From 78ee5fb270505a07be586f7e6f9aef9405bc672f Mon Sep 17 00:00:00 2001
From: Alen Alex <71920951+AlenGeoAlex@users.noreply.github.com>
Date: Tue, 18 Apr 2023 20:24:46 +0530
Subject: [PATCH] Added MailChecker.java

---
 .../java/io/github/fgribreau/MailChecker.java | 104 ++++++++++++++++++
 1 file changed, 104 insertions(+)
 create mode 100644 platform/java/src/main/java/io/github/fgribreau/MailChecker.java

diff --git a/platform/java/src/main/java/io/github/fgribreau/MailChecker.java b/platform/java/src/main/java/io/github/fgribreau/MailChecker.java
new file mode 100644
index 00000000..f0f814bf
--- /dev/null
+++ b/platform/java/src/main/java/io/github/fgribreau/MailChecker.java
@@ -0,0 +1,104 @@
+package io.github.fgribreau;
+
+import java.util.*;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+/**
+ * Cross-language temporary (disposable/throwaway) email detection library. Covers 55 734+ fake email providers.
+ * Written in Java 8
+ */
+public final class MailChecker {
+
+  /**
+   * A class to hold of constants which will be parsed through the generator.js
+   */
+  private static final class MailCheckerConstants {
+    /**
+     * Contains all the blacklisted domains present in the database at https://github.com/FGRibreau/mailchecker/blob/master/list.txt
+     */
+    static final HashSet<String> BLACKLISTED = new HashSet<>(Arrays.asList({{& listSTR }}));
+    //static final HashSet<String> BLACKLISTED_SET = new HashSet<>(Arrays.asList("test.com", "test2.com"));
+
+    /**
+     * Provides a regex-pattern for matching whether the provided email is a valid email.
+     * For more: See https://fightingforalostcause.net/content/misc/2006/compare-email-regex.php
+     */
+    static final String VALIDATION_REGEX = "/^{{& unanchoredRegexpString }}$/";
+    //static final String VALIDATION_REGEX = "/^(?!(?:(?:\\x22?\\x5C[\\x00-\\x7E]\\x22?)|(?:\\x22?[^\\x5C\\x22]\\x22?)){255,})(?!(?:(?:\\x22?\\x5C[\\x00-\\x7E]\\x22?)|(?:\\x22?[^\\x5C\\x22]\\x22?)){65,}@)(?:(?:[\\x21\\x23-\\x27\\x2A\\x2B\\x2D\\x2F-\\x39\\x3D\\x3F\\x5E-\\x7E]+)|(?:\\x22(?:[\\x01-\\x08\\x0B\\x0C\\x0E-\\x1F\\x21\\x23-\\x5B\\x5D-\\x7F]|(?:\\x5C[\\x00-\\x7F]))*\\x22))(?:\\.(?:(?:[\\x21\\x23-\\x27\\x2A\\x2B\\x2D\\x2F-\\x39\\x3D\\x3F\\x5E-\\x7E]+)|(?:\\x22(?:[\\x01-\\x08\\x0B\\x0C\\x0E-\\x1F\\x21\\x23-\\x5B\\x5D-\\x7F]|(?:\\x5C[\\x00-\\x7F]))*\\x22)))*@(?:(?:(?!.*[^.]{64,})(?:(?:(?:xn--)?[a-z0-9]+(?:-[a-z0-9]+)*\\.){1,126}){1,}(?:(?:[a-z][a-z0-9]*)|(?:(?:xn--)[a-z0-9]+))(?:-[a-z0-9]+)*)|(?:\\[(?:(?:IPv6:(?:(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){7})|(?:(?!(?:.*[a-f0-9][:\\]]){7,})(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){0,5})?::(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){0,5})?)))|(?:(?:IPv6:(?:(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){5}:)|(?:(?!(?:.*[a-f0-9]:){5,})(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){0,3})?::(?:[a-f0-9]{1,4}(?::[a-f0-9]{1,4}){0,3}:)?)))?(?:(?:25[0-5])|(?:2[0-4][0-9])|(?:1[0-9]{2})|(?:[1-9]?[0-9]))(?:\\.(?:(?:25[0-5])|(?:2[0-4][0-9])|(?:1[0-9]{2})|(?:[1-9]?[0-9]))){3}))\\]))$/";
+  }
+
+  /**
+   * Regex Pattern Matcher
+   */
+  private static final Pattern VALIDATOR_PATTERN;
+
+  /**
+   * Static initializer to initialize {@link MailChecker#VALIDATOR_PATTERN}
+   */
+  static {
+    VALIDATOR_PATTERN = Pattern.compile(MailCheckerConstants.VALIDATION_REGEX);
+  }
+
+  /**
+   * Checks whether a provided email is valid or not?
+   * This will also return false, if the passed string is null or empty
+   * @param emailAddress An email address
+   * @return true is the specified email is valid, false otherwise
+   */
+  public static boolean isValidEmail(final String emailAddress){
+    if(emailAddress == null || emailAddress.isEmpty())
+      return false;
+
+    final String emailAddressLowerCase = emailAddress.toLowerCase();
+
+    final Matcher matcher = VALIDATOR_PATTERN.matcher(emailAddress);
+    if(!matcher.matches())
+      return false;
+
+    for (String eachSuffix : getAllDomainSuffix(emailAddress)) {
+      if(MailCheckerConstants.BLACKLISTED_SET.contains(eachSuffix))
+        return true;
+    }
+
+    return false;
+  }
+
+  /**
+   * Get all the blacklisted domain providers.
+   * This will only provide domains which are present at the moment, if new domains are added via {@link MailChecker#addCustomDomains(String...)} or {@link MailChecker#addCustomDomains(Collection)}
+   * one should get a new copy by calling it over again.
+   * @return A copy of all the blacklisted domains
+   */
+  public static Collection<String> blacklist(){
+    return new HashSet<>(MailCheckerConstants.BLACKLISTED_SET);
+  }
+
+  /**
+   * Add a domain to the blacklisted list temporarily
+   * @param domains Domains to be added
+   */
+  public static void addCustomDomains(String... domains){
+    addCustomDomains(Arrays.asList(domains));
+  }
+
+  /**
+   * Add a domain to the blacklisted list temporarily
+   * @param domains Domains to be added
+   */
+  public static void addCustomDomains(Collection<String> domains){
+    MailCheckerConstants.BLACKLISTED_SET.addAll(domains);
+  }
+
+  private static List<String> getAllDomainSuffix(String emailAddress) {
+    String[] components = emailAddress.split("@")[1].split("\\.");
+    List<String> domainSuffixes = new ArrayList<>();
+    for (int n = 0; n < components.length; n++) {
+      String domainSuffix = String.join(".", Arrays.copyOfRange(components, n, components.length));
+      domainSuffixes.add(domainSuffix);
+    }
+    return domainSuffixes;
+  }
+
+
+}