import { Request, Response } from 'express';
import Event, { IEvent } from '../model/event.model';
import EventDay from '../model/eventDay.model';
import User from '../model/user.model';
import crypto from 'crypto';
import sendMail from '../util/mailer.util';
import mongoose from 'mongoose';
import { deleteEventDays } from '../util/eventDay.util';

interface IEventRequest extends Request {
  userId?: string;
}

// Helper: Generate unique event code
const generateEventCode = async (orgName: string, theme: string): Promise<string> => {
  const orgPrefix = orgName.substring(0, 4).toUpperCase().replace(/[^A-Z]/g, '');
  const themePrefix = theme.substring(0, 4).toUpperCase().replace(/[^A-Z]/g, '');
  const random = Math.floor(1000 + Math.random() * 9000);

  let code = `${orgPrefix}-${themePrefix}-${random}`;
  let exists = await Event.findOne({ code });

  while (exists) {
    const newRandom = Math.floor(1000 + Math.random() * 9000);
    code = `${orgPrefix}-${themePrefix}-${newRandom}`;
    exists = await Event.findOne({ code });
  }

  return code;
};

// Helper: Calculate distance between two coordinates (Haversine formula)
const calculateDistance = (
  lat1: number, lon1: number,
  lat2: number, lon2: number
): number => {
  const R = 6371e3; // Earth radius in meters
  const φ1 = lat1 * Math.PI / 180;
  const φ2 = lat2 * Math.PI / 180;
  const Δφ = (lat2 - lat1) * Math.PI / 180;
  const Δλ = (lon2 - lon1) * Math.PI / 180;

  const a = Math.sin(Δφ / 2) * Math.sin(Δφ / 2) +
    Math.cos(φ1) * Math.cos(φ2) *
    Math.sin(Δλ / 2) * Math.sin(Δλ / 2);
  const c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));

  return R * c; // Distance in meters
};

// ==================== CREATE EVENT ====================
export const createEvent = async (req: IEventRequest, res: Response) => {
  try {
    const userId = req.userId;
    const user = await User.findById(userId).populate('organization');

    if (!user) {
      return res.status(404).json({ message: 'User not found' });
    }

    // Allow trainers, organizations, and admins to create events
    const allowedRoles = ['trainer', 'organization', 'admin'];
    if (!allowedRoles.includes(user.role)) {
      return res.status(403).json({
        message: 'Only trainers, organizations, and admins can create events'
      });
    }

    // Verification checks based on role
    if (user.role === 'trainer') {
      // Check if trainer is verified
      if (user.organizationVerificationStatus !== 'verified') {
        return res.status(403).json({
          message: 'Only verified trainers can create events',
          verificationStatus: user.organizationVerificationStatus
        });
      }
    } else if (user.role === 'organization') {
      // Check if organization is verified
      if (user.verificationStatus !== 'approved') {
        return res.status(403).json({
          message: 'Only verified organizations can create events',
          verificationStatus: user.verificationStatus
        });
      }
    }
    // Admins don't need verification checks

    const {
      title, theme, description, capacity,
      startDate, endDate, type, venue,
      longitude, latitude, geofenceRadius,
      onlineLink, allowSelfJoin = true,
      defaultStartTime = "09:00",
      defaultEndTime = "17:00"
    } = req.body;

    // Validation
    if (!title || !theme || !capacity || !startDate || !endDate || !type) {
      return res.status(400).json({ message: 'Missing required fields' });
    }

    if (new Date(endDate) <= new Date(startDate)) {
      return res.status(400).json({ message: 'End date must be after start date' });
    }

    // Validate time format (HH:MM)
    const timeRegex = /^([0-1]?[0-9]|2[0-3]):[0-5][0-9]$/;
    if (!timeRegex.test(defaultStartTime) || !timeRegex.test(defaultEndTime)) {
      return res.status(400).json({ message: 'Invalid time format. Use HH:MM (e.g., 16:00)' });
    }

