Function getCursorLocation

src/main/get-cursor-node.js:19–81

* Find the location of the cursor in the AST, represented in one of the * following ways: * * { "cursorNode": } - the cursor is WITHIN * * { "nodeBeforeCursor": | undefined, * "nodeAfterCursor": | undefined } * - the cursor is BETWEEN and <node2

(ast, options)

 * the other possibilities otherwise.
 */
function getCursorLocation(ast, options) {
  const { cursorOffset, locStart, locEnd, getVisitorKeys } = options;

  const nodeContainsCursor = (node) =>
    locStart(node) <= cursorOffset && locEnd(node) >= cursorOffset;

  let cursorNode = ast;
  const nodesContainingCursor = [ast];

  for (const node of getDescendants(ast, {
    getVisitorKeys,
    filter: nodeContainsCursor,
  })) {
    nodesContainingCursor.push(node);
    cursorNode = node;
  }

  if (isLeaf(cursorNode, { getVisitorKeys })) {
    return { cursorNode };
  }

  // We've established that the cursor is NOT contained in a leaf node of the
  // AST. We instead need to find two nodes (which needn't necessarily be
  // leaves) of the AST that the cursor lies *between*.

  let nodeBeforeCursor;
  let nodeAfterCursor;
  let nodeBeforeCursorEndIndex = -1;
  let nodeAfterCursorStartIndex = Number.POSITIVE_INFINITY;

  while (
    nodesContainingCursor.length > 0 &&
    (nodeBeforeCursor === undefined || nodeAfterCursor === undefined)
  ) {
    cursorNode = nodesContainingCursor.pop();
    const foundBeforeNode = nodeBeforeCursor !== undefined;
    const foundAfterNode = nodeAfterCursor !== undefined;
    for (const node of getChildren(cursorNode, { getVisitorKeys })) {
      if (!foundBeforeNode) {
        const nodeEnd = locEnd(node);
        if (nodeEnd <= cursorOffset && nodeEnd > nodeBeforeCursorEndIndex) {
          nodeBeforeCursor = node;
          nodeBeforeCursorEndIndex = nodeEnd;
        }
      }
      if (!foundAfterNode) {
        const nodeStart = locStart(node);
        if (
          nodeStart >= cursorOffset &&
          nodeStart < nodeAfterCursorStartIndex
        ) {
          nodeAfterCursor = node;
          nodeAfterCursorStartIndex = nodeStart;
        }
      }
    }
  }