From c04608df953eca010fabd4ff5e1a9dacd2f7b4bc Mon Sep 17 00:00:00 2001
From: Steve Hu <stevehu@gmail.com>
Date: Fri, 9 Nov 2018 16:37:20 -0500
Subject: [PATCH] fixes #325 add monad-result module to wrap success T and
 failure Status

---
 monad-result/pom.xml                          | 54 ++++++++++++++
 .../java/com/networknt/monad/Failure.java     | 38 ++++++++++
 .../main/java/com/networknt/monad/Result.java | 73 +++++++++++++++++++
 .../java/com/networknt/monad/Success.java     | 53 ++++++++++++++
 .../java/com/networknt/monad/ResultTest.java  | 25 +++++++
 .../src/test/resources/logback-test.xml       | 72 ++++++++++++++++++
 pom.xml                                       |  6 ++
 7 files changed, 321 insertions(+)
 create mode 100644 monad-result/pom.xml
 create mode 100644 monad-result/src/main/java/com/networknt/monad/Failure.java
 create mode 100644 monad-result/src/main/java/com/networknt/monad/Result.java
 create mode 100644 monad-result/src/main/java/com/networknt/monad/Success.java
 create mode 100644 monad-result/src/test/java/com/networknt/monad/ResultTest.java
 create mode 100644 monad-result/src/test/resources/logback-test.xml

diff --git a/monad-result/pom.xml b/monad-result/pom.xml
new file mode 100644
index 0000000000..fe60835d0b
--- /dev/null
+++ b/monad-result/pom.xml
@@ -0,0 +1,54 @@
+<!--
+  ~ Copyright (c) 2016 Network New Technologies Inc.
+  ~
+  ~ Licensed 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.
+  -->
+
+<project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://maven.apache.org/POM/4.0.0"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <parent>
+        <groupId>com.networknt</groupId>
+        <artifactId>light-4j</artifactId>
+        <version>1.5.22-SNAPSHOT</version>
+        <relativePath>..</relativePath>
+    </parent>
+
+    <artifactId>monad-result</artifactId>
+    <packaging>jar</packaging>
+    <description>A monad result wraps a T if success and Status if failure.</description>
+
+    <dependencies>
+        <dependency>
+            <groupId>com.networknt</groupId>
+            <artifactId>status</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.slf4j</groupId>
+            <artifactId>slf4j-api</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>ch.qos.logback</groupId>
+            <artifactId>logback-classic</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+</project>
diff --git a/monad-result/src/main/java/com/networknt/monad/Failure.java b/monad-result/src/main/java/com/networknt/monad/Failure.java
new file mode 100644
index 0000000000..e00f1a9394
--- /dev/null
+++ b/monad-result/src/main/java/com/networknt/monad/Failure.java
@@ -0,0 +1,38 @@
+package com.networknt.monad;
+
+import com.networknt.status.Status;
+
+import java.util.NoSuchElementException;
+
+public final class Failure<T> implements Result<T> {
+
+    private final Status error;
+
+    private Failure(Status error) {
+        this.error = error;
+    }
+
+    public static <T> Result<T> of(Status error) {
+        return new Failure<>(error);
+    }
+
+    @Override
+    public boolean isSuccess() {
+        return false;
+    }
+
+    @Override
+    public Status getError() {
+        return error;
+    }
+
+    @Override
+    public T getResult() {
+        throw new NoSuchElementException("There is no result is Failure");
+    }
+
+    @Override
+    public String toString() {
+        return String.format("Failure[%s]", error.toString());
+    }
+}
diff --git a/monad-result/src/main/java/com/networknt/monad/Result.java b/monad-result/src/main/java/com/networknt/monad/Result.java
new file mode 100644
index 0000000000..c3870ace19
--- /dev/null
+++ b/monad-result/src/main/java/com/networknt/monad/Result.java
@@ -0,0 +1,73 @@
+package com.networknt.monad;
+
+import com.networknt.status.Status;
+import java.util.function.BiFunction;
+import java.util.function.Consumer;
+import java.util.function.Function;
+
+public interface Result<T> {
+
+    boolean isSuccess();
+
+    default boolean isFailure() {
+        return !isSuccess();
+    }
+
+    Status getError();
+
+    T getResult();
+
+    /*
+        Use this method when you want to apply a function on the insides of the Result
+        without unwrapping it. Mapper won't be invoked if the Result is Failure
+     */
+    default <R> Result<R> map(Function<? super T, ? extends R> mapper) {
+        return isSuccess() ?