    // Validate end time is after start time
    const [startHour, startMin] = defaultStartTime.split(':').map(Number);
    const [endHour, endMin] = defaultEndTime.split(':').map(Number);
    if (endHour < startHour || (endHour === startHour && endMin <= startMin)) {
      return res.status(400).json({ message: 'End time must be after start time' });
    }

    if ((type === 'in-person' || type === 'hybrid') && (!longitude || !latitude || !venue)) {
      return res.status(400).json({
        message: 'Location (longitude, latitude) and venue required for in-person/hybrid events'
      });
    }

    if ((type === 'online' || type === 'hybrid') && !onlineLink) {
      return res.status(400).json({ message: 'Online link required for online/hybrid events' });
    }

    // Generate unique code and join token
    // Determine organization based on user role
    let eventOrganization: any;
    let orgName: string;

    if (user.role === 'trainer') {
      // Trainers: use their organization
      eventOrganization = user.organization;
      orgName = (user.organization as any)?.username || 'ORG';
    } else if (user.role === 'organization') {
      // Organizations: use themselves as the organization
      eventOrganization = userId;
      orgName = user.username || 'ORG';
    } else {
      // Admins: use their organization if they have one, otherwise use their own ID
      eventOrganization = user.organization || userId;
      orgName = user.organization ? (user.organization as any)?.username : user.username || 'ORG';
    }

    const code = await generateEventCode(orgName, theme);
    const joinToken = crypto.randomBytes(32).toString('hex');

    const eventData: any = {
      title,
      code,
      theme,
      description,
      organization: eventOrganization,
      createdBy: userId,
      capacity,
      startDate: new Date(startDate),
      endDate: new Date(endDate),
      defaultStartTime,
      defaultEndTime,
      type,
      joinToken,
      allowSelfJoin,
      status: 'published'
    };

    if (type === 'in-person' || type === 'hybrid') {
      eventData.venue = venue;
      eventData.location = {
        type: 'Point',
        coordinates: [parseFloat(longitude), parseFloat(latitude)]
      };
      eventData.geofenceRadius = geofenceRadius || 100;
    }

    if (type === 'online' || type === 'hybrid') {
      eventData.onlineLink = onlineLink;
    }

    const event = new Event(eventData);
    await event.save();

    return res.status(201).json({
      message: 'Event created successfully',
      event: {
        _id: event._id,
        title: event.title,
        code: event.code,
        theme: event.theme,
        startDate: event.startDate,
        endDate: event.endDate,
        type: event.type,
        capacity: event.capacity,
        joinToken: event.joinToken
      }
    });
  } catch (err: any) {
    console.error(err);
    return res.status(500).json({ message: 'Server error', error: err.message });
  }
};

// ==================== SEARCH EVENTS ====================
export const searchEvents = async (req: IEventRequest, res: Response) => {
  try {
    const {
      query, // text search
      theme,
      organization,
      type,
      status = 'published',
      startDate,
      endDate,
      page = 1,
      limit = 20
    } = req.query;

    const filter: any = { status };

    // Text search on title, theme, description
    if (query) {
      filter.$text = { $search: query as string };
    }

    if (theme) filter.theme = theme;
    if (organization) filter.organization = organization;
    if (type) filter.type = type;

    // Date range filter
    if (startDate || endDate) {
      filter.startDate = {};
      if (startDate) filter.startDate.$gte = new Date(startDate as string);
      if (endDate) filter.startDate.$lte = new Date(endDate as string);
    }

    const skip = (Number(page) - 1) * Number(limit);

    const events = await Event.find(filter)
      .populate('organization', 'username organizationType')
      .populate('createdBy', 'username profilePhoto')
      .select('-joinToken -participants.attendance')
      .sort({ startDate: 1 })
      .skip(skip)
      .limit(Number(limit));

    const total = await Event.countDocuments(filter);

    // Add participant count to each event
    const eventsWithCount = events.map(event => ({
      ...event.toObject(),
      participantCount: event.participants.length,
      isCapacityFull: event.participants.length >= event.capacity
    }));

    return res.json({
      events: eventsWithCount,
      pagination: {
        total,
        page: Number(page),
        limit: Number(limit),
        totalPages: Math.ceil(total / Number(limit))
      }
    });
  } catch (err: any) {
    console.error(err);
    return res.status(500).json({ message: 'Server error', error: err.message });
  }
};

