using System.Security.Cryptography;
using System.Text.RegularExpressions;
using Microsoft.EntityFrameworkCore;
using radiuscontroller.Data;
using radiuscontroller.Models;

namespace radiuscontroller.Services;

public interface IRadiusService
{
    Task<SystemConfigDto> GetSystemConfigAsync();
    Task UpdateSystemConfigAsync(int defaultSessionTimeMinutes, long defaultDataLimitMb);
    Task<RegistrationResultDto> RegisterGuestAsync(string guestName);
    Task<List<UserUsageDto>> GetAllUsersWithUsageAsync();
    Task<List<RadAcct>> GetActiveSessionsAsync();
    Task UpdateUserLimitsAsync(int profileId, int newSessionTimeMinutes, long newDataLimitMb);
    Task RevokeUserAsync(int profileId);
    Task DeleteUserAsync(int profileId);
    Task ResetUserPasswordAsync(int profileId, string newPassword);
    Task EnsureDatabaseCreatedAndSeededAsync();
}

public class RadiusService : IRadiusService
{
    private readonly RadiusDbContext _db;
    private readonly ILogger<RadiusService> _logger;

    public RadiusService(RadiusDbContext db, ILogger<RadiusService> logger)
    {
        _db = db;
        _logger = logger;
    }

    public async Task<SystemConfigDto> GetSystemConfigAsync()
    {
        var settings = await _db.SystemSettings.ToDictionaryAsync(s => s.Key, s => s.Value);

        int sessionTime = 60; // 60 minutes default
        if (settings.TryGetValue("default_session_time", out var sessionStr) && int.TryParse(sessionStr, out var parsedSession))
        {
            sessionTime = parsedSession;
        }

        long dataLimit = 500; // 500 MB default
        if (settings.TryGetValue("default_data_limit", out var dataStr) && long.TryParse(dataStr, out var parsedData))
        {
            dataLimit = parsedData;
        }

        return new SystemConfigDto
        {
            DefaultSessionTimeMinutes = sessionTime,
            DefaultDataLimitMb = dataLimit
        };
    }

    public async Task UpdateSystemConfigAsync(int defaultSessionTimeMinutes, long defaultDataLimitMb)
    {
        await SetOrUpdateSettingAsync("default_session_time", defaultSessionTimeMinutes.ToString());
        await SetOrUpdateSettingAsync("default_data_limit", defaultDataLimitMb.ToString());
        await _db.SaveChangesAsync();
    }

    private async Task SetOrUpdateSettingAsync(string key, string value)
    {
        var existing = await _db.SystemSettings.FirstOrDefaultAsync(s => s.Key == key);
        if (existing != null)
        {
            existing.Value = value;
            existing.UpdatedAt = DateTime.UtcNow;
        }
        else
        {
            _db.SystemSettings.Add(new SystemSetting
            {
                Key = key,
                Value = value,
                UpdatedAt = DateTime.UtcNow
            });
        }
    }

    public async Task<RegistrationResultDto> RegisterGuestAsync(string guestName)
    {
        if (string.IsNullOrWhiteSpace(guestName))
        {
            throw new ArgumentException("Guest name cannot be empty.", nameof(guestName));
        }

        var config = await GetSystemConfigAsync();

        // Format clean username base
        string cleanName = Regex.Replace(guestName.Trim().ToLowerInvariant(), @"[^a-z0-9]", "");
        if (string.IsNullOrEmpty(cleanName)) cleanName = "guest";
        if (cleanName.Length > 12) cleanName = cleanName[..12];

        string username = $"{cleanName}_{RandomNumberGenerator.GetInt32(1000, 9999)}";
        string password = GenerateReadablePassword(8);

        // Save Cleartext-Password for FreeRADIUS
        _db.RadCheck.Add(new RadCheck
        {
            Username = username,
            Attribute = "Cleartext-Password",
            Op = ":=",
            Value = password
        });

        // Set Session-Timeout (in seconds)
        long sessionTimeoutSeconds = (long)config.DefaultSessionTimeMinutes * 60;
        _db.RadReply.Add(new RadReply
        {
            Username = username,
            Attribute = "Session-Timeout",
            Op = "=",
            Value = sessionTimeoutSeconds.ToString()
        });

