static DataValidationValues ResolveValidationType(string? type)
    {
        return (type ?? "list").Trim().ToLowerInvariant() switch
        {
            "whole" or "whole_number" => DataValidationValues.Whole,
            "decimal" => DataValidationValues.Decimal,
            "date" => DataValidationValues.Date,
            "text_length" => DataValidationValues.TextLength,
            "custom" => DataValidationValues.Custom,
            _ => DataValidationValues.List,
        };
    }

    // ═══════════════════════════════════════════════════
    //  Style index resolution for data cells
    // ═══════════════════════════════════════════════════

    // StyleIndex layout (base indices built by CreateStylesheet):
    //   0 = default (no style)
    //   1 = header  (bold, theme header bg)
    //   2 = stripe  (theme stripe bg)
    //   3 = summary (bold, gray bg)
    //   4..3+N = number-format variants of default (plain, even-row): base=4
    //
    // For each unique (numFmt, isStripe, alignment) we build extra CellFormats.
    // To keep it simple, we encode them linearly after index 3.
    // BuildExtraFormats returns a mapping used both in stylesheet creation and here.
    //
    // ExtraFormat key: (colIndex, isStripe)
    // We pre-compute these in CreateStylesheet and expose via static registry pattern.
    //
    // To avoid complex cross-method state, we compute style index inline using the
    // same deterministic formula used when building CellFormats in CreateStylesheet.

    private static uint ResolveDataStyleIndex(
        int colIndex,
        int dataRowIndex,
        bool isStyled,
        List<string?> numFmts,
        List<string?> alignments,
        List<(string code, uint id)> customFmtRegistry)
    {
        if (!isStyled && numFmts.Count == 0 && alignments.Count == 0)
            return 0;

        // Base: 4 reserved indices (0=default, 1=header, 2=stripe, 3=summary)
        // Extra formats start at index 4.
        // Layout: for each col (0..maxCol-1), two entries: [plain, stripe]
        // combined (colIndex, isStripe) into a single ordinal.

        bool isStripe = isStyled && dataRowIndex % 2 == 0;

        var maxCol = Math.Max(numFmts.Count, alignments.Count);
        if (maxCol == 0)
        {
            // No per-column formats, just use built-in stripes
            if (!isStyled) return 0;
            return isStripe ? (uint)2 : (uint)0;
        }

        if (colIndex >= maxCol)
        {
            // Column beyond per-column format definitions — fall back to default/stripe
            if (!isStyled) return 0;
            return isStripe ? (uint)2 : (uint)0;
        }

        // Extra style index = 4 + colIndex * 2 + (isStripe ? 1 : 0)
        return (uint)(4 + colIndex * 2 + (isStripe ? 1 : 0));
    }

    // ═══════════════════════════════════════════════════
    //  Stylesheet
    // ═══════════════════════════════════════════════════

    private static Stylesheet CreateStylesheet(
        bool isStyled,
        ThemeColors theme,
        List<(string code, uint id)> customFmtRegistry,
        List<string?> allNumFmts,
        List<string?>? allAlignments = null)
    {
        var stylesheet = new Stylesheet();

        // ── NumberingFormats (must come first) ───────────────────
        if (customFmtRegistry.Count > 0)
        {
            var nfSection = new NumberingFormats();
            foreach (var (code, id) in customFmtRegistry)
            {
                nfSection.Append(new NumberingFormat
                {
                    NumberFormatId = id,
                    FormatCode = code,
                });
            }
            nfSection.Count = (uint)customFmtRegistry.Count;
            stylesheet.Append(nfSection);
        }

        // ── Fonts ─────────────────────────────────────────────────
        var fonts = new Fonts(
            new Font( // 0: default
                new FontSize { Val = 11 },
                new FontName { Val = "Noto Sans KR" }
            ),
            new Font( // 1: bold white (header)
                new Bold(),
                new FontSize { Val = 11 },
                new Color { Rgb = theme.HeaderFg },
                new FontName { Val = "Noto Sans KR" }
            ),
            new Font( // 2: bold (summary row)
                new Bold(),
                new FontSize { Val = 11 },
                new FontName { Val = "Noto Sans KR" }
            )
        );
        stylesheet.Append(fonts);

