Merged in feature/from-pantheon (pull request #16)

code from pantheon

* code from pantheon

wp/wp-content/plugins/wordpress-seo/src/actions/semrush/semrush-login-action.php

@@ -0,0 +1,60 @@
+<?php
+
+namespace Yoast\WP\SEO\Actions\SEMrush;
+
+use Yoast\WP\SEO\Config\SEMrush_Client;
+use Yoast\WP\SEO\Exceptions\OAuth\Authentication_Failed_Exception;
+
+/**
+ * Class SEMrush_Login_Action
+ */
+class SEMrush_Login_Action {
+
+	/**
+	 * The SEMrush_Client instance.
+	 *
+	 * @var SEMrush_Client
+	 */
+	protected $client;
+
+	/**
+	 * SEMrush_Login_Action constructor.
+	 *
+	 * @param SEMrush_Client $client The API client.
+	 */
+	public function __construct( SEMrush_Client $client ) {
+		$this->client = $client;
+	}
+
+	/**
+	 * Authenticates with SEMrush to request the necessary tokens.
+	 *
+	 * @param string $code The authentication code to use to request a token with.
+	 *
+	 * @return object The response object.
+	 */
+	public function authenticate( $code ) {
+		// Code has already been validated at this point. No need to do that again.
+		try {
+			$tokens = $this->client->request_tokens( $code );
+
+			return (object) [
+				'tokens' => $tokens->to_array(),
+				'status' => 200,
+			];
+		} catch ( Authentication_Failed_Exception $e ) {
+			return $e->get_response();
+		}
+	}
+
+	/**
+	 * Performs the login request, if necessary.
+	 */
+	public function login() {
+		if ( $this->client->has_valid_tokens() ) {
+			return;
+		}
+
+		// Prompt with login screen.
+	}
+}