using SQLLinter.Infrastructure.Interfaces;
using System.Text;
using System.Text.RegularExpressions;

namespace SQLLinter.Infrastructure.Parser;

public class SqlStreamReaderBuilder : ISqlStreamReaderBuilder
{
    private static readonly Regex _placeholderRegex = new Regex(@"\$\((?<placeholder>[^)]+)\)", RegexOptions.Compiled);

    public StreamReader CreateReader(Stream sqlFileStream)
    {
        var sqlText = new StreamReader(sqlFileStream);
        sqlFileStream.Seek(0, SeekOrigin.Begin);
        var sql = ReplaceSqlPlaceholders(sqlText.ReadToEnd());
        return new StreamReader(new MemoryStream(sqlText.CurrentEncoding.GetBytes(sql)));
    }

    private string ReplaceSqlPlaceholders(string sql)
    {
        var matches = _placeholderRegex.Matches(sql);

        if (matches.Count == 0)
        {
            return sql;
        }

        var newSql = new StringBuilder();
        var i = 0;

        foreach (Match match in matches)
        {
            var placeholder = match.Groups["placeholder"].Value;
            var replacement = match.Value;
            newSql.Append(sql.Substring(i, match.Index - i));
            newSql.Append(replacement);
            i = match.Index + match.Length;
        }

        newSql.Append(sql.Substring(i));

        return newSql.ToString();
    }
}