        // ── Fills ─────────────────────────────────────────────────
        var fills = new Fills(
            new Fill(new PatternFill { PatternType = PatternValues.None }),       // 0: none (required)
            new Fill(new PatternFill { PatternType = PatternValues.Gray125 }),    // 1: gray125 (required)
            new Fill(new PatternFill                                              // 2: theme header bg
            {
                PatternType = PatternValues.Solid,
                ForegroundColor = new ForegroundColor { Rgb = theme.HeaderBg },
                BackgroundColor = new BackgroundColor { Indexed = 64 }
            }),
            new Fill(new PatternFill                                              // 3: theme stripe bg
            {
                PatternType = PatternValues.Solid,
                ForegroundColor = new ForegroundColor { Rgb = theme.StripeBg },
                BackgroundColor = new BackgroundColor { Indexed = 64 }
            }),
            new Fill(new PatternFill                                              // 4: light gray (summary)
            {
                PatternType = PatternValues.Solid,
                ForegroundColor = new ForegroundColor { Rgb = "FFE8E8E8" },
                BackgroundColor = new BackgroundColor { Indexed = 64 }
            })
        );
        stylesheet.Append(fills);

        // ── Borders ───────────────────────────────────────────────
        var borders = new Borders(
            new Border( // 0: no border
                new LeftBorder(), new RightBorder(),
                new TopBorder(), new BottomBorder(), new DiagonalBorder()
            ),
            new Border( // 1: thin border
                new LeftBorder(new Color { Rgb = "FFD9D9D9" }) { Style = BorderStyleValues.Thin },
                new RightBorder(new Color { Rgb = "FFD9D9D9" }) { Style = BorderStyleValues.Thin },
                new TopBorder(new Color { Rgb = "FFD9D9D9" }) { Style = BorderStyleValues.Thin },
                new BottomBorder(new Color { Rgb = "FFD9D9D9" }) { Style = BorderStyleValues.Thin },
                new DiagonalBorder()
            )
        );
        stylesheet.Append(borders);

        // ── CellFormats ───────────────────────────────────────────
        // Indices 0-3: reserved base formats (same as before)
        // Indices 4+: per-column extra formats (plain + stripe per column)

        var cellFormats = new CellFormats();

        // 0: default
        cellFormats.Append(new CellFormat
        {
            FontId = 0, FillId = 0, BorderId = isStyled ? (uint)1 : 0,
            ApplyBorder = isStyled
        });

        // 1: header (bold, theme header bg, center)
        cellFormats.Append(new CellFormat
        {
            FontId = 1, FillId = 2, BorderId = 1,
            ApplyFont = true, ApplyFill = true, ApplyBorder = true,
            Alignment = new Alignment
            {
                Horizontal = HorizontalAlignmentValues.Center,
                Vertical = VerticalAlignmentValues.Center
            }
        });

        // 2: stripe row (theme stripe bg)
        cellFormats.Append(new CellFormat
        {
            FontId = 0, FillId = 3, BorderId = 1,
            ApplyFill = true, ApplyBorder = true
        });

        // 3: summary row (bold + gray bg)
        cellFormats.Append(new CellFormat
        {
            FontId = 2, FillId = 4, BorderId = 1,
            ApplyFont = true, ApplyFill = true, ApplyBorder = true
        });

        // 4+: per-column formats (plain + stripe), two entries per column
        int maxCol = Math.Max(allNumFmts.Count, allAlignments?.Count ?? 0);
        for (int ci = 0; ci < maxCol; ci++)
        {
            var fmtStr = ci < allNumFmts.Count ? allNumFmts[ci] : null;
            var (isBuiltIn, builtInId, customCode) = ResolveNumberFormat(fmtStr);
            uint numFmtId = isBuiltIn ? builtInId : GetCustomFmtId(customCode!, customFmtRegistry);
            bool applyNumFmt = numFmtId != 0;

            var alignStr = (allAlignments != null && ci < allAlignments.Count) ? allAlignments[ci] : null;
            var horizAlign = alignStr switch
            {
                "right"  => HorizontalAlignmentValues.Right,
                "center" => HorizontalAlignmentValues.Center,
                _        => HorizontalAlignmentValues.Left,
            };
            bool applyAlign = !string.IsNullOrEmpty(alignStr);

