From 485e07067ba30907825e39185eaf22eb58afb80b Mon Sep 17 00:00:00 2001
From: Ramon Wenger <ramon.wenger@iterativ.ch>
Date: Tue, 19 Dec 2023 20:22:55 +0100
Subject: [PATCH] Add new directive responsible for saving selections

---
 client/src/components/ContentBlock.vue |   1 +
 client/src/directives/highlight.ts     | 123 +++++++++++++++++++++++++
 2 files changed, 124 insertions(+)
 create mode 100644 client/src/directives/highlight.ts

diff --git a/client/src/components/ContentBlock.vue b/client/src/components/ContentBlock.vue
index 47efc129..9d8982be 100644
--- a/client/src/components/ContentBlock.vue
+++ b/client/src/components/ContentBlock.vue
@@ -3,6 +3,7 @@
     :class="{ 'hideable-element--greyed-out': isHidden }"
     class="content-block__container hideable-element content-list__parent"
     ref="wrapper"
+    v-highlight
   >
     <div
       :class="specialClass"
diff --git a/client/src/directives/highlight.ts b/client/src/directives/highlight.ts
new file mode 100644
index 00000000..64f99f4c
--- /dev/null
+++ b/client/src/directives/highlight.ts
@@ -0,0 +1,123 @@
+import { DirectiveBinding, VNode } from 'vue';
+import * as rangy from 'rangy';
+import log from 'loglevel';
+import Mark from 'mark.js';
+
+const TOP_TRESHOLD = 0;
+const BOTTOM_TRESHOLD = window.innerHeight || document.documentElement.clientHeight;
+const NODE_BEFORE_AND_AFTER = 2; // Rangy does not define constants for `compareNode`, so we do it here
+
+const isInsideViewport = (position: number) => {
+  return position >= TOP_TRESHOLD && position <= BOTTOM_TRESHOLD;
+};
+
+const findClosestAncestor = (node: Node, tag: string): HTMLElement | null => {
+  let currentNode: Node | null = node;
+  while (currentNode && currentNode.nodeName.toLowerCase() !== tag && currentNode.nodeName.toLowerCase() !== 'body') {
+    currentNode = currentNode.parentNode;
+  }
+  if (currentNode) {
+    return currentNode as HTMLElement;
+  }
+  return null;
+};
+const findClosestAncestorWithClass = (node: Node, className: string): HTMLElement | null => {
+  let currentNode: Node | null = node;
+  while (
+    currentNode && // current node exists
+    // current node is not an HTMLElement, so probably a TextNode
+    // or, current node does not contain the class
+    (!(currentNode instanceof HTMLElement) || !currentNode.classList.contains(className)) &&
+    // we have not arrived at the top yet
+    currentNode.nodeName.toLowerCase() !== 'body'
+  ) {
+    // so, we continue looking
+    currentNode = currentNode.parentNode;
+  }
+  if (currentNode instanceof HTMLElement && currentNode.classList.contains(className)) {
+    // make sure we're not up at the body element
+    return currentNode as HTMLElement;
+  }
+  return null;
+};
+
+const findPositionInParent = (element: HTMLElement, className: string = 'content-component'): number => {
+  /*
+   * currently, a content block has the structure
+   * div.content-block__container
+   *  div.content-block
+   *    div.content-block__visibility
+   *    div.content-block__title
+   *    div.content-component
+   *    div.content-component
+   *    [...]
+   *    div.content-component
+   *
+   * We only care about the .content-component divs, not the others
+   *
+   */
+
+  if (!element.parentElement) {
+    log.error('element has no parent', element);
+    return -1; // element has no parent, probably somehow ended up at the top. But this should probably never happen in our application
+  }
+  const children = Array.from(element.parentElement.children).filter((child) => child.classList.contains(className));
+  return children.indexOf(element);
+};
+
+const getSelectionHandler = (el: HTMLElement) => (_e: Event) => {
+  const rect = el.getBoundingClientRect();
+  if (isInsideViewport(rect.top) || isInsideViewport(rect.bottom)) {
+    // the listener only does something if the `el` is visible in the viewport, to save resources
+
+    console.log(el);
+    console.log(rect);
+    // now we check if the selection is inside our container
+
+    const selection = rangy.getSelection();
+    if (selection.rangeCount && !selection.isCollapsed) {
+      const range = selection.getRangeAt(0);
+      if (range.intersectsNode(el)) {
+        // the selection is inside our container, so we can do something with it
+        console.log('selection is inside our container');
+        console.log(el);
+        console.log(range.compareNode(el));
+        const { startContainer, endContainer } = range;
+        const startAncestor = findClosestAncestor(startContainer, 'p');
+        const endAncestor = findClosestAncestor(endContainer, 'p');
+        console.log('same?');
+        console.log(startAncestor === endAncestor);
+
+        if (startAncestor === endAncestor) {
+          const parent = findClosestAncestorWithClass(startContainer, 'content-component');
+          console.log(parent);
+          if (parent) {
+            // our selection is wholly inside the container node, we continue with it
+            const position = findPositionInParent(parent);
+            console.log(`selection is inside our container at ${position}`);
+
+            const { start, end } = range.toCharacterRange(parent);
+            console.log(start, end);
+            const instance = new Mark(parent);
+            instance.markRanges([{ start, length: end - start }]);
+          }
+        }
+      }
+    }
+  }
+};
+
+const addListener = (el: HTMLElement, binding: DirectiveBinding, vnode: VNode, prevVnode: VNode) => {
+  log.debug('registering a selection handler');
+  document.addEventListener('selectionchange', getSelectionHandler(el));
+};
+
+const removeListener = (el: HTMLElement, binding: DirectiveBinding, vnode: VNode, prevVnode: VNode) => {
+  log.debug('removing a selection handler');
+  document.removeEventListener('selectionchange', getSelectionHandler(el));
+};
+
+export default {
+  mounted: addListener,
+  unmounted: removeListener,
+};