+                Success.of(mapper.apply(getResult())) :
+                (Failure<R>) this;
+    }
+
+    /*
+        Use this method when you your mapping function is returning a Result<T> (which will make
+        the return type the Result<Result<T>> using just 'map').
+     */
+    default <R> Result<R> flatMap(Function<? super T, Result<R>> mapper) {
+        return isSuccess() ?
+                mapper.apply(getResult()) :
+                (Failure<R>) this;
+    }
+
+    /*
+        Use this method if you want to reduce your Result to some type R. For example at the
+        end of the flow, you could convert it to two different client responses depending on
+        the insides.
+     */
+    default <R> R fold(Function<? super T, ? extends R> successFunction, Function<Failure<R>, ? extends R> failureFunction) {
+        return isSuccess() ?
+                successFunction.apply(getResult()) :
+                failureFunction.apply((Failure<R>) this);
+    }
+
+    /*
+        Use this method when you have two instances of Result and you want to invoke a function on
+        their insides without unwrapping them separately. If both of them are Failures then only
+        the first (this) Failure will be returned.
+     */
+    default <R, Z> Result<Z> lift(Result<R> other, BiFunction<? super T, ? super R, ? extends Z> function) {
+        return flatMap(first -> other.map(second -> function.apply(first, second)));
+    }
+
+    default Result<T> ifSuccess(Consumer<? super T> successConsumer) {
+        if (isSuccess()) {
+            successConsumer.accept(this.getResult());
+        }
+        return this;
+    }
+
+    default Result<T> ifFailure(Consumer<Failure<T>> failureConsumer) {
+        if (isFailure()) {
+            failureConsumer.accept((Failure<T>) this);
+        }
+        return this;
+    }
+}
diff --git a/monad-result/src/main/java/com/networknt/monad/Success.java b/monad-result/src/main/java/com/networknt/monad/Success.java
new file mode 100644
index 0000000000..5df2774608
--- /dev/null
+++ b/monad-result/src/main/java/com/networknt/monad/Success.java
@@ -0,0 +1,53 @@
+package com.networknt.monad;
+
+import com.networknt.status.Status;
+
+import java.util.NoSuchElementException;
+import java.util.Optional;
+
+public final class Success<T> implements Result<T> {
+
+    public static final Result<Void> SUCCESS = new Success<>(null);
+
+    public static final Result OPTIONAL_SUCCESS = Success.ofOptional(null);
+
+    @SuppressWarnings("unchecked")
+    static <T> Result<Optional<T>> emptyOptional() {
+        return (Result<Optional<T>>) OPTIONAL_SUCCESS;
+    }
+
+    private final T result;
+
+    public static <T> Result<T> of(T result) {
+        return new Success<>(result);
+    }
+
+    public static <T> Result<Optional<T>> ofOptional(T result) {
+        return new Success<>(Optional.ofNullable(result));
+    }
+
+    private Success(T result) {
+        this.result = result;
+    }
+
+    @Override
+    public boolean isSuccess() {
+        return true;
+    }
+
+    @Override
+    public Status getError() {
+        throw new NoSuchElementException("There is no error in Success");
+    }
+
+    @Override
+    public T getResult() {
+        return result;
+    }
+
+    @Override
+    public String toString() {
+        final String value = result != null ? result.toString() : "";
+        return String.format("Success[%s]", value);
+    }
+}
diff --git a/monad-result/src/test/java/com/networknt/monad/ResultTest.java b/monad-result/src/test/java/com/networknt/monad/ResultTest.java
new file mode 100644
index 0000000000..862c12e687
--- /dev/null
+++ b/monad-result/src/test/java/com/networknt/monad/ResultTest.java
@@ -0,0 +1,25 @@
+package com.networknt.monad;
+
+import com.networknt.status.Status;
+import org.junit.Assert;
+import org.junit.Test;
+
+import static com.networknt.monad.Success.SUCCESS;
+
+public class ResultTest {
+    @Test
+    public void testResult() {
+        Status status = new Status(400, "ERR00000", "DEMO_STATUS", "This is an error", "ERROR");
+        Assert.assertTrue(SUCCESS.isSuccess());
+        Assert.assertTrue(!Failure.of(status).isSuccess());
+        Assert.assertTrue(!SUCCESS.isFailure());
+        Assert.assertTrue(Failure.of(status).isFailure());
+
+        Result result = Failure.of(status);
+        Assert.assertTrue(result.getError().equals(status));
+
+        String stringResult = "String result";
+        result = Success.of(stringResult);
+        Assert.assertEquals(stringResult, result.getResult());
+   }
+}
diff --git a/monad-result/src/test/resources/logback-test.xml b/monad-result/src/test/resources/logback-test.xml
new file mode 100644
index 0000000000..07c9df25e1
--- /dev/null
+++ b/monad-result/src/test/resources/logback-test.xml
@@ -0,0 +1,72 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+  ~ Copyright (c) 2016 Network New Technologies Inc.