        // Set Max-Octets (in bytes)
        long maxOctetsBytes = config.DefaultDataLimitMb * 1024 * 1024;
        _db.RadReply.Add(new RadReply
        {
            Username = username,
            Attribute = "Max-Octets",
            Op = "=",
            Value = maxOctetsBytes.ToString()
        });

        // Create Guest Profile record
        var profile = new GuestProfile
        {
            GuestName = guestName.Trim(),
            Username = username,
            CreatedAt = DateTime.UtcNow,
            SessionTimeMinutes = config.DefaultSessionTimeMinutes,
            DataLimitMb = config.DefaultDataLimitMb,
            Status = "Active"
        };
        _db.GuestProfiles.Add(profile);

        await _db.SaveChangesAsync();

        return new RegistrationResultDto
        {
            GuestName = profile.GuestName,
            Username = username,
            Password = password,
            SessionTimeMinutes = config.DefaultSessionTimeMinutes,
            DataLimitMb = config.DefaultDataLimitMb,
            ExpirationEstimate = DateTime.UtcNow.AddMinutes(config.DefaultSessionTimeMinutes)
        };
    }

    public async Task<List<UserUsageDto>> GetAllUsersWithUsageAsync()
    {
        var profiles = await _db.GuestProfiles.OrderByDescending(p => p.CreatedAt).ToListAsync();
        var passwords = await _db.RadCheck
            .Where(rc => rc.Attribute == "Cleartext-Password")
            .ToDictionaryAsync(rc => rc.Username, rc => rc.Value);

        // Group accounting data by username
        var acctStats = await _db.RadAcct
            .GroupBy(ra => ra.Username)
            .Select(g => new
            {
                Username = g.Key,
                TotalInput = g.Sum(x => x.AcctInputOctets ?? 0),
                TotalOutput = g.Sum(x => x.AcctOutputOctets ?? 0),
                TotalSessionTime = g.Sum(x => x.AcctSessionTime ?? 0),
                IsConnected = g.Any(x => x.AcctStopTime == null)
            })
            .ToDictionaryAsync(g => g.Username);

        var result = new List<UserUsageDto>();

        foreach (var p in profiles)
        {
            passwords.TryGetValue(p.Username, out var pwd);
            acctStats.TryGetValue(p.Username, out var acct);

            result.Add(new UserUsageDto
            {
                ProfileId = p.Id,
                GuestName = p.GuestName,
                Username = p.Username,
                Password = pwd ?? "••••••••",
                CreatedAt = p.CreatedAt,
                SessionTimeMinutes = p.SessionTimeMinutes,
                DataLimitMb = p.DataLimitMb,
                Status = p.Status,
                TotalInputOctets = acct?.TotalInput ?? 0,
                TotalOutputOctets = acct?.TotalOutput ?? 0,
                TotalSessionTimeSeconds = acct?.TotalSessionTime ?? 0,
                IsCurrentlyConnected = acct?.IsConnected ?? false
            });
        }

        return result;
    }

    public async Task<List<RadAcct>> GetActiveSessionsAsync()
    {
        return await _db.RadAcct
            .Where(ra => ra.AcctStopTime == null)
            .OrderByDescending(ra => ra.AcctStartTime)
            .ToListAsync();
    }

    public async Task UpdateUserLimitsAsync(int profileId, int newSessionTimeMinutes, long newDataLimitMb)
    {
        var profile = await _db.GuestProfiles.FindAsync(profileId);
        if (profile == null) return;

        profile.SessionTimeMinutes = newSessionTimeMinutes;
        profile.DataLimitMb = newDataLimitMb;

        // Update RadReply Session-Timeout
        var sessionReply = await _db.RadReply.FirstOrDefaultAsync(rr => rr.Username == profile.Username && rr.Attribute == "Session-Timeout");
        if (sessionReply != null)
        {
            sessionReply.Value = (newSessionTimeMinutes * 60).ToString();
        }
        else
        {
            _db.RadReply.Add(new RadReply
            {
                Username = profile.Username,
                Attribute = "Session-Timeout",
                Op = "=",
                Value = (newSessionTimeMinutes * 60).ToString()
            });
        }

