// src/hooks/useUserStats.ts
import { useEffect, useState } from 'react';
import { doc, onSnapshot, updateDoc, increment } from 'firebase/firestore';
import { db, auth } from '../firebase';
import { UserStats } from '../types/user';

export const useUserStats = () => {
  const [stats, setStats] = useState<UserStats | undefined>(undefined);

  useEffect(() => {
    if (!auth.currentUser) return;

    const userRef = doc(db, 'users', auth.currentUser.uid);
    const unsubscribe = onSnapshot(userRef, async (docSnap) => {
      if (docSnap.exists()) {
        const data = docSnap.data();

        // Ensure stats exist
        let userStats: UserStats = data.stats || {
          textsHumanized: 0,
          wordsProcessed: 0,
          gptAverage: 0,
          totalSessions: 0,
          totalDuration: 0,
          averageSessionTime: 0,
        };

        // Backfill totalDuration if missing
        if (userStats.totalDuration === undefined) {
          const estimatedDuration =
            (userStats.averageSessionTime ?? 0) * (userStats.totalSessions ?? 1);
          await updateDoc(userRef, { 'stats.totalDuration': estimatedDuration });
          userStats.totalDuration = estimatedDuration;
        }

        // Always recalc averageSessionTime
        const avgTime =
          (userStats.totalSessions && userStats.totalDuration)
            ? userStats.totalDuration / userStats.totalSessions
            : 0;

        userStats.averageSessionTime = avgTime;

        setStats(userStats);
      }
    });

    return () => unsubscribe();
  }, []);

  const updateStats = async (newStats: Partial<UserStats>) => {
    if (!auth.currentUser || !stats) return;

    const userRef = doc(db, 'users', auth.currentUser.uid);

    // Calculate new totalDuration if averageSessionTime or totalSessions are updated
    let updatedTotalDuration = stats.totalDuration;
    let updatedTotalSessions = stats.totalSessions;

    if (newStats.totalSessions !== undefined) {
      updatedTotalSessions += newStats.totalSessions;
    }

    if (newStats.averageSessionTime !== undefined) {
      updatedTotalDuration = updatedTotalSessions * newStats.averageSessionTime;
    } else if (newStats.totalDuration !== undefined) {
      updatedTotalDuration = stats.totalDuration + newStats.totalDuration;
    }

    const newAvgSessionTime =
      updatedTotalSessions > 0 ? updatedTotalDuration / updatedTotalSessions : 0;

    await updateDoc(userRef, {
      'stats.textsHumanized':
        newStats.textsHumanized !== undefined
          ? increment(newStats.textsHumanized)
          : increment(0),
      'stats.wordsProcessed':
        newStats.wordsProcessed !== undefined
          ? increment(newStats.wordsProcessed)
          : increment(0),
      'stats.totalSessions':
        newStats.totalSessions !== undefined
          ? increment(newStats.totalSessions)
          : increment(0),
      'stats.gptAverage':
        newStats.gptAverage !== undefined ? newStats.gptAverage : stats.gptAverage,
      'stats.totalDuration': updatedTotalDuration,
      'stats.averageSessionTime': newAvgSessionTime,
    });
  };

  return { stats, updateStats };
};