ApiClient.java

/*
 * STACKIT Network Load Balancer API
 * This API offers an interface to provision and manage load balancing servers in your STACKIT project. It also has the possibility of pooling target servers for load balancing purposes.  For each load balancer provided, two VMs are deployed in your OpenStack project subject to a fee.
 *
 * The version of the OpenAPI document: 2.0.0
 *
 *
 * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
 * https://openapi-generator.tech
 * Do not edit the class manually.
 */

package cloud.stackit.sdk.loadbalancer;

import cloud.stackit.sdk.core.KeyFlowAuthenticator;
import cloud.stackit.sdk.core.config.CoreConfiguration;
import cloud.stackit.sdk.core.exception.ApiException;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.UnsupportedEncodingException;
import java.lang.reflect.Type;
import java.net.URLConnection;
import java.net.URLEncoder;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.security.GeneralSecurityException;
import java.security.KeyStore;
import java.security.SecureRandom;
import java.security.cert.Certificate;
import java.security.cert.CertificateException;
import java.security.cert.CertificateFactory;
import java.text.DateFormat;
import java.time.LocalDate;
import java.time.OffsetDateTime;
import java.time.format.DateTimeFormatter;
import java.util.*;
import java.util.Map.Entry;
import java.util.concurrent.TimeUnit;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import javax.net.ssl.*;
import okhttp3.*;
import okhttp3.internal.http.HttpMethod;
import okhttp3.internal.tls.OkHostnameVerifier;
import okhttp3.logging.HttpLoggingInterceptor;
import okhttp3.logging.HttpLoggingInterceptor.Level;
import okio.Buffer;
import okio.BufferedSink;
import okio.Okio;

/** ApiClient class. */
public class ApiClient {

	protected String basePath = "https://load-balancer.api.stackit.cloud";
	protected List<ServerConfiguration> servers =
			new ArrayList<ServerConfiguration>(
					Arrays.asList(
							new ServerConfiguration(
									"https://load-balancer.api.stackit.cloud",
									"No description provided",
									new HashMap<String, ServerVariable>() {
										{
											put(
													"region",
													new ServerVariable(
															"No description provided",
															"global",
															new HashSet<String>()));
										}
									})));
	protected Integer serverIndex = 0;
	protected Map<String, String> serverVariables = null;
	protected boolean debugging = false;
	protected Map<String, String> defaultHeaderMap = new HashMap<String, String>();
	protected Map<String, String> defaultCookieMap = new HashMap<String, String>();
	protected String tempFolderPath = null;

	protected DateFormat dateFormat;
	protected DateFormat datetimeFormat;
	protected boolean lenientDatetimeFormat;
	protected int dateLength;

	protected InputStream sslCaCert;
	protected boolean verifyingSsl;
	protected KeyManager[] keyManagers;
	protected String tlsServerName;

	protected OkHttpClient httpClient;
	protected JSON json;

	protected HttpLoggingInterceptor loggingInterceptor;

	protected CoreConfiguration configuration;

	/**
	 * Basic constructor for ApiClient.
	 *
	 * <p>Not recommended for production use, use the one with the OkHttpClient parameter instead.
	 *
	 * @throws IOException thrown when a file can not be found
	 */
	public ApiClient() throws IOException {
		this(null, new CoreConfiguration());
	}

	/**
	 * Basic constructor for ApiClient
	 *
	 * <p>Not recommended for production use, use the one with the OkHttpClient parameter instead.
	 *
	 * @param config a {@link cloud.stackit.sdk.core.config.CoreConfiguration} object
	 * @throws IOException thrown when a file can not be found
	 */
	public ApiClient(CoreConfiguration config) throws IOException {
		this(null, config);
	}

	/**
	 * Constructor for ApiClient with OkHttpClient parameter. Recommended for production use.
	 *
	 * @param httpClient a OkHttpClient object
	 * @throws IOException thrown when a file can not be found
	 */
	public ApiClient(OkHttpClient httpClient) throws IOException {
		this(httpClient, new CoreConfiguration());
	}

	/**
	 * Constructor for ApiClient with OkHttpClient parameter. Recommended for production use.
	 *
	 * @param httpClient a OkHttpClient object
	 * @param config a {@link cloud.stackit.sdk.core.config.CoreConfiguration} object
	 * @throws IOException thrown when a file can not be found
	 */
	public ApiClient(OkHttpClient httpClient, CoreConfiguration config) throws IOException {
		init();

		if (config.getCustomEndpoint() != null && !config.getCustomEndpoint().trim().isEmpty()) {
			basePath = config.getCustomEndpoint();
		}
		if (config.getDefaultHeader() != null) {
			defaultHeaderMap = config.getDefaultHeader();
		}
		this.configuration = config;

		if (httpClient == null) {
			initHttpClient();
			KeyFlowAuthenticator authenticator = new KeyFlowAuthenticator(this.httpClient, config);
			this.httpClient = this.httpClient.newBuilder().authenticator(authenticator).build();
		} else {
			// Authorization has to be configured manually in case a custom http client object is
			// passed
			this.httpClient = httpClient;
		}
	}

	protected void initHttpClient() {
		initHttpClient(Collections.<Interceptor>emptyList());
	}

	protected void initHttpClient(List<Interceptor> interceptors) {
		OkHttpClient.Builder builder = new OkHttpClient.Builder();
		builder.addNetworkInterceptor(getProgressInterceptor());
		for (Interceptor interceptor : interceptors) {
			builder.addInterceptor(interceptor);
		}

		httpClient = builder.build();
	}

	protected void init() {
		verifyingSsl = true;

		json = new JSON();

		// Set default User-Agent.
		setUserAgent("stackit-sdk-java/loadbalancer");
	}

	/**
	 * Get base path
	 *
	 * @return Base path
	 */
	public String getBasePath() {
		return basePath;
	}

