import { useState, useEffect, useCallback, useRef } from 'react';
import { collection, query, where, onSnapshot, doc, getDoc, writeBatch, arrayUnion, deleteDoc, updateDoc, arrayRemove, deleteField } from 'firebase/firestore';
import { ref, set, update, push, serverTimestamp, remove } from 'firebase/database';
import { cryptoService } from '@/lib/crypto-service';
import type { User, Group, GroupInvitation, GroupType, Contact, GroupSendingMode, ChatRecipient } from '@/lib/types';
import { useAuth } from '@/contexts/auth-context';
import { useFirebase } from '@/contexts/firebase-context';
import { useSettings } from '@/contexts/settings-context';
import { useContacts } from '@/contexts/contacts-context';
import { storageService } from '@/lib/storage-service';

interface UseGroupsProps {
    setRecipient: (recipient: ChatRecipient | null | ((prev: ChatRecipient | null) => ChatRecipient | null)) => void;
}

export const useGroupsCore = ({ setRecipient }: UseGroupsProps) => {
    const { currentUser } = useAuth();
    const { db, rtdb } = useFirebase();
    const { contacts } = useContacts();
    const { addToast, playSound, t } = useSettings();
    
    const [groups, setGroups] = useState<Group[]>([]);
    const [groupInvitations, setGroupInvitations] = useState<GroupInvitation[]>([]);
    const previousGroupsRef = useRef<Group[]>([]);


    useEffect(() => {
        if (!currentUser) {
            setGroups([]);
            setGroupInvitations([]);
            return;
        }

        let isMounted = true;
        
        // Load cached groups first
        storageService.getGroups().then(cachedGroups => {
            if (isMounted && cachedGroups.length > 0) {
                const sortedGroups = cachedGroups.sort((a, b) => a.info.name.localeCompare(b.info.name));
                setGroups(sortedGroups);
                previousGroupsRef.current = sortedGroups;
            }
        });

        const groupsQuery = query(collection(db, 'groups'), where(`members.${currentUser.uid}`, '==', true));
        const groupsUnsub = onSnapshot(groupsQuery, (snapshot) => {
            const fetchedGroups = snapshot.docs.map(doc => ({ id: doc.id, ...doc.data() } as Group));
            const sortedGroups = fetchedGroups.sort((a, b) => a.info.name.localeCompare(b.info.name));
            
            const prevGroupIds = new Set(previousGroupsRef.current.map(g => g.id));
            const currentGroupIds = new Set(sortedGroups.map(g => g.id));

            prevGroupIds.forEach(id => {
                if (!currentGroupIds.has(id)) {
                    setRecipient(prevRecipient => {
                        if (prevRecipient && prevRecipient.uid === id) {
                            addToast(t('You have been removed from the group.'));
                            return null;
                        }
                        return prevRecipient;
                    });
                }
            });
            
            if (isMounted) {
                setGroups(sortedGroups);
                storageService.saveGroups(sortedGroups);
            }
            previousGroupsRef.current = sortedGroups;
        });

        const invitationsUnsub = onSnapshot(collection(db, 'users', currentUser.uid, 'groupInvitations'), (snapshot) => {
            if (isMounted) {
                setGroupInvitations(snapshot.docs.map(doc => doc.data() as GroupInvitation));
            }
        });

        return () => {
            isMounted = false;
            groupsUnsub();
            invitationsUnsub();
        };
    }, [currentUser, db, setRecipient, addToast, t]);

    const resetGroupKeys = useCallback(async (groupId: string, newMemberUids?: string[]) => {
        if (!currentUser) throw new Error("Current user not found for key reset.");
    
        try {
            cryptoService.clearGroupKeyCache(groupId);
    
            const groupRef = doc(db, 'groups', groupId);
            const groupSnap = await getDoc(groupRef);
            if (!groupSnap.exists()) throw new Error("Group not found for key reset.");
    
            const groupData = groupSnap.data() as Group;
            const finalMemberUids = newMemberUids || Object.keys(groupData.members);
    
            if (finalMemberUids.length === 0) {
                await updateDoc(groupRef, { encryptedKeys: {}, keyLastRotatedAt: Date.now() });
                return;
            }
    
            const { encryptedKeys, groupKeyString } = await cryptoService.createEncryptedGroupKey(finalMemberUids, rtdb);
            
