using MesETL.App.Const;
using MesETL.App.HostedServices.Abstractions;
using MesETL.App.Options;
using MesETL.App.Services;
using MesETL.App.Services.ETL;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Logging;
using Microsoft.Extensions.Options;

namespace MesETL.App.HostedServices;

public record FileInputInfo
{
    public required string FileName { get; init; }
    public required string TableName { get; init; }
    public required string Database { get; init; }
    public required int Part { get; init; }
    public required string[] Headers { get; init; }
}

/// <summary>
/// 从输入目录中导入文件
/// </summary>
public class FileInputService : IInputService
{
    private readonly ILogger _logger;
    private readonly DataRecordQueue _producerQueue;
    private readonly IOptions<DataInputOptions> _dataInputOptions;
    private readonly ProcessContext _context;
    private readonly DataReaderFactory _dataReaderFactory;
    private readonly long _memoryThreshold;

    public FileInputService(ILogger<FileInputService> logger,
            IOptions<DataInputOptions> dataInputOptions,
            ProcessContext context, 
            [FromKeyedServices(Const.ConstVar.Producer)] DataRecordQueue producerQueue, 
            DataReaderFactory dataReaderFactory, 
            IConfiguration configuration)
    {
        _logger = logger;
        _dataInputOptions = dataInputOptions;
        _context = context;
        _producerQueue = producerQueue;
        _dataReaderFactory = dataReaderFactory;
        _memoryThreshold = (long)(configuration.GetValue<double>("MemoryThreshold", 8) * 1024 * 1024 * 1024);
    }

    public async Task ExecuteAsync(CancellationToken cancellationToken)
    {
        var inputDir = _dataInputOptions.Value.InputDir ?? throw new ApplicationException("未配置文件输入目录");
        _logger.LogInformation("***** 输入服务已启动，工作目录为：{InputDir} *****", inputDir);

        var orderedInfo = GetOrderedInputInfo(inputDir);
        
        foreach (var info in orderedInfo)
        {
            var file = Path.GetFileName(info.FileName);
            _logger.LogInformation("正在读取文件：{FileName}, 对应的数据表：{TableName}", file, info.TableName);
            using var source = _dataReaderFactory.CreateReader(info.FileName, info.TableName, info.Headers);
            var count = 0;
            
            while (await source.ReadAsync())
            {
                if (GC.GetTotalMemory(false) > _memoryThreshold)
                {
                    _logger.LogWarning("内存使用率过高，暂缓输入");
                    GC.Collect();
                    GC.Collect();
                    await Task.Delay(3000, cancellationToken);
                }
                var record = source.Current;
                await _producerQueue.EnqueueAsync(record);
                count++;
                _context.AddInput();
            }

            _context.AddTableInput(info.TableName, count);
            _logger.LogInformation("文件 {File} 输入完成", file);
            _dataInputOptions.Value.OnTableInputCompleted?.Invoke(info.TableName);
        }

        _context.CompleteInput();
        _logger.LogInformation("***** 输入服务已执行完毕 *****");
    }

    public IEnumerable<FileInputInfo> GetOrderedInputInfo(string dir)
    {
        var metaBuilder = _dataInputOptions.Value.FileInputMetaBuilder;
        if(metaBuilder is null) throw new ApplicationException("未配置文件名->表名的映射委托函数");
        var files = Directory.GetFiles(dir);
        FileInputInfo[] infoArr = files
            .Select(f => metaBuilder(f))
            .Where(info => info is not null).ToArray()!;
        
        var orderedInfo = GetFilesInOrder(infoArr).ToArray();
        
        _logger.LogInformation("***** 输入目录中发现 {Count} 个文件， {InfoCount} 个文件可用，{OrderedCount} 个文件符合当前输入配置 *****", 
            files.Length, infoArr.Length, orderedInfo.Length);
        foreach (var info in orderedInfo.GroupBy(i => i.TableName))
        {
            _logger.LogDebug("表 {TableName} 发现 {FileCount} 个对应文件：\n{FileName}", 
                info.Key, info.Count(), string.Join('\n', info.Select(f => f.FileName)));
        }

        return orderedInfo;
    }

    /// <summary>
    /// 读取配置，按照配置的表顺序来返回
    /// </summary>
    /// <returns></returns>
    private IEnumerable<FileInputInfo> GetFilesInOrder(FileInputInfo[] inputFiles)
    {
        var tableOrder = _dataInputOptions.Value.TableOrder ?? typeof(TableNames).GetFields().Select(f => f.GetValue(null) as string).ToArray();
        var ignoreTable = _dataInputOptions.Value.TableIgnoreList;
        if (tableOrder is null or { Length: 0 })
            return inputFiles;

        return Yield();

        IEnumerable<FileInputInfo> Yield()
        {
            foreach (var tableName in tableOrder)
            {
                var targets = inputFiles.Where(f =>
                    f.TableName.Equals(tableName, StringComparison.OrdinalIgnoreCase) &&
                    !ignoreTable.Contains(f.TableName));

                foreach (var target in targets)
                {
                    yield return target;
                }
            }
        }
    }
}