ConversationIdentifier.cs

using System.Threading.Tasks;

namespace SlackNet.Bot;

public abstract class ConversationIdentifier
{
    public abstract Task<string> ConversationId(ISlackBot bot);

    public static implicit operator ConversationIdentifier(string name) => new ConversationByName(name);
    public static implicit operator ConversationIdentifier(Conversation conversation) => new ConversationByRef(conversation);
        
    public static implicit operator ConversationIdentifier(Hub hub) => new ConversationByHubIdentifier(hub);
    public static implicit operator ConversationIdentifier(HubIdentifier hubId) => new ConversationByHubIdentifier(hubId);
}

public class ConversationByName : ConversationIdentifier
{
    private readonly string _name;

    /// <param name="name">Channel, group or IM name, with leading # or @ symbol as appropriate.</param>
    public ConversationByName(string name) => _name = name;

    public override async Task<string> ConversationId(ISlackBot bot) =>
        (await bot.GetConversationByName(_name).ConfigureAwait(false)).Id;
}

public class ConversationByRef : ConversationIdentifier
{
    private readonly Conversation _conversation;
    public ConversationByRef(Conversation conversation) => _conversation = conversation;

    public override Task<string> ConversationId(ISlackBot bot) => Task.FromResult(_conversation.Id);
}

class ConversationByHubIdentifier : ConversationIdentifier
{
    private readonly HubIdentifier _hubIdentifier;
    public ConversationByHubIdentifier(HubIdentifier hubIdentifier) => _hubIdentifier = hubIdentifier;
        
    public override Task<string> ConversationId(ISlackBot bot) => _hubIdentifier.HubId(bot);
}