using Backend.Data.InMemory;

namespace Backend.Data;

/// <summary>
/// Single place where a storage backend is chosen. To add a real database, implement
/// <see cref="IUserRepository"/> and register it under a new provider name here;
/// controllers stay untouched.
/// </summary>
public static class PersistenceServiceCollectionExtensions
{
    public static IServiceCollection AddPersistence(
        this IServiceCollection services,
        IConfiguration configuration)
    {
        services.Configure<PersistenceOptions>(configuration.GetSection(PersistenceOptions.SectionName));

        var provider = configuration.GetSection(PersistenceOptions.SectionName).Get<PersistenceOptions>()?.Provider
            ?? PersistenceProviders.InMemory;

        switch (provider)
        {
            case PersistenceProviders.InMemory:
                // Singleton because the store itself holds the data.
                services.AddSingleton<IUserRepository, InMemoryUserRepository>();
                break;

            default:
                throw new InvalidOperationException(
                    $"Unknown persistence provider '{provider}'. Supported providers: " +
                    $"'{PersistenceProviders.InMemory}'. Register additional providers in " +
                    $"{nameof(PersistenceServiceCollectionExtensions)}.");
        }

        return services;
    }
}