Created the DialogflowIntegration to get messages directly from the dialogflow api

src/main/java/de/gnmyt/autoresponder/integration/DialogflowIntegration.java

@@ -0,0 +1,77 @@
+package de.gnmyt.autoresponder.integration;
+
+import com.google.api.gax.core.FixedCredentialsProvider;
+import com.google.auth.oauth2.GoogleCredentials;
+import com.google.auth.oauth2.ServiceAccountCredentials;
+import com.google.cloud.dialogflow.v2.*;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
+
+public class DialogflowIntegration {
+
+    private static final Logger LOG = LoggerFactory.getLogger(DialogflowIntegration.class);
+
+    private final SessionsClient sessionsClient;
+    private final String projectId;
+
+    private String languageCode = "en";
+
+    /**
+     * Constructor of the {@link DialogflowIntegration}
+     *
+     * @param credentialsFile Your credentials file to access the dialogflow api. Follow our guide in the readme if you want to use it
+     * @throws IOException Throws whenever the integration could not connect to the api
+     */
+    public DialogflowIntegration(File credentialsFile) throws IOException {
+        GoogleCredentials credentials = GoogleCredentials.fromStream(new FileInputStream(credentialsFile));
+        SessionsSettings settings = SessionsSettings.newBuilder().setCredentialsProvider(FixedCredentialsProvider.create(credentials)).build();
+
+        projectId = ((ServiceAccountCredentials) credentials).getProjectId();
+        sessionsClient = SessionsClient.create(settings);
+    }
+
+    /**
+     * Gets a message from the dialogflow api
+     *
+     * @param message   The message the user sent
+     * @param sessionId The session id to identify the user (for a better conversation)
+     * @return the message from the dialogflow api
+     */
+    public String getMessage(String message, String sessionId) {
+        try {
+            return detectTextIntents(languageCode, "hello", "user");
+        } catch (Exception e) {
+            LOG.error("Could not process intent message: " + e.getMessage());
+            return "Error while processing intent";
+        }
+    }
+
+    /**
+     * Gets the intent text from the api
+     *
+     * @param languageCode The language code you want to give to the session
+     * @param message      The message the user sent
+     * @param sessionId    The session id to identify the user (for a better conversation)
+     * @return the message from the dialogflow api
+     */
+    public String detectTextIntents(String languageCode, String message, String sessionId) {
+        TextInput.Builder textInput = TextInput.newBuilder().setText(message).setLanguageCode(languageCode);
+        QueryInput queryInput = QueryInput.newBuilder().setText(textInput).build();
+
+        return sessionsClient.detectIntent(SessionName.of(projectId, sessionId), queryInput).getQueryResult().getFulfillmentText();
+    }
+
+    /**
+     * Sets the default language code
+     *
+     * @param languageCode The new language code
+     */
+    public void setLanguageCode(String languageCode) {
+        this.languageCode = languageCode;
+    }
+
+}