import React, { useState, useCallback, useContext } from 'react';
import {
    View, Text, StyleSheet, SectionList, TouchableOpacity,
    RefreshControl, StatusBar, Alert, Linking
} from 'react-native';
import { useFocusEffect } from '@react-navigation/native';
import { AuthContext } from '../context/AuthContext';
import { useSafeAreaInsets } from 'react-native-safe-area-context';
import api from '../services/api';
import Colors from '../constants/Colors';

const TasksScreen = ({ navigation }) => {
    const { userInfo } = useContext(AuthContext);
    const insets = useSafeAreaInsets();
    const [sections, setSections] = useState([]);
    const [refreshing, setRefreshing] = useState(false);
    const [activeFilter, setActiveFilter] = useState('ALL'); // ALL, PENDING, DONE

    const groupByDay = (followups) => {
        const map = {};
        const today = new Date();
        today.setHours(0, 0, 0, 0);
        const tomorrow = new Date(today.getTime() + 86400000);

        followups.forEach(f => {
            const d = new Date(f.date);
            d.setHours(0, 0, 0, 0);
            let label;
            if (d.getTime() === today.getTime()) label = 'Today';
            else if (d.getTime() < today.getTime()) label = `Overdue — ${d.toLocaleDateString('en-IN', { day: 'numeric', month: 'short' })}`;
            else if (d.getTime() === tomorrow.getTime()) label = 'Tomorrow';
            else label = d.toLocaleDateString('en-IN', { weekday: 'long', day: 'numeric', month: 'short' });

            if (!map[label]) map[label] = { title: label, data: [], ts: d.getTime() };
            map[label].data.push(f);
        });

        return Object.values(map).sort((a, b) => a.ts - b.ts);
    };

    const fetchTasks = async () => {
        try {
            const params = new URLSearchParams({ userId: userInfo.id });
            if (activeFilter !== 'ALL') params.append('status', activeFilter);
            const res = await api.get(`/followups?${params.toString()}`);
            setSections(groupByDay(res.data));
        } catch (e) {
            console.error('TasksScreen fetch error', e);
        } finally {
            setRefreshing(false);
        }
    };

    useFocusEffect(useCallback(() => { fetchTasks(); }, [activeFilter]));

    const handleMarkDone = async (id) => {
        Alert.alert('Mark as Done?', 'This will complete the task and dismiss the notification.', [
            { text: 'Cancel', style: 'cancel' },
            {
                text: 'Done ✓', onPress: async () => {
                    try {
                        await api.patch(`/followups/${id}`, { status: 'DONE' });
                        fetchTasks();
                    } catch (e) {
                        Alert.alert('Error', 'Could not update task.');
                    }
                }
            }
        ]);
    };

    const handleCall = (phone) => {
        if (!phone) return;
        Linking.openURL(`tel:${phone}`);
    };

    const renderTask = ({ item }) => {
        const isPending = item.status === 'PENDING';
        const isOverdue = isPending && new Date(item.date) < new Date();
        return (
            <View style={[styles.card, isOverdue && styles.cardOverdue, !isPending && styles.cardDone]}>
                <View style={[styles.dot, { backgroundColor: isOverdue ? '#ef4444' : isPending ? Colors.primary : '#10b981' }]} />
                <View style={{ flex: 1 }}>
                    <View style={{ flexDirection: 'row', alignItems: 'center', justifyContent: 'space-between' }}>
                        <Text style={styles.clientName}>{item.client?.name || 'Unknown Client'}</Text>
                        {item.client?.phone && (
                            <TouchableOpacity onPress={() => handleCall(item.client.phone)}>
                                <Text style={styles.callIcon}>📞</Text>
                            </TouchableOpacity>
                        )}
                    </View>
                    <Text style={styles.notes} numberOfLines={2}>{item.notes}</Text>
                    <Text style={styles.time}>
                        {new Date(item.date).toLocaleTimeString([], { hour: '2-digit', minute: '2-digit' })}
                        {item.user?.name ? `  •  Assigned by ${item.user.name}` : ''}
                    </Text>
                </View>
                {isPending && (
                    <TouchableOpacity style={styles.doneBtn} onPress={() => handleMarkDone(item.id)}>
                        <Text style={styles.doneBtnText}>Done</Text>
                    </TouchableOpacity>
                )}
                {!isPending && (
                    <View style={styles.completedBadge}>
                        <Text style={styles.completedText}>✓</Text>
                    </View>
                )}
            </View>
        );
    };

    return (
        <View style={styles.container}>
            <StatusBar backgroundColor={Colors.primary} barStyle="light-content" />
            <View style={[styles.header, { paddingTop: insets.top + 16 }]}>
                <Text style={styles.headerTitle}>My Tasks</Text>
                <Text style={styles.headerSub}>Sorted by date</Text>
                <View style={styles.filterRow}>
                    {['ALL', 'PENDING', 'DONE'].map(f => (
                        <TouchableOpacity
                            key={f}
                            style={[styles.filterBtn, activeFilter === f && styles.filterBtnActive]}
                            onPress={() => setActiveFilter(f)}
                        >
                            <Text style={[styles.filterText, activeFilter === f && styles.filterTextActive]}>{f}</Text>
                        </TouchableOpacity>
                    ))}
                </View>
            </View>

