using System.Text.RegularExpressions;
using ZstdSharp;

namespace ConsoleApp2.Helpers;

public static partial class DumpDataHelper
{
    [GeneratedRegex(@"'.+\.dat'")]
    private static partial Regex MatchDatFile();
    [GeneratedRegex(@"\([^)]*\)")]
    private static partial Regex MatchBrackets();
    
    /// <summary>
    /// 从MyDumper导出的SQL文件内容中读取表头
    /// </summary>
    /// <param name="content"></param>
    /// <returns></returns>
    /// <exception cref="ArgumentException"></exception>
    public static string[] GetCsvHeadersFromSqlFile(string content)
    {
        var match = MatchBrackets().Match(content);
        if (!match.Success)
            throw new ArgumentException("输入的SQL内容有误，无法提取表头", nameof(content));
        return ParseHeader(match.ValueSpan);
        
        string[] ParseHeader(ReadOnlySpan<char> headerStr)
        {
            headerStr = headerStr[1..^1];
            Span<Range> ranges = stackalloc Range[50];
            var count = headerStr.Split(ranges, ',');
            var arr = new string[count];

            for (var i = 0; i < count; i++)
            {
                arr[i] = headerStr[ranges[i]].Trim("@`").ToString(); // 消除列名的反引号，如果是变量则消除@
            }
        
            return arr;
        }
    }
    
    /// <summary>
    /// 从MyDumper导出的Csv文件名解析出表名
    /// </summary>
    /// <param name="filePath"></param>
    /// <returns></returns>
    public static string GetTableNameFromCsvFileName(ReadOnlySpan<char> filePath)
    {
        filePath = filePath[(filePath.LastIndexOf('\\') + 1)..];
        var firstDotIdx = -1;
        var secondDotIdx = -1;
        var times = 0;
        for (var i = 0; i < filePath.Length; i++)
        {
            if (filePath[i] == '.')
            {
                ++times;
                if(times == 1)
                    firstDotIdx = i;
                if (times == 2)
                {
                    secondDotIdx = i;
                    break;
                }
            }
        }

        return filePath[(firstDotIdx+1)..secondDotIdx].ToString();
    }

    /// <summary>
    /// 从MyDumper导出的SQL文件内容中读取CSV文件名
    /// </summary>
    /// <param name="txt"></param>
    /// <param name="regex"></param>
    /// <returns></returns>
    public static Task<string[]> GetCsvFileNamesFromSqlFileAsync(string txt, Regex regex)
    {
        //var txt = await File.ReadAllTextAsync(filePath);
        var matches = regex.Matches(txt);
        return Task.FromResult(matches.Select(match => match.ValueSpan[1..^1].ToString()).ToArray());
    }
    
    /// <summary>
    /// 检查字符串是否为16进制
    /// </summary>
    /// <param name="str"></param>
    /// <returns></returns>
    public static bool CheckHexField(string? str)
    {
        if (string.IsNullOrWhiteSpace(str))
            return false;
        
        if (str.StartsWith('\"'))
            return false;

        var isAllDigit = true; 

        foreach (var c in str)
        {
            if (!char.IsAsciiHexDigit(c))
                return false;
            if (!char.IsNumber(c))
                isAllDigit = false;
        }

        if (isAllDigit) //避免全数字
            return false;

        return true;
    }
    
    /// <summary>
    /// 将输入流以ZSTD标准解压为字符串
    /// </summary>
    /// <param name="stream"></param>
    /// <returns></returns>
    public static async Task<string> DecompressZstAsStringAsync(Stream stream)
    {
        await using var ds = new DecompressionStream(stream);
        var reader = new StreamReader(ds);
        return await reader.ReadToEndAsync();
    }

}