// 配置优化参数
var config = new OpenXmlConfiguration
{
    EnableSharedStrings = false, // 关闭共享字符串表
    AutoFilterMode = AutoFilterMode.None, // 禁用自动筛选
    FillMergedCells = false // 不处理合并单元格
};

// 分页流式写入
await MiniExcel.SaveAsAsync("output.xlsx", GetDataChunks(), configuration: config);

IEnumerable<IDictionary<string, object>> GetDataChunks()
{
    var pageSize = 50000;
    for (int page = 0; ; page++)
    {
        var data = QueryDatabase(page * pageSize, pageSize);
        if (!data.Any()) yield break;
        
        foreach (var item in data)
        {
            yield return new Dictionary<string, object>
            {
                ["ID"] = item.Id,
                ["Name"] = item.Name,
                ["CreateTime"] = item.CreateTime.ToString("yyyy-MM-dd")
            };
        }
    }
}

using (var package = new ExcelPackage())
{
    var sheet = package.Workbook.Worksheets.Add("Data");
    int row = 1;

    // 批量写入头信息
    sheet.Cells["A1:C1"].LoadFromArrays(new[] { new[] { "ID", "Name", "CreateTime" } });

    // 分块写入（每50000行保存一次）
    foreach (var chunk in GetDataChunks(50000))
    {
        sheet.Cells[row+1, 1].LoadFromCollection(chunk);
        row += chunk.Count;
        
        if (row % 50000 == 0)
        {
            package.Save(); // 分段保存
            sheet.Cells.ClearFormulas();
        }
    }
    
    package.SaveAs(new FileInfo("output_epplus.xlsx"));
}

[BenchmarkDotNet.Attributes.SimpleJob]
public class ExcelBenchmarks
{
    private List<DataModel> _testData = GenerateTestData(1_000_000);

    [Benchmark]
    public void MiniExcelExport() => MiniExcel.SaveAs("mini.xlsx", _testData);

    [Benchmark]
    public void EPPlusExport() 
    {
        using var pkg = new ExcelPackage();
        var sheet = pkg.Workbook.Worksheets.Add("Data");
        sheet.Cells.LoadFromCollection(_testData);
        pkg.SaveAs("epplus.xlsx");
    }

    [Benchmark]
    public void NPOIExport()
    {
        var workbook = new XSSFWorkbook();
        var sheet = workbook.CreateSheet("Data");
        for (int i = 0; i < _testData.Count; i++)
        {
            var row = sheet.CreateRow(i);
            row.CreateCell(0).SetCellValue(_testData[i].Id);
            row.CreateCell(1).SetCellValue(_testData[i].Name);
        }
        using var fs = new FileStream("npoi.xlsx", FileMode.Create);
        workbook.Write(fs);
    }
}

// 先用 EPPlus 创建带样式的模板
using (var pkg = new ExcelPackage(new FileInfo("template.xlsx")))
{
    var sheet = pkg.Workbook.Worksheets[0];
    sheet.Cells["A1"].Value = "动态报表";
    pkg.Save();
}

// 用 MiniExcel 填充大数据量
var data = GetBigData();
MiniExcel.SaveAsByTemplate("output.xlsx", "template.xlsx", data);

public async Task ExportShardedDataAsync()
{
    var totalRecords = 5_000_000;
    var shardSize = 100_000;
    var shards = totalRecords / shardSize;

    var tasks = new List<Task>();
    for (int i = 0; i < shards; i++)
    {
        var start = i * shardSize;
        tasks.Add(Task.Run(async () => 
        {
            using var stream = new FileStream($"shard_{i}.xlsx", FileMode.Create);
            await MiniExcel.SaveAsAsync(stream, QueryData(start, shardSize));
        }));
    }

    await Task.WhenAll(tasks);
    MergeShardFiles(shards);
}

private void MergeShardFiles(int shardCount)
{
    using var merger = new ExcelPackage();
    var mergedSheet = merger.Workbook.Worksheets.Add("Data");
    
    int row = 1;
    for (int i = 0; i < shardCount; i++)
    {
        var shardData = MiniExcel.Query($"shard_{i}.xlsx");
        mergedSheet.Cells[row, 1].LoadFromDictionaries(shardData);
        row += shardData.Count();
    }
    
    merger.SaveAs(new FileInfo("final.xlsx"));
}

// Program.cs 全局配置
AppContext.SetSwitch("System.Buffers.ArrayPool.UseShared", true); // 启用共享数组池

// 运行时配置（runtimeconfig.template.json）
{
  "configProperties": {
    "System.GC.HeapHardLimit": "0x100000000", // 4GB 内存限制
    "System.GC.HeapHardLimitPercent": "70",
    "System.GC.Server": true
  }
}

// Dapper 分页优化
public IEnumerable<DataModel> GetPagedData(long checkpoint, int size)
{
    return _conn.Query<DataModel>(
        @"SELECT Id, Name, CreateTime 
        FROM BigTable 
        WHERE Id > @Checkpoint 
        ORDER BY Id 
        OFFSET 0 ROWS 
        FETCH NEXT @Size ROWS ONLY 
        OPTION (RECOMPILE)", // 强制重新编译执行计划
        new { checkpoint, size });
}

try
{
    await ExportDataAsync();
}
catch (MiniExcelException ex) when (ex.ErrorCode == "DISK_FULL")
{
    await CleanTempFilesAsync();
    await RetryExportAsync();
}
catch (SqlException ex) when (ex.Number == 1205) // 死锁重试
{
    await Task.Delay(1000);
    await RetryExportAsync();
}
finally
{
    _semaphore.Release(); // 释放信号量
}

// 优化分页查询
var lastId = 0;
while (true)
{
    var data = Query($"SELECT * FROM Table WHERE Id > {lastId} ORDER BY Id FETCH NEXT 50000 ROWS ONLY");
    if (!data.Any()) break;
    lastId = data.Last().Id;
}

try {
    // 核心逻辑
} 
catch (IOException ex) when (ex.Message.Contains("磁盘空间")) {
    // 磁盘异常处理
}
catch (SqlException ex) when (ex.Number == 1205) {
    // 数据库死锁处理
}
catch (Exception ex) {
    // 通用异常处理
}

// 错误示例：未释放ExcelPackage
var pkg = new ExcelPackage(); // 必须包裹在using中
pkg.SaveAs("leak.xlsx");

// 正确用法
using (var pkg = new ExcelPackage())
{
    // 操作代码
}

// 错误示例：未正确释放资源
var workbook = new XSSFWorkbook();
// 正确用法
using (var fs = new FileStream("data.xlsx", FileMode.Create))
{
    workbook.Write(fs);
}

try
{
    await ExportAsync();
}
catch (MiniExcelException ex) when (ex.ErrorCode == "DISK_FULL")
{
    _logger.LogError("磁盘空间不足: {Message}", ex.Message);
    await CleanTempFilesAsync();
    throw new UserFriendlyException("导出失败，请联系管理员");
}
catch (DbException ex) when (ex.IsTransient)
{
    _logger.LogWarning("数据库暂时性错误，尝试重试");
    await Task.Delay(1000);
    await RetryExportAsync();
}
finally
{
    _exportSemaphore.Release();
}