            <SectionList
                sections={sections}
                keyExtractor={item => item.id}
                renderItem={renderTask}
                renderSectionHeader={({ section }) => (
                    <View style={styles.sectionHeader}>
                        <Text style={styles.sectionTitle}>{section.title}</Text>
                        <Text style={styles.sectionCount}>{section.data.length} task{section.data.length !== 1 ? 's' : ''}</Text>
                    </View>
                )}
                refreshControl={<RefreshControl refreshing={refreshing} onRefresh={() => { setRefreshing(true); fetchTasks(); }} colors={[Colors.primary]} />}
                contentContainerStyle={{ paddingBottom: 40 }}
                ListEmptyComponent={
                    <View style={styles.empty}>
                        <Text style={styles.emptyIcon}>🎉</Text>
                        <Text style={styles.emptyTitle}>All Clear!</Text>
                        <Text style={styles.emptySub}>No tasks match this filter.</Text>
                    </View>
                }
            />
        </View>
    );
};

const styles = StyleSheet.create({
    container: { flex: 1, backgroundColor: '#f1f5f9' },
    header: { backgroundColor: Colors.primary, paddingHorizontal: 20, paddingBottom: 20 },
    headerTitle: { color: 'white', fontSize: 26, fontWeight: '900' },
    headerSub: { color: 'rgba(255,255,255,0.7)', fontSize: 12, marginTop: 2, marginBottom: 14 },
    filterRow: { flexDirection: 'row', gap: 8 },
    filterBtn: { paddingHorizontal: 16, paddingVertical: 6, borderRadius: 20, backgroundColor: 'rgba(255,255,255,0.2)' },
    filterBtnActive: { backgroundColor: 'white' },
    filterText: { color: 'rgba(255,255,255,0.8)', fontSize: 12, fontWeight: '700' },
    filterTextActive: { color: Colors.primary },
    sectionHeader: { flexDirection: 'row', justifyContent: 'space-between', alignItems: 'center', paddingHorizontal: 16, paddingTop: 20, paddingBottom: 8 },
    sectionTitle: { fontSize: 13, fontWeight: '900', color: '#475569', textTransform: 'uppercase', letterSpacing: 0.5 },
    sectionCount: { fontSize: 11, color: '#94a3b8', fontWeight: '700' },
    card: { backgroundColor: 'white', marginHorizontal: 16, marginBottom: 8, borderRadius: 14, padding: 14, flexDirection: 'row', alignItems: 'center', elevation: 2, shadowColor: '#000', shadowOffset: { width: 0, height: 1 }, shadowOpacity: 0.06, shadowRadius: 4 },
    cardOverdue: { borderLeftWidth: 4, borderLeftColor: '#ef4444' },
    cardDone: { opacity: 0.65 },
    dot: { width: 10, height: 10, borderRadius: 5, marginRight: 12 },
    clientName: { fontSize: 14, fontWeight: '800', color: '#1e293b', marginBottom: 3, flex: 1 },
    callIcon: { fontSize: 18, paddingHorizontal: 10 },
    notes: { fontSize: 12, color: '#64748b', lineHeight: 17, marginBottom: 5 },
    time: { fontSize: 10, color: '#94a3b8', fontWeight: '600' },
    doneBtn: { backgroundColor: Colors.primary, paddingHorizontal: 14, paddingVertical: 8, borderRadius: 10, marginLeft: 10 },
    doneBtnText: { color: 'white', fontSize: 11, fontWeight: '900' },
    completedBadge: { width: 28, height: 28, borderRadius: 14, backgroundColor: '#dcfce7', justifyContent: 'center', alignItems: 'center', marginLeft: 10 },
    completedText: { color: '#16a34a', fontWeight: '900', fontSize: 14 },
    empty: { alignItems: 'center', paddingTop: 80 },
    emptyIcon: { fontSize: 48, marginBottom: 12 },
    emptyTitle: { fontSize: 18, fontWeight: '800', color: '#1e293b' },
    emptySub: { fontSize: 13, color: '#94a3b8', marginTop: 6 },
});

export default TasksScreen;