// ==================== GET NEARBY EVENTS ====================
export const getNearbyEvents = async (req: IEventRequest, res: Response) => {
  try {
    const { longitude, latitude, maxDistance = 50000 } = req.query; // default 50km

    if (!longitude || !latitude) {
      return res.status(400).json({ message: 'Location (longitude, latitude) required' });
    }

    const events = await Event.find({
      status: 'published',
      location: {
        $near: {
          $geometry: {
            type: 'Point',
            coordinates: [parseFloat(longitude as string), parseFloat(latitude as string)]
          },
          $maxDistance: Number(maxDistance)
        }
      },
      startDate: { $gte: new Date() } // Only upcoming events
    })
      .populate('organization', 'username organizationType')
      .populate('createdBy', 'username profilePhoto')
      .select('-joinToken -participants.attendance')
      .limit(20);

    const eventsWithDistance = events.map(event => {
      const distance = event.location ? calculateDistance(
        parseFloat(latitude as string),
        parseFloat(longitude as string),
        event.location.coordinates[1],
        event.location.coordinates[0]
      ) : null;

      return {
        ...event.toObject(),
        distance: distance ? Math.round(distance) : null,
        participantCount: event.participants.length,
        isCapacityFull: event.participants.length >= event.capacity
      };
    });

    return res.json({ events: eventsWithDistance });
  } catch (err: any) {
    console.error(err);
    return res.status(500).json({ message: 'Server error', error: err.message });
  }
};

// ==================== GET EVENT DASHBOARD ====================
export const getEventDashboard = async (req: IEventRequest, res: Response) => {
  try {
    const userId = req.userId;
    const now = new Date();

    // User's upcoming events
    const upcomingEvents = await Event.find({
      'participants.user': userId,
      startDate: { $gt: now },
      status: 'published'
    })
      .populate('organization', 'username')
      .sort({ startDate: 1 })
      .limit(10);

    // User's past events
    const pastEvents = await Event.find({
      'participants.user': userId,
      endDate: { $lt: now },
      status: { $in: ['completed', 'published'] }
    })
      .populate('organization', 'username')
      .sort({ endDate: -1 })
      .limit(10);

    // Recommended events (same themes as user's past events)
    const userThemes = [...new Set(pastEvents.map(e => e.theme))];
    const recommended = await Event.find({
      status: 'published',
      startDate: { $gt: now },
      theme: { $in: userThemes },
      'participants.user': { $ne: userId }
    })
      .populate('organization', 'username')
      .limit(5);

    return res.json({
      upcoming: upcomingEvents.map(e => ({
        ...e.toObject(),
        participantCount: e.participants.length
      })),
      past: pastEvents.map(e => {
        const participantCount = e.participants.length;
        return {
          ...e.toObject(),
          participantCount
        };
      }),
      recommended: recommended.map(e => ({
        ...e.toObject(),
        participantCount: e.participants.length
      }))
    });
  } catch (err: any) {
    console.error(err);
    return res.status(500).json({ message: 'Server error', error: err.message });
  }
};

// ==================== JOIN EVENT BY CODE ====================
export const joinEventByCode = async (req: IEventRequest, res: Response) => {
  try {
    const userId = req.userId;
    const { code } = req.body;

    if (!code) {
      return res.status(400).json({ message: 'Event code required' });
    }

    const event = await Event.findOne({ code: code.toUpperCase(), status: 'published' });

    if (!event) {
      return res.status(404).json({ message: 'Event not found or not published' });
    }

    // Check if already joined
    if (event.participants.find(p => p.user.toString() === userId)) {
      return res.status(400).json({ message: 'Already joined this event' });
    }

    // Check capacity
    if (event.participants.length >= event.capacity) {
      // Add to waitlist
      if (!event.waitlist.includes(userId as any)) {
        event.waitlist.push(userId as any);
        await event.save();
      }
      return res.status(400).json({
        message: 'Event is full. You have been added to the waitlist.',
        waitlisted: true
      });
    }

