Nexus.Reader/src/NexusReader.Infrastructure/DependencyInjection.cs

using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Configuration;
using Pgvector.EntityFrameworkCore;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.AI;
using GeminiDotnet;
using GeminiDotnet.Extensions.AI;
using NexusReader.Data.Persistence;

using NexusReader.Application.Abstractions.Services;
using NexusReader.Infrastructure.Services;
using NexusReader.Infrastructure.Configuration;
using Polly;
using Polly.Retry;
using NexusReader.Domain.Entities;
using Microsoft.AspNetCore.Identity;
using Microsoft.AspNetCore.Authorization;
using NexusReader.Application.Security.Authorization;

namespace NexusReader.Infrastructure;

public static class DependencyInjection
{
    public static IServiceCollection AddInfrastructure(this IServiceCollection services, IConfiguration configuration)
    {
        var pgConnectionString = configuration.GetConnectionString("PostgresConnection");
        if (!string.IsNullOrEmpty(pgConnectionString))
        {
            services.AddDbContextFactory<AppDbContext>(options =>
                options.UseNpgsql(pgConnectionString, x => x.UseVector()));
        }
        else
        {
            var sqliteConnectionString = configuration.GetConnectionString("SqliteConnection") ?? "Data Source=nexus.db";
            services.AddDbContextFactory<AppDbContext>(options =>
                options.UseSqlite(sqliteConnectionString));
        }

        services.Configure<AiSettings>(configuration.GetSection(AiSettings.SectionName));
        services.Configure<StripeSettings>(configuration.GetSection(StripeSettings.SectionName));
        var aiSettings = configuration.GetSection(AiSettings.SectionName).Get<AiSettings>() ?? new AiSettings();

        Console.WriteLine($"[Infrastructure] AI Configured: Model={aiSettings.Model}, KeyPresent={!string.IsNullOrWhiteSpace(aiSettings.ApiKey) && aiSettings.ApiKey != "PLACEHOLDER"}");

        if (string.IsNullOrWhiteSpace(aiSettings.ApiKey) || aiSettings.ApiKey == "PLACEHOLDER")
        {
            Console.WriteLine("[Infrastructure] WARNING: AI API Key is missing or placeholder!");
        }

        services.AddResiliencePipeline("ai-retry", builder =>
        {
            builder.AddRetry(new RetryStrategyOptions
            {
                ShouldHandle = new PredicateBuilder().Handle<Exception>(ex => 
                    ex.Message.Contains("429") || ex.Message.Contains("Too Many Requests") || ex.Message.Contains("quota")),
                BackoffType = DelayBackoffType.Exponential,
                UseJitter = true,
                MaxRetryAttempts = aiSettings.RetryAttempts,
                Delay = TimeSpan.FromSeconds(2)
            });
        });

        services.AddChatClient(new GeminiChatClient(new GeminiClientOptions 
        { 
            ApiKey = aiSettings.ApiKey, 
            ModelId = aiSettings.Model 
        }));

        services.AddEmbeddingGenerator(new GeminiEmbeddingGenerator(new GeminiClientOptions
        {
            ApiKey = aiSettings.ApiKey,
            ModelId = aiSettings.EmbeddingModel ?? "text-embedding-004"
        }));

        services.AddScoped<IKnowledgeService, KnowledgeService>();
        services.AddTransient<IEpubService, EpubService>();

        services.AddAuthorizationCore(options =>
        {
            options.AddPolicy("ProUser", policy => policy.Requirements.Add(new ProUserRequirement()));
        });

        services.AddScoped<IAuthorizationHandler, ProUserHandler>();

        services.AddScoped<IInfrastructureMarker, InfrastructureMarker>();

        return services;
    }

    public static System.Reflection.Assembly Assembly => typeof(DependencyInjection).Assembly;
}

public interface IInfrastructureMarker { }
internal class InfrastructureMarker : IInfrastructureMarker { }