            const newKeyVersion = Date.now();

            if (finalMemberUids.includes(currentUser.uid)) {
                 cryptoService.storeGroupKey(groupId, newKeyVersion, groupKeyString);
            }
           
            await updateDoc(groupRef, { encryptedKeys: encryptedKeys, keyLastRotatedAt: newKeyVersion });
    
            await push(ref(rtdb, `chats/${groupId}/messages`), {
                sender: 'system',
                text: t('systemKeyReset'),
                timestamp: serverTimestamp(),
                isSystemMessage: true,
            });
    
            addToast(t('groupKeyResetSuccess'), { variant: "default" });
    
        } catch (error) {
            console.error("Failed to reset group keys:", error);
            addToast(t('groupKeyResetError'), { variant: "destructive" });
            throw error;
        }
    }, [currentUser, rtdb, db, addToast, t]);

    const createGroup = useCallback(async (name: string, photoURL: string, memberUids: string[], groupType: GroupType) => {
        if (!currentUser) return;
        
        try {
            const newGroupRef = doc(collection(db, 'groups'));
            const groupId = newGroupRef.id;
            
            const defaultPhoto = `https://api.dicebear.com/8.x/identicon/svg?seed=${name}`;
            const allMemberUids = [currentUser.uid, ...memberUids];
            
            const { encryptedKeys, groupKeyString } = await cryptoService.createEncryptedGroupKey(allMemberUids, rtdb);
            const keyVersion = Date.now();
            cryptoService.storeGroupKey(groupId, keyVersion, groupKeyString);
            
            const groupData: Omit<Group, 'id'> = {
                info: {
                    name,
                    photoURL: photoURL || defaultPhoto,
                    createdBy: currentUser.uid,
                    createdAt: Date.now(),
                    type: groupType,
                    settings: { sendingMode: 'everyone' }
                },
                members: { [currentUser.uid]: true, ...Object.fromEntries(memberUids.map(uid => [uid, true])) },
                admins: { [currentUser.uid]: true },
                encryptedKeys: encryptedKeys,
                keyLastRotatedAt: keyVersion,
            };

            const batch = writeBatch(db);
            batch.set(newGroupRef, groupData);

            allMemberUids.forEach(uid => {
                 batch.update(doc(db, 'users', uid), { groups: arrayUnion(groupId) });
            })

            await batch.commit();
            
            const participantsForRtdb = Object.fromEntries(allMemberUids.map(uid => [uid, true]));
            await set(ref(rtdb, `chats/${groupId}/participants`), participantsForRtdb);

            addToast(t('groupCreated', { name }));
        } catch (error: any) {
            addToast(t('groupCreateError', { error: error.message }), { variant: 'destructive' });
            console.error(error);
        }
    }, [currentUser, addToast, db, rtdb, t]);

    const acceptGroupInvitation = async (invitation: GroupInvitation) => {
        if (!currentUser) return;
        try {
            const groupDoc = await getDoc(doc(db, 'groups', invitation.groupId));
            if (!groupDoc.exists()) throw new Error("Group does not exist.");

            const batch = writeBatch(db);
            batch.update(doc(db, 'groups', invitation.groupId), { [`members.${currentUser.uid}`]: true });
            batch.update(doc(db, 'users', currentUser.uid), { groups: arrayUnion(invitation.groupId) });
            batch.delete(doc(db, 'users', currentUser.uid, 'groupInvitations', invitation.groupId));
            
            await batch.commit();

            await set(ref(rtdb, `chats/${invitation.groupId}/participants/${currentUser.uid}`), true);
            
            await push(ref(rtdb, `chats/${invitation.groupId}/messages`), {
                sender: 'system',
                text: t('systemUserJoined', { name: currentUser.displayName }),
                timestamp: serverTimestamp(),
                isSystemMessage: true,
            });

            addToast(t('joinedGroup', { name: invitation.groupName }));
        } catch (error) {
            console.error("Error accepting group invitation:", error);
            addToast(t('joinGroupError'), { variant: 'destructive' });
        }
    };
    
