Playa/extensions/Volcanic.AgenticCore.Extensions.Mcp/McpUserSettings.cs

using System.Text.Json;
using System.Text.Json.Serialization;
using Microsoft.Extensions.Logging;

namespace Volcanic.AgenticCore.Extensions.Mcp;

/// <summary>Reads <c>"mcpServers"</c> from <c>&lt;agent dir&gt;/settings.json</c> (the same file that lists extensions).</summary>
internal static class McpUserSettings
{
    public const string AgentDirVariable = "VOLCANIC_AGENT_DIR";

    private static readonly JsonSerializerOptions Json = new()
    {
        PropertyNameCaseInsensitive = true,
        ReadCommentHandling = JsonCommentHandling.Skip,
        AllowTrailingCommas = true,
        Converters = { new JsonStringEnumConverter() },
    };

    /// <summary><c>VOLCANIC_AGENT_DIR</c>, else <c>~/.volcanic/agent</c>.</summary>
    public static string AgentDir(Func<string, string?> getEnv) =>
        getEnv(AgentDirVariable) is { Length: > 0 } dir
            ? dir
            : Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.UserProfile), ".volcanic", "agent");

    /// <summary>Servers in document order. A missing file or section is empty; a malformed file is logged and ignored.</summary>
    public static IReadOnlyList<KeyValuePair<string, McpServerConfig>> Load(string agentDir, ILogger logger)
    {
        var path = Path.Combine(agentDir, "settings.json");
        if (!File.Exists(path)) return [];
        try
        {
            using var doc = JsonDocument.Parse(File.ReadAllText(path),
                new JsonDocumentOptions { CommentHandling = JsonCommentHandling.Skip, AllowTrailingCommas = true });
            if (doc.RootElement.ValueKind != JsonValueKind.Object
                || !doc.RootElement.TryGetProperty("mcpServers", out var servers)
                || servers.ValueKind != JsonValueKind.Object) return [];
            var result = new List<KeyValuePair<string, McpServerConfig>>();
            foreach (var server in servers.EnumerateObject())
                result.Add(new(server.Name, server.Value.Deserialize<McpServerConfig>(Json) ?? new McpServerConfig()));
            return result;
        }
        catch (Exception ex) when (ex is JsonException or IOException or UnauthorizedAccessException or NotSupportedException)
        {
            logger.LogWarning("Ignoring mcpServers in {Path}: {Message}", path, ex.Message);
            return [];
        }
    }
}