Prompt Title: Mailchimp integration instructions.

To integrate the age-restricted vending machine Android application with Mailchimp using a custom template for transactional emails, follow these steps:

1. Obtain a Mailchimp API key: Log in to your Mailchimp account, navigate to Account -> Extras -> API Keys, and generate a new API key.

2. Create a custom email template in Mailchimp: Log in to your Mailchimp account, navigate to Campaigns -> Email Templates, and create a new template. Design the template as needed for the transactional receipt, and make sure to include placeholder tags (e.g., |RECEIPT_HTML|) that will be replaced with the receipt data when sending the email. Save the template and note down its ID.

3. Add required dependencies to the Android app: Add the following dependencies to the app's build.gradle (Module) file:

gradleCopy code
dependencies {
    implementation 'com.squareup.retrofit2:retrofit:2.9.0'
    implementation 'com.squareup.retrofit2:converter-gson:2.9.0'
}

4. Create a Mailchimp API interface:

Create an interface called MailchimpAPI in your app's source code. Define a method to send transactional emails using Mailchimp's Transactional Email API:

javaCopy code
import retrofit2.Call;
import retrofit2.http.Body;
import retrofit2.http.Header;
import retrofit2.http.POST;

public interface MailchimpAPI {
    @POST("send-template")
    Call<Void> sendEmailWithTemplate(
        @Header("Authorization") String apiKey,
        @Body MailchimpTemplateEmailRequest templateEmailRequest
    );
}

5. Create a model class for the API request:

Create a model class called MailchimpTemplateEmailRequest to hold the necessary data for sending transactional emails using a custom template:

javaCopy code
public class MailchimpTemplateEmailRequest {
    private String from_email;
    private String to_email;
    private String subject;
    private String template_name;
    private Map<String, String> global_merge_vars;

    // Add constructor, getters, and setters here
}

6. Create a Retrofit instance and implement the API call:

Create a MailchimpClient class to manage the Mailchimp API calls using Retrofit:

javaCopy code
import retrofit2.Retrofit;
import retrofit2.converter.gson.GsonConverterFactory;

public class MailchimpClient {
    private static final String BASE_URL = "https://mandrillapp.com/api/1.0/messages/";

    public static MailchimpAPI getClient() {
        Retrofit retrofit = new Retrofit.Builder()
                .baseUrl(BASE_URL)
                .addConverterFactory(GsonConverterFactory.create())
                .build();

        return retrofit.create(MailchimpAPI.class);
    }
}

7. Update the vending machine's code to send an email receipt using the custom template:

Once the customer has completed their purchase and the printed receipt data is available, create a new MailchimpTemplateEmailRequest object with the receipt data and call the sendEmailWithTemplate method:

javaCopy code
MailchimpAPI mailchimpAPI = MailchimpClient.getClient();
String apiKey = "YOUR_API_KEY_HERE";
String receiptHtml = "HTML version of the receipt data";
String templateId = "YOUR_TEMPLATE_ID_HERE";

MailchimpTemplateEmailRequest templateEmailRequest = new MailchimpTemplateEmailRequest();
templateEmailRequest.setFrom_email("[email protected]");
templateEmailRequest.setTo_email(customerEmailAddress);
templateEmailRequest.setSubject("Your Receipt from Age Restricted Vending Machine");
templateEmailRequest.setTemplate_name(templateId);

Map<String, String> global_merge_vars = new HashMap<>();
global_merge_vars.put("RECEIPT_HTML", receiptHtml);
templateEmailRequest.setGlobal_merge_vars(global_merge_vars);

mailchimpAPI.sendEmailWithTemplate