pgLabII/pgLabII.PgUtils/ConnectionStrings/ConnectionStringService.cs

using FluentResults;

namespace pgLabII.PgUtils.ConnectionStrings;

/// <summary>
/// Composite implementation that composes multiple codecs to detect, parse, format and convert
/// PostgreSQL connection strings between formats.
/// </summary>
public sealed class ConnectionStringService : IConnectionStringService
{
    private readonly Dictionary<ConnStringFormat, IConnectionStringCodec> _codecs;
    private readonly IConnectionStringCodec[] _all;

    public ConnectionStringService(IEnumerable<IConnectionStringCodec> codecs)
    {
        _all = codecs?.ToArray() ?? Array.Empty<IConnectionStringCodec>();
        _codecs = _all.GroupBy(c => c.Format).ToDictionary(g => g.Key, g => g.First());
    }

    /// <summary>
    /// Creates a service pre-configured with built-in codecs (Libpq, Npgsql, Url, Jdbc).
    /// </summary>
    public static ConnectionStringService CreateDefault()
        => new(new IConnectionStringCodec[] { new LibpqCodec(), new NpgsqlCodec(), new UrlCodec(), new JdbcCodec() });

    public Result<ConnStringFormat> DetectFormat(string input)
    {
        if (string.IsNullOrWhiteSpace(input))
            return Result.Fail<ConnStringFormat>("Empty input");

        // URL: postgresql:// or postgres:// or JDBC jdbc:postgresql://
        var trimmed = input.TrimStart();
        if (trimmed.StartsWith("jdbc:postgresql://", StringComparison.OrdinalIgnoreCase))
        {
            return Result.Ok(ConnStringFormat.Jdbc);
        }
        if (trimmed.StartsWith("postgresql://", StringComparison.OrdinalIgnoreCase) ||
            trimmed.StartsWith("postgres://", StringComparison.OrdinalIgnoreCase))
        {
            return Result.Ok(ConnStringFormat.Url);
        }

        // Heuristic for Npgsql: presence of ';' separator and typical keys like Host= or Username=
        // Also many .NET conn strings end with a trailing semicolon but not required.
        if (trimmed.Contains(';'))
        {
            var firstEq = trimmed.IndexOf('=');
            var firstSemi = trimmed.IndexOf(';');
            if (firstEq > 0 && (firstSemi > firstEq || firstSemi == -1))
            {
                // quick key sample
                var key = trimmed.Substring(0, firstEq).Trim();
                if (key.Length > 0)
                    return Result.Ok(ConnStringFormat.Npgsql);
            }
        }

        // Fallback to libpq if it looks like space-separated key=value or single pair
        // Very loose heuristic: contains '=' and either a space-separated sequence or quotes
        if (trimmed.Contains('='))
        {
            return Result.Ok(ConnStringFormat.Libpq);
        }

        return Result.Fail<ConnStringFormat>("Unable to detect format");
    }

    public Result<ConnectionDescriptor> ParseToDescriptor(string input)
    {
        var fmtRes = DetectFormat(input);
        if (fmtRes.IsFailed) return Result.Fail<ConnectionDescriptor>(fmtRes.Errors);
        var fmt = fmtRes.Value;
        if (!_codecs.TryGetValue(fmt, out var codec))
            return Result.Fail<ConnectionDescriptor>($"No codec registered for {fmt}");
        return codec.TryParse(input);
    }

    public Result<string> FormatFromDescriptor(ConnectionDescriptor descriptor, ConnStringFormat targetFormat)
    {
        if (!_codecs.TryGetValue(targetFormat, out var codec))
            return Result.Fail<string>($"No codec registered for {targetFormat}");
        return codec.TryFormat(descriptor);
    }

    public Result<string> Convert(string input, ConnStringFormat targetFormat)
    {
        var parseRes = ParseToDescriptor(input);
        if (parseRes.IsFailed) return Result.Fail<string>(parseRes.Errors);
        return FormatFromDescriptor(parseRes.Value, targetFormat);
    }
}