+  ~
+  ~ Licensed 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.
+  -->
+
+<configuration>
+    TODO create logger for audit only.
+    http://stackoverflow.com/questions/2488558/logback-to-log-different-messages-to-two-files
+    <turboFilter class="ch.qos.logback.classic.turbo.MarkerFilter">
+        <Marker>PROFILER</Marker>
+        <!--<OnMatch>DENY</OnMatch>-->
+        <OnMatch>NEUTRAL</OnMatch>
+    </turboFilter>
+
+    <appender name="stdout" class="ch.qos.logback.core.ConsoleAppender">
+    <!-- encoders are assigned the type
+         ch.qos.logback.classic.encoder.PatternLayoutEncoder by default -->
+        <encoder>
+            <pattern>%d{HH:mm:ss.SSS} [%thread] %-5marker %-5level %logger{36} - %msg%n</pattern>
+        </encoder>
+    </appender>
+
+    <appender name="log" class="ch.qos.logback.core.FileAppender">
+        <File>target/test.log</File>
+        <Append>false</Append>
+        <layout class="ch.qos.logback.classic.PatternLayout">
+            <Pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %class{36}:%L %M - %msg%n</Pattern>
+        </layout>
+    </appender>
+
+    <!--audit log-->
+    <appender name="audit" class="ch.qos.logback.core.rolling.RollingFileAppender">
+        <file>target/audit.log</file> <!-- logfile location -->
+        <encoder>
+            <pattern>%-5level [%thread] %date{ISO8601} %F:%L - %msg%n</pattern> <!-- the layout pattern used to format log entries -->
+            <immediateFlush>true</immediateFlush>
+        </encoder>
+        <rollingPolicy class="ch.qos.logback.core.rolling.FixedWindowRollingPolicy">
+            <fileNamePattern>target/audit.log.%i.zip</fileNamePattern>
+            <minIndex>1</minIndex>
+            <maxIndex>5</maxIndex> <!-- max number of archived logs that are kept -->
+        </rollingPolicy>
+        <triggeringPolicy class="ch.qos.logback.core.rolling.SizeBasedTriggeringPolicy">
+            <maxFileSize>200MB</maxFileSize> <!-- The size of the logfile that triggers a switch to a new logfile, and the current one archived -->
+        </triggeringPolicy>
+    </appender>
+
+    <root level="trace">
+        <appender-ref ref="stdout" />
+    </root>
+
+    <logger name="com.networknt" level="trace">
+        <appender-ref ref="log"/>
+    </logger>
+
+    <logger name="Audit" level="trace" additivity="false">
+        <appender-ref ref="audit"/>
+    </logger>
+
+</configuration>
diff --git a/pom.xml b/pom.xml
index b0065b39c4..5f8714968f 100644
--- a/pom.xml
+++ b/pom.xml
@@ -142,6 +142,7 @@
         <module>deref-token</module>
         <module>ip-whitelist</module>
         <module>encode-decode</module>
+        <module>monad-result</module>
     </modules>
 
     <dependencyManagement>
@@ -339,6 +340,11 @@
                 <artifactId>encode-decode</artifactId>
                 <version>${project.version}</version>
             </dependency>
+            <dependency>
+                <groupId>com.networknt</groupId>
+                <artifactId>monad-result</artifactId>
+                <version>${project.version}</version>
+            </dependency>
             <dependency>
                 <groupId>com.networknt</groupId>
                 <artifactId>server</artifactId>