using System.Globalization;
using Npgsql;

namespace pgLabII.PgUtils.ConnectionStrings;

/// <summary>
/// Shared helper utilities for codecs to reduce duplication (SSL mode mapping, host:port parsing/formatting,
/// URL query parsing, and .NET/libpq quoting helpers).
/// </summary>
internal static class CodecCommon
{
    // SSL mapping
    public static SslMode ParseSslModeLoose(string s)
        => s.Trim().ToLowerInvariant() switch
        {
            "disable" => SslMode.Disable,
            "allow" => SslMode.Allow,
            "prefer" => SslMode.Prefer,
            "require" => SslMode.Require,
            "verify-ca" or "verifyca" => SslMode.VerifyCA,
            "verify-full" or "verifyfull" => SslMode.VerifyFull,
            _ => throw new ArgumentException($"Not a valid SSL Mode: {s}")
        };

    public static string FormatSslModeUrlLike(SslMode mode) => mode switch
    {
        SslMode.Disable => "disable",
        SslMode.Allow => "allow",
        SslMode.Prefer => "prefer",
        SslMode.Require => "require",
        SslMode.VerifyCA => "verify-ca",
        SslMode.VerifyFull => "verify-full",
        _ => "prefer"
    };
   

    // host:port parsing for plain or [IPv6]:port
    public static void ParseHostPort(string hostPart, out string host, out ushort? port)
    {
        host = hostPart;
        port = null;
        if (string.IsNullOrWhiteSpace(hostPart)) 
            return;
        
        if (hostPart[0] == '[')
        {
            int end = hostPart.IndexOf(']');
            if (end > 0)
            {
                host = hostPart[1..end];
                if (end + 1 < hostPart.Length && hostPart[end + 1] == ':')
                {
                    string ps = hostPart[(end + 2)..];
                    if (ushort.TryParse(ps, NumberStyles.Integer, CultureInfo.InvariantCulture, out var p))
                        port = p;
                }
            }
            return;
        }
        int colon = hostPart.LastIndexOf(':');
        if (colon > 0 && colon < hostPart.Length - 1)
        {
            var ps = hostPart.Substring(colon + 1);
            if (ushort.TryParse(ps, NumberStyles.Integer, CultureInfo.InvariantCulture, out var p))
            {
                host = hostPart.Substring(0, colon);
                port = p;
            }
        }
    }

    public static string FormatHost(HostEndpoint h)
    {
        var host = h.Host;
        if (host.Contains(':') && !host.StartsWith("[")) 
            host = "[" + host + "]"; // IPv6
        
        return h.Port.HasValue ? host + ":" + h.Port.Value.ToString(CultureInfo.InvariantCulture) : host;
    }
    
    public static string[] SplitHosts(string hostList)
        => hostList.Split(',', StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries);

    public static Dictionary<string, string> ParseQuery(string query)
    {
        var dict = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
        if (string.IsNullOrEmpty(query)) return dict;
        foreach (var kv in query.Split('&', StringSplitOptions.RemoveEmptyEntries))
        {
            var parts = kv.Split('=', 2);
            var key = Uri.UnescapeDataString(parts[0]);
            var val = parts.Length > 1 ? Uri.UnescapeDataString(parts[1]) : string.Empty;
            dict[key] = val;
        }
        return dict;
    }
}