            // plain (odd rows)
            var plainFmt = new CellFormat
            {
                FontId = 0, FillId = 0,
                BorderId = isStyled ? (uint)1 : 0,
                NumberFormatId = numFmtId,
                ApplyBorder = isStyled,
                ApplyNumberFormat = applyNumFmt,
                ApplyAlignment = applyAlign,
            };
            if (applyAlign)
                plainFmt.Alignment = new Alignment { Horizontal = horizAlign };
            cellFormats.Append(plainFmt);

            // stripe (even rows)
            var stripeFmt = new CellFormat
            {
                FontId = 0, FillId = isStyled ? (uint)3 : 0,
                BorderId = isStyled ? (uint)1 : 0,
                NumberFormatId = numFmtId,
                ApplyFill = isStyled,
                ApplyBorder = isStyled,
                ApplyNumberFormat = applyNumFmt,
                ApplyAlignment = applyAlign,
            };
            if (applyAlign)
                stripeFmt.Alignment = new Alignment { Horizontal = horizAlign };
            cellFormats.Append(stripeFmt);
        }

        stylesheet.Append(cellFormats);

        return stylesheet;
    }

    private static uint GetCustomFmtId(string code, List<(string code, uint id)> registry)
    {
        foreach (var (c, id) in registry)
            if (c == code) return id;
        return 0;
    }

    // Build registry of custom number formats (deduplicated), assigning IDs from 164+
    private static List<(string code, uint id)> CollectCustomFormats(IEnumerable<string?> numFmts)
    {
        var registry = new List<(string code, uint id)>();
        uint nextId = 164;
        foreach (var fmt in numFmts)
        {
            if (string.IsNullOrEmpty(fmt) || fmt == "text") continue;
            var (isBuiltIn, _, customCode) = ResolveNumberFormat(fmt);
            if (isBuiltIn || customCode == null) continue;
            if (registry.Any(r => r.code == customCode)) continue;
            registry.Add((customCode, nextId++));
        }
        return registry;
    }

    // ═══════════════════════════════════════════════════
    //  Column widths
    // ═══════════════════════════════════════════════════

    private static Columns? CreateColumns(JsonElement args, int colCount)
    {
        var hasWidths = args.SafeTryGetProperty("col_widths", out var widthsArr) && widthsArr.ValueKind == JsonValueKind.Array;

        var columns = new Columns();
        for (int i = 0; i < colCount; i++)
        {
            double width = 15;
            if (hasWidths && i < widthsArr.GetArrayLength())
                width = widthsArr[i].GetDouble();

            columns.Append(new Column
            {
                Min = (uint)(i + 1),
                Max = (uint)(i + 1),
                Width = width,
                CustomWidth = true,
            });
        }

        return columns;
    }

    // ═══════════════════════════════════════════════════
    //  Summary row
    // ═══════════════════════════════════════════════════

    private static void AddSummaryRow(SheetData sheetData, JsonElement summary,
        uint rowNum, int colCount, int dataRowCount, bool isStyled)
    {
        var label = summary.SafeTryGetProperty("label", out var lbl) ? lbl.SafeGetString() ?? "합계" : "합계";
        var colFormulas = summary.SafeTryGetProperty("columns", out var cols) ? cols : default;

        var summaryRow = new Row { RowIndex = rowNum };

        var labelCell = new Cell
        {
            CellReference = GetCellReference(0, (int)rowNum - 1),
            DataType = CellValues.String,
            CellValue = new CellValue(label),
            StyleIndex = isStyled ? (uint)3 : 0,
        };
        summaryRow.Append(labelCell);

