BotSharp/src/Infrastructure/BotSharp.MCP/Functions/McpToolFunction.cs

using BotSharp.Abstraction.Conversations.Models;
using BotSharp.Abstraction.Functions;
using McpDotNet.Client;
using McpDotNet.Protocol.Types;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text.Json;
using System.Threading.Tasks;

namespace BotSharp.Core.Mcp.Functions;

public class McpToolFunction : IFunctionCallback
{
    private readonly Tool _tool;
    private readonly IMcpClient _client;

    public McpToolFunction(Tool tool, IMcpClient client)
    {
        _tool = tool ?? throw new ArgumentNullException(nameof(tool));
        _client = client ?? throw new ArgumentNullException(nameof(client));
    }

    public string Name => _tool.Name;

    public async Task<bool> Execute(RoleDialogModel message)
    {
        // Convert arguments to dictionary format expected by mcpdotnet
        Dictionary<string, object> argDict = JsonToDictionary(message.FunctionArgs);
        
        // Call the tool through mcpdotnet
        var result = await _client.CallToolAsync(
            _tool.Name,
            argDict.Count == 0 ? new() : argDict
        );

        // Extract the text content from the result
        var json = string.Join("\n", result.Content
            .Where(c => c.Type == "text")
            .Select(c => c.Text));
        message.Content = json;
        message.Data = JsonSerializer.Deserialize(json,typeof(object));
        return true;
    }

    private static Dictionary<string, object> JsonToDictionary(string? json)
    {
        if (string.IsNullOrEmpty(json))
            return [];

        using JsonDocument doc = JsonDocument.Parse(json);
        JsonElement root = doc.RootElement;
        return JsonElementToDictionary(root);
    }

    private static Dictionary<string, object> JsonElementToDictionary(JsonElement element)
    {
        Dictionary<string, object> dictionary = [];

        if (element.ValueKind == JsonValueKind.Object)
        {
            foreach (JsonProperty property in element.EnumerateObject())
            {
                dictionary[property.Name] = JsonElementToValue(property.Value);
            }
        }

        return dictionary;
    }

    private static object? JsonElementToValue(JsonElement element) => element.ValueKind switch
    {
        JsonValueKind.Object => JsonElementToDictionary(element),
        JsonValueKind.Array => element.EnumerateArray().Select(JsonElementToValue).ToList(),
        JsonValueKind.String => element.GetString(),
        JsonValueKind.Number when element.TryGetInt32(out int intValue) => intValue,
        JsonValueKind.Number when element.TryGetInt64(out long longValue) => longValue,
        JsonValueKind.Number when element.TryGetDouble(out double doubleValue) => doubleValue,
        JsonValueKind.Number when element.TryGetDecimal(out decimal decimalValue) => decimalValue,
        JsonValueKind.Number when element.TryGetByte(out byte byteValue) => byteValue,
        JsonValueKind.Number when element.TryGetSByte(out sbyte sbyteValue) => sbyteValue,
        JsonValueKind.Number when element.TryGetUInt16(out ushort uint16Value) => uint16Value,
        JsonValueKind.Number when element.TryGetUInt32(out uint uint32Value) => uint32Value,
        JsonValueKind.Number when element.TryGetUInt64(out ulong uint64Value) => uint64Value,
        JsonValueKind.Number when element.TryGetDateTime(out DateTime dateTimeValue) => dateTimeValue,
        JsonValueKind.Number when element.TryGetDateTimeOffset(out DateTimeOffset dateTimeOffsetValue) => dateTimeOffsetValue,
        JsonValueKind.Number when element.TryGetGuid(out Guid guidValue) => guidValue,
        JsonValueKind.Number => element.GetRawText(),
        JsonValueKind.True => true,
        JsonValueKind.False => false,
        JsonValueKind.Null => null,
        JsonValueKind.Undefined => string.Empty, // JsonElement is undefined (there is no value).
        _ => throw new ArgumentOutOfRangeException(nameof(element.ValueKind), element.ValueKind, "Unexpected JsonValueKind encountered.")
    };

}