package example;

import freemarker.template.Template;
import freemarker.template.TemplateException;
import org.junit.jupiter.api.Test;

import java.io.IOException;
import java.io.Reader;
import java.io.StringReader;
import java.io.StringWriter;
import java.util.HashMap;
import java.util.Map;
import java.util.Optional;

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertTrue;

public class FreemarkerTest {

  public static final String TEMPLATE_NAME = "HELLO_WORLD";

  public Optional<String> hello(String name) {

    if (name == null) {
      return Optional.empty();
    }

    String templateStr = "Hello, ${name}";
    Reader reader = new StringReader(templateStr);
    StringWriter writer = new StringWriter();
    Template template;
    try {
      template = new Template(TEMPLATE_NAME, reader);
    } catch (IOException e) {
      return Optional.empty();
    }
    Map<String, Object> model = new HashMap<>();
    model.put("name", name);
    try {
      template.process(model, writer);
    } catch (TemplateException e) {
      System.err.println(e.getMessage());
      return Optional.empty();
    } catch (IOException e) {
      System.err.println(e.getMessage());
      return Optional.empty();
    }
    return Optional.ofNullable(writer.toString());
  }

  @Test
  void processTemplateTest() {
    assertTrue(hello(null).isEmpty());
    assertTrue(hello("Fabian").isPresent());
    assertEquals("Hello, World", hello("World").get());
  }
}