Identity<T> implements Functor<T>

src/main/java/net/kemitix/mon/Identity.java

@@ -0,0 +1,45 @@
+/**
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2017 Paul Campbell
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
+ * and associated documentation files (the "Software"), to deal in the Software without restriction,
+ * including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all copies
+ * or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
+ * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
+ * AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+ * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+package net.kemitix.mon;
+
+import lombok.RequiredArgsConstructor;
+
+import java.util.function.Function;
+
+/**
+ * Identity.
+ *
+ * @param <T> the type of the identity content
+ *
+ * @author Paul Campbell (pcampbell@kemitix.net)
+ */
+@RequiredArgsConstructor
+class Identity<T> implements Functor<T> {
+
+    private final T value;
+
+    @Override
+    public <R> Identity<R> map(final Function<T, R> f) {
+        return new Identity<>(f.apply(value));
+    }
+
+}

src/test/java/net/kemitix/mon/Address.java

@@ -0,0 +1,39 @@
+/**
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2017 Paul Campbell
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
+ * and associated documentation files (the "Software"), to deal in the Software without restriction,
+ * including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all copies
+ * or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
+ * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
+ * AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+ * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+package net.kemitix.mon;
+
+import lombok.RequiredArgsConstructor;
+
+/**
+ * .
+ *
+ * @author Paul Campbell (pcampbell@kemitix.net)
+ */
+@RequiredArgsConstructor
+class Address {
+
+    private final String street;
+
+    String getStreet() {
+        return street;
+    }
+}

src/test/java/net/kemitix/mon/Customer.java

@@ -0,0 +1,40 @@
+/**
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2017 Paul Campbell
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
+ * and associated documentation files (the "Software"), to deal in the Software without restriction,
+ * including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all copies
+ * or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
+ * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
+ * AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+ * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+package net.kemitix.mon;
+
+import lombok.RequiredArgsConstructor;
+
+/**
+ * .
+ *
+ * @author Paul Campbell (pcampbell@kemitix.net)
+ */
+@RequiredArgsConstructor
+class Customer {
+
+    private final Address address;
+
+    Address getAddress() {
+        return address;
+    }
+
+}

src/test/java/net/kemitix/mon/IdentityTest.java

@@ -0,0 +1,37 @@
+package net.kemitix.mon;
+
+import org.assertj.core.api.WithAssertions;
+import org.junit.Test;
+
+/**
+ * Tests for {@link Identity}.
+ *
+ * @author Paul Campbell (pcampbell@kemitix.net)
+ */
+public class IdentityTest implements WithAssertions {
+
+    @Test
+    public void canMapIdentityFromStringToInteger() {
+        //given
+        final Identity<String> idString = new Identity<>("abc");
+        //when
+        final Identity<Integer> idInt = idString.map(String::length);
+        //then
+        idInt.map(id -> assertThat(id).isEqualTo(3));
+    }
+
+    @Test
+    public void canFluentlyComposeFunctions() {
+        //given
+        final Customer customer = new Customer(new Address("Park Place"));
+        //when
+        final Identity<byte[]> idBytes = new Identity<>(customer).map(Customer::getAddress)
+                                                                 .map(Address::getStreet)
+                                                                 .map((String s) -> s.substring(0, 3))
+                                                                 .map(String::toLowerCase)
+                                                                 .map(String::getBytes);
+        //then
+        idBytes.map(bytes -> assertThat(bytes).isEqualTo("par".getBytes()));
+    }
+
+}