	/**
	 * Set base path
	 *
	 * @param basePath Base path of the URL (e.g https://load-balancer.api.stackit.cloud)
	 * @return An instance of ApiClient
	 */
	public ApiClient setBasePath(String basePath) {
		this.basePath = basePath;
		this.serverIndex = null;
		return this;
	}

	public List<ServerConfiguration> getServers() {
		return servers;
	}

	public ApiClient setServers(List<ServerConfiguration> servers) {
		this.servers = servers;
		return this;
	}

	public Integer getServerIndex() {
		return serverIndex;
	}

	public ApiClient setServerIndex(Integer serverIndex) {
		this.serverIndex = serverIndex;
		return this;
	}

	public Map<String, String> getServerVariables() {
		return serverVariables;
	}

	public ApiClient setServerVariables(Map<String, String> serverVariables) {
		this.serverVariables = serverVariables;
		return this;
	}

	/**
	 * Get HTTP client
	 *
	 * @return An instance of OkHttpClient
	 */
	public OkHttpClient getHttpClient() {
		return httpClient;
	}

	/**
	 * Get JSON
	 *
	 * @return JSON object
	 */
	public JSON getJSON() {
		return json;
	}

	/**
	 * Set JSON
	 *
	 * @param json JSON object
	 * @return Api client
	 */
	public ApiClient setJSON(JSON json) {
		this.json = json;
		return this;
	}

	/**
	 * True if isVerifyingSsl flag is on
	 *
	 * @return True if isVerifySsl flag is on
	 */
	public boolean isVerifyingSsl() {
		return verifyingSsl;
	}

	/**
	 * Configure whether to verify certificate and hostname when making https requests. Default to
	 * true. NOTE: Do NOT set to false in production code, otherwise you would face multiple types
	 * of cryptographic attacks.
	 *
	 * @param verifyingSsl True to verify TLS/SSL connection
	 * @return ApiClient
	 */
	public ApiClient setVerifyingSsl(boolean verifyingSsl) {
		this.verifyingSsl = verifyingSsl;
		applySslSettings();
		return this;
	}

	/**
	 * Get SSL CA cert.
	 *
	 * @return Input stream to the SSL CA cert
	 */
	public InputStream getSslCaCert() {
		return sslCaCert;
	}

	/**
	 * Configure the CA certificate to be trusted when making https requests. Use null to reset to
	 * default.
	 *
	 * @param sslCaCert input stream for SSL CA cert
	 * @return ApiClient
	 */
	public ApiClient setSslCaCert(InputStream sslCaCert) {
		this.sslCaCert = sslCaCert;
		applySslSettings();
		return this;
	}

	/**
	 * Getter for the field <code>keyManagers</code>.
	 *
	 * @return an array of {@link javax.net.ssl.KeyManager} objects
	 */
	public KeyManager[] getKeyManagers() {
		return keyManagers;
	}

	/**
	 * Configure client keys to use for authorization in an SSL session. Use null to reset to
	 * default.
	 *
	 * @param managers The KeyManagers to use
	 * @return ApiClient
	 */
	public ApiClient setKeyManagers(KeyManager[] managers) {
		this.keyManagers = managers;
		applySslSettings();
		return this;
	}

	/**
	 * Get TLS server name for SNI (Server Name Indication).
	 *
	 * @return The TLS server name
	 */
	public String getTlsServerName() {
		return tlsServerName;
	}

	/**
	 * Set TLS server name for SNI (Server Name Indication). This is used to verify the server
	 * certificate against a specific hostname instead of the hostname in the URL.
	 *
	 * @param tlsServerName The TLS server name to use for certificate verification
	 * @return ApiClient
	 */
	public ApiClient setTlsServerName(String tlsServerName) {
		this.tlsServerName = tlsServerName;
		applySslSettings();
		return this;
	}

	/**
	 * Getter for the field <code>dateFormat</code>.
	 *
	 * @return a {@link java.text.DateFormat} object
	 */
	public DateFormat getDateFormat() {
		return dateFormat;
	}

	/**
	 * Setter for the field <code>dateFormat</code>.
	 *
	 * @param dateFormat a {@link java.text.DateFormat} object
	 * @return a {@link cloud.stackit.sdk.loadbalancer.ApiClient} object
	 */
	public ApiClient setDateFormat(DateFormat dateFormat) {
		JSON.setDateFormat(dateFormat);
		return this;
	}

	/**
	 * Set SqlDateFormat.
	 *
	 * @param dateFormat a {@link java.text.DateFormat} object
	 * @return a {@link cloud.stackit.sdk.loadbalancer.ApiClient} object
	 */
	public ApiClient setSqlDateFormat(DateFormat dateFormat) {
		JSON.setSqlDateFormat(dateFormat);
		return this;
	}

	/**
	 * Set OffsetDateTimeFormat.
	 *
	 * @param dateFormat a {@link java.time.format.DateTimeFormatter} object
	 * @return a {@link cloud.stackit.sdk.loadbalancer.ApiClient} object
	 */
	public ApiClient setOffsetDateTimeFormat(DateTimeFormatter dateFormat) {
		JSON.setOffsetDateTimeFormat(dateFormat);
		return this;
	}

	/**
	 * Set LocalDateFormat.
	 *
	 * @param dateFormat a {@link java.time.format.DateTimeFormatter} object
	 * @return a {@link cloud.stackit.sdk.loadbalancer.ApiClient} object
	 */
	public ApiClient setLocalDateFormat(DateTimeFormatter dateFormat) {
		JSON.setLocalDateFormat(dateFormat);
		return this;
	}

	/**
	 * Set LenientOnJson.
	 *
	 * @param lenientOnJson a boolean
	 * @return a {@link cloud.stackit.sdk.loadbalancer.ApiClient} object
	 */
	public ApiClient setLenientOnJson(boolean lenientOnJson) {
		JSON.setLenientOnJson(lenientOnJson);
		return this;
	}

	/**
	 * Set the User-Agent header's value (by adding to the default header map).
	 *
	 * @param userAgent HTTP request's user agent
	 * @return ApiClient
	 */
	public ApiClient setUserAgent(String userAgent) {
		addDefaultHeader("User-Agent", userAgent);
		return this;
	}

	/**
	 * Add a default header.
	 *
	 * @param key The header's key
	 * @param value The header's value
	 * @return ApiClient
	 */
	public ApiClient addDefaultHeader(String key, String value) {
		defaultHeaderMap.put(key, value);
		return this;
	}

