feat: add slice convinience method to maps

Author: mattnichols

common/src/main/java/com/mx/path/core/common/collection/MultiValueMap.java

@@ -1,11 +1,13 @@
 package com.mx.path.core.common.collection;
 
 import java.util.Collection;
+import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
+import java.util.regex.Pattern;
 
 /**
  * A multi-value backed collection that acts like a multi-value map. This can be used interchangeably with other {@link MultiValueMappable} classes.
@@ -285,6 +287,32 @@ public int size() {
     return getRawMap().size();
   }
 
+  /**
+   * Create a new MultiValueMap containing only keys matching the provided {@link Pattern}.
+   *
+   * @param pattern {@link Pattern}
+   * @return new MultiValueMap
+   */
+  public MultiValueMap<K, V> slice(Pattern pattern) {
+    return slice(Collections.singletonList(pattern));
+  }
+
+  /**
+   * Create a new MultiValueMap containing only keys matching at least one provided {@link Pattern}.
+   *
+   * @param keyPatterns list of {@link Pattern}
+   * @return new MultiValueMap
+   */
+  public MultiValueMap<K, V> slice(Collection<Pattern> keyPatterns) {
+    MultiValueMap<K, V> result = new MultiValueMap<>();
+
+    rawMap.keySet().stream().filter((key) -> keyPatterns.stream().anyMatch((p) -> p.asPredicate().test(key.toString()))).forEach((key) -> {
+      result.put(key, get(key));
+    });
+
+    return result;
+  }
+
   /**
    * Convert to a {@link SingleValueMap}
    * Implementation Note: It is expected that multi-values are maintained in the

common/src/main/java/com/mx/path/core/common/collection/SingleValueMap.java

@@ -2,10 +2,12 @@
 
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
+import java.util.regex.Pattern;
 
 /**
  * A multi-value backed collection that acts like a single-value map. This can be used interchangeably with other {@link MultiValueMappable} classes.
@@ -246,6 +248,32 @@ public int size() {
     return getRawMap().size();
   }
 
+  /**
+   * Create a new SingleValueMap containing only keys matching the provided {@link Pattern}.
+   *
+   * @param pattern {@link Pattern}
+   * @return new SingleValueMap
+   */
+  public SingleValueMap<K, V> slice(Pattern pattern) {
+    return slice(Collections.singletonList(pattern));
+  }
+
+  /**
+   * Create a new SingleValueMap containing only keys matching at least one provided {@link Pattern}.
+   *
+   * @param keyPatterns list of {@link Pattern}
+   * @return new SingleValueMap
+   */
+  public SingleValueMap<K, V> slice(Collection<Pattern> keyPatterns) {
+    SingleValueMap<K, V> result = new SingleValueMap<>();
+
+    rawMap.keySet().stream().filter((key) -> keyPatterns.stream().anyMatch((p) -> p.asPredicate().test(key.toString()))).forEach((key) -> {
+      result.put(key, get(key));
+    });
+
+    return result;
+  }
+
   /**
    * Convert to regular Map
    *

common/src/test/groovy/com/mx/path/core/common/collection/MultiValueMapTest.groovy

@@ -1,6 +1,8 @@
 package com.mx.path.core.common.collection
 
 
+import java.util.regex.Pattern
+
 import spock.lang.Specification
 
 class MultiValueMapTest extends Specification {
@@ -131,6 +133,34 @@ class MultiValueMapTest extends Specification {
     empty.size() == 0
   }
 
+  def "slice"() {
+    given:
+    subject.add("key1", "value1")
+    subject.add("x-key1", "value1")
+    subject.add("key2", "value2")
+    subject.add("x-key2", "value2")
+
+    when:
+    def result = subject.slice(Pattern.compile("^x-"))
+
+    then:
+    result.size() == 2
+    result.keySet().contains("x-key1")
+    result.keySet().contains("x-key2")
+
+    when:
+    result = subject.slice([
+      Pattern.compile("^x-"),
+      Pattern.compile("key2")
+    ])
+
+    then:
+    result.size() == 3
+    result.keySet().contains("x-key1")
+    result.keySet().contains("key2")
+    result.keySet().contains("x-key2")
+  }
+
   def "isEmpty"() {
     when:
     subject.addAll("numbers", new LinkedList().tap {

common/src/test/groovy/com/mx/path/core/common/collection/SingleValueMapTest.groovy

@@ -1,6 +1,8 @@
 package com.mx.path.core.common.collection
 
 
+import java.util.regex.Pattern
+
 import spock.lang.Specification
 
 class SingleValueMapTest extends Specification {
@@ -55,6 +57,34 @@ class SingleValueMapTest extends Specification {
     empty.size() == 0
   }
 
+  def "slice"() {
+    given:
+    subject.put("key1", "value1")
+    subject.put("x-key1", "value1")
+    subject.put("key2", "value2")
+    subject.put("x-key2", "value2")
+
+    when:
+    def result = subject.slice(Pattern.compile("^x-"))
+
+    then:
+    result.size() == 2
+    result.keySet().contains("x-key1")
+    result.keySet().contains("x-key2")
+
+    when:
+    result = subject.slice([
+      Pattern.compile("^x-"),
+      Pattern.compile("key2")
+    ])
+
+    then:
+    result.size() == 3
+    result.keySet().contains("x-key1")
+    result.keySet().contains("key2")
+    result.keySet().contains("x-key2")
+  }
+
   def "isEmpty"() {
     when:
     subject.clear()