1 files changed, 97 insertions, 0 deletions
diff --git a/devtools/client/debugger/src/utils/ast.js b/devtools/client/debugger/src/utils/ast.js
new file mode 100644
index 0000000000..cbdd13aa83
--- /dev/null
+++ b/devtools/client/debugger/src/utils/ast.js
@@ -0,0 +1,97 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at <http://mozilla.org/MPL/2.0/>. */
+
+export function findBestMatchExpression(symbols, tokenPos) {
+  if (!symbols) {
+    return null;
+  }
+
+  const { line, column } = tokenPos;
+  const { memberExpressions, identifiers, literals } = symbols;
+  const members = memberExpressions.filter(({ computed }) => !computed);
+
+  return []
+    .concat(identifiers, members, literals)
+    .reduce((found, expression) => {
+      const overlaps =
+        expression.location.start.line == line &&
+        expression.location.start.column <= column &&
+        expression.location.end.column >= column;
+
+      if (overlaps) {
+        return expression;
+      }
+
+      return found;
+    }, null);
+}
+
+// Check whether location A starts after location B
+export function positionAfter(a, b) {
+  return (
+    a.start.line > b.start.line ||
+    (a.start.line === b.start.line && a.start.column > b.start.column)
+  );
+}
+
+export function containsPosition(a, b) {
+  const bColumn = b.column || 0;
+  const startsBefore =
+    a.start.line < b.line ||
+    (a.start.line === b.line && a.start.column <= bColumn);
+  const endsAfter =
+    a.end.line > b.line || (a.end.line === b.line && a.end.column >= bColumn);
+
+  return startsBefore && endsAfter;
+}
+
+function findClosestofSymbol(declarations, location) {
+  if (!declarations) {
+    return null;
+  }
+
+  return declarations.reduce((found, currNode) => {
+    if (
+      currNode.name === "anonymous" ||
+      !containsPosition(currNode.location, {
+        line: location.line,
+        column: location.column || 0,
+      })
+    ) {
+      return found;
+    }
+
+    if (!found) {
+      return currNode;
+    }
+
+    if (found.location.start.line > currNode.location.start.line) {
+      return found;
+    }
+    if (
+      found.location.start.line === currNode.location.start.line &&
+      found.location.start.column > currNode.location.start.column
+    ) {
+      return found;
+    }
+
+    return currNode;
+  }, null);
+}
+
+export function findClosestFunction(symbols, location) {
+  if (!symbols) {
+    return null;
+  }
+
+  return findClosestofSymbol(symbols.functions, location);
+}
+
+export function findClosestClass(symbols, location) {
+  if (!symbols) {
+    return null;
+  }
+
+  return findClosestofSymbol(symbols.classes, location);
+}