import { useState, useEffect, useRef, useCallback } from 'react';
import { useRouter } from 'next/router';
import FunctionCard from '../FunctionCard/FunctionCard';
import Loader from '../Loader';
import api from '../../utils/api';
import useAPI from '../../hooks/useAPI';
import './FunctionsList.css';

const FunctionsList = (props) => {

    const { categoryId } = useRouter().query;
    let pageFunctions = 1;

    // State de recherche et de catégories
    const [, categories]                = useAPI('/categories');
    const [inputSearch, setInputSearch] = useState({ search: "", selectedCategory: categoryId || "0" });

    // State pour afficher les fonctions
    const [functionsData, setFunctionsData]         = useState({ hasMore: true, rows: [] });
    const [isLoadingFunctions, setLoadingFunctions] = useState(true);

    // Récupère la catégorie avec la query categoryId
    useEffect(() => {
        if (categoryId) {
            handleChange({ target: { name: "selectedCategory", value: categoryId } });
        }
    }, [categoryId]);

    // Récupère les fonctions si la catégorie/recherche change
    useEffect(() => {
        pageFunctions = 1;
        getFunctionsData().then((data) => setFunctionsData(data));
    }, [inputSearch]);

    // Permet la pagination au scroll
    const observer = useRef();
    const lastFunctionCardRef = useCallback((node) => {
        if (isLoadingFunctions) return;
        if (observer.current) observer.current.disconnect();
        observer.current = new IntersectionObserver((entries) => {
            if (entries[0].isIntersecting && functionsData.hasMore) {
                pageFunctions += 1;
                getFunctionsData().then((data) => {
                    setFunctionsData((oldData) => {
                        return { 
                            hasMore: data.hasMore, 
                            rows: [...oldData.rows, ...data.rows] 
                        }
                    });
                }); 
            }
        }, { threshold: 1 });
        if (node) observer.current.observe(node);
    }, [isLoadingFunctions, functionsData.hasMore]);

    const getFunctionsData = () => {
        setLoadingFunctions(true);
        return new Promise(async (next) => {
            const URL = `${(props.isAdmin) ? "/admin/functions" : "/functions"}?page=${pageFunctions}&limit=10&categoryId=${inputSearch.selectedCategory}&search=${inputSearch.search}`;
            const result = await api.get(URL, {
                headers: {
                    ...(props.isAdmin && props.token != undefined) && { 'Authorization': props.token }
                }
            });
            setLoadingFunctions(false);
            next(result.data);
        });
    }

    const handleChange = (event) => {
        const inputSearchNew = { ...inputSearch };
        inputSearchNew[event.target.name] = event.target.value;
        setInputSearch(inputSearchNew);
    }

    return (
        <div className="container text-center">
            <div className="row justify-content-center">
                {props.children}
            </div>

            <div className="Functions__search-container row justify-content-center">
                <select name="selectedCategory" value={inputSearch.selectedCategory} onChange={handleChange} className="Functions__select Functions__form-control">
                    <option value="0">Toutes catégories</option>
                    {categories.map((category) => (
                        <option key={category.id} value={category.id} className="Functions__select-option" style={{ backgroundColor: category.color }}>{category.name}</option>
                    ))}
                </select>
                <input value={inputSearch.search} onChange={handleChange} type="search" className="Functions__form-control Functions__search-input" name="search" id="search" placeholder="🔎 Rechercher..."></input>
            </div>

            <div className="row justify-content-center">
                {functionsData.rows.map((currentFunction, index) => {
                    // Si c'est le dernier élément
                    if (functionsData.rows.length === index + 1) {
                        return <FunctionCard isAdmin={props.isAdmin} key={currentFunction.id} ref={lastFunctionCardRef} { ...currentFunction } />;
                    }
                    return <FunctionCard isAdmin={props.isAdmin} key={currentFunction.id} { ...currentFunction } />;
                })}
            </div>
            {isLoadingFunctions && <Loader />}
        </div>
    );
}

export default FunctionsList;