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/*
 * Copyright 2010 The Closure Compiler Authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.google.javascript.jscomp;

import com.google.common.collect.ImmutableSet;
import com.google.javascript.jscomp.NodeTraversal.AbstractPostOrderCallback;
import com.google.javascript.jscomp.regex.RegExpTree;
import com.google.javascript.rhino.Node;
import com.google.javascript.rhino.Token;

/**
 * Look for references to the global RegExp object that would cause
 * regular expressions to be unoptimizable, and checks that regular expressions
 * are syntactically valid.
 */
class CheckRegExp extends AbstractPostOrderCallback implements CompilerPass {

  static final DiagnosticType REGEXP_REFERENCE =
    DiagnosticType.warning("JSC_REGEXP_REFERENCE",
        "References to the global RegExp object prevents " +
        "optimization of regular expressions.");
  static final DiagnosticType MALFORMED_REGEXP = DiagnosticType.warning(
        "JSC_MALFORMED_REGEXP",
        "Malformed Regular Expression: {0}");

  private static final ImmutableSet REGEXP_PROPERTY_SKIPLIST =
      ImmutableSet.of(
          "$1",
          "$2",
          "$3",
          "$4",
          "$5",
          "$6",
          "$7",
          "$8",
          "$9",
          "$_",
          "$input",
          // The following would also be skiplisted, but they aren't valid
          // identifiers, so can't be accessed with the '.' operator anyway.
          // "$*", "$&", "$+", "$`", "$'",
          "input",
          "lastMatch",
          "lastParen",
          "leftContext",
          "rightContext",
          "global",
          "ignoreCase",
          "lastIndex",
          "multiline",
          "source");

  private final AbstractCompiler compiler;
  private final boolean reportErrors;
  private boolean globalRegExpPropertiesUsed = false;

  public boolean isGlobalRegExpPropertiesUsed() {
    return globalRegExpPropertiesUsed;
  }

  public CheckRegExp(AbstractCompiler compiler, boolean reportErrors) {
    this.compiler = compiler;
    this.reportErrors = reportErrors;
  }

  @Override
  public void process(Node externs, Node root) {
    NodeTraversal.traverse(compiler, root, this);
  }

  @Override
  public void visit(NodeTraversal t, Node n, Node parent) {
    if (NodeUtil.isReferenceName(n)) {
      String name = n.getString();
      if (name.equals("RegExp") && t.getScope().getVar(name) == null) {
        Token parentType = parent.getToken();
        boolean first = (n == parent.getFirstChild());
        if (!((parentType == Token.NEW && first)
            || (parentType == Token.CALL && first)
            || (parentType == Token.INSTANCEOF && !first)
            || parentType == Token.EQ
            || parentType == Token.NE
            || parentType == Token.SHEQ
            || parentType == Token.SHNE
            || parentType == Token.CASE
            || (parentType == Token.GETPROP
                && first
                && !REGEXP_PROPERTY_SKIPLIST.contains(parent.getString())))) {
          if (reportErrors) {
            t.report(n, REGEXP_REFERENCE);
          }
          globalRegExpPropertiesUsed = true;
        }
      }

      // Check the syntax of regular expression patterns.
    } else if (reportErrors && n.isRegExp()) {
      String pattern = n.getFirstChild().getString();
      String flags = n.hasTwoChildren() ? n.getLastChild().getString() : "";
      try {
        RegExpTree.parseRegExp(pattern, flags);
      } catch (IllegalArgumentException | IndexOutOfBoundsException ex) {
        t.report(n, MALFORMED_REGEXP, ex.getMessage());
      }
    }
  }
}