    // Add participant
    event.participants.push({
      user: userId as any,
      joinedAt: new Date(),
      joinMethod: 'code'
    } as any);

    await event.save();

    // Send confirmation email
    const user = await User.findById(userId);
    if (user) {
      await sendMail({
        to: user.email,
        subject: `Registered for ${event.title}`,
        text: `You have successfully registered for ${event.title} (${event.code})`,
        html: `<p>You have successfully registered for <strong>${event.title}</strong></p>
               <p>Code: ${event.code}</p>
               <p>Start: ${event.startDate.toLocaleString()}</p>`
      });
    }

    return res.json({
      message: 'Successfully joined event',
      event: {
        _id: event._id,
        title: event.title,
        code: event.code,
        startDate: event.startDate,
        endDate: event.endDate,
        type: event.type,
        venue: event.venue,
        onlineLink: event.onlineLink
      }
    });
  } catch (err: any) {
    console.error(err);
    return res.status(500).json({ message: 'Server error', error: err.message });
  }
};

// ==================== JOIN EVENT BY LINK ====================
export const joinEventByLink = async (req: IEventRequest, res: Response) => {
  try {
    const userId = req.userId;
    const { eventId, token } = req.body;

    if (!eventId || !token) {
      return res.status(400).json({ message: 'Event ID and token required' });
    }

    const event = await Event.findOne({
      _id: eventId,
      joinToken: token,
      status: 'published'
    });

    if (!event) {
      return res.status(404).json({ message: 'Invalid event link' });
    }

    // Check if already joined
    if (event.participants.find(p => p.user.toString() === userId)) {
      return res.status(400).json({ message: 'Already joined this event' });
    }

    // Check capacity
    if (event.participants.length >= event.capacity) {
      if (!event.waitlist.includes(userId as any)) {
        event.waitlist.push(userId as any);
        await event.save();
      }
      return res.status(400).json({
        message: 'Event is full. You have been added to the waitlist.',
        waitlisted: true
      });
    }

    // Add participant
    event.participants.push({
      user: userId as any,
      joinedAt: new Date(),
      joinMethod: 'link'
    } as any);

    await event.save();

    return res.json({
      message: 'Successfully joined event',
      event: {
        _id: event._id,
        title: event.title,
        code: event.code,
        startDate: event.startDate,
        endDate: event.endDate
      }
    });
  } catch (err: any) {
    console.error(err);
    return res.status(500).json({ message: 'Server error', error: err.message });
  }
};

// ==================== GET EVENT DETAILS ====================
export const getEventDetails = async (req: IEventRequest, res: Response) => {
  try {
    const { eventId } = req.params;
    const userId = req.userId;

    const event = await Event.findById(eventId)
      .populate('organization', 'username email organizationType')
      .populate('createdBy', 'username email profilePhoto workDesignation')
      .populate('participants.user', 'username profilePhoto');

    if (!event) {
      return res.status(404).json({ message: 'Event not found' });
    }

    const isParticipant = event.participants.find(p => p.user._id.toString() === userId);
    const isCreator = event.createdBy._id.toString() === userId;

    const response: any = {
      ...event.toObject(),
      participantCount: event.participants.length,
      isCapacityFull: event.participants.length >= event.capacity,
      isJoined: !!isParticipant,
      isCreator
    };

    // Only show join token to creator
    if (!isCreator) {
      delete response.joinToken;
    }

    // Only show participant details if joined or creator
    if (!isParticipant && !isCreator) {
      response.participants = undefined;
    }

    return res.json(response);
  } catch (err: any) {
    console.error(err);
    return res.status(500).json({ message: 'Server error', error: err.message });
  }
};

// ==================== GET CREATOR'S EVENTS ====================
export const getTrainerEvents = async (req: IEventRequest, res: Response) => {
  try {
    const creatorId = req.userId;
    const { status } = req.query;

    const filter: any = { createdBy: creatorId };
    if (status) filter.status = status;

    const events = await Event.find(filter)
      .populate('organization', 'username')
      .sort({ startDate: -1 });