	/**
	 * Add a default cookie.
	 *
	 * @param key The cookie's key
	 * @param value The cookie's value
	 * @return ApiClient
	 */
	public ApiClient addDefaultCookie(String key, String value) {
		defaultCookieMap.put(key, value);
		return this;
	}

	/**
	 * Check that whether debugging is enabled for this API client.
	 *
	 * @return True if debugging is enabled, false otherwise.
	 */
	public boolean isDebugging() {
		return debugging;
	}

	/**
	 * Enable/disable debugging for this API client.
	 *
	 * @param debugging To enable (true) or disable (false) debugging
	 * @return ApiClient
	 */
	public ApiClient setDebugging(boolean debugging) {
		if (debugging != this.debugging) {
			if (debugging) {
				loggingInterceptor = new HttpLoggingInterceptor();
				loggingInterceptor.setLevel(Level.BODY);
				httpClient = httpClient.newBuilder().addInterceptor(loggingInterceptor).build();
			} else {
				final OkHttpClient.Builder builder = httpClient.newBuilder();
				builder.interceptors().remove(loggingInterceptor);
				httpClient = builder.build();
				loggingInterceptor = null;
			}
		}
		this.debugging = debugging;
		return this;
	}

	/**
	 * The path of temporary folder used to store downloaded files from endpoints with file
	 * response. The default value is <code>null</code>, i.e. using the system's default temporary
	 * folder.
	 *
	 * @see <a
	 *     href="https://docs.oracle.com/javase/7/docs/api/java/nio/file/Files.html#createTempFile(java.lang.String,%20java.lang.String,%20java.nio.file.attribute.FileAttribute...)">createTempFile</a>
	 * @return Temporary folder path
	 */
	public String getTempFolderPath() {
		return tempFolderPath;
	}

	/**
	 * Set the temporary folder path (for downloading files)
	 *
	 * @param tempFolderPath Temporary folder path
	 * @return ApiClient
	 */
	public ApiClient setTempFolderPath(String tempFolderPath) {
		this.tempFolderPath = tempFolderPath;
		return this;
	}

	/**
	 * Get connection timeout (in milliseconds).
	 *
	 * @return Timeout in milliseconds
	 */
	public int getConnectTimeout() {
		return httpClient.connectTimeoutMillis();
	}

	/**
	 * Sets the connect timeout (in milliseconds). A value of 0 means no timeout, otherwise values
	 * must be between 1 and {@link java.lang.Integer#MAX_VALUE}.
	 *
	 * @param connectionTimeout connection timeout in milliseconds
	 * @return Api client
	 */
	public ApiClient setConnectTimeout(int connectionTimeout) {
		httpClient =
				httpClient
						.newBuilder()
						.connectTimeout(connectionTimeout, TimeUnit.MILLISECONDS)
						.build();
		return this;
	}

	/**
	 * Get read timeout (in milliseconds).
	 *
	 * @return Timeout in milliseconds
	 */
	public int getReadTimeout() {
		return httpClient.readTimeoutMillis();
	}

	/**
	 * Sets the read timeout (in milliseconds). A value of 0 means no timeout, otherwise values must
	 * be between 1 and {@link java.lang.Integer#MAX_VALUE}.
	 *
	 * @param readTimeout read timeout in milliseconds
	 * @return Api client
	 */
	public ApiClient setReadTimeout(int readTimeout) {
		httpClient =
				httpClient.newBuilder().readTimeout(readTimeout, TimeUnit.MILLISECONDS).build();
		return this;
	}

	/**
	 * Get write timeout (in milliseconds).
	 *
	 * @return Timeout in milliseconds
	 */
	public int getWriteTimeout() {
		return httpClient.writeTimeoutMillis();
	}

	/**
	 * Sets the write timeout (in milliseconds). A value of 0 means no timeout, otherwise values
	 * must be between 1 and {@link java.lang.Integer#MAX_VALUE}.
	 *
	 * @param writeTimeout connection timeout in milliseconds
	 * @return Api client
	 */
	public ApiClient setWriteTimeout(int writeTimeout) {
		httpClient =
				httpClient.newBuilder().writeTimeout(writeTimeout, TimeUnit.MILLISECONDS).build();
		return this;
	}

	/**
	 * Format the given parameter object into string.
	 *
	 * @param param Parameter
	 * @return String representation of the parameter
	 */
	public String parameterToString(Object param) {
		if (param == null) {
			return "";
		} else if (param instanceof Date
				|| param instanceof OffsetDateTime
				|| param instanceof LocalDate) {
			// Serialize to json string and remove the " enclosing characters
			String jsonStr = JSON.serialize(param);
			return jsonStr.substring(1, jsonStr.length() - 1);
		} else if (param instanceof Collection) {
			StringBuilder b = new StringBuilder();
			for (Object o : (Collection) param) {
				if (b.length() > 0) {
					b.append(",");
				}
				b.append(o);
			}
			return b.toString();
		} else {
			return String.valueOf(param);
		}
	}

	/**
	 * Formats the specified query parameter to a list containing a single {@code Pair} object.
	 *
	 * <p>Note that {@code value} must not be a collection.
	 *
	 * @param name The name of the parameter.
	 * @param value The value of the parameter.
	 * @return A list containing a single {@code Pair} object.
	 */
	public List<Pair> parameterToPair(String name, Object value) {
		List<Pair> params = new ArrayList<Pair>();

		// preconditions
		if (name == null || name.isEmpty() || value == null || value instanceof Collection) {
			return params;
		}

		params.add(new Pair(name, parameterToString(value)));
		return params;
	}

	/**
	 * Formats the specified collection query parameters to a list of {@code Pair} objects.
	 *
	 * <p>Note that the values of each of the returned Pair objects are percent-encoded.
	 *
	 * @param collectionFormat The collection format of the parameter.
	 * @param name The name of the parameter.
	 * @param value The value of the parameter.
	 * @return A list of {@code Pair} objects.
	 */
	public List<Pair> parameterToPairs(String collectionFormat, String name, Collection<?> value) {
		List<Pair> params = new ArrayList<Pair>();

