fix some tests

fix merge issues

src/elements/VideoContainer/VideoContainer.tsx

@@ -0,0 +1,97 @@
+import React from 'react';
+import Preview from '../Preview/Preview';
+import style from './VideoContainer.module.css';
+import {VideoUnloadedType} from '../../api/VideoTypes';
+
+interface props {
+    data: VideoUnloadedType[]
+}
+
+interface state {
+    loadeditems: VideoUnloadedType[];
+    selectionnr: number;
+}
+
+/**
+ * A videocontainer storing lots of Preview elements
+ * includes scroll handling and loading of preview infos
+ */
+class VideoContainer extends React.Component<props, state> {
+    // stores current index of loaded elements
+    loadindex: number = 0;
+
+    constructor(props: props) {
+        super(props);
+
+        this.state = {
+            loadeditems: [],
+            selectionnr: 0
+        };
+    }
+
+    componentDidMount(): void {
+        document.addEventListener('scroll', this.trackScrolling);
+
+        this.loadPreviewBlock(16);
+    }
+
+    render(): JSX.Element {
+        return (
+            <div className={style.maincontent}>
+                {this.state.loadeditems.map(elem => (
+                    <Preview
+                        key={elem.movie_id}
+                        name={elem.movie_name}
+                        movie_id={elem.movie_id}/>
+                ))}
+                {/*todo css for no items to show*/}
+                {this.state.loadeditems.length === 0 ?
+                    'no items to show!' : null}
+                {this.props.children}
+            </div>
+        );
+    }
+
+    componentWillUnmount(): void {
+        this.setState({});
+        // unbind scroll listener when unmounting component
+        document.removeEventListener('scroll', this.trackScrolling);
+    }
+
+    /**
+     * load previews to the container
+     * @param nr number of previews to load
+     */
+    loadPreviewBlock(nr: number): void {
+        console.log('loadpreviewblock called ...');
+        let ret = [];
+        for (let i = 0; i < nr; i++) {
+            // only add if not end
+            if (this.props.data.length > this.loadindex + i) {
+                ret.push(this.props.data[this.loadindex + i]);
+            }
+        }
+
+        this.setState({
+            loadeditems: [
+                ...this.state.loadeditems,
+                ...ret
+            ]
+        });
+
+
+        this.loadindex += nr;
+    }
+
+    /**
+     * scroll event handler -> load new previews if on bottom
+     */
+    trackScrolling = (): void => {
+        // comparison if current scroll position is on bottom --> 200 is bottom offset to trigger load
+        if (window.innerHeight + document.documentElement.scrollTop + 200 >= document.documentElement.offsetHeight) {
+            this.loadPreviewBlock(8);
+        }
+    };
+}
+
+export default VideoContainer;