package com.sendgrid;

import java.io.IOException;

import java.util.HashMap;

import java.util.Map;

import java.util.concurrent.ExecutorService;

import java.util.concurrent.Executors;

/**

* This class is the base interface to the Twilio SendGrid Web API.

*/

public abstract class BaseInterface implements SendGridAPI {

private static final String VERSION = "4.10.3";

private static final String USER_AGENT = "sendgrid/" + VERSION + ";java";

private static final int RATE_LIMIT_RESPONSE_CODE = 429;

private static final int THREAD_POOL_SIZE = 8;

private static final Map<String, String> allowedRegionsHostMap;

static {

//todo: change this to Map.of() when we've moved on from Java 8

allowedRegionsHostMap = new HashMap<>();

allowedRegionsHostMap.put("eu", "api.eu.sendgrid.com");

allowedRegionsHostMap.put("global", "api.sendgrid.com");

}

private ExecutorService pool;

/**

* The host to which to connect.

*/

private String host;

/**

* The API version.

*/

private String version;

/**

* The HTTP client.

*/

private Client client;

/**

* The request headers container.

*/

private Map<String, String> requestHeaders;

/**

* The number of times to try after a rate limit.

*/

private int rateLimitRetry;

/**

* The number of milliseconds to sleep between retries.

*/

private int rateLimitSleep;

/**

* The subuser to be impersonated.

*/

private String subuser;

/**

* Construct a new API wrapper.

*/

public BaseInterface() {

this.client = new Client();

}

/**

* Construct a new API wrapper.

*

* @param test is true if you are unit testing

*/

public BaseInterface(final Boolean test) {

this.client = new Client(test);

}

/**

* Construct a new API wrapper.

*

* @param client the Client to use (allows to customize its configuration)

*/

public BaseInterface(final Client client) {

this.client = client;

}

/**

* Initialize the client.

*

* @param auth authorization header value

* @param host the base URL for the API

*/

public void initialize(final String auth, final String host) {

this.host = host;

this.version = "v3";

this.requestHeaders = new HashMap<>();

this.requestHeaders.put("Authorization", auth);

this.requestHeaders.put("User-Agent", USER_AGENT);

this.requestHeaders.put("Accept", "application/json");

this.rateLimitRetry = 5;

this.rateLimitSleep = 1100;

this.pool = Executors.newFixedThreadPool(THREAD_POOL_SIZE);

}

/**

* Get the current library version.

*

* @return the current version

*/

public String getLibraryVersion() {

return VERSION;

}

/**

* Get the API version.

*

* @return the current API version

*/

public String getVersion() {

return this.version;

}

/**

* Set the API version.

*

* @param version the new version

*/

public void setVersion(final String version) {

this.version = version;

}

/**

* Get the request headers.

*

* @return the request headers

*/

public Map<String, String> getRequestHeaders() {

return this.requestHeaders;

}

/**

* Add/update a request header.

*

* @param key the header key

* @param value the header value

* @return the new set of request headers

*/

public Map<String, String> addRequestHeader(final String key, final String value) {

this.requestHeaders.put(key, value);

return getRequestHeaders();

}

/**

* Remove a request header.

*

* @param key the header key to remove

* @return the new set of request headers

*/

public Map<String, String> removeRequestHeader(final String key) {

this.requestHeaders.remove(key);

return getRequestHeaders();

}

/**

* Get the host.

*

* @return the host

*/

public String getHost() {

return this.host;

}

/**

* Set the host.

*

* @param host the new host

*/

public void setHost(final String host) {

this.host = host;

}

/**

* Get the maximum number of retries on a rate limit response.

* The default is 5.

*

* @return the number of retries on a rate limit

*/

public int getRateLimitRetry() {

return this.rateLimitRetry;

}

/**

* Set the maximum number of retries on a rate limit response.