    const declineGroupInvitation = async (invitation: GroupInvitation) => {
         if (!currentUser) return;
         try {
             await deleteDoc(doc(db, 'users', currentUser.uid, 'groupInvitations', invitation.groupId));
             addToast(t('invitationDeclined'));
         } catch(error) {
             console.error("Error declining group invitation:", error);
             addToast(t('declineInvitationError'), { variant: "destructive" });
         }
    };

    const updateGroupInfo = useCallback(async (groupId: string, newInfo: { name?: string; photoURL?: string; description?: string; }) => {
        const groupRef = doc(db, 'groups', groupId);
        const updates: { [key: string]: any } = {};
        if (newInfo.name) updates['info.name'] = newInfo.name;
        if (newInfo.photoURL) updates['info.photoURL'] = newInfo.photoURL;
        if (newInfo.description !== undefined) updates['info.description'] = newInfo.description;
        
        await updateDoc(groupRef, updates);
        addToast(t('groupInfoUpdated'));
    }, [addToast, db, t]);
    
    const leaveGroup = useCallback(async (groupId: string) => {
        if (!currentUser) return;
        try {
            const groupRef = doc(db, 'groups', groupId);
            const groupSnap = await getDoc(groupRef);
            if (!groupSnap.exists()) return;
            const groupData = groupSnap.data() as Group;
            const remainingMembers = Object.keys(groupData.members).filter(uid => uid !== currentUser.uid);

            const batch = writeBatch(db);
            batch.update(groupRef, {
                [`members.${currentUser.uid}`]: deleteField(),
                [`admins.${currentUser.uid}`]: deleteField(),
                [`encryptedKeys.${currentUser.uid}`]: deleteField(),
            });
            batch.update(doc(db, 'users', currentUser.uid), {
                groups: arrayRemove(groupId)
            });
            await batch.commit();

            await remove(ref(rtdb, `chats/${groupId}/participants/${currentUser.uid}`));

            await push(ref(rtdb, `chats/${groupId}/messages`), {
                sender: 'system',
                text: t('systemUserLeft', { name: currentUser.displayName }),
                timestamp: serverTimestamp(),
                isSystemMessage: true,
            });
            
            await resetGroupKeys(groupId, remainingMembers);
            
            addToast(t('leftGroup'));
            setRecipient(null);

        } catch (error) {
            console.error("Error leaving group:", error);
            addToast(t('leaveGroupError'), { variant: 'destructive' });
        }
    }, [currentUser, addToast, db, rtdb, resetGroupKeys, t, setRecipient]);

    const removeMemberFromGroup = useCallback(async (groupId: string, memberUid: string, memberName: string) => {
        if (!currentUser) return;
        try {
            const groupRef = doc(db, 'groups', groupId);
            const groupSnap = await getDoc(groupRef);
            if (!groupSnap.exists()) return;
            const groupData = groupSnap.data() as Group;
            const remainingMembers = Object.keys(groupData.members).filter(uid => uid !== memberUid);
            
            const batch = writeBatch(db);
            batch.update(groupRef, {
                [`members.${memberUid}`]: deleteField(),
                [`admins.${memberUid}`]: deleteField(),
                [`encryptedKeys.${memberUid}`]: deleteField(),
            });
            batch.update(doc(db, 'users', memberUid), {
                groups: arrayRemove(groupId)
            });
            await batch.commit();
            
            await remove(ref(rtdb, `chats/${groupId}/participants/${memberUid}`));

            await push(ref(rtdb, `chats/${groupId}/messages`), {
                sender: 'system',
                text: t('systemUserRemoved', { user: memberName, admin: currentUser.displayName }),
                timestamp: serverTimestamp(),
                isSystemMessage: true,
            });
            
            await resetGroupKeys(groupId, remainingMembers);

            addToast(t('memberRemoved', { name: memberName }));
        } catch (error) {
            console.error("Error removing member:", error);
            addToast(t('removeMemberError'), { variant: 'destructive' });
        }
    }, [currentUser, addToast, db, rtdb, resetGroupKeys, t]);

    const addMembersToGroup = useCallback(async (groupId: string, newMemberUids: string[]) => {
        if (!currentUser) return;
    
        try {
            const groupRef = doc(db, 'groups', groupId);
            const groupSnap = await getDoc(groupRef);
            if (!groupSnap.exists()) throw new Error("Group not found.");
            
            const groupData = groupSnap.data() as Group;
    
