From ea13959c914ec81f1b554d5542fd9c793fd7e68f Mon Sep 17 00:00:00 2001
From: Divlo <contact@divlo.fr>
Date: Sat, 21 Mar 2020 18:24:10 +0100
Subject: [PATCH] frontend: Pagination au scroll

---
 .../components/FunctionCard/FunctionCard.js   | 11 ++---
 frontend/pages/functions.js                   | 40 ++++++++++---------
 2 files changed, 28 insertions(+), 23 deletions(-)

diff --git a/frontend/components/FunctionCard/FunctionCard.js b/frontend/components/FunctionCard/FunctionCard.js
index 5e485aa..6864524 100644
--- a/frontend/components/FunctionCard/FunctionCard.js
+++ b/frontend/components/FunctionCard/FunctionCard.js
@@ -1,9 +1,9 @@
 import Link from 'next/link';
-import { useState, Fragment } from 'react';
+import { useState, Fragment, forwardRef } from 'react';
 import Loader from '../Loader/Loader';
 import './FunctionCard.css';
 
-const FunctionCard = (props) => {
+const FunctionCard = forwardRef((props, ref) => {
 
     const [isLoading, setIsLoading] = useState(true);
 
@@ -14,8 +14,9 @@ const FunctionCard = (props) => {
     return (
         <Link href={`/functions/${props.slug}`}>
             <Fragment>
-                <div className={"FunctionCard col-sm-24 col-md-10 col-xl-7"}>
-                    {isLoading && <Loader width="100px" height="100px" />} 
+                {/* Elément à une hauteur pendant chargement */}
+                <div ref={ref} style={isLoading ? { height: "200px", justifyContent: "center" } : null} className={"FunctionCard col-sm-24 col-md-10 col-xl-7"}>
+                    {isLoading && <Loader width="125px" height="125px" />} 
                     <div className={`FunctionCard__container ${isLoading ? "d-none" : ""}`}>
                         <div className="FunctionCard__top">
                             <img onLoad={handleLoad} className="FunctionCard__image" alt={props.title} src={props.image} />
@@ -31,6 +32,6 @@ const FunctionCard = (props) => {
             </Fragment>
         </Link>
     );
-} 
+}) 
 
 export default FunctionCard;
\ No newline at end of file
diff --git a/frontend/pages/functions.js b/frontend/pages/functions.js
index eed3271..ebbd659 100644
--- a/frontend/pages/functions.js
+++ b/frontend/pages/functions.js
@@ -1,4 +1,4 @@
-import { Fragment, useState, useEffect } from 'react';
+import { Fragment, useState, useEffect, useRef, useCallback } from 'react';
 import HeadTag from '../components/HeadTag';
 import FunctionCard from '../components/FunctionCard/FunctionCard';
 import Loader from '../components/Loader/Loader';
@@ -18,6 +18,19 @@ const Functions = () => {
     const [isLoadingFunctions, setLoadingFunctions] = useState(true);
     const [pageFunctions, setPageFunctions]         = useState(1);
 
+    // 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) {
+                setPageFunctions(pageFunctions + 1);
+            }
+        }, { threshold: 1 });
+        if (node) observer.current.observe(node);
+    }, [isLoadingFunctions, functionsData.hasMore]);
+
     const getFunctionsData = () => {
         setLoadingFunctions(true);
         return new Promise(async (next) => {
@@ -40,10 +53,6 @@ const Functions = () => {
         getFunctionsData().then((data) => setFunctionsData(data));
     }, [inputSearch.selectedCategory, inputSearch.search]);
 
-    const loadMore = () => {
-        setPageFunctions(pageFunctions + 1);
-    }
-
     const handleChange = (event) => {
         const inputSearchNew = { ...inputSearch };
         inputSearchNew[event.target.name] = event.target.value;
@@ -74,20 +83,15 @@ const Functions = () => {
                 </div>
     
                 <div className="row justify-content-center">
-                    {functionsData.rows.map((f) => (
-                        <FunctionCard key={f.id} slug={f.slug} image={API_URL + f.image} title={f.title} description={f.description} category={f.categorie} publicationDate={new Date(f.createdAt).toLocaleDateString('fr-FR')} />   
-                    ))}
+                    {functionsData.rows.map((f, index) => {
+                        // Si c'est le dernier élément
+                        if (functionsData.rows.length === index + 1) {
+                            return <FunctionCard ref={lastFunctionCardRef} key={f.id} slug={f.slug} image={API_URL + f.image} title={f.title} description={f.description} category={f.categorie} publicationDate={new Date(f.createdAt).toLocaleDateString('fr-FR')} />;
+                        }
+                        return <FunctionCard key={f.id} slug={f.slug} image={API_URL + f.image} title={f.title} description={f.description} category={f.categorie} publicationDate={new Date(f.createdAt).toLocaleDateString('fr-FR')} />;
+                    })}
                 </div>
-                {    
-                    isLoadingFunctions ?
-                        <Loader width="100px" height="100px" />
-                    : functionsData.hasMore ?
-                        <div className="row justify-content-center">
-                            <button className="btn btn-dark" style={{marginBottom: "50px"}} onClick={loadMore}>Charger plus de fonctions ?</button> 
-                        </div>
-                    :
-                        null
-                }
+                {isLoadingFunctions && <Loader width="100px" height="100px" />}
             </div>
         </Fragment>
     );