<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
   </dependency>
 
   <dependency>
    <groupId>org.springframework.experimental.ai</groupId>
    <artifactId>spring-ai-openai-spring-boot-starter</artifactId>
    <version>0.7.1-SNAPSHOT</version>
   </dependency>
 
   <dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <optional>true</optional>
   </dependency>

<repository>
   <id>spring-milestones</id>
   <name>Spring Milestones</name>
   <url>https://repo.spring.io/milestone</url>
   <snapshots>
    <enabled>false</enabled>
   </snapshots>
  </repository>
  <repository>
   <id>spring-snapshots</id>
   <name>Spring Snapshots</name>
   <url>https://repo.spring.io/snapshot</url>
   <releases>
    <enabled>false</enabled>
   </releases>
  </repository>

spring:
  ai:
    openai.api-key: YOUR_KEY

@RestController
@RequiredArgsConstructor
public class PromptController {

    private final PromptService promptService;

    @PostMapping("/starter")
    public ResponseEntity<String> generateSentenceStarter(@RequestBody Map<String, String> params) {
        String language = params.get("language");
        String topic = params.get("topic");
        return ResponseEntity.ok(promptService.generateSentences(language, topic));
    }
}

@Service
@RequiredArgsConstructor
public class PromptService {

    private final AiClient aiClient;

    public String generateSentences(String language, String topic) {
        String userText = """
                 Start a sentence in {language} about this topic {topic} and ask the student to think about continuing the story to practice grammar and new words. 
                 If the sentence is in Japanese,
                 always write back in Hiragana and provide the Romaji equivalent in brackets.
                 Also, translate it into English.
                 """;
        PromptTemplate userPromptTemplate = new PromptTemplate(userText);
        Message userMessage = userPromptTemplate.createMessage(Map.of("language", language, "topic", topic));

        String systemText = """
                You are a helpful AI assistant that helps students in practicing foreign languages. Respond in the style of an encouraging teacher.
                """;
        SystemPromptTemplate systemPromptTemplate = new SystemPromptTemplate(systemText);

        Message systemMessage = systemPromptTemplate.createMessage();
        
        Prompt prompt = new Prompt(List.of(userMessage, systemMessage));
        return aiClient.generate(prompt).getGeneration().getText();
    }
}

curl -X POST -H "Content-Type: application/json" -d '{"language": "japanese", "topic": "clothes"}' http://localhost:8080/starter

あなたは明日友達とショッピングに行く予定です。何を著て行く予定ですか？
(Anata wa ashita tomodachi to shoppingu ni iku yotei desu. Nani o kite iku yotei desu ka?)
Translation: You are planning to go shopping with your friend tomorrow. What are you planning to wear?

public String provideFeedback(String userText) {
        Message userMessage = new UserMessage("Is this sentence correct: " + userText);

        String instructions = """
                You are a helpful AI assistant that helps students in practicing foreign languages.
                You should provide feedback to the students to correct the grammar and make the sentence in the foreign language sound native.
                Check and correct the user text {text}. Tell the student if the sentence is correct. If the sentence is in Japanese,
                always write back in Hiragana and provide the Romaji equivalent in brackets.
                """;
        AssistantPromptTemplate assistantPromptTemplate = new AssistantPromptTemplate(instructions);
        Message assistantPromptTemplateMessage = assistantPromptTemplate.createMessage(Map.of("text", userText));

        Prompt prompt = new Prompt(List.of(userMessage, assistantPromptTemplateMessage));
        return aiClient.generate(prompt).getGeneration().getText();
    }

@PostMapping("/feedback")
        public ResponseEntity<String> provideFeedback(@RequestBody Map<String, String> params) {
            String text = params.get("text");
            return ResponseEntity.ok(promptService.provideFeedback(text));
        }

curl -X POST -H "Content-Type: application/json" -d '{"text": "Kirei dzubon o kaimashita. Murasakiiro no sukaato mo kaimashita. Kono sukaato wa kirei da ga takai desu."}' http://localhost:8080/feedback

The sentence you provided is mostly correct. Here is the corrected version:

きれいなズボンを買いました。紫色のスカートも買いました。このスカートはきれいだが高いです。
(Kirei na zubon o kaimashita. Murasakiiro no sukāto mo kaimashita. Kono sukāto wa kirei da ga takai desu.)

Translation: I bought a nice pair of pants. I also bought a purple skirt. This skirt is beautiful, but expensive.

Well done! Your sentence is grammatically correct and the vocabulary usage is appropriate. Keep up the good work!