            if (!groupData.admins[currentUser.uid]) {
                addToast(t('adminsOnlyAction'), { variant: 'destructive' });
                return;
            }
    
            const membersToAdd = newMemberUids.filter(uid => !groupData.members[uid]);
            if (membersToAdd.length === 0) {
                addToast(t('allMembersAlreadyInGroup'), { variant: "default" });
                return;
            }
    
            const batch = writeBatch(db);
            const memberUpdates: { [key: string]: any } = {};
            const participantUpdates: { [key: string]: true } = {};
            
            membersToAdd.forEach(uid => {
                memberUpdates[`members.${uid}`] = true;
                participantUpdates[uid] = true;
                batch.update(doc(db, 'users', uid), { groups: arrayUnion(groupId) });
            });
    
            batch.update(groupRef, memberUpdates);
            await batch.commit();
    
            await update(ref(rtdb, `chats/${groupId}/participants`), participantUpdates);

            const updatedGroupSnap = await getDoc(groupRef);
            if (!updatedGroupSnap.exists()) throw new Error("Group disappeared after member update.");
            const updatedGroupData = updatedGroupSnap.data() as Group;
            const finalMemberUids = Object.keys(updatedGroupData.members);
    
            await resetGroupKeys(groupId, finalMemberUids);
    
            const addedContacts = contacts.filter(c => membersToAdd.includes(c.uid)).map(c => c.name).join(', ');
            await push(ref(rtdb, `chats/${groupId}/messages`), {
                sender: 'system',
                text: t('systemUserAdded', { admin: currentUser.displayName, users: addedContacts }),
                timestamp: serverTimestamp(),
                isSystemMessage: true,
            });
    
            addToast(t('membersAdded', { count: membersToAdd.length }));
    
        } catch (error) {
            console.error("Failed to add members:", error);
            addToast(t('addMembersError'), { variant: 'destructive' });
        }
    }, [currentUser, contacts, addToast, db, rtdb, resetGroupKeys, t]);

    const toggleGroupAdmin = useCallback(async (groupId: string, memberUid: string, isCurrentlyAdmin: boolean) => {
        const groupRef = doc(db, 'groups', groupId);
        if (isCurrentlyAdmin) {
            await updateDoc(groupRef, { [`admins.${memberUid}`]: deleteField() });
            addToast(t('demotedToMember'));
        } else {
            await updateDoc(groupRef, { [`admins.${memberUid}`]: true });
            addToast(t('promotedToAdmin'));
        }
    }, [addToast, db, t]);

    const updateGroupSendingMode = useCallback(async (groupId: string, mode: GroupSendingMode) => {
         const groupRef = doc(db, 'groups', groupId);
         await updateDoc(groupRef, { 'info.settings.sendingMode': mode });
         addToast(t('groupSettingsUpdated'));
    }, [addToast, db, t]);

    const toggleMuteMember = useCallback(async (groupId: string, memberUid: string, memberName: string, isCurrentlyMuted: boolean) => {
        if (!currentUser) return;
        const groupRef = doc(db, 'groups', groupId);
        const updatePath = `info.mutedMembers.${memberUid}`;
        const systemMessageText = isCurrentlyMuted 
            ? t('systemUnmuted', { user: memberName, admin: currentUser.displayName })
            : t('systemMuted', { user: memberName, admin: currentUser.displayName });
        
        if (isCurrentlyMuted) {
            await updateDoc(groupRef, { [updatePath]: deleteField() });
        } else {
            await updateDoc(groupRef, { [updatePath]: true });
        }
        
        await push(ref(rtdb, `chats/${groupId}/messages`), {
            sender: 'system',
            text: systemMessageText,
            timestamp: serverTimestamp(),
            isSystemMessage: true,
        });

        addToast(isCurrentlyMuted ? t('memberUnmuted', { name: memberName }) : t('memberMuted', { name: memberName }));
        
    }, [addToast, db, currentUser, rtdb, t]);


    return {
        groups,
        groupInvitations,
        createGroup,
        acceptGroupInvitation,
        declineGroupInvitation,
        updateGroupInfo,
        addMembersToGroup,
        removeMemberFromGroup,
        leaveGroup,
        toggleGroupAdmin,
        updateGroupSendingMode,
        toggleMuteMember,
        resetGroupKeys
    };
};