using Microsoft.Extensions.Options;

namespace ECMJobRunner.WebCron.ProfileWorker;

/// <summary>
/// Extension methods for configuring ProfileWorker services in the DI container.
/// </summary>
public static class DependencyInjection
{
    /// <summary>
    /// Registers ProfileWorker background service and related dependencies.
    /// </summary>
    /// <param name="services">The service collection to configure.</param>
    /// <param name="configuration">Application configuration containing ProfileWorker settings.</param>
    /// <returns>The configured service collection for method chaining.</returns>
    /// <remarks>
    /// Registers the following services:
    /// <list type="bullet">
    /// <item><description><see cref="ProfileWorkerOptions"/> - Configuration options from appsettings.json</description></item>
    /// <item><description><see cref="ProfileWorker"/> - Singleton background service (also registered as IHostedService)</description></item>
    /// <item><description><see cref="ProfileCache"/> - Singleton cache for profile state</description></item>
    /// <item><description><see cref="ProfileWork"/> - Scoped service for profile synchronization logic</description></item>
    /// </list>
    /// </remarks>
    public static IServiceCollection AddProfileWorker(this IServiceCollection services, IConfiguration configuration)
    {
        // Configure ProfileWorker options from appsettings.json
        services.Configure<ProfileWorkerOptions>(
            configuration.GetSection(ProfileWorkerOptions.SectionName));

        // Validate options at startup
        services.AddSingleton<IValidateOptions<ProfileWorkerOptions>, ProfileWorkerOptionsValidator>();

        // Register ProfileWorker as both HostedService and singleton (for health check access)
        services.AddSingleton<ProfileWorker>();
        services.AddHostedService(sp => sp.GetRequiredService<ProfileWorker>());
        
        services.AddSingleton<ProfileCache>();
        services.AddScoped<ProfileWork>();
        
        return services;
    }
}

/// <summary>
/// Validates <see cref="ProfileWorkerOptions"/> configuration at application startup.
/// Ensures IntervalMS is within acceptable bounds to prevent misconfiguration.
/// </summary>
internal class ProfileWorkerOptionsValidator : IValidateOptions<ProfileWorkerOptions>
{
    /// <summary>
    /// Validates the ProfileWorker options.
    /// </summary>
    /// <param name="name">The name of the options instance (not used).</param>
    /// <param name="options">The options to validate.</param>
    /// <returns>
    /// <see cref="ValidateOptionsResult.Success"/> if valid, 
    /// or <see cref="ValidateOptionsResult.Fail"/> with error message if invalid.
    /// </returns>
    /// <remarks>
    /// Validation rules:
    /// <list type="bullet">
    /// <item><description>IntervalMS must be greater than 0</description></item>
    /// <item><description>IntervalMS should be at least 100ms to avoid excessive CPU usage</description></item>
    /// </list>
    /// </remarks>
    public ValidateOptionsResult Validate(string? name, ProfileWorkerOptions options)
    {
        if (options.IntervalMS <= 0)
        {
            return ValidateOptionsResult.Fail("ProfileWorker:IntervalMs must be greater than 0");
        }

        if (options.IntervalMS < 100)
        {
            return ValidateOptionsResult.Fail("ProfileWorker:IntervalMs should be at least 100ms to avoid excessive CPU usage");
        }

        return ValidateOptionsResult.Success;
    }
}