using System.Collections.ObjectModel;
using Npgsql;

namespace pgLabII.PgUtils.ConnectionStrings;

public ref struct PqConnectionStringParser
{
    // Note possible keywords
    // host
    //hostaddr 
    //port
    //dbname
    //user
    //password
    //passfile
    //channel_binding
    //connect_timeout
    //client_encoding
    //options
    //application_name
    //fallback_application_name
    //keepalives
    //keepalives_idle
    //keepalives_interval
    //keepalives_count
    //tcp_user_timeout
    //replication
    //gssencmode
    //sslmode
    //requiresll
    //sslcompression
    //sslcert
    //sslkey
    //sslpassword
    //sslrootcert
    //sslcrl
    //sslcrldir
    //sslsni
    //requirepeer
    //ssl_min_protocol_version
    //ssl_max_protocol_version
    //krbsrvname
    //gsslib
    //service
    //target_session_attrs

    public static IDictionary<string, string> Parse(string input)
    {
        return new PqConnectionStringParser(
            new PqConnectionStringTokenizer(input)
            ).Parse();
    }

    private readonly IPqConnectionStringTokenizer tokenizer;
    private readonly Dictionary<string, string> result = new();

    public PqConnectionStringParser(IPqConnectionStringTokenizer tokenizer)
    {
        this.tokenizer = tokenizer;
    }

    public IDictionary<string, string> Parse()
    {
        result.Clear();

        while (!tokenizer.Eof)
            ParsePair();

        return result;
    }

    private void ParsePair()
    {
        string kw = tokenizer.GetKeyword();
        tokenizer.ConsumeEquals();
        string v = tokenizer.GetValue();
        result.Add(kw, v);
        //switch (kw)
        //{
        //    case "host":
        //    case "hostaddr":
        //        result.Host = v.ToString();
        //        break;
        //    case "port":
        //        result.Port = int.Parse(v);
        //        break;
        //    case "dbname":
        //        result.Database = v.ToString();
        //        break;
        //    case "user":
        //        result.Username = v.ToString();
        //        break;
        //    case "password":
        //        result.Password = v.ToString();
        //        break;
        //    case "connect_timeout":
        //        result.Timeout = int.Parse(v);
        //        break;
        //    case "application_name":
        //        result.ApplicationName = v.ToString();
        //        break;
        //    case "options":
        //        result.Options = v.ToString();
        //        break;
        //    case "sslmode":
        //        result.SslMode = ToSslMode(v);
        //        break;
        //    default:
        //        // Todo what do we do with values we do not support/recognize?
        //        break;
        //}
    }

    private SslMode ToSslMode(ReadOnlySpan<char> v)
        => v switch
        {
            "disable" => SslMode.Disable,
            "allow" => SslMode.Allow,
            "prefer" => SslMode.Prefer,
            "require" => SslMode.Require,
            "verify-ca" => SslMode.VerifyCA,
            "verify-full" => SslMode.VerifyFull,
            _ => throw new ArgumentException("Not a valid SSL mode"),
        };

}