Avoid unnecessary (and expensive) work when matching path wildcards. (#207, #97)

`SimpleRegexTrie` is only used to determine whether a field name matches a pattern. The result of this computation only depends on these two values, not on the underlying data. So we can cache and reuse the result across the whole transformation process.

It might be possible to implement the matching in a more optimized way for this particular use case, but it's delegated to `SimpleRegexTrie` for compatibility and maintainability purposes.

Author: blackwinter

metafix/src/main/java/org/metafacture/metafix/Value.java

@@ -21,6 +21,7 @@
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.ConcurrentModificationException;
+import java.util.HashMap;
 import java.util.HashSet;
 import java.util.LinkedHashMap;
 import java.util.List;
@@ -459,9 +460,10 @@ public void remove(final int index) {
      */
     public static class Hash extends AbstractValueType {
 
-        private final Map<String, Value> map = new LinkedHashMap<>();
+        private static final Map<String, Map<String, Boolean>> TRIE_CACHE = new HashMap<>();
+        private static final SimpleRegexTrie<String> TRIE = new SimpleRegexTrie<>();
 
-        private final SimpleRegexTrie<String> trie = new SimpleRegexTrie<>();
+        private final Map<String, Value> map = new LinkedHashMap<>();
 
         /**
          * Creates an empty instance of {@link Hash}.
@@ -695,8 +697,12 @@ private Stream<String> findFields(final String pattern) {
         }
 
         private <T> T matchFields(final String pattern, final BiFunction<Stream<String>, Predicate<String>, T> function) {
-            trie.put(pattern, pattern);
-            return function.apply(map.keySet().stream(), f -> trie.get(f).contains(pattern));
+            final Map<String, Boolean> matcher = TRIE_CACHE.computeIfAbsent(pattern, k -> {
+                TRIE.put(k, k);
+                return new HashMap<>();
+            });
+
+            return function.apply(map.keySet().stream(), f -> matcher.computeIfAbsent(f, k -> TRIE.get(k).contains(pattern)));
         }
 
     }

metafix/src/test/java/org/metafacture/metafix/HashValueTest.java

@@ -16,8 +16,6 @@
 
 package org.metafacture.metafix;
 
-import org.metafacture.commons.tries.SimpleRegexTrie;
-
 import nl.jqno.equalsverifier.EqualsVerifier;
 import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.Test;
@@ -46,8 +44,6 @@ public HashValueTest() {
     public void shouldSatisfyEqualsContract() {
         EqualsVerifier.forClass(Value.Hash.class)
             .withPrefabValues(Value.class, Value.newArray(), Value.newHash())
-            .withPrefabValues(SimpleRegexTrie.class, new SimpleRegexTrie<String>(), new SimpleRegexTrie<String>())
-            .withIgnoredFields("trie")
             .verify();
     }