Email — Verification

Overview

This skill adds email address verification via a click-to-verify link. The MixinEmailVerification handles the verification callback; verifiedEmails tracks verified addresses.

Backend

This component is for sending an email to users with a verification link which the user can click to prove they own the email address.

To check if an email address has been verified

Use the prefabricated module mo:caffeineai-email-verification/verifiedEmails.mo which cannot be modified.

module {
  public type State = {
    var verifiedEmails : Set.Set<Text>;
  };

  public func new() : State {
    {
      var verifiedEmails = Set.empty<Text>();
    };
  };

  public func contains(state : State, email : Text) : Bool;

  public func iter(state : State) : Iter.Iter<Text>;

  public func size(state : State) : Nat;
};

To check whether an email is verified use the contains function. Do NOT try to track the email verification status independently by storing it against the user profile.

To handle the verification link

Use the prefabricated module mo:caffeineai-email-verification/verificationMixin.mo which cannot be modified.

The MixinEmailVerification handles calls to the verification link to verify an email address.

import MixinEmailVerification "mo:caffeineai-email-verification/verificationMixin";

For sending users a verification email

• This extension depends on the extension-email for sending emails.
• Use the sendVerificationEmail function.
• It returns a SendResult which is #ok if the email is sent successfully otherwise #err(error) with the error text.
• Each recipient receives an individual email with a specific verification link for them
• The htmlBody MUST contain the placeholder text {{VERIFICATION_URL}}

module {
  public type SendResult = {
    #ok;
    #err : Text;
  };

  public func sendVerificationEmail(
    fromUsername : Text,
    recipients : [Text],
    subject : Text,
    htmlBody : Text,
  ) : async SendResult;
};

Example usage with endpoints for registering a user and for checking whether a user is verified.

import Map "mo:core/Map";
import Runtime "mo:core/Runtime";
import Principal "mo:core/Principal";
import Text "mo:core/Text";
import EmailClient "mo:caffeineai-email/emailClient";
import MixinEmailVerification "mo:caffeineai-email-verification/verificationMixin";
import VerifiedEmails "mo:caffeineai-email-verification/verifiedEmails";

actor {
  // Stores which emails are verified
  let verifiedEmails = VerifiedEmails.new();

  // User profiles storage
  let users = Map.empty<Principal, User>();

  // Email to principal mapping for uniqueness check
  let emailToPrincipal = Map.empty<Text, Principal>();

  // Handles the verification link and updates the verifiedEmails store
  include MixinEmailVerification(verifiedEmails);

  type User = {
    name : Text;
    email : Text;
  };

  public shared ({ caller }) func registerUser(email : Text, name : Text) : async () {
    if (users.containsKey(caller)) {
      Runtime.trap("User already registered");
    };
    if (emailToPrincipal.containsKey(email)) {
      Runtime.trap("Email already registered");
    };

    let user : User = {
      name;
      email;
    };
    users.add(caller, user);
    emailToPrincipal.add(email, caller);
    let result = await EmailClient.sendVerificationEmail(
      "no-reply",
      [email],
      "Welcome to Our Service",
      "Hello " # name # ",<br><br>Thank you for registering with our service. Please <a href=\"{{VERIFICATION_URL}}\">click here</a> to verify your email address<br><br>Best regards,<br>The Team",
    );

    switch (result) {
      case (#ok) {};
      case (#err(error)) {
        Runtime.trap("Couldn't send verification email: " # error);
      };
    };
  };

  public shared ({ caller }) func isEmailVerified() : async Bool {
    switch (users.get(caller)) {
      case (null) {
        Runtime.trap("User not registered");
      };
      case (?user) {
        VerifiedEmails.contains(verifiedEmails, user.email);
      };
    };
  };
};

Frontend

If there is a UI for the admin to enter the content of a verification email then indicate that the placeholder text {{VERIFICATION_URL}} must be present in the email body.