        // Update RadReply Max-Octets
        var dataReply = await _db.RadReply.FirstOrDefaultAsync(rr => rr.Username == profile.Username && rr.Attribute == "Max-Octets");
        long maxOctetsBytes = newDataLimitMb * 1024 * 1024;
        if (dataReply != null)
        {
            dataReply.Value = maxOctetsBytes.ToString();
        }
        else
        {
            _db.RadReply.Add(new RadReply
            {
                Username = profile.Username,
                Attribute = "Max-Octets",
                Op = "=",
                Value = maxOctetsBytes.ToString()
            });
        }

        await _db.SaveChangesAsync();
    }

    public async Task RevokeUserAsync(int profileId)
    {
        var profile = await _db.GuestProfiles.FindAsync(profileId);
        if (profile == null) return;

        profile.Status = "Revoked";

        // Remove Cleartext-Password and insert Auth-Type := Reject
        var checks = await _db.RadCheck.Where(rc => rc.Username == profile.Username).ToListAsync();
        _db.RadCheck.RemoveRange(checks);

        _db.RadCheck.Add(new RadCheck
        {
            Username = profile.Username,
            Attribute = "Auth-Type",
            Op = ":=",
            Value = "Reject"
        });

        await _db.SaveChangesAsync();
    }

    public async Task DeleteUserAsync(int profileId)
    {
        var profile = await _db.GuestProfiles.FindAsync(profileId);
        if (profile == null) return;

        var username = profile.Username;

        var checks = await _db.RadCheck.Where(rc => rc.Username == username).ToListAsync();
        var replies = await _db.RadReply.Where(rr => rr.Username == username).ToListAsync();

        _db.RadCheck.RemoveRange(checks);
        _db.RadReply.RemoveRange(replies);
        _db.GuestProfiles.Remove(profile);

        await _db.SaveChangesAsync();
    }

    public async Task ResetUserPasswordAsync(int profileId, string newPassword)
    {
        var profile = await _db.GuestProfiles.FindAsync(profileId);
        if (profile == null) return;

        var check = await _db.RadCheck.FirstOrDefaultAsync(rc => rc.Username == profile.Username && rc.Attribute == "Cleartext-Password");
        if (check != null)
        {
            check.Value = newPassword;
        }
        else
        {
            _db.RadCheck.Add(new RadCheck
            {
                Username = profile.Username,
                Attribute = "Cleartext-Password",
                Op = ":=",
                Value = newPassword
            });
        }

        if (profile.Status == "Revoked")
        {
            profile.Status = "Active";
            var rejectCheck = await _db.RadCheck.FirstOrDefaultAsync(rc => rc.Username == profile.Username && rc.Attribute == "Auth-Type");
            if (rejectCheck != null)
            {
                _db.RadCheck.Remove(rejectCheck);
            }
        }

        await _db.SaveChangesAsync();
    }

    public async Task EnsureDatabaseCreatedAndSeededAsync()
    {
        try
        {
            await _db.Database.EnsureCreatedAsync();

            if (!await _db.SystemSettings.AnyAsync())
            {
                _db.SystemSettings.Add(new SystemSetting { Key = "default_session_time", Value = "60", UpdatedAt = DateTime.UtcNow });
                _db.SystemSettings.Add(new SystemSetting { Key = "default_data_limit", Value = "500", UpdatedAt = DateTime.UtcNow });
            }

            await _db.SaveChangesAsync();
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Database initialization warning (Database might be populated via Docker init.sql script).");
        }
    }

    private static string GenerateReadablePassword(int length)
    {
        const string chars = "ABCDEFGHJKLMNPQRSTUVWXYZ23456789";
        var result = new char[length];
        for (int i = 0; i < length; i++)
        {
            result[i] = chars[RandomNumberGenerator.GetInt32(chars.Length)];
        }
        return new string(result);
    }
}