		// preconditions
		if (name == null || name.isEmpty() || value == null || value.isEmpty()) {
			return params;
		}

		// create the params based on the collection format
		if ("multi".equals(collectionFormat)) {
			for (Object item : value) {
				params.add(new Pair(name, escapeString(parameterToString(item))));
			}
			return params;
		}

		// collectionFormat is assumed to be "csv" by default
		String delimiter = ",";

		// escape all delimiters except commas, which are URI reserved
		// characters
		if ("ssv".equals(collectionFormat)) {
			delimiter = escapeString(" ");
		} else if ("tsv".equals(collectionFormat)) {
			delimiter = escapeString("\t");
		} else if ("pipes".equals(collectionFormat)) {
			delimiter = escapeString("|");
		}

		StringBuilder sb = new StringBuilder();
		for (Object item : value) {
			sb.append(delimiter);
			sb.append(escapeString(parameterToString(item)));
		}

		params.add(new Pair(name, sb.substring(delimiter.length())));

		return params;
	}

	/**
	 * Formats the specified free-form query parameters to a list of {@code Pair} objects.
	 *
	 * @param value The free-form query parameters.
	 * @return A list of {@code Pair} objects.
	 */
	public List<Pair> freeFormParameterToPairs(Object value) {
		List<Pair> params = new ArrayList<>();

		// preconditions
		if (value == null || !(value instanceof Map)) {
			return params;
		}

		@SuppressWarnings("unchecked")
		final Map<String, Object> valuesMap = (Map<String, Object>) value;

		for (Map.Entry<String, Object> entry : valuesMap.entrySet()) {
			params.add(new Pair(entry.getKey(), parameterToString(entry.getValue())));
		}

		return params;
	}

	/**
	 * Formats the specified collection path parameter to a string value.
	 *
	 * @param collectionFormat The collection format of the parameter.
	 * @param value The value of the parameter.
	 * @return String representation of the parameter
	 */
	public String collectionPathParameterToString(String collectionFormat, Collection value) {
		// create the value based on the collection format
		if ("multi".equals(collectionFormat)) {
			// not valid for path params
			return parameterToString(value);
		}

		// collectionFormat is assumed to be "csv" by default
		String delimiter = ",";

		if ("ssv".equals(collectionFormat)) {
			delimiter = " ";
		} else if ("tsv".equals(collectionFormat)) {
			delimiter = "\t";
		} else if ("pipes".equals(collectionFormat)) {
			delimiter = "|";
		}

		StringBuilder sb = new StringBuilder();
		for (Object item : value) {
			sb.append(delimiter);
			sb.append(parameterToString(item));
		}

		return sb.substring(delimiter.length());
	}

	/**
	 * Sanitize filename by removing path. e.g. ../../sun.gif becomes sun.gif
	 *
	 * @param filename The filename to be sanitized
	 * @return The sanitized filename
	 */
	public String sanitizeFilename(String filename) {
		return filename.replaceFirst("^.*[/\\\\]", "");
	}

	/**
	 * Check if the given MIME is a JSON MIME. JSON MIME examples: application/json
	 * application/json; charset=UTF8 APPLICATION/JSON application/vnd.company+json "* / *" is also
	 * default to JSON
	 *
	 * @param mime MIME (Multipurpose Internet Mail Extensions)
	 * @return True if the given MIME is JSON, false otherwise.
	 */
	public boolean isJsonMime(String mime) {
		String jsonMime = "(?i)^(application/json|[^;/ \t]+/[^;/ \t]+[+]json)[ \t]*(;.*)?$";
		return mime != null && (mime.matches(jsonMime) || mime.equals("*/*"));
	}

	/**
	 * Select the Accept header's value from the given accepts array: if JSON exists in the given
	 * array, use it; otherwise use all of them (joining into a string)
	 *
	 * @param accepts The accepts array to select from
	 * @return The Accept header to use. If the given array is empty, null will be returned (not to
	 *     set the Accept header explicitly).
	 */
	public String selectHeaderAccept(String[] accepts) {
		if (accepts.length == 0) {
			return null;
		}
		for (String accept : accepts) {
			if (isJsonMime(accept)) {
				return accept;
			}
		}
		return StringUtil.join(accepts, ",");
	}

	/**
	 * Select the Content-Type header's value from the given array: if JSON exists in the given
	 * array, use it; otherwise use the first one of the array.
	 *
	 * @param contentTypes The Content-Type array to select from
	 * @return The Content-Type header to use. If the given array is empty, returns null. If it
	 *     matches "any", JSON will be used.
	 */
	public String selectHeaderContentType(String[] contentTypes) {
		if (contentTypes.length == 0) {
			return null;
		}

		if (contentTypes[0].equals("*/*")) {
			return "application/json";
		}

		for (String contentType : contentTypes) {
			if (isJsonMime(contentType)) {
				return contentType;
			}
		}

		return contentTypes[0];
	}

	/**
	 * Escape the given string to be used as URL query value.
	 *
	 * @param str String to be escaped
	 * @return Escaped string
	 */
	public String escapeString(String str) {
		try {
			return URLEncoder.encode(str, "utf8").replaceAll("\\+", "%20");
		} catch (UnsupportedEncodingException e) {
			return str;
		}
	}

	/**
	 * Deserialize response body to Java object, according to the return type and the Content-Type
	 * response header.
	 *
	 * @param <T> Type
	 * @param response HTTP response
	 * @param returnType The type of the Java object
	 * @return The deserialized Java object
	 * @throws cloud.stackit.sdk.core.exception.ApiException If fail to deserialize response body,
	 *     i.e. cannot read response body or the Content-Type of the response is not supported.
	 */
	@SuppressWarnings("unchecked")
	public <T> T deserialize(Response response, Type returnType) throws ApiException {
		if (response == null || returnType == null) {
			return null;
		}

		if ("byte[]".equals(returnType.toString())) {
			// Handle binary response (byte array).
			try {
				return (T) response.body().bytes();
			} catch (IOException e) {
				throw new ApiException(e);
			}
		} else if (returnType.equals(File.class)) {
			// Handle file downloading.
			return (T) downloadFileFromResponse(response);
		}

