Add missing anchorElements file

packages/web/lib/anchorElements.ts

@@ -0,0 +1,69 @@
+const ANCHOR_ELEMENTS_BLOCKED_ATTRIBUTES = [
+  'omnivore-highlight-id',
+  'data-twitter-tweet-id',
+  'data-instagram-id',
+]
+
+// We search in reverse so we can find the last element
+// that is visible on the page
+export const getTopOmnivoreAnchorElement = (
+  articleContentElement: HTMLElement
+): string | undefined => {
+  let topVisibleRect: Element | undefined = undefined
+  const anchors = Array.from(
+    document.querySelectorAll(`[data-omnivore-anchor-idx]`)
+  ).reverse()
+
+  for (const anchor of anchors) {
+    const rect = anchor.getBoundingClientRect()
+    if (rect.top >= 0 && rect.bottom <= articleContentElement.clientHeight) {
+      if (
+        topVisibleRect &&
+        topVisibleRect.getBoundingClientRect().top < rect.top
+      ) {
+        continue
+      }
+      topVisibleRect = anchor
+    }
+  }
+
+  return topVisibleRect?.getAttribute(`data-omnivore-anchor-idx`) ?? undefined
+}
+
+export function parseDomTree(
+  pageNode: HTMLDivElement | null
+): HTMLDivElement[] {
+  if (!pageNode || pageNode.childNodes.length == 0) {
+    return []
+  }
+
+  const nodesToVisitStack: [HTMLDivElement] = [pageNode]
+  const visitedNodeList = []
+
+  while (nodesToVisitStack.length > 0) {
+    const currentNode = nodesToVisitStack.pop()
+    if (
+      currentNode?.nodeType !== Node.ELEMENT_NODE ||
+      // Avoiding dynamic elements from being counted as anchor-allowed elements
+      ANCHOR_ELEMENTS_BLOCKED_ATTRIBUTES.some((attrib) =>
+        currentNode.hasAttribute(attrib)
+      )
+    ) {
+      continue
+    }
+    visitedNodeList.push(currentNode)
+    ;[].slice
+      .call(currentNode.childNodes)
+      .reverse()
+      .forEach(function (node) {
+        nodesToVisitStack.push(node)
+      })
+  }
+
+  visitedNodeList.shift()
+  visitedNodeList.forEach((node, index) => {
+    // start from index 1, index 0 reserved for anchor unknown.
+    node.setAttribute('data-omnivore-anchor-idx', (index + 1).toString())
+  })
+  return visitedNodeList
+}