    // Get day-level statistics for each event
    const eventsWithStats = await Promise.all(events.map(async event => {
      const eventDays = await EventDay.find({ event: event._id });
      const totalDays = eventDays.length;
      const completedDays = eventDays.filter(day => day.isCompleted).length;

      // Calculate total attendance across all days
      const totalAttendance = eventDays.reduce((sum, day) => sum + day.attendance.length, 0);
      const averageAttendancePerDay = totalDays > 0 ? totalAttendance / totalDays : 0;

      return {
        ...event.toObject(),
        participantCount: event.participants.length,
        totalDays,
        completedDays,
        averageAttendancePerDay: Math.round(averageAttendancePerDay * 100) / 100,
        waitlistCount: event.waitlist.length
      };
    }));

    return res.json({ events: eventsWithStats });
  } catch (err: any) {
    console.error(err);
    return res.status(500).json({ message: 'Server error', error: err.message });
  }
};

// ==================== UPDATE EVENT ====================
export const updateEvent = async (req: IEventRequest, res: Response) => {
  try {
    const creatorId = req.userId;
    const { eventId } = req.params;
    const updates = req.body;

    const event = await Event.findOne({ _id: eventId, createdBy: creatorId });

    if (!event) {
      return res.status(404).json({ message: 'Event not found or unauthorized' });
    }

    // Don't allow changing certain fields
    delete updates.code;
    delete updates.joinToken;
    delete updates.organization;
    delete updates.createdBy;
    delete updates.participants;

    Object.assign(event, updates);
    await event.save();

    return res.json({
      message: 'Event updated successfully',
      event
    });
  } catch (err: any) {
    console.error(err);
    return res.status(500).json({ message: 'Server error', error: err.message });
  }
};

// ==================== DELETE EVENT ====================
export const deleteEvent = async (req: IEventRequest, res: Response) => {
  try {
    const creatorId = req.userId;
    const { eventId } = req.params;

    const event = await Event.findOne({
      _id: eventId,
      createdBy: creatorId
    });

    if (!event) {
      return res.status(404).json({ message: 'Event not found or unauthorized' });
    }

    // Delete all associated EventDay records and photos
    await deleteEventDays(eventId);

    // Delete the event
    await Event.findByIdAndDelete(eventId);

    return res.json({ message: 'Event deleted successfully' });
  } catch (err: any) {
    console.error(err);
    return res.status(500).json({ message: 'Server error', error: err.message });
  }
};

// ==================== GET ORGANIZATION EVENT STATS ====================
export const getOrganizationEventStats = async (req: IEventRequest, res: Response) => {
  try {
    const { organizationId } = req.params;

    // Calculate date range (last 365 days)
    const endDate = new Date();
    const startDate = new Date();
    startDate.setFullYear(startDate.getFullYear() - 1);

    const events = await Event.aggregate([
      {
        $match: {
          organization: new mongoose.Types.ObjectId(organizationId),
          startDate: { $gte: startDate, $lte: endDate },
          status: { $in: ['published', 'ongoing', 'completed'] }
        }
      },
      {
        $group: {
          _id: { $dateToString: { format: "%Y-%m-%d", date: "$startDate" } },
          count: { $sum: 1 }
        }
      },
      {
        $project: {
          date: "$_id",
          count: 1,
          _id: 0
        }
      }
    ]);

    return res.json({ stats: events });
  } catch (err: any) {
    console.error(err);
    return res.status(500).json({ message: 'Server error', error: err.message });
  }
};

// ==================== GET LIVE EVENTS ====================
// Returns events that are currently ongoing (within date range) but don't have started training sessions
export const getLiveEvents = async (req: IEventRequest, res: Response) => {
  try {
    const now = new Date();

    // Find all events that have started training sessions
    const startedTrainingDays = await EventDay.find({
      hasStarted: true,
      isCompleted: false
    }).distinct('event');