		ResponseBody respBody = response.body();
		if (respBody == null) {
			return null;
		}

		String contentType = response.headers().get("Content-Type");
		if (contentType == null) {
			// ensuring a default content type
			contentType = "application/json";
		}
		try {
			if (isJsonMime(contentType)) {
				if (returnType.equals(String.class)) {
					String respBodyString = respBody.string();
					if (respBodyString.isEmpty()) {
						return null;
					}
					// Use String-based deserialize for String return type with fallback
					return JSON.deserialize(respBodyString, returnType);
				} else {
					// Use InputStream-based deserialize which supports responses > 2GB
					return JSON.deserialize(respBody.byteStream(), returnType);
				}
			} else if (returnType.equals(String.class)) {
				String respBodyString = respBody.string();
				if (respBodyString.isEmpty()) {
					return null;
				}
				// Expecting string, return the raw response body.
				return (T) respBodyString;
			} else {
				throw new ApiException(
						"Content type \""
								+ contentType
								+ "\" is not supported for type: "
								+ returnType,
						response.code(),
						response.headers().toMultimap(),
						response.body().string());
			}
		} catch (IOException e) {
			throw new ApiException(e);
		}
	}

	/**
	 * Serialize the given Java object into request body according to the object's class and the
	 * request Content-Type.
	 *
	 * @param obj The Java object
	 * @param contentType The request Content-Type
	 * @return The serialized request body
	 * @throws cloud.stackit.sdk.core.exception.ApiException If fail to serialize the given object
	 */
	public RequestBody serialize(Object obj, String contentType) throws ApiException {
		if (obj instanceof byte[]) {
			// Binary (byte array) body parameter support.
			return RequestBody.create((byte[]) obj, MediaType.parse(contentType));
		} else if (obj instanceof File) {
			// File body parameter support.
			return RequestBody.create((File) obj, MediaType.parse(contentType));
		} else if ("text/plain".equals(contentType) && obj instanceof String) {
			return RequestBody.create((String) obj, MediaType.parse(contentType));
		} else if (isJsonMime(contentType)) {
			String content;
			if (obj != null) {
				content = JSON.serialize(obj);
			} else {
				content = null;
			}
			return RequestBody.create(content, MediaType.parse(contentType));
		} else if (obj instanceof String) {
			return RequestBody.create((String) obj, MediaType.parse(contentType));
		} else {
			throw new ApiException("Content type \"" + contentType + "\" is not supported");
		}
	}

	/**
	 * Download file from the given response.
	 *
	 * @param response An instance of the Response object
	 * @throws cloud.stackit.sdk.core.exception.ApiException If fail to read file content from
	 *     response and write to disk
	 * @return Downloaded file
	 */
	public File downloadFileFromResponse(Response response) throws ApiException {
		try {
			File file = prepareDownloadFile(response);
			BufferedSink sink = Okio.buffer(Okio.sink(file));
			sink.writeAll(response.body().source());
			sink.close();
			return file;
		} catch (IOException e) {
			throw new ApiException(e);
		}
	}

	/**
	 * Prepare file for download
	 *
	 * @param response An instance of the Response object
	 * @return Prepared file for the download
	 * @throws java.io.IOException If fail to prepare file for download
	 */
	public File prepareDownloadFile(Response response) throws IOException {
		String filename = null;
		String contentDisposition = response.header("Content-Disposition");
		if (contentDisposition != null && !"".equals(contentDisposition)) {
			// Get filename from the Content-Disposition header.
			Pattern pattern = Pattern.compile("filename=['\"]?([^'\"\\s]+)['\"]?");
			Matcher matcher = pattern.matcher(contentDisposition);
			if (matcher.find()) {
				filename = sanitizeFilename(matcher.group(1));
			}
		}

		String prefix = null;
		String suffix = null;
		if (filename == null) {
			prefix = "download-";
			suffix = "";
		} else {
			int pos = filename.lastIndexOf(".");
			if (pos == -1) {
				prefix = filename + "-";
			} else {
				prefix = filename.substring(0, pos) + "-";
				suffix = filename.substring(pos);
			}
			// Files.createTempFile requires the prefix to be at least three characters long
			if (prefix.length() < 3) prefix = "download-";
		}

		if (tempFolderPath == null) return Files.createTempFile(prefix, suffix).toFile();
		else return Files.createTempFile(Paths.get(tempFolderPath), prefix, suffix).toFile();
	}

	/**
	 * {@link #execute(Call, Type)}
	 *
	 * @param <T> Type
	 * @param call An instance of the Call object
	 * @return ApiResponse&lt;T&gt;
	 * @throws cloud.stackit.sdk.core.exception.ApiException If fail to execute the call
	 */
	public <T> ApiResponse<T> execute(Call call) throws ApiException {
		return execute(call, null);
	}

	/**
	 * Execute HTTP call and deserialize the HTTP response body into the given return type.
	 *
	 * @param returnType The return type used to deserialize HTTP response body
	 * @param <T> The return type corresponding to (same with) returnType
	 * @param call Call
	 * @return ApiResponse object containing response status, headers and data, which is a Java
	 *     object deserialized from response body and would be null when returnType is null.
	 * @throws cloud.stackit.sdk.core.exception.ApiException If fail to execute the call
	 */
	public <T> ApiResponse<T> execute(Call call, Type returnType) throws ApiException {
		try {
			Response response = call.execute();
			T data = handleResponse(response, returnType);
			return new ApiResponse<T>(response.code(), response.headers().toMultimap(), data);
		} catch (IOException e) {
			throw new ApiException(e);
		}
	}

	/**
	 * {@link #executeAsync(Call, Type, ApiCallback)}
	 *
	 * @param <T> Type
	 * @param call An instance of the Call object
	 * @param callback ApiCallback&lt;T&gt;
	 */
	public <T> void executeAsync(Call call, ApiCallback<T> callback) {
		executeAsync(call, null, callback);
	}

