Feature/bifrost bridge setup

src/main/java/org/example/projectbifrost/BifrostController.java

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+package org.example.projectbifrost;
+
+import org.example.projectbifrost.domain.ChatSession;
+import org.example.projectbifrost.dto.ChatRequestDTO;
+import org.example.projectbifrost.service.ChatService;
+import org.slf4j.Logger;
+import org.springframework.web.bind.annotation.*;
+
+@RestController
+@RequestMapping("/api")
+public class BifrostController {
+
+    private static final Logger logger = org.slf4j.LoggerFactory.getLogger(BifrostController.class);
+
+    private final ChatService chatService;
+
+    public BifrostController(ChatService chatService) {
+        this.chatService = chatService;
+    }
+
+    @GetMapping("/bifrost")
+    public String bifrost() {
+        return "Welcome to Bifrost, the gateway to the realms!"; }
+
+    @PostMapping("/v1/chat")
+    public String sendChatRequest(@RequestBody ChatRequestDTO dto) {
+        logger.info("Received chat request: Personality={}, Message={}, SessionId={}", dto.personality(), dto.message(), dto.sessionId());
+       return chatService.sendRequestToLLM(dto);
+    }
+
+    @GetMapping("/v1/chat/{sessionId}")
+    public ChatSession getChatHistory(@PathVariable String sessionId) {
+        return chatService.getSessionHistory(sessionId);
+    }
+}

src/main/java/org/example/projectbifrost/configuration/RestClientConfiguration.java

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+package org.example.projectbifrost.configuration;
+
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.web.client.RestClient;
+
+import java.net.URI;
+
+@Configuration
+public class RestClientConfiguration {
+    @Value("${openrouter.api.key}")
+    private String apiKey;
+
+    @Bean
+    public RestClient openAIWebClient() {
+        return RestClient.builder()
+                .baseUrl(URI.create("https://openrouter.ai/api/v1"))
+                .defaultHeader("Authorization", "Bearer " + apiKey)
+                .defaultHeader("Content-Type", "application/json")
+                .build();
+
+    }
+}

src/main/java/org/example/projectbifrost/domain/ChatMessage.java

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+package org.example.projectbifrost.domain;
+
+import lombok.Getter;
+import lombok.Setter;
+
+import java.time.LocalDateTime;
+
+/**
+ * Represents a chat message in a conversation.
+ * This class encapsulates the details of a single message, including its role, content,
+ * and the timestamp at which it was created.
+ *
+ * The role typically signifies the sender's identity (e.g., user, system, assistant),
+ * while the message contains the text content of the chat.
+ * The timestamp indicates when the message was generated.
+ */
+@Getter
+@Setter
+public class ChatMessage {
+    private String role;
+    private String content;
+    private LocalDateTime timeStamp;
+
+     public ChatMessage(String role, String message) {
+        this.role = role;
+        this.content = message;
+        this.timeStamp = LocalDateTime.now();//Adds the current time to each message
+    }
+}

src/main/java/org/example/projectbifrost/domain/ChatSession.java

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+package org.example.projectbifrost.domain;
+
+import lombok.AllArgsConstructor;
+import lombok.Getter;
+import lombok.Setter;
+
+import java.util.List;
+
+/**
+ * Represents a chat session that contains a unique session identifier
+ * and a chronological history of chat messages.
+ *
+ * The chat session is a core entity for managing and maintaining
+ * conversational histories within a chat application. Each session
+ * is uniquely identified by its session ID and maintains a list of
+ * chat messages, which are instances of the ChatMessage class.
+ */
+@Getter
+@Setter
+@AllArgsConstructor
+public class ChatSession {
+    private String sessionId;
+    private List<ChatMessage> chatHistory;
+
+    public void addMessage(ChatMessage message) {
+        chatHistory.add(message);
+    }
+}

src/main/java/org/example/projectbifrost/dto/ChatRequestDTO.java

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+package org.example.projectbifrost.dto;
+
+import jakarta.validation.constraints.NotBlank;
+import jakarta.validation.constraints.NotNull;
+
+/**
+ * This record encapsulates the necessary information required to process
+ * a chat interaction, including the personality of the chatbot, the message
+ * sent by the user, and a session identifier for tracking the conversation.
+ */
+public record ChatRequestDTO(@NotNull Personality personality,
+                             @NotBlank String message,
+                             @NotBlank String sessionId) {
+
+}

