Add class NodaMailChecker for checking mail address validity and caching that

src/NodaMailChecker.php

@@ -0,0 +1,110 @@
+<?PHP
+/**
+ * Contains a class for checking the validity of mail addresses and their
+ * hostnames, cached through the central noda DB.
+ *
+ * @author Joshua Ramon Enslin <joshua@museum-digital.de>
+ */
+declare(strict_types = 1);
+
+/**
+ * Contains static functions for checking the validity of mail addresses.
+ */
+final class NodaMailChecker {
+    /**
+     * Splits a mail address and returns the hostname.
+     *
+     * @param string $mail_address Mail address.
+     *
+     * @return string
+     */
+    public static function getDomainFromMailAddress(string $mail_address):string {
+
+        $mail_address = MD_STD_IN::sanitize_email($mail_address);
+
+        $addressParts = explode('@', $mail_address);
+        if (empty($addressParts[1])) {
+            throw new MDInvalidEmail("Failed to get mail domain");
+        }
+        $domain = $addressParts[1];
+
+        if (str_contains($domain, '.') === false) {
+            throw new MDInvalidEmail("Failed to find a dot in the mail domain");
+        }
+
+        return $domain;
+
+    }
+
+    /**
+     * Checks if a mail hostname is accessible.
+     *
+     * @param string $mail_domain Hostname of the mail address.
+     *
+     * @return string
+     */
+    public static function validateMailDomainAccessibility(string $mail_domain):string {
+
+        $mxRecords = [];
+        getmxrr($mail_domain, $mxRecords);
+        $mxRecords = array_diff($mxRecords, ['0.0.0.0', '', null]);
+
+        if (empty($mxRecords)) return "";
+
+        return MD_STD_IN::sanitize_text(implode(',', $mxRecords));
+
+    }
+
+    /**
+     * Checks if a mail hostname is accessible.
+     *
+     * @param MDMysqli $mysqli      DB connection.
+     * @param string   $mail_domain Hostname of the mail address.
+     *
+     * @return boolean
+     */
+    public static function validateMailDomainAccessibilityCached(MDMysqli $mysqli, string $mail_domain):bool {
+
+        $result = $mysqli->query_by_stmt("SELECT `valid`, `hostname`
+            FROM `" . DATABASENAME_NODA . "`.`misc_mail_hostname_validity`
+            WHERE `hostname` = ?", "s", $mail_domain);
+
+        if ($cur = $result->fetch_row()) {
+            $result->close();
+            return (bool)$cur[0];
+        }
+        $result->close();
+
+        $target_hostnames = self::validateMailDomainAccessibility($mail_domain);
+        $validity = !empty($target_hostnames);
+
+        $insertStmt = $mysqli->do_prepare("INSERT
+            INTO `" . DATABASENAME_NODA . "`.`misc_mail_hostname_validity`
+            (`hostname`, `valid`, `resolved_hostnames`)
+            VALUES
+            (?, ?, ?)");
+
+        $insertStmt->bind_param("sis", $mail_domain, $validity, $target_hostnames);
+        $insertStmt->execute();
+
+        $insertStmt->close();
+
+        return $validity;
+
+    }
+
+    /**
+     * Checks a mail address for the validity of its hostname.
+     *
+     * @param MDMysqli $mysqli       DB connection.
+     * @param string   $mail_address Hostname of the mail address.
+     *
+     * @return boolean
+     */
+    public static function validateMailByDomainAccessibilityCached(MDMysqli $mysqli, string $mail_address):bool {
+
+        $domain = self::getDomainFromMailAddress($mail_address);
+        return self::validateMailDomainAccessibilityCached($mysqli, $domain);
+
+    }
+}