	/**
	 * Execute HTTP call asynchronously.
	 *
	 * @param <T> Type
	 * @param call The callback to be executed when the API call finishes
	 * @param returnType Return type
	 * @param callback ApiCallback
	 * @see #execute(Call, Type)
	 */
	@SuppressWarnings("unchecked")
	public <T> void executeAsync(Call call, final Type returnType, final ApiCallback<T> callback) {
		call.enqueue(
				new Callback() {
					@Override
					public void onFailure(Call call, IOException e) {
						callback.onFailure(new ApiException(e), 0, null);
					}

					@Override
					public void onResponse(Call call, Response response) throws IOException {
						T result;
						try {
							result = (T) handleResponse(response, returnType);
						} catch (ApiException e) {
							callback.onFailure(e, response.code(), response.headers().toMultimap());
							return;
						} catch (Exception e) {
							callback.onFailure(
									new ApiException(e),
									response.code(),
									response.headers().toMultimap());
							return;
						}
						callback.onSuccess(
								result, response.code(), response.headers().toMultimap());
					}
				});
	}

	/**
	 * Handle the given response, return the deserialized object when the response is successful.
	 *
	 * @param <T> Type
	 * @param response Response
	 * @param returnType Return type
	 * @return Type
	 * @throws cloud.stackit.sdk.core.exception.ApiException If the response has an unsuccessful
	 *     status code or fail to deserialize the response body
	 */
	public <T> T handleResponse(Response response, Type returnType) throws ApiException {
		if (response.isSuccessful()) {
			if (returnType == null || response.code() == 204) {
				// returning null if the returnType is not defined,
				// or the status code is 204 (No Content)
				if (response.body() != null) {
					try {
						response.body().close();
					} catch (Exception e) {
						throw new ApiException(
								response.message(),
								e,
								response.code(),
								response.headers().toMultimap());
					}
				}
				return null;
			} else {
				return deserialize(response, returnType);
			}
		} else {
			String respBody = null;
			if (response.body() != null) {
				try {
					respBody = response.body().string();
				} catch (IOException e) {
					throw new ApiException(
							response.message(),
							e,
							response.code(),
							response.headers().toMultimap());
				}
			}
			throw new ApiException(
					response.message(), response.code(), response.headers().toMultimap(), respBody);
		}
	}

	/**
	 * Build HTTP call with the given options.
	 *
	 * @param baseUrl The base URL
	 * @param path The sub-path of the HTTP URL
	 * @param method The request method, one of "GET", "HEAD", "OPTIONS", "POST", "PUT", "PATCH" and
	 *     "DELETE"
	 * @param queryParams The query parameters
	 * @param collectionQueryParams The collection query parameters
	 * @param body The request body object
	 * @param headerParams The header parameters
	 * @param cookieParams The cookie parameters
	 * @param formParams The form parameters
	 * @param authNames The authentications to apply
	 * @param callback Callback for upload/download progress
	 * @return The HTTP call
	 * @throws cloud.stackit.sdk.core.exception.ApiException If fail to serialize the request body
	 *     object
	 */
	public Call buildCall(
			String baseUrl,
			String path,
			String method,
			List<Pair> queryParams,
			List<Pair> collectionQueryParams,
			Object body,
			Map<String, String> headerParams,
			Map<String, String> cookieParams,
			Map<String, Object> formParams,
			String[] authNames,
			ApiCallback callback)
			throws ApiException {
		Request request =
				buildRequest(
						baseUrl,
						path,
						method,
						queryParams,
						collectionQueryParams,
						body,
						headerParams,
						cookieParams,
						formParams,
						authNames,
						callback);

		return httpClient.newCall(request);
	}

	/**
	 * Build an HTTP request with the given options.
	 *
	 * @param baseUrl The base URL
	 * @param path The sub-path of the HTTP URL
	 * @param method The request method, one of "GET", "HEAD", "OPTIONS", "POST", "PUT", "PATCH" and
	 *     "DELETE"
	 * @param queryParams The query parameters
	 * @param collectionQueryParams The collection query parameters
	 * @param body The request body object
	 * @param headerParams The header parameters
	 * @param cookieParams The cookie parameters
	 * @param formParams The form parameters
	 * @param authNames The authentications to apply
	 * @param callback Callback for upload/download progress
	 * @return The HTTP request
	 * @throws cloud.stackit.sdk.core.exception.ApiException If fail to serialize the request body
	 *     object
	 */
	public Request buildRequest(
			String baseUrl,
			String path,
			String method,
			List<Pair> queryParams,
			List<Pair> collectionQueryParams,
			Object body,
			Map<String, String> headerParams,
			Map<String, String> cookieParams,
			Map<String, Object> formParams,
			String[] authNames,
			ApiCallback callback)
			throws ApiException {
		final String url = buildUrl(baseUrl, path, queryParams, collectionQueryParams);

		// prepare HTTP request body
		RequestBody reqBody;
		String contentType = headerParams.get("Content-Type");
		String contentTypePure = contentType;
		if (contentTypePure != null && contentTypePure.contains(";")) {
			contentTypePure = contentType.substring(0, contentType.indexOf(";"));
		}
		if (!HttpMethod.permitsRequestBody(method)) {
			reqBody = null;
		} else if ("application/x-www-form-urlencoded".equals(contentTypePure)) {
			reqBody = buildRequestBodyFormEncoding(formParams);
		} else if ("multipart/form-data".equals(contentTypePure)) {
			reqBody = buildRequestBodyMultipart(formParams);
		} else if (body == null) {
			if ("DELETE".equals(method)) {
				// allow calling DELETE without sending a request body
				reqBody = null;
			} else {
				// use an empty request body (for POST, PUT and PATCH)
				reqBody =
						RequestBody.create(
								"", contentType == null ? null : MediaType.parse(contentType));
			}
		} else {
			reqBody = serialize(body, contentType);
		}

		List<Pair> updatedQueryParams = new ArrayList<>(queryParams);

		final Request.Builder reqBuilder =
				new Request.Builder()
						.url(buildUrl(baseUrl, path, updatedQueryParams, collectionQueryParams));
		processHeaderParams(headerParams, reqBuilder);
		processCookieParams(cookieParams, reqBuilder);

