src/services/MatchingQueue.js

class MatchingQueue {
  constructor() {
    this.queue = []; // Array of { socketId, user }
  }

  add(socketId, user) {
    this.queue.push({ socketId, user, joinedAt: Date.now() });
  }

  remove(socketId) {
    this.queue = this.queue.filter(client => client.socketId !== socketId);
  }

  findMatch(currentUser) {
    // 1. Filter out self and blocked users (omitted for MVP basics)
    const candidates = this.queue.filter(c => c.user._id !== currentUser._id);
    
    if (candidates.length === 0) return null;

    // 2. Priority: Opposite Gender
    const oppositeGender = candidates.find(
      c => c.user.profile.gender !== currentUser.profile.gender
    );

    if (oppositeGender) return oppositeGender;

    // 3. Fallback: Anyone (First in, First out)
    return candidates[0];
  }
}

export default new MatchingQueue();