using Microsoft.Extensions.Logging;
using ZstdSharp;

namespace MesETL.App.Services.ETL;

/// <summary>
/// 解压ZST文件，从中读取CSV数据
/// </summary>
public class ZstReader : CsvReader
{
    protected new readonly Lazy<StreamReader> Reader;
    private Stream? _stream;


    public ZstReader(string filePath, string tableName, string[] headers, string delimiter = ",", char quoteChar = '\"', ILogger? logger = null) 
        : base(filePath, tableName, headers, delimiter, quoteChar, logger)
    {
        Reader = new Lazy<StreamReader>(() =>
        {
             _stream = new DecompressionStream(File.OpenRead(filePath));
            return new StreamReader(_stream);
        }, false);
    }
        
    public ZstReader(Stream stream, string tableName, string[] headers, string delimiter = ",", char quoteChar = '\"', ILogger? logger = null) 
        : base(stream, tableName, headers, delimiter, quoteChar, logger)
    {
        var ds = new DecompressionStream(stream);
        Reader = new Lazy<StreamReader>(() => new StreamReader(ds), false);
    }

    public override async ValueTask<bool> ReadAsync()
    {
        var str = await Reader.Value.ReadLineAsync();
        if (string.IsNullOrWhiteSpace(str))
            return false;

        var fields = ParseRowFaster(str, QuoteChar, Delimiter[0]);
        Current = new DataRecord(fields, TableName, Headers);
        return true;
    }

    public override void Dispose()
    {
        base.Dispose();
        if (Reader.IsValueCreated)
        {
            Reader.Value.Dispose();
            _stream?.Dispose();
        }
    }

}