From 092d43172a5fe276f58957b451c5016ccc85888d Mon Sep 17 00:00:00 2001
From: Hammy <sgoudham@gmail.com>
Date: Mon, 7 Jun 2021 02:39:26 +0100
Subject: [PATCH] Create APIMapper class

---
 src/main/java/org/goudham/me/APIMapper.java | 125 ++++++++++++++++++++
 1 file changed, 125 insertions(+)
 create mode 100644 src/main/java/org/goudham/me/APIMapper.java

diff --git a/src/main/java/org/goudham/me/APIMapper.java b/src/main/java/org/goudham/me/APIMapper.java
new file mode 100644
index 0000000..b398f76
--- /dev/null
+++ b/src/main/java/org/goudham/me/APIMapper.java
@@ -0,0 +1,125 @@
+package org.goudham.me;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.JavaType;
+import com.fasterxml.jackson.databind.JsonNode;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.type.TypeFactory;
+import org.goudham.me.api.entity.series.FilteredSeries;
+import org.goudham.me.api.entity.series.Series;
+import org.goudham.me.api.entity.waifu.Waifu;
+import org.goudham.me.exception.APIMapperException;
+
+import java.util.List;
+
+/**
+ * Maps API Information to Java POJO's
+ *
+ */
+class APIMapper {
+    private final ObjectMapper objectMapper;
+
+    APIMapper() {
+        objectMapper = new ObjectMapper();
+    }
+
+    /**
+     * Honestly I don't really know how this works
+     *
+     * @param entity The actual class of the given entity. E.g {@link Waifu#getClass()}
+     * @param <T> The type of entity to be returned. E.g {@link Waifu} or {@link Series}
+     * @return {@link JavaType}
+     *
+     */
+    private <T> JavaType listOf(Class<T> entity) {
+        return TypeFactory.defaultInstance().constructCollectionType(List.class, entity);
+    }
+
+    /**
+     * Using the given {@code entity}, {@link ObjectMapper} deserializes the given Json
+     * into a Java POJO
+     *
+     * @param result The result of the previous API response
+     * @param entity The actual class of the given entity. E.g {@link Waifu#getClass()}
+     * @param <T> The type of entity to be returned. E.g {@link Waifu} or {@link Series}
+     * @return {@link Response}
+     * @throws APIMapperException If {@link ObjectMapper} is not able to deserialize JSON to Java POJO properly
+     *
+     */
+    <T> Response<T> deserialize(Result result, Class<T> entity) throws APIMapperException {
+        Integer statusCode = result.getStatusCode();
+        String body = result.getBody();
+        T newEntity = null;
+
+        if (statusCode == 200) {
+            try {
+                String data = getJsonTree(body);
+                newEntity = objectMapper.readValue(data, entity);
+            } catch (JsonProcessingException jpe) {
+                throwAPIMapperException(jpe);
+            }
+        }
+
+        return new Response<>(statusCode, body, newEntity);
+    }
+
+    /**
+     * Using the given {@code entity}, {@link ObjectMapper} deserializes the given Json
+     * into a Java POJO. This method enables support for retrieving {@link List} of entities
+     *
+     * @param result The result of the previous API response
+     * @param entity The actual class of the given entity. E.g {@link Waifu#getClass()}
+     * @param <T> List of entities to be returned. E.g {@link List} of {@link FilteredSeries}
+     * @return {@link Response}
+     * @throws APIMapperException If {@link ObjectMapper} is not able to deserialize JSON to Java POJO properly
+     */
+    <T> Response<List<T>> deserializeToList(Result result, Class<T> entity) throws APIMapperException {
+        Integer statusCode = result.getStatusCode();
+        String body = result.getBody();
+        List<T> listOfEntity = null;
+
+        if (statusCode == 200) {
+            try {
+                String data = getJsonTree(body);
+                listOfEntity = objectMapper.readValue(data, listOf(entity));
+            } catch (JsonProcessingException jpe) {
+                throwAPIMapperException(jpe);
+            }
+        }
+
+        return new Response<>(statusCode, body, listOfEntity);
+    }
+
+    /**
+     * Helper method for reducing duplicate code in {@code deserialize()}
+     * and {@code deserializeToList()}
+     * <br>
+     * Returns the proper json data to deserialize
+     *
+     * @param jsonBody jsonBody returned by the API
+     * @return {@link String}
+     * @throws JsonProcessingException If {@link ObjectMapper} is not able to
+     * read the given {@code jsonBody}
+     */
+    private String getJsonTree(String jsonBody) throws JsonProcessingException {
+        JsonNode parent = objectMapper.readTree(jsonBody);
+        return parent.get("data").toString();
+    }
+
+
+    /**
+     * Helper method for reducing duplicate code in {@code deserialize()}
+     * and {@code deserializeToList()}
+     *
+     * @param throwable Type of throwable to throw
+     * @throws APIMapperException Purpose of the method
+     */
+    private void throwAPIMapperException(Throwable throwable) throws APIMapperException {
+        String customExceptionMessage = "If you are seeing this message, " +
+                "this is more than likely a fault in my logic. " +
+                "Please raise an issue including the printed stacktrace :D";
+        String exceptionMessage = "\n\n" + customExceptionMessage + "\n\n" + throwable.getMessage();
+
+        throw new APIMapperException(exceptionMessage, throwable);
+    }
+}