Github user dennisgove commented on a diff in the pull request:
https://github.com/apache/lucene-solr/pull/171#discussion_r107805373
--- Diff:
solr/solrj/src/java/org/apache/solr/client/solrj/io/eval/DatePartEvaluator.java
---
@@ -0,0 +1,169 @@
+/*
+ * 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.solr.client.solrj.io.eval;
+
+import java.io.IOException;
+import java.time.Instant;
+import java.time.LocalDateTime;
+import java.time.ZoneOffset;
+import java.time.format.DateTimeParseException;
+import java.time.temporal.ChronoField;
+import java.time.temporal.IsoFields;
+import java.time.temporal.TemporalAccessor;
+import java.time.temporal.UnsupportedTemporalTypeException;
+import java.util.Arrays;
+import java.util.Date;
+import java.util.Locale;
+
+import org.apache.solr.client.solrj.io.Tuple;
+import org.apache.solr.client.solrj.io.stream.expr.Explanation;
+import org.apache.solr.client.solrj.io.stream.expr.StreamExpression;
+import
org.apache.solr.client.solrj.io.stream.expr.StreamExpressionParameter;
+import org.apache.solr.client.solrj.io.stream.expr.StreamFactory;
+
+/**
+ * Provides numeric Date/Time stream evaluators
+ */
+public class DatePartEvaluator extends NumberEvaluator {
+
+ public enum FUNCTION {year, month, day, dayOfYear, dayOfQuarter, hour,
minute, quarter, week, second, epoch}
+
+ private final FUNCTION function;
+
+ public DatePartEvaluator(StreamExpression expression, StreamFactory
factory) throws IOException {
+ super(expression, factory);
+
+ String functionName = expression.getFunctionName();
+
+ try {
+ this.function = FUNCTION.valueOf(functionName);
+ } catch (IllegalArgumentException e) {
+ throw new IOException(String.format(Locale.ROOT, "Invalid date
expression %s - expecting one of %s", functionName,
Arrays.toString(FUNCTION.values())));
+ }
+
+ if (1 != subEvaluators.size()) {
+ throw new IOException(String.format(Locale.ROOT, "Invalid expression
%s - expecting one value but found %d", expression, subEvaluators.size()));
+ }
+ }
+
+ @Override
+ public Number evaluate(Tuple tuple) throws IOException {
+
+ Instant instant = null;
+ TemporalAccessor date = null;
+
+ //First evaluate the parameter
+ StreamEvaluator streamEvaluator = subEvaluators.get(0);
+ Object tupleValue = streamEvaluator.evaluate(tuple);
+
+ if (tupleValue == null) return null;
+
+ if (tupleValue instanceof String) {
+ instant = getInstant((String) tupleValue);
+ } else if (tupleValue instanceof Instant) {
+ instant = (Instant) tupleValue;
+ } else if (tupleValue instanceof Date) {
+ instant = ((Date) tupleValue).toInstant();
+ } else if (tupleValue instanceof TemporalAccessor) {
+ date = ((TemporalAccessor) tupleValue);
+ }
+
+ if (instant != null) {
+ if (function.equals(FUNCTION.epoch)) return instant.toEpochMilli();
+ date = LocalDateTime.ofInstant(instant, ZoneOffset.UTC);
+ }
+
+ if (date != null) {
+ return evaluate(date);
+ }
+
+ throw new IOException(String.format(Locale.ROOT, "Invalid parameter %s
- The parameter must be a string formatted ISO_INSTANT or of type Instant,Date
or LocalDateTime.", String.valueOf(tupleValue)));
+ }
+
+ private Instant getInstant(String dateStr) throws IOException {
+
+ if (dateStr != null && !dateStr.isEmpty()) {
+ try {
+ return Instant.parse(dateStr);
+ } catch (DateTimeParseException e) {
+ throw new IOException(String.format(Locale.ROOT, "Invalid
parameter %s - The String must be formatted in the ISO_INSTANT date format.",
dateStr));
+ }
+ }
+ return null;
+ }
+
+ /**
+ * Evaluate the date based on the specified function
+ *
+ * @param date
+ * @return the evaluated value
+ */
+ private Number evaluate(TemporalAccessor date) throws IOException {
--- End diff --
If you were to break this class into multiple (one for each evaluator) then
this function should def exist in a parent class so keep the logic in a
singular place.
The way I could see the hierarchy working is something like this
```
ComplexEvaluator
TemporalEvaluator
YearEvaluator
MonthOfYearEvaluator
DayOfMonthEvalator
DayNameEvaluator
....
```
Basically, if some evaluator extends NumberEvaluator then that means this
evaluator works over numbers, not that it returns a number. In a sense, when
the sub-evaluators are executed they need to return something that is a Number.
Following that logic, these evaluators work over temporal objects, so they
extend TemporalEvaluator.
They can return whatever type they need to (String, Number, etc...) but
they must have a temporal value to work from.
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