[GitHub] [incubator-pinot] akshayrai commented on a change in pull request #4377: [TE] support entity group expression

[GitBox <gi...@apache.org>]

akshayrai commented on a change in pull request #4377: [TE] support entity group expression
URL: https://github.com/apache/incubator-pinot/pull/4377#discussion_r298777834
 
 

 ##########
 File path: thirdeye/thirdeye-pinot/src/main/java/org/apache/pinot/thirdeye/detection/ExpressionParser.java
 ##########
 @@ -0,0 +1,141 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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 org.apache.pinot.thirdeye.detection;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Stack;
+import java.util.stream.Collectors;
+
+
+/**
+ * Util class used by TriggerConditionGrouper to parse trigger condition expression.
+ */
+public class ExpressionParser {
+
+  static final String PROP_AND = "and";
+  static final String PROP_OR = "or";
+  static final String PROP_OPERATOR = "operator";
+  static final String PROP_LEFT_OP = "leftOp";
+  static final String PROP_RIGHT_OP = "rightOp";
+  static final String PROP_VALUE = "value";
+
+  static final String OPERATOR_AND = "&&";
+  static final String OPERATOR_OR = "||";
+  static final String OPERATOR_LEFT_BRACKET = "(";
+  static final String OPERATOR_RIGHT_BRACKET = ")";
+
+  static final String[] operators = new String[] {OPERATOR_AND, OPERATOR_OR, OPERATOR_LEFT_BRACKET, OPERATOR_RIGHT_BRACKET};
+
+  /**
+   * Parse expression into operation tree.
+   *
+   * @param expression The expression string.
+   * @return Operation tree.
+   */
+  public static Map<String, Object> generateOperators(String expression) {
+    List<String> tokens = ExpressionParser.tokenize(expression);
+    List<String> rpn = generateRPN(tokens);
+    Stack<Map<String, Object>> stack = new Stack<>();
+    for (String token : rpn) {
+      Map<String, Object> objectMap = new HashMap<>();
+      if (token.equals(OPERATOR_AND)) {
+        objectMap.put(PROP_RIGHT_OP, stack.pop());
+        objectMap.put(PROP_LEFT_OP, stack.pop());
+        objectMap.put(PROP_OPERATOR, PROP_AND);
+      } else if (token.equals(OPERATOR_OR)) {
+        objectMap.put(PROP_RIGHT_OP, stack.pop());
+        objectMap.put(PROP_LEFT_OP, stack.pop());
+        objectMap.put(PROP_OPERATOR, PROP_OR);
+      } else {
+        objectMap.put(PROP_VALUE, token);
+      }
+      stack.push(objectMap);
+    }
+    return stack.peek();
+  }
+
+  private static String getOperator(String expression, int index) {
+    for (String operator : operators) {
+      if (expression.length() >= index + operator.length()
+          && expression.substring(index, index + operator.length()).equals(operator)) {
+        return operator;
+      }
+    }
+    return "";
+  }
+
+  private static List<String> tokenize(String expression) {
+    List<String> tokens = new ArrayList<>();
+    StringBuilder sb = new StringBuilder();
+    int i = 0;
+    while(i < expression.length()) {
+      String operator = getOperator(expression, i);
+      if (!operator.isEmpty()) {
+        if (sb.length() > 0) {
+          tokens.add(sb.toString());
+          sb.setLength(0);
+        }
+        tokens.add(operator);
+        i += operator.length();
+      } else {
+        sb.append(expression.charAt(i++));
+      }
+    }
+    if (sb.length() > 0) {
+      tokens.add(sb.toString());
+    }
+    return tokens.stream().map(String::trim).filter(x -> !x.isEmpty()).collect(Collectors.toList());
+  }
+
+  private static List<String> generateRPN(List<String> tokens) {
 
 Review comment:
   Include javadoc

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