		// Associate callback with request (if not null) so interceptor can
		// access it when creating ProgressResponseBody
		reqBuilder.tag(callback);

		Request request = null;

		if (callback != null && reqBody != null) {
			ProgressRequestBody progressRequestBody = new ProgressRequestBody(reqBody, callback);
			request = reqBuilder.method(method, progressRequestBody).build();
		} else {
			request = reqBuilder.method(method, reqBody).build();
		}

		return request;
	}

	/**
	 * Build full URL by concatenating base path, the given sub path and query parameters.
	 *
	 * @param baseUrl The base URL
	 * @param path The sub path
	 * @param queryParams The query parameters
	 * @param collectionQueryParams The collection query parameters
	 * @return The full URL
	 */
	public String buildUrl(
			String baseUrl, String path, List<Pair> queryParams, List<Pair> collectionQueryParams) {
		final StringBuilder url = new StringBuilder();
		if (baseUrl != null) {
			url.append(baseUrl).append(path);
		} else {
			String baseURL;
			if (serverIndex != null) {
				if (serverIndex < 0 || serverIndex >= servers.size()) {
					throw new ArrayIndexOutOfBoundsException(
							String.format(
									java.util.Locale.ROOT,
									"Invalid index %d when selecting the host settings. Must be less than %d",
									serverIndex,
									servers.size()));
				}
				baseURL = servers.get(serverIndex).URL(serverVariables);
			} else {
				baseURL = basePath;
			}
			url.append(baseURL).append(path);
		}

		if (queryParams != null && !queryParams.isEmpty()) {
			// support (constant) query string in `path`, e.g. "/posts?draft=1"
			String prefix = path.contains("?") ? "&" : "?";
			for (Pair param : queryParams) {
				if (param.getValue() != null) {
					if (prefix != null) {
						url.append(prefix);
						prefix = null;
					} else {
						url.append("&");
					}
					String value = parameterToString(param.getValue());
					url.append(escapeString(param.getName()))
							.append("=")
							.append(escapeString(value));
				}
			}
		}

		if (collectionQueryParams != null && !collectionQueryParams.isEmpty()) {
			String prefix = url.toString().contains("?") ? "&" : "?";
			for (Pair param : collectionQueryParams) {
				if (param.getValue() != null) {
					if (prefix != null) {
						url.append(prefix);
						prefix = null;
					} else {
						url.append("&");
					}
					String value = parameterToString(param.getValue());
					// collection query parameter value already escaped as part of parameterToPairs
					url.append(escapeString(param.getName())).append("=").append(value);
				}
			}
		}

		return url.toString();
	}

	/**
	 * Set header parameters to the request builder, including default headers.
	 *
	 * @param headerParams Header parameters in the form of Map
	 * @param reqBuilder Request.Builder
	 */
	public void processHeaderParams(Map<String, String> headerParams, Request.Builder reqBuilder) {
		for (Entry<String, String> param : headerParams.entrySet()) {
			reqBuilder.header(param.getKey(), parameterToString(param.getValue()));
		}
		for (Entry<String, String> header : defaultHeaderMap.entrySet()) {
			if (!headerParams.containsKey(header.getKey())) {
				reqBuilder.header(header.getKey(), parameterToString(header.getValue()));
			}
		}
	}

	/**
	 * Set cookie parameters to the request builder, including default cookies.
	 *
	 * @param cookieParams Cookie parameters in the form of Map
	 * @param reqBuilder Request.Builder
	 */
	public void processCookieParams(Map<String, String> cookieParams, Request.Builder reqBuilder) {
		for (Entry<String, String> param : cookieParams.entrySet()) {
			reqBuilder.addHeader(
					"Cookie",
					String.format(
							java.util.Locale.ROOT, "%s=%s", param.getKey(), param.getValue()));
		}
		for (Entry<String, String> param : defaultCookieMap.entrySet()) {
			if (!cookieParams.containsKey(param.getKey())) {
				reqBuilder.addHeader(
						"Cookie",
						String.format(
								java.util.Locale.ROOT, "%s=%s", param.getKey(), param.getValue()));
			}
		}
	}

	/**
	 * Build a form-encoding request body with the given form parameters.
	 *
	 * @param formParams Form parameters in the form of Map
	 * @return RequestBody
	 */
	public RequestBody buildRequestBodyFormEncoding(Map<String, Object> formParams) {
		okhttp3.FormBody.Builder formBuilder = new okhttp3.FormBody.Builder();
		for (Entry<String, Object> param : formParams.entrySet()) {
			formBuilder.add(param.getKey(), parameterToString(param.getValue()));
		}
		return formBuilder.build();
	}

	/**
	 * Build a multipart (file uploading) request body with the given form parameters, which could
	 * contain text fields and file fields.
	 *
	 * @param formParams Form parameters in the form of Map
	 * @return RequestBody
	 */
	public RequestBody buildRequestBodyMultipart(Map<String, Object> formParams) {
		MultipartBody.Builder mpBuilder = new MultipartBody.Builder().setType(MultipartBody.FORM);
		for (Entry<String, Object> param : formParams.entrySet()) {
			if (param.getValue() instanceof File) {
				File file = (File) param.getValue();
				addPartToMultiPartBuilder(mpBuilder, param.getKey(), file);
			} else if (param.getValue() instanceof List) {
				List list = (List) param.getValue();
				for (Object item : list) {
					if (item instanceof File) {
						addPartToMultiPartBuilder(mpBuilder, param.getKey(), (File) item);
					} else {
						addPartToMultiPartBuilder(mpBuilder, param.getKey(), param.getValue());
					}
				}
			} else {
				addPartToMultiPartBuilder(mpBuilder, param.getKey(), param.getValue());
			}
		}
		return mpBuilder.build();
	}

	/**
	 * Guess Content-Type header from the given file (defaults to "application/octet-stream").
	 *
	 * @param file The given file
	 * @return The guessed Content-Type
	 */
	public String guessContentTypeFromFile(File file) {
		String contentType = URLConnection.guessContentTypeFromName(file.getName());
		if (contentType == null) {
			return "application/octet-stream";
		} else {
			return contentType;
		}
	}

