import React, { useEffect } from "react";
import { Searchbar } from 'react-native-paper';
import { ScrollView, ActivityIndicator, StyleSheet, SafeAreaView, FlatList } from 'react-native';
import { Title } from 'react-native-paper';
import API from "../API";
import CourseCard from "../components/CourseCard";
import { useSnapshot } from 'valtio';
import GlobalState from '../contexts/GlobalState.js';


const getCourses = async (profileObj) => {
    let courses;
    let popular;
    await API.getCourses().then((data) => {
        courses = data.groups;
        popular = [...data.groups].sort((a, b) => {
            return Object.keys(b.subscribed).length - Object.keys(a.subscribed).length;
        });
    });
    let watching = {};
    let watchingProms = [];
    Object.keys(profileObj.data).forEach((videoId) => {
        if (profileObj.data[videoId].profileId) {
            let profileId = profileObj.data[videoId].profileId;
            watchingProms.push(API.getUserProfile(profileId).then(profile => {
                if (!profile.isCourse)
                    return 0;
                if (!watching[profileId])
                    watching[profileId] = { profile, progress: [], mostRecent: 0 };
                if (watching[profileId].mostRecent < profileObj.data[videoId].ts)
                    watching[profileId].mostRecent = profileObj.data[videoId].ts;
                watching[profileId].progress.push(profileObj.data[videoId]);
            }));
        }
    });
    let watchingArray = [];
    await Promise.all(watchingProms).then(() => {
        for (const courseId in watching) {
            watchingArray.push(watching[courseId]);
        }
        watchingArray = watchingArray.sort((a, b) => {
            return b.mostRecent - a.mostRecent;
        });
    });
    return {
        courses,
        popular,
        watching: watchingArray,
    }
}

const Courses = () => {
    const gState = useSnapshot(GlobalState);
    const viewer = gState.me;
    const [searchQuery, setSearchQuery] = React.useState('');
    const [groups, setGroups] = React.useState([]);
    const [popular, setPopular] = React.useState([]);
    const [watching, setWatching] = React.useState([]);
    const [queryTimer, setQueryTimer] = React.useState(0);

    useEffect(async () => {
        let r = await getCourses(viewer);
        setGroups(r.courses || []);
        setPopular(r.popular || []);
        setWatching(r.watching || []);
    }, [])

    const onChangeSearch = query => {
        setSearchQuery(query);
        if (queryTimer) clearTimeout(queryTimer);
        let timerId = setTimeout(() => {
            if (!query) {
                return API.getCourses('').then((data) => {
                    setGroups(data.groups || []);
                });
            }
            API.searchCourses(query).then((data) => {
                setGroups(data.groups || []);
            })

        }, 300);
        setQueryTimer(timerId);
    };
    const renderProfile = (({ item }) => {
        return (<CourseCard profileObj={item} />);
    });
    const watchingCourse = (({ item }) => {
        return (<CourseCard profileObj={item.profile} />);
    });
    return (
        <SafeAreaView style={styles.container}>
            <Searchbar
                placeholder="Search Users"
                onChangeText={onChangeSearch}
                value={searchQuery}
            />
            {groups.length ? <></> : <ActivityIndicator />}
            <ScrollView>
                <Title>Continue Watching:</Title>
                <FlatList
                    horizontal={true}
                    data={watching}
                    renderItem={watchingCourse}
                    keyExtractor={item => item.profile._id}
                />
                <Title>Recently Added:</Title>
                <FlatList
                    horizontal={true}
                    data={groups}
                    renderItem={renderProfile}
                    keyExtractor={item => item._id}
                />
                <Title>Popular:</Title>
                <FlatList
                    horizontal={true}
                    data={popular}
                    renderItem={renderProfile}
                    keyExtractor={item => item._id}
                />
            </ScrollView>
        </SafeAreaView>
    )
}

export default Courses;

const styles = StyleSheet.create({
    container: {
    },
});