// -----------------------------------------------------------------------------
// VexGateServiceCollectionExtensions.cs
// Sprint: SPRINT_20260106_003_002_SCANNER_vex_gate_service
// Task: T028 - Add gate policy to tenant configuration
// Description: Service collection extensions for registering VEX gate services.
// -----------------------------------------------------------------------------

using Microsoft.Extensions.Caching.Memory;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Options;

namespace StellaOps.Scanner.Gate;

/// <summary>
/// Extension methods for registering VEX gate services.
/// </summary>
public static class VexGateServiceCollectionExtensions
{
    /// <summary>
    /// Adds VEX gate services with configuration from the specified section.
    /// </summary>
    /// <param name="services">The service collection.</param>
    /// <param name="configuration">The configuration root.</param>
    /// <returns>The service collection for chaining.</returns>
    public static IServiceCollection AddVexGate(
        this IServiceCollection services,
        IConfiguration configuration)
    {
        ArgumentNullException.ThrowIfNull(services);
        ArgumentNullException.ThrowIfNull(configuration);

        // Bind and validate options
        services.AddOptions<VexGateOptions>()
            .Bind(configuration.GetSection(VexGateOptions.SectionName))
            .ValidateDataAnnotations()
            .ValidateOnStart();

        // Register policy from options
        services.AddSingleton<VexGatePolicy>(sp =>
        {
            var options = sp.GetRequiredService<IOptions<VexGateOptions>>();
            if (!options.Value.Enabled)
            {
                // Return a permissive policy when disabled
                return new VexGatePolicy
                {
                    DefaultDecision = VexGateDecision.Pass,
                    Rules = [],
                };
            }

            return options.Value.ToPolicy();
        });

        // Register core services
        services.AddSingleton<IVexGatePolicy, VexGatePolicyEvaluator>();

        // Register caching with configured limits
        services.AddSingleton<IMemoryCache>(sp =>
        {
            var options = sp.GetRequiredService<IOptions<VexGateOptions>>();
            return new MemoryCache(new MemoryCacheOptions
            {
                SizeLimit = options.Value.Cache.MaxEntries,
            });
        });

        // Register VEX gate service
        services.AddSingleton<IVexGateService, VexGateService>();

        return services;
    }

    /// <summary>
    /// Adds VEX gate services with explicit options.
    /// </summary>
    /// <param name="services">The service collection.</param>
    /// <param name="configureOptions">The options configuration action.</param>
    /// <returns>The service collection for chaining.</returns>
    public static IServiceCollection AddVexGate(
        this IServiceCollection services,
        Action<VexGateOptions> configureOptions)
    {
        ArgumentNullException.ThrowIfNull(services);
        ArgumentNullException.ThrowIfNull(configureOptions);

        // Configure and validate options
        services.AddOptions<VexGateOptions>()
            .Configure(configureOptions)
            .ValidateDataAnnotations()
            .ValidateOnStart();

        // Register policy from options
        services.AddSingleton<VexGatePolicy>(sp =>
        {
            var options = sp.GetRequiredService<IOptions<VexGateOptions>>();
            if (!options.Value.Enabled)
            {
                return new VexGatePolicy
                {
                    DefaultDecision = VexGateDecision.Pass,
                    Rules = [],
                };
            }

            return options.Value.ToPolicy();
        });

        // Register core services
        services.AddSingleton<IVexGatePolicy, VexGatePolicyEvaluator>();

        // Register caching with configured limits
        services.AddSingleton<IMemoryCache>(sp =>
        {
            var options = sp.GetRequiredService<IOptions<VexGateOptions>>();
            return new MemoryCache(new MemoryCacheOptions
            {
                SizeLimit = options.Value.Cache.MaxEntries,
            });
        });

        // Register VEX gate service
        services.AddSingleton<IVexGateService, VexGateService>();

        return services;
    }

    /// <summary>
    /// Adds VEX gate services with default policy.
    /// </summary>
    /// <param name="services">The service collection.</param>
    /// <returns>The service collection for chaining.</returns>
    public static IServiceCollection AddVexGateWithDefaultPolicy(this IServiceCollection services)
    {
        ArgumentNullException.ThrowIfNull(services);

        // Configure with default options
        services.AddOptions<VexGateOptions>()
            .Configure(options =>
            {
                options.Enabled = true;
                var defaultPolicy = VexGatePolicy.Default;
                options.DefaultDecision = defaultPolicy.DefaultDecision.ToString();
                options.Rules = defaultPolicy.Rules
                    .Select(VexGateRuleOptions.FromRule)
                    .ToList();
            })
            .ValidateDataAnnotations()
            .ValidateOnStart();

        // Register default policy
        services.AddSingleton<VexGatePolicy>(_ => VexGatePolicy.Default);

        // Register core services
        services.AddSingleton<IVexGatePolicy, VexGatePolicyEvaluator>();

        // Register caching with default limits
        services.AddSingleton<IMemoryCache>(_ => new MemoryCache(new MemoryCacheOptions
        {
            SizeLimit = 10000,
        }));

        // Register VEX gate service
        services.AddSingleton<IVexGateService, VexGateService>();

        return services;
    }
}