sebmck/6to5

import type { Scope } from "@babel/traverse";
import * as t from "@babel/types";

function getObjRef(node, nodes, file, scope) {
  let ref;
  if (t.isSuper(node)) {
    // Super cannot be directly assigned so lets return it directly
    return node;
  } else if (t.isIdentifier(node)) {
    if (scope.hasBinding(node.name)) {
      // this variable is declared in scope so we can be 100% sure
      // that evaluating it multiple times wont trigger a getter
      // or something else
      return node;
    } else {
      // could possibly trigger a getter so we need to only evaluate
      // it once
      ref = node;
    }
  } else if (t.isMemberExpression(node)) {
    ref = node.object;

    if (t.isSuper(ref) || (t.isIdentifier(ref) && scope.hasBinding(ref.name))) {
      // the object reference that we need to save is locally declared
      // so as per the previous comment we can be 100% sure evaluating
      // it multiple times will be safe
      // Super cannot be directly assigned so lets return it also
      return ref;
    }
  } else {
    throw new Error(`We can't explode this node type ${node.type}`);
  }

  const temp = scope.generateUidIdentifierBasedOnNode(ref);
  scope.push({ id: temp });
  nodes.push(t.assignmentExpression("=", t.cloneNode(temp), t.cloneNode(ref)));
  return temp;
}

function getPropRef(node, nodes, file, scope) {
  const prop = node.property;
  const key = t.toComputedKey(node, prop);
  if (t.isLiteral(key) && t.isPureish(key)) return key;

  const temp = scope.generateUidIdentifierBasedOnNode(prop);
  scope.push({ id: temp });
  nodes.push(t.assignmentExpression("=", t.cloneNode(temp), t.cloneNode(prop)));
  return temp;
}

export default function (
  node: Object,
  nodes: Array<Object>,
  file,
  scope: Scope,
  allowedSingleIdent?: boolean,
): {
  uid: Object,
  ref: Object,
} {
  let obj;
  if (t.isIdentifier(node) && allowedSingleIdent) {
    obj = node;
  } else {
    obj = getObjRef(node, nodes, file, scope);
  }

  let ref, uid;

  if (t.isIdentifier(node)) {
    ref = t.cloneNode(node);
    uid = obj;
  } else {
    const prop = getPropRef(node, nodes, file, scope);
    const computed = node.computed || t.isLiteral(prop);
    uid = t.memberExpression(t.cloneNode(obj), t.cloneNode(prop), computed);
    ref = t.memberExpression(t.cloneNode(obj), t.cloneNode(prop), computed);
  }

  return {
    uid: uid,
    ref: ref,
  };
}