const User = require("../models/User");
const PointTransaction = require("../models/PointTransaction");
const Badge = require("../models/Badge");
const UserBadge = require("../models/UserBadge");

/**
 * Point rewards for different actions
 */
const POINT_VALUES = {
  STREET_ADOPTION: 100,
  TASK_COMPLETION: 50,
  POST_CREATION: 10,
  EVENT_PARTICIPATION: 75,
};

/**
 * Awards points to a user with transaction tracking
 *
 * @param {string} userId - User ID
 * @param {number} amount - Points to award (can be negative for deductions)
 * @param {string} type - Transaction type (street_adoption, task_completion, etc.)
 * @param {string} description - Human-readable description
 * @param {Object} relatedEntity - Related entity {entityType, entityId}
 * @returns {Promise<Object>} - Updated user and transaction
 */
async function awardPoints(
  userId,
  amount,
  type,
  description,
  relatedEntity = {}
) {
  try {
    // Get current user
    const user = await User.findById(userId);
    if (!user) {
      throw new Error("User not found");
    }

    // Calculate new balance
    const currentBalance = user.points || 0;
    const newBalance = currentBalance + amount;

    // Update user points
    const updatedUser = await User.update(userId, { points: newBalance });

    // Create transaction record
    const transaction = await PointTransaction.create({
      user: userId,
      amount: amount,
      transactionType: type,
      description: description,
      relatedEntity: relatedEntity,
      balanceAfter: newBalance,
    });

    // Check for new badges
    await checkAndAwardBadges(userId, newBalance);

    return {
      user: updatedUser,
      transaction: transaction,
      newBalance: newBalance,
    };
  } catch (error) {
    console.error("Error awarding points:", error);
    throw error;
  }
}

/**
 * Get user's current point balance
 */
async function getUserPoints(userId) {
  try {
    const user = await User.findById(userId);
    return user ? user.points || 0 : 0;
  } catch (error) {
    console.error("Error getting user points:", error);
    throw error;
  }
}

/**
 * Get user's transaction history
 */
async function getUserTransactionHistory(userId, limit = 50, skip = 0) {
  try {
    return await PointTransaction.findByUser(userId, limit, skip);
  } catch (error) {
    console.error("Error getting transaction history:", error);
    throw error;
  }
}

/**
 * Check if user qualifies for new badges and award them
 */
async function checkAndAwardBadges(userId, userPoints = null) {
  try {
    // Get user's current points if not provided
    if (userPoints === null) {
      userPoints = await getUserPoints(userId);
    }

    // Get user's stats for badge checking
    const userStats = await getUserStats(userId);
    const userBadges = await UserBadge.findByUser(userId);

    // Get all available badges
    const allBadges = await Badge.findAll();

    // Check each badge criteria
    for (const badge of allBadges) {
      // Skip if user already has this badge
      if (userBadges.some(ub => ub.badgeId === badge._id)) {
        continue;
      }

      let qualifies = false;

      // Check different badge criteria
      switch (badge.criteria.type) {
        case 'points_earned':
          qualifies = userPoints >= badge.criteria.threshold;
          break;
        case 'street_adoptions':
          qualifies = userStats.streetAdoptions >= badge.criteria.threshold;
          break;
        case 'task_completions':
          qualifies = userStats.taskCompletions >= badge.criteria.threshold;
          break;
        case 'post_creations':
          qualifies = userStats.postCreations >= badge.criteria.threshold;
          break;
        case 'event_participations':
          qualifies = userStats.eventParticipations >= badge.criteria.threshold;
          break;
        case 'consecutive_days':
          qualifies = userStats.consecutiveDays >= badge.criteria.threshold;
          break;
        case 'special':
          // Special badges are awarded manually
          qualifies = false;
          break;
      }

      if (qualifies) {
        await awardBadge(userId, badge._id);
      }
    }
  } catch (error) {
    console.error("Error checking badges:", error);
    throw error;
  }
}

/**
 * Award a specific badge to a user
 */
async function awardBadge(userId, badgeId) {
  try {
    // Get badge details
    const badge = await Badge.findById(badgeId);
    if (!badge) {
      throw new Error("Badge not found");
    }

    // Create user badge record
    const userBadge = await UserBadge.create({
      userId: userId,
      badgeId: badgeId,
      awardedAt: new Date().toISOString(),
    });

    // Award points for earning badge (if it's a rare or higher badge)
    let pointsAwarded = 0;
    if (badge.rarity === 'rare') {
      pointsAwarded = 50;
    } else if (badge.rarity === 'epic') {
      pointsAwarded = 100;
    } else if (badge.rarity === 'legendary') {
      pointsAwarded = 200;
    }

    if (pointsAwarded > 0) {
      await awardPoints(
        userId,
        pointsAwarded,
        'badge_earned',
        `Earned ${badge.name} badge`,
        { entityType: 'Badge', entityId: badgeId }
      );
    }

    return userBadge;
  } catch (error) {
    console.error("Error awarding badge:", error);
    throw error;
  }
}

/**
 * Get user statistics for badge checking
 */
async function getUserStats(userId) {
  try {
    // This would typically involve querying various collections
    // For now, return basic stats - this should be enhanced
    const user = await User.findById(userId);
    
    return {
      streetAdoptions: 0, // Would query Street collection
      taskCompletions: 0, // Would query Task collection
      postCreations: 0, // Would query Post collection
      eventParticipations: 0, // Would query Event participation
      consecutiveDays: 0, // Would calculate from login history
    };
  } catch (error) {
    console.error("Error getting user stats:", error);
    throw error;
  }
}

/**
 * Get user's badges
 */
async function getUserBadges(userId) {
  try {
    const userBadges = await UserBadge.findByUser(userId);
    const badges = [];

    for (const userBadge of userBadges) {
      const badge = await Badge.findById(userBadge.badgeId);
      if (badge) {
        badges.push({
          ...badge,
          awardedAt: userBadge.awardedAt,
        });
      }
    }

    return badges;
  } catch (error) {
    console.error("Error getting user badges:", error);
    throw error;
  }
}

/**
 * Redeem points for a reward
 */
async function redeemPoints(userId, rewardId, pointsCost) {
  try {
    const currentPoints = await getUserPoints(userId);
    
    if (currentPoints < pointsCost) {
      throw new Error("Insufficient points");
    }

    // Deduct points
    const result = await awardPoints(
      userId,
      -pointsCost,
      'reward_redemption',
      `Redeemed reward ${rewardId}`,
      { entityType: 'Reward', entityId: rewardId }
    );

    return result;
  } catch (error) {
    console.error("Error redeeming points:", error);
    throw error;
  }
}

/**
 * Get leaderboard
 */
async function getLeaderboard(limit = 10) {
  try {
    // This would typically use a more efficient query
    const users = await User.findAll();
    
    // Sort by points (this should be done at database level for efficiency)
    const sortedUsers = users
      .filter(user => user.points > 0)
      .sort((a, b) => b.points - a.points)
      .slice(0, limit);

    return sortedUsers.map((user, index) => ({
      rank: index + 1,
      userId: user._id,
      username: user.username,
      points: user.points,
      badges: [], // Would populate if needed
    }));
  } catch (error) {
    console.error("Error getting leaderboard:", error);
    throw error;
  }
}

module.exports = {
  awardPoints,
  getUserPoints,
  getUserTransactionHistory,
  checkAndAwardBadges,
  awardBadge,
  getUserBadges,
  redeemPoints,
  getLeaderboard,
  POINT_VALUES,
};