using Microsoft.Extensions.Configuration;
using StellaOps.Doctor.Models;
using StellaOps.Doctor.Plugins;
using System.Globalization;

namespace StellaOps.Doctor.Plugins.Security.Checks;

/// <summary>
/// Validates rate limiting configuration.
/// </summary>
public sealed class RateLimitingCheck : IDoctorCheck
{
    /// <inheritdoc />
    public string CheckId => "check.security.ratelimit";

    /// <inheritdoc />
    public string Name => "Rate Limiting";

    /// <inheritdoc />
    public string Description => "Validates rate limiting is configured to prevent abuse";

    /// <inheritdoc />
    public DoctorSeverity DefaultSeverity => DoctorSeverity.Warn;

    /// <inheritdoc />
    public IReadOnlyList<string> Tags => ["security", "ratelimit", "api"];

    /// <inheritdoc />
    public TimeSpan EstimatedDuration => TimeSpan.FromMilliseconds(50);

    /// <inheritdoc />
    public bool CanRun(DoctorPluginContext context) => true;

    /// <inheritdoc />
    public Task<DoctorCheckResult> RunAsync(DoctorPluginContext context, CancellationToken ct)
    {
        var result = context.CreateResult(CheckId, "stellaops.doctor.security", DoctorCategory.Security.ToString());

        var rateLimitEnabled = context.Configuration.GetValue<bool?>("RateLimiting:Enabled")
            ?? context.Configuration.GetValue<bool?>("Security:RateLimiting:Enabled");

        if (rateLimitEnabled == null)
        {
            return Task.FromResult(result
                .Info("Rate limiting configuration not found")
                .WithEvidence("Rate limiting", e =>
                {
                    e.Add("Configured", "false");
                    e.Add("Recommendation", "Consider enabling rate limiting for API protection");
                })
                .Build());
        }

        if (rateLimitEnabled != true)
        {
            return Task.FromResult(result
                .Warn("Rate limiting is disabled")
                .WithEvidence("Rate limiting", e =>
                {
                    e.Add("Enabled", "false");
                    e.Add("Recommendation", "Enable rate limiting to prevent API abuse");
                })
                .WithCauses("Rate limiting explicitly disabled in configuration")
                .WithRemediation(r => r
                    .AddManualStep(1, "Enable rate limiting", "Set RateLimiting:Enabled to true")
                    .WithRunbookUrl("docs/doctor/articles/security/security-ratelimit.md"))
                .WithVerification("stella doctor --check check.security.ratelimit")
                .Build());
        }

        var permitLimit = context.Configuration.GetValue<int?>("RateLimiting:PermitLimit")
            ?? context.Configuration.GetValue<int?>("Security:RateLimiting:PermitLimit")
            ?? 100;

        var windowSeconds = context.Configuration.GetValue<int?>("RateLimiting:WindowSeconds")
            ?? context.Configuration.GetValue<int?>("Security:RateLimiting:WindowSeconds")
            ?? 60;

        var queueLimit = context.Configuration.GetValue<int?>("RateLimiting:QueueLimit")
            ?? context.Configuration.GetValue<int?>("Security:RateLimiting:QueueLimit")
            ?? 0;

        var issues = new List<string>();

        if (permitLimit > 10000)
        {
            issues.Add($"Rate limit permit count ({permitLimit}) is very high");
        }

        if (windowSeconds < 1)
        {
            issues.Add("Rate limit window is less than 1 second");
        }
        else if (windowSeconds > 3600)
        {
            issues.Add($"Rate limit window ({windowSeconds}s) is very long - may not effectively prevent bursts");
        }

        var requestsPerSecond = (double)permitLimit / windowSeconds;
        if (requestsPerSecond > 1000)
        {
            issues.Add($"Effective rate ({requestsPerSecond:F0} req/s) may be too permissive");
        }

        if (issues.Count > 0)
        {
            return Task.FromResult(result
                .Warn($"{issues.Count} rate limiting configuration issue(s)")
                .WithEvidence("Rate limiting", e =>
                {
                    e.Add("Enabled", "true");
                    e.Add("PermitLimit", permitLimit.ToString(CultureInfo.InvariantCulture));
                    e.Add("WindowSeconds", windowSeconds.ToString(CultureInfo.InvariantCulture));
                    e.Add("QueueLimit", queueLimit.ToString(CultureInfo.InvariantCulture));
                    e.Add("EffectiveRatePerSecond", requestsPerSecond.ToString("F2", CultureInfo.InvariantCulture));
                })
                .WithCauses(issues.ToArray())
                .Build());
        }

        return Task.FromResult(result
            .Pass("Rate limiting is properly configured")
            .WithEvidence("Rate limiting", e =>
            {
                e.Add("Enabled", "true");
                e.Add("PermitLimit", permitLimit.ToString(CultureInfo.InvariantCulture));
                e.Add("WindowSeconds", windowSeconds.ToString(CultureInfo.InvariantCulture));
                e.Add("QueueLimit", queueLimit.ToString(CultureInfo.InvariantCulture));
                e.Add("EffectiveRatePerSecond", requestsPerSecond.ToString("F2", CultureInfo.InvariantCulture));
            })
            .Build());
    }
}