    // Find events that are within their date range but NOT in the started training list
    const ongoingEvents = await Event.find({
      status: { $in: ['published', 'ongoing'] },
      startDate: { $lte: now },
      endDate: { $gte: now },
      _id: { $nin: startedTrainingDays }, // Exclude events with started training
      location: { $exists: true, $ne: null } // Only events with location
    })
      .populate('organization', 'username organizationType')
      .populate('createdBy', 'username profilePhoto')
      .select('-joinToken');

    const eventsWithCount = ongoingEvents.map(event => ({
      ...event.toObject(),
      participantCount: event.participants.length,
      isCapacityFull: event.participants.length >= event.capacity
    }));

    return res.json({ events: eventsWithCount });
  } catch (err: any) {
    console.error(err);
    return res.status(500).json({ message: 'Server error', error: err.message });
  }
};

// ==================== GET LIVE TRAINING EVENTS ====================
export const getLiveTrainingEvents = async (req: IEventRequest, res: Response) => {
  try {
    const now = new Date();

    // Find all event days that have started but not completed
    const liveTrainingDays = await EventDay.find({
      hasStarted: true,
      isCompleted: false
    }).populate({
      path: 'event',
      populate: [
        { path: 'organization', select: 'username organizationType' },
        { path: 'createdBy', select: 'username profilePhoto' }
      ]
    });

    // Filter and map to events with location data
    const liveTrainingEvents = liveTrainingDays
      .filter(eventDay => {
        const event = eventDay.event as any;
        // Only include events with location data
        return event && event.location && event.location.coordinates;
      })
      .map(eventDay => {
        const event = eventDay.event as any;
        return {
          ...event.toObject(),
          currentEventDay: {
            _id: eventDay._id,
            date: eventDay.date,
            dayNumber: eventDay.dayNumber,
            startTime: eventDay.startTime,
            endTime: eventDay.endTime,
            hasStarted: eventDay.hasStarted,
            isCompleted: eventDay.isCompleted
          },
          participantCount: event.participants.length,
          isCapacityFull: event.participants.length >= event.capacity,
          isLiveTraining: true
        };
      });

    // Remove duplicates (same event can have multiple live days)
    const uniqueEvents = Array.from(
      new Map(liveTrainingEvents.map(event => [event._id.toString(), event])).values()
    );

    return res.json({ events: uniqueEvents });
  } catch (err: any) {
    console.error(err);
    return res.status(500).json({ message: 'Server error', error: err.message });
  }
};

// ==================== GET ALL EVENTS (ADMIN) ====================
export const getAllEventsForAdmin = async (req: IEventRequest, res: Response) => {
  try {
    const { status, page = 1, limit = 20 } = req.query;

    const filter: any = {};
    if (status) filter.status = status;

    const skip = (Number(page) - 1) * Number(limit);

    const events = await Event.find(filter)
      .populate('organization', 'username organizationType')
      .populate('createdBy', 'username profilePhoto')
      .sort({ createdAt: -1 })
      .skip(skip)
      .limit(Number(limit));

    const total = await Event.countDocuments(filter);

    // Get day-level statistics for each event
    const eventsWithStats = await Promise.all(events.map(async event => {
      const eventDays = await EventDay.find({ event: event._id });
      const totalDays = eventDays.length;
      const completedDays = eventDays.filter(day => day.isCompleted).length;
      const liveDays = eventDays.filter(day => {
        const now = new Date();
        return day.hasStarted && !day.isCompleted &&
          now >= day.startTime && now <= day.endTime;
      }).length;

      return {
        ...event.toObject(),
        participantCount: event.participants.length,
        totalDays,
        completedDays,
        liveDays,
        waitlistCount: event.waitlist.length
      };
    }));

    return res.json({
      events: eventsWithStats,
      pagination: {
        total,
        page: Number(page),
        limit: Number(limit),
        totalPages: Math.ceil(total / Number(limit))
      }
    });
  } catch (err: any) {
    console.error(err);
    return res.status(500).json({ message: 'Server error', error: err.message });
  }
};