using Microsoft.EntityFrameworkCore;
using radiuscontroller.Data;
using radiuscontroller.Models;

namespace radiuscontroller.Services;

/// <summary>
/// Background service that periodically checks all active guest accounts
/// and disables them if their time has expired or data cap has been reached.
/// Time starts from the moment the user was created (guest_profiles.created_at).
/// </summary>
public class AccountEnforcementService : BackgroundService
{
    private readonly IServiceScopeFactory _scopeFactory;
    private readonly ILogger<AccountEnforcementService> _logger;
    private static readonly TimeSpan CheckInterval = TimeSpan.FromSeconds(30);

    public AccountEnforcementService(IServiceScopeFactory scopeFactory, ILogger<AccountEnforcementService> logger)
    {
        _scopeFactory = scopeFactory;
        _logger = logger;
    }

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
    {
        _logger.LogInformation("AccountEnforcementService started. Checking every {Interval}s.", CheckInterval.TotalSeconds);

        // Wait a bit for the app to fully start
        await Task.Delay(TimeSpan.FromSeconds(10), stoppingToken);

        while (!stoppingToken.IsCancellationRequested)
        {
            try
            {
                await EnforceAccountLimitsAsync(stoppingToken);
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "Error during account enforcement check.");
            }

            await Task.Delay(CheckInterval, stoppingToken);
        }
    }

    private async Task EnforceAccountLimitsAsync(CancellationToken ct)
    {
        using var scope = _scopeFactory.CreateScope();
        var db = scope.ServiceProvider.GetRequiredService<RadiusDbContext>();

        var activeProfiles = await db.GuestProfiles
            .Where(p => p.Status == "Active")
            .ToListAsync(ct);

        if (activeProfiles.Count == 0) return;

        var now = DateTime.UtcNow;
        var disabledCount = 0;
        var changesMade = false;

        foreach (var profile in activeProfiles)
        {
            string? reason = null;

            // 1. Check time expiration: created_at + session_time_minutes
            var expiresAt = profile.CreatedAt.AddMinutes(profile.SessionTimeMinutes);
            if (now >= expiresAt)
            {
                reason = "Time expired";
            }

            // 2. Check data cap: read from guest_data_usage table
            if (reason == null && profile.DataLimitMb > 0)
            {
                var usage = await db.GuestDataUsage.FirstOrDefaultAsync(du => du.Username == profile.Username, ct);
                var totalOctets = (usage?.TotalInputOctets ?? 0) + (usage?.TotalOutputOctets ?? 0);

                long dataLimitBytes = profile.DataLimitMb * 1024 * 1024;
                if (totalOctets >= dataLimitBytes)
                {
                    reason = $"Data cap reached ({totalOctets / (1024 * 1024)} MB / {profile.DataLimitMb} MB)";
                }
            }

            if (reason != null)
            {
                // Disable the account
                profile.Status = "Expired";

                // Remove Cleartext-Password from radcheck so FreeRADIUS rejects future auth
                var checks = await db.RadCheck
                    .Where(rc => rc.Username == profile.Username)
                    .ToListAsync(ct);
                db.RadCheck.RemoveRange(checks);

                // Insert Auth-Type := Reject to explicitly deny
                db.RadCheck.Add(new RadCheck
                {
                    Username = profile.Username,
                    Attribute = "Auth-Type",
                    Op = ":=",
                    Value = "Reject"
                });

                _logger.LogInformation("Account '{Username}' disabled. Reason: {Reason}", profile.Username, reason);

                // Find active sessions to disconnect them instantly via RADIUS CoA (PoD)
                var activeSessions = await db.RadAcct
                    .Where(ra => ra.Username == profile.Username && ra.AcctStopTime == null)
                    .Select(ra => new { ra.NasIpAddress, ra.CallingStationId, ra.AcctSessionId })
                    .ToListAsync(ct);

                var radiusSecret = Environment.GetEnvironmentVariable("RADIUS_SECRET") ?? "radpass";

                foreach (var session in activeSessions)
                {
                    if (string.IsNullOrWhiteSpace(session.NasIpAddress)) continue;

                    try
                    {
                        var payload = $"User-Name=\\\"{profile.Username}\\\"\\nCalling-Station-Id=\\\"{session.CallingStationId}\\\"\\nAcct-Session-Id=\\\"{session.AcctSessionId}\\\"\\n";
                        var process = new System.Diagnostics.Process
                        {
                            StartInfo = new System.Diagnostics.ProcessStartInfo
                            {
                                FileName = "sh",
                                Arguments = $"-c \"printf '{payload}' | radclient -x {session.NasIpAddress}:3799 disconnect '{radiusSecret}'\"",
                                RedirectStandardOutput = true,
                                RedirectStandardError = true,
                                UseShellExecute = false,
                                CreateNoWindow = true
                            }
                        };
                        process.Start();
                        await process.WaitForExitAsync(ct);
                        _logger.LogInformation("Sent RADIUS Disconnect-Request to NAS {NasIp} for user {Username} (MAC: {Mac})", session.NasIpAddress, profile.Username, session.CallingStationId);
                    }
                    catch (Exception ex)
                    {
                        _logger.LogError(ex, "Failed to send RADIUS Disconnect-Request to NAS {NasIp}", session.NasIpAddress);
                    }
                }

                disabledCount++;
                changesMade = true;
            }
        }

        if (changesMade)
        {
            await db.SaveChangesAsync(ct);
            if (disabledCount > 0)
            {
                _logger.LogInformation("Enforcement check complete. {Count} account(s) disabled.", disabledCount);
            }
        }
    }
}