journal/Journal.AI/ServiceCollectionExtensions.cs

using Journal.Core.Services.Ai;
using Journal.Core.Services.Config;
using Microsoft.Extensions.DependencyInjection;

namespace Journal.AI;

public static class ServiceCollectionExtensions
{
    /// <summary>
    /// Registers LLamaSharp-based AI and Coach services.
    /// Call this AFTER <c>AddFragmentServices()</c> so that <c>IJournalConfigService</c> is available.
    /// When the provider is "llamasharp", this replaces the default <c>IAiService</c> registration.
    /// </summary>
    public static IServiceCollection AddLlamaSharpServices(this IServiceCollection services)
    {
        // Override IAiService — last registration wins in MS DI
        services.AddSingleton<IAiService>(provider =>
        {
            var config = provider.GetRequiredService<IJournalConfigService>().Current;

            if (string.Equals(config.AiProvider, "llamasharp", StringComparison.OrdinalIgnoreCase))
            {
                try
                {
                    return new LlamaSharpAiService(config);
                }
                catch (Exception ex)
                {
                    return new DisabledAiService(
                        provider: "llamasharp",
                        message: $"LLamaSharp unavailable: {ex.Message}",
                        healthy: false);
                }
            }

            return new DisabledAiService(config.AiProvider);
        });

        // Register coach service
        services.AddSingleton<ICoachService>(provider =>
        {
            var config = provider.GetRequiredService<IJournalConfigService>().Current;
            var ai = provider.GetRequiredService<IAiService>();

            if (ai is LlamaSharpAiService llamaAi)
                return new LlamaSharpCoachService(llamaAi);

            if (string.Equals(config.AiProvider, "none", StringComparison.OrdinalIgnoreCase))
                return new DisabledCoachService();

            return new DisabledCoachService(
                $"Coach requires llamasharp provider (current: {config.AiProvider}).");
        });

        return services;
    }
}