"use client";

import { useState, useCallback, useEffect } from 'react';
import { onAuthStateChanged, signInAnonymously, User as FirebaseUser, signOut as firebaseSignOut } from "firebase/auth";
import { doc, getDoc, onSnapshot, updateDoc, arrayUnion, collection, query, where, getDocs, writeBatch } from "firebase/firestore";
import { ref, set, serverTimestamp } from 'firebase/database';
import { cryptoService } from '@/lib/crypto-service';
import { fingerprintService } from '@/lib/fingerprint-service';
import type { User } from '@/lib/types';
import { useFirebase } from '@/contexts/firebase-context';
import { Capacitor } from '@capacitor/core';
import { Device } from '@capacitor/device';
import { useToast } from '@/hooks/use-toast';


export const useAuthCore = () => {
    const { auth, db, rtdb } = useFirebase();
    const { toast } = useToast();
    const addToast = useCallback((message: string, options?: { variant?: 'default' | 'destructive' }) => {
        toast({ title: message, variant: options?.variant });
    }, [toast]);
    
    const [currentUser, setCurrentUser] = useState<User | null>(null);
    const [authStatus, setAuthStatus] = useState<'loading' | 'onboarding' | 'recovery' | 'authenticated'>('loading');
    
    const handleAuthenticatedUser = useCallback(async (user: FirebaseUser) => {
        const userProfileRef = doc(db, 'users', user.uid);
        const userSnap = await getDoc(userProfileRef);

        if (userSnap.exists()) {
            localStorage.setItem('userId', user.uid); // Save userId for Capacitor
            await cryptoService.setupUserKeys(user.uid, rtdb);
            
            const fingerprint = await fingerprintService.generate();
            const existingData = userSnap.data();
            if (fingerprint && (!existingData.deviceFingerprints || !existingData.deviceFingerprints.includes(fingerprint))) {
                await updateDoc(userProfileRef, {
                    deviceFingerprints: arrayUnion(fingerprint)
                });
            }

            const unsub = onSnapshot(userProfileRef, (doc) => {
                if (doc.exists()) {
                    setCurrentUser({ uid: doc.id, ...doc.data() } as User);
                } else {
                    setCurrentUser(null);
                    setAuthStatus('onboarding');
                }
            });
            setAuthStatus('authenticated');
            return unsub;
        } else {
            setAuthStatus('onboarding');
        }
        return () => {};
    }, [db, rtdb]);

    const recoverAccount = useCallback(async (recoveryId: string): Promise<boolean> => {
        if (!auth.currentUser) {
            addToast("Authentication not initialized. Please wait and try again.", { variant: "destructive" });
            return false;
        }
        const newUid = auth.currentUser.uid;

        // 1. Find original UID from recoveryId
        const recoveryDocRef = doc(db, 'recovery', recoveryId);
        const recoverySnap = await getDoc(recoveryDocRef);
        if (!recoverySnap.exists()) {
            addToast("Invalid Recovery ID.", { variant: "destructive" });
            return false;
        }
        const originalUid = recoverySnap.data().uid;

        if (originalUid === newUid) {
            addToast("This account is already active on this device.", { variant: "default" });
            await handleAuthenticatedUser(auth.currentUser);
            return true;
        }
        
        addToast("Account found! Migrating to new device...");

        try {
            const batch = writeBatch(db);

            const originalProfileRef = doc(db, 'users', originalUid);
            const originalProfileSnap = await getDoc(originalProfileRef);
            if (!originalProfileSnap.exists()) {
                throw new Error("Original user profile not found. The account may be corrupted.");
            }
            const originalProfileData = originalProfileSnap.data() as User;
            const publicId = originalProfileData.publicId;

            const newProfileData = { ...originalProfileData, uid: newUid };
            batch.set(doc(db, 'users', newUid), newProfileData);
            batch.update(doc(db, 'publicIds', publicId), { uid: newUid });
            batch.update(recoveryDocRef, { uid: newUid });

            // To be safe, we are not deleting the old user document.
            // This prevents data loss if the user is logged in on another device.
            
            await batch.commit();

            addToast("Account recovered successfully!");
            await handleAuthenticatedUser(auth.currentUser);
            return true;

        } catch (error: any) {
            console.error("Account migration failed:", error);
            addToast(`Recovery failed: ${error.message}`, { variant: "destructive" });
            return false;
        }
    }, [auth, db, addToast, handleAuthenticatedUser]);


    useEffect(() => {
        let isMounted = true;
        const unsubscribe = onAuthStateChanged(auth, async (user) => {
            if (!isMounted) return;
            if (user) {
                await handleAuthenticatedUser(user);
            } else {
                try {
                    await signInAnonymously(auth);
                } catch (error) {
                    console.error("Anonymous sign-in failed:", error);
                    if (isMounted) setAuthStatus('recovery'); // Go to recovery if sign-in fails
                }
            }
        });

        return () => {
            isMounted = false;
            unsubscribe();
        };
    }, [auth, handleAuthenticatedUser]);
    
    const signOutUser = useCallback(async () => {
        const userToSignOut = auth.currentUser;
        if (!userToSignOut && !currentUser) {
            setAuthStatus('recovery');
            window.location.reload();
            return;
        };
        
        const uidToUpdate = currentUser?.uid || userToSignOut?.uid;

        try {
            if(uidToUpdate) {
                const presenceRef = ref(rtdb, `presence/${uidToUpdate}`);
                await set(presenceRef, { isOnline: false, lastSeen: serverTimestamp() });
            }
            await firebaseSignOut(auth);
        } catch (error) {
            console.error("Sign out error:", error);
        } finally {
            setCurrentUser(null);
            setAuthStatus('recovery');
            window.location.reload();
        }
    }, [auth, rtdb, currentUser]);

    const updateUserProfile = useCallback(async (profileData: Partial<Pick<User, 'displayName' | 'photoURL' | 'bio' | 'status' | 'privacySettings'>>) => {
        if (!currentUser) return;
        const userRef = doc(db, 'users', currentUser.uid);
        await updateDoc(userRef, profileData);
    }, [currentUser, db]);


    return {
        currentUser,
        authStatus,
        setAuthStatus,
        signOutUser,
        recoverAccount,
        updateUserProfile,
        auth,
        handleAuthenticatedUser,
    };
};