        for (int ci = 1; ci < colCount; ci++)
        {
            var colLetter = GetColumnLetter(ci);
            var cell = new Cell
            {
                CellReference = GetCellReference(ci, (int)rowNum - 1),
                StyleIndex = isStyled ? (uint)3 : 0,
            };

            if (colFormulas.ValueKind == JsonValueKind.Object &&
                colFormulas.SafeTryGetProperty(colLetter, out var funcName))
            {
                var func = funcName.SafeGetString()?.ToUpper() ?? "SUM";
                var startRow = 2;
                var endRow = startRow + dataRowCount - 1;
                cell.CellFormula = new CellFormula($"={func}({colLetter}{startRow}:{colLetter}{endRow})");
            }

            summaryRow.Append(cell);
        }

        sheetData.Append(summaryRow);
    }

    // ═══════════════════════════════════════════════════
    //  Parameter parsing helpers
    // ═══════════════════════════════════════════════════

    private static List<string?> ParseNumberFormats(JsonElement args, string key)
    {
        var result = new List<string?>();
        if (!args.SafeTryGetProperty(key, out var arr) || arr.ValueKind != JsonValueKind.Array)
            return result;
        foreach (var el in arr.EnumerateArray())
            result.Add(el.ValueKind == JsonValueKind.Null ? null : el.SafeGetString());
        return result;
    }

    private static List<string?> ParseAlignments(JsonElement args, string key)
    {
        var result = new List<string?>();
        if (!args.SafeTryGetProperty(key, out var arr) || arr.ValueKind != JsonValueKind.Array)
            return result;
        foreach (var el in arr.EnumerateArray())
            result.Add(el.ValueKind == JsonValueKind.Null ? null : el.SafeGetString()?.ToLower());
        return result;
    }

    private static int CountFormulaCells(JsonElement rows)
    {
        if (rows.ValueKind != JsonValueKind.Array)
            return 0;

        var count = 0;
        foreach (var row in rows.EnumerateArray())
        {
            if (row.ValueKind != JsonValueKind.Array)
                continue;

            foreach (var cell in row.EnumerateArray())
            {
                var text = cell.ToString();
                if (!string.IsNullOrWhiteSpace(text) && text.StartsWith('='))
                    count++;
            }
        }

        return count;
    }

    private static bool HasSummaryItems(JsonElement summarySheet, string propertyName)
    {
        return summarySheet.ValueKind == JsonValueKind.Object
               && summarySheet.SafeTryGetProperty(propertyName, out var items)
               && items.ValueKind == JsonValueKind.Array
               && items.GetArrayLength() > 0;
    }

    private static string BuildFeatureList(bool isStyled, bool freezeHeader,
        bool hasMerges, bool hasSummary, bool hasNumFmts, bool hasAlignments, string? theme)
    {
        var features = new List<string>();
        if (isStyled) features.Add("스타일 적용");
        if (theme != null) features.Add($"테마:{theme}");
        if (freezeHeader) features.Add("틀 고정");
        if (hasMerges) features.Add("셀 병합");
        if (hasSummary) features.Add("요약행");
        if (hasNumFmts) features.Add("숫자형식");
        if (hasAlignments) features.Add("정렬");
        return features.Count > 0 ? $" [{string.Join(", ", features)}]" : "";
    }

    // ═══════════════════════════════════════════════════
    //  Utilities
    // ═══════════════════════════════════════════════════

    private static string GetColumnLetter(int colIndex)
    {
        var result = "";
        while (colIndex >= 0)
        {
            result = (char)('A' + colIndex % 26) + result;
            colIndex = colIndex / 26 - 1;
        }
        return result;
    }

    private static string GetCellReference(int colIndex, int rowIndex)
        => $"{GetColumnLetter(colIndex)}{rowIndex + 1}";

    /// <summary>{icon:name} 패턴을 유니코드 심볼로 치환합니다.</summary>
    private static string ResolveInlineIcons(string text)
        => System.Text.RegularExpressions.Regex.Replace(text, @"\{icon:(\w+)\}", m =>
        {
            var name = m.Groups[1].Value;
            return IconLibrary.Contains(name) ? IconLibrary.Resolve(name) : m.Value;
        });
}