*

* @param rateLimitRetry the maximum retry count

*/

public void setRateLimitRetry(final int rateLimitRetry) {

this.rateLimitRetry = rateLimitRetry;

}

/**

* Get the duration of time (in milliseconds) to sleep between

* consecutive rate limit retries. The Twilio SendGrid API enforces

* the rate limit to the second. The default value is 1.1 seconds.

*

* @return the sleep duration

*/

public int getRateLimitSleep() {

return this.rateLimitSleep;

}

/**

* Set the duration of time (in milliseconds) to sleep between

* consecutive rate limit retries.

*

* @param rateLimitSleep the sleep duration

*/

public void setRateLimitSleep(final int rateLimitSleep) {

this.rateLimitSleep = rateLimitSleep;

}

/**

* Impersonate subuser for subsequent requests

*

* @param subuser the subuser to be impersonated

*/

public void addImpersonateSubuser(final String subuser) {

this.subuser = subuser;

this.addRequestHeader("on-behalf-of", subuser);

}

/**

* Stop Impersonating the subuser

*/

public void removeImpersonateSubuser() {

this.subuser = null;

this.removeRequestHeader("on-behalf-of");

}

/**

* Get the impersonated subuser or null if empty

*

* @return the impersonated subuser

*/

public String getImpersonateSubuser() {

return this.subuser;

}

/**

* Makes the call to the Twilio SendGrid API, override this method for testing.

*

* @param request the request to make

* @return the response object

* @throws IOException in case of a network error

*/

public Response makeCall(final Request request) throws IOException {

return client.api(request);

}

/**

* Class api sets up the request to the Twilio SendGrid API, this is main interface.

*

* @param request the request object

* @return the response object

* @throws IOException in case of a network error

*/

public Response api(final Request request) throws IOException {

final Request req = new Request();

req.setMethod(request.getMethod());

req.setBaseUri(this.host);

req.setEndpoint("/" + version + "/" + request.getEndpoint());

req.setBody(request.getBody());

req.getHeaders().putAll(this.requestHeaders);

req.getHeaders().putAll(request.getHeaders());

req.getQueryParams().putAll(request.getQueryParams());

return makeCall(req);

}

/**

* Attempt an API call. This method executes the API call asynchronously

* on an internal thread pool. If the call is rate limited, the thread

* will retry up to the maximum configured time.

*

* @param request the API request

*/

public void attempt(final Request request) {

this.attempt(request, new APICallback() {

@Override

public void error(final Exception ex) {

}

public void response(final Response r) {

}

});

}

/**

* Attempt an API call. This method executes the API call asynchronously

* on an internal thread pool. If the call is rate limited, the thread

* will retry up to the maximum configured time. The supplied callback

* will be called in the event of an error, or a successful response.

*

* @param request the API request

* @param callback the callback

*/

public void attempt(final Request request, final APICallback callback) {

this.pool.execute(new Runnable() {

@Override

public void run() {

Response response;

// Retry until the retry limit has been reached.

for (int i = 0; i < rateLimitRetry; ++i) {

try {

response = api(request);

} catch (IOException ex) {

// Stop retrying if there is a network error.

callback.error(ex);

return;

}

// We have been rate limited.

if (response.getStatusCode() == RATE_LIMIT_RESPONSE_CODE) {

try {

Thread.sleep(rateLimitSleep);

} catch (InterruptedException ex) {

// Can safely ignore this exception and retry.

}

} else {

callback.response(response);

return;

}

}

// Retries exhausted. Return error.

callback.error(new RateLimitException(request, rateLimitRetry));

}

});

}

/*

* Client libraries contain setters for specifying region/edge.

* This allows support global and eu regions only. This set will likely expand in the future.

* Global should be the default

* Global region means the message should be sent through:

* HTTP: api.sendgrid.com

* EU region means the message should be sent through:

* HTTP: api.eu.sendgrid.com

*/

public void setDataResidency(String region){

if (allowedRegionsHostMap.containsKey(region)){

this.host = allowedRegionsHostMap.get(region);

}

else{

throw new IllegalArgumentException("region can only be \"eu\" or \"global\"");

}

}

}