	/**
	 * Add a Content-Disposition Header for the given key and file to the MultipartBody Builder.
	 *
	 * @param mpBuilder MultipartBody.Builder
	 * @param key The key of the Header element
	 * @param file The file to add to the Header
	 */
	protected void addPartToMultiPartBuilder(
			MultipartBody.Builder mpBuilder, String key, File file) {
		Headers partHeaders =
				Headers.of(
						"Content-Disposition",
						"form-data; name=\"" + key + "\"; filename=\"" + file.getName() + "\"");
		MediaType mediaType = MediaType.parse(guessContentTypeFromFile(file));
		mpBuilder.addPart(partHeaders, RequestBody.create(file, mediaType));
	}

	/**
	 * Add a Content-Disposition Header for the given key and complex object to the MultipartBody
	 * Builder.
	 *
	 * @param mpBuilder MultipartBody.Builder
	 * @param key The key of the Header element
	 * @param obj The complex object to add to the Header
	 */
	protected void addPartToMultiPartBuilder(
			MultipartBody.Builder mpBuilder, String key, Object obj) {
		RequestBody requestBody;
		if (obj instanceof String) {
			requestBody = RequestBody.create((String) obj, MediaType.parse("text/plain"));
		} else {
			String content;
			if (obj != null) {
				content = JSON.serialize(obj);
			} else {
				content = null;
			}
			requestBody = RequestBody.create(content, MediaType.parse("application/json"));
		}

		Headers partHeaders = Headers.of("Content-Disposition", "form-data; name=\"" + key + "\"");
		mpBuilder.addPart(partHeaders, requestBody);
	}

	/**
	 * Get network interceptor to add it to the httpClient to track download progress for async
	 * requests.
	 */
	protected Interceptor getProgressInterceptor() {
		return new Interceptor() {
			@Override
			public Response intercept(Interceptor.Chain chain) throws IOException {
				final Request request = chain.request();
				final Response originalResponse = chain.proceed(request);
				if (request.tag() instanceof ApiCallback) {
					final ApiCallback callback = (ApiCallback) request.tag();
					return originalResponse
							.newBuilder()
							.body(new ProgressResponseBody(originalResponse.body(), callback))
							.build();
				}
				return originalResponse;
			}
		};
	}

	/**
	 * Apply SSL related settings to httpClient according to the current values of verifyingSsl and
	 * sslCaCert.
	 */
	protected void applySslSettings() {
		try {
			TrustManager[] trustManagers;
			HostnameVerifier hostnameVerifier;
			if (!verifyingSsl) {
				trustManagers =
						new TrustManager[] {
							new X509TrustManager() {
								@Override
								public void checkClientTrusted(
										java.security.cert.X509Certificate[] chain, String authType)
										throws CertificateException {}

								@Override
								public void checkServerTrusted(
										java.security.cert.X509Certificate[] chain, String authType)
										throws CertificateException {}

								@Override
								public java.security.cert.X509Certificate[] getAcceptedIssuers() {
									return new java.security.cert.X509Certificate[] {};
								}
							}
						};
				hostnameVerifier =
						new HostnameVerifier() {
							@Override
							public boolean verify(String hostname, SSLSession session) {
								return true;
							}
						};
			} else {
				TrustManagerFactory trustManagerFactory =
						TrustManagerFactory.getInstance(TrustManagerFactory.getDefaultAlgorithm());

				if (sslCaCert == null) {
					trustManagerFactory.init((KeyStore) null);
				} else {
					char[] password = null; // Any password will work.
					CertificateFactory certificateFactory = CertificateFactory.getInstance("X.509");
					Collection<? extends Certificate> certificates =
							certificateFactory.generateCertificates(sslCaCert);
					if (certificates.isEmpty()) {
						throw new IllegalArgumentException(
								"expected non-empty set of trusted certificates");
					}
					KeyStore caKeyStore = newEmptyKeyStore(password);
					int index = 0;
					for (Certificate certificate : certificates) {
						String certificateAlias = "ca" + (index++);
						caKeyStore.setCertificateEntry(certificateAlias, certificate);
					}
					trustManagerFactory.init(caKeyStore);
				}
				trustManagers = trustManagerFactory.getTrustManagers();
				if (tlsServerName != null && !tlsServerName.isEmpty()) {
					hostnameVerifier =
							new HostnameVerifier() {
								@Override
								public boolean verify(String hostname, SSLSession session) {
									// Verify the certificate against tlsServerName instead of the
									// actual hostname
									return OkHostnameVerifier.INSTANCE.verify(
											tlsServerName, session);
								}
							};
				} else {
					hostnameVerifier = OkHostnameVerifier.INSTANCE;
				}
			}

			SSLContext sslContext = SSLContext.getInstance("TLS");
			sslContext.init(keyManagers, trustManagers, new SecureRandom());
			httpClient =
					httpClient
							.newBuilder()
							.sslSocketFactory(
									sslContext.getSocketFactory(),
									(X509TrustManager) trustManagers[0])
							.hostnameVerifier(hostnameVerifier)
							.build();
		} catch (GeneralSecurityException e) {
			throw new RuntimeException(e);
		}
	}

	protected KeyStore newEmptyKeyStore(char[] password) throws GeneralSecurityException {
		try {
			KeyStore keyStore = KeyStore.getInstance(KeyStore.getDefaultType());
			keyStore.load(null, password);
			return keyStore;
		} catch (IOException e) {
			throw new AssertionError(e);
		}
	}

	/**
	 * Convert the HTTP request body to a string.
	 *
	 * @param requestBody The HTTP request object
	 * @return The string representation of the HTTP request body
	 * @throws cloud.stackit.sdk.core.exception.ApiException If fail to serialize the request body
	 *     object into a string
	 */
	protected String requestBodyToString(RequestBody requestBody) throws ApiException {
		if (requestBody != null) {
			try {
				final Buffer buffer = new Buffer();
				requestBody.writeTo(buffer);
				return buffer.readUtf8();
			} catch (final IOException e) {
				throw new ApiException(e);
			}
		}

		// empty http request body
		return "";
	}
}