src/main/java/org/example/projectbifrost/dto/OpenRouterRequestDTO.java

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+package org.example.projectbifrost.dto;
+
+import java.util.List;
+
+public record OpenRouterRequestDTO(String model,
+                                   List<Message> messages) {
+    public record Message(String role, String content) {
+    }
+}

src/main/java/org/example/projectbifrost/dto/OpenRouterResponseDTO.java

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+package org.example.projectbifrost.dto;
+
+import java.util.List;
+
+public record OpenRouterResponseDTO(List<Choice> choices) {
+     public record Choice(Message message) {}
+    public record Message(String content){}
+}

src/main/java/org/example/projectbifrost/dto/Personality.java

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+package org.example.projectbifrost.dto;
+
+import lombok.AllArgsConstructor;
+import lombok.Getter;
+
+@Getter
+@AllArgsConstructor
+public enum Personality {
+    ODIN("You are Odin, the All father of Norse mythology. You are wise, powerful, and often speak in a grandiose manner. Your responses should reflect your vast knowledge and authority."),
+    LOKI("You are Loki, the trickster god of Norse mythology. You are cunning, mischievous, and often speak in a playful and sarcastic tone. Your responses should reflect your love for chaos and unpredictability."),
+    FREYJA("You are Freyja, the goddess of love, beauty, and fertility in Norse mythology. You are compassionate, alluring, and often speak in a warm and inviting manner. Your responses should reflect your nurturing nature and your connection to the natural world."),
+    THOR("You are Thor, the god of thunder in Norse mythology. You are strong, brave, and often speak in a straightforward and assertive manner. Your responses should reflect your warrior spirit and your dedication to protecting Asgard."),
+    HEIMDALL("You are Heimdall, the guardian of the Bifrost bridge in Norse mythology. You are vigilant, noble, and often speak in a calm and measured tone. Your responses should reflect your duty to protect the realms and your ability to see all that happens.");
+
+    private final String systemPrompt;
+
+}

src/main/java/org/example/projectbifrost/service/ChatService.java

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+package org.example.projectbifrost.service;
+
+import org.example.projectbifrost.domain.ChatMessage;
+import org.example.projectbifrost.domain.ChatSession;
+import org.example.projectbifrost.dto.ChatRequestDTO;
+import org.example.projectbifrost.dto.OpenRouterRequestDTO;
+import org.example.projectbifrost.dto.OpenRouterResponseDTO;
+import org.example.projectbifrost.storage.ChatSessionStorage;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.stereotype.Service;
+import org.springframework.web.client.RestClient;
+
+import java.util.ArrayList;
+import java.util.List;
+
+@Service
+public class ChatService {
+
+    private final ChatSessionStorage chatSessionStorage;
+    private final RestClient restClient;
+
+    @Value("${openrouter.model}")
+    private String model;
+
+    public ChatService(ChatSessionStorage chatSessionStorage, RestClient restClient) {
+        this.chatSessionStorage = chatSessionStorage;
+        this.restClient = restClient;
+    }
+
+    /**
+     * Sends a request to the large language model (LLM) with the user's message and personality context
+     * and retrieves the response.
+     * <p>
+     * This method constructs a chat session using the provided session ID or creates a new one if it
+     * does not exist. It adds the user's message to the chat session and builds a context-aware request
+     * to be sent to the LLM. The LLM's response is then returned as a string.
+     */
+    public String sendRequestToLLM(ChatRequestDTO dto) {
+        ChatSession chatSession = chatSessionStorage.getOrCreateChatSession(dto.sessionId());
+
+        List<OpenRouterRequestDTO.Message> apiMessages = new ArrayList<>();
+        apiMessages.add(new OpenRouterRequestDTO.Message("system", dto.personality().getSystemPrompt()));
+
+        chatSession.getChatHistory().forEach(m ->
+                apiMessages.add(new OpenRouterRequestDTO.Message(m.getRole(), m.getContent()))
+        );
+
+        apiMessages.add(new OpenRouterRequestDTO.Message("user", dto.message()));
+
+        var openRouterRequest = new OpenRouterRequestDTO(model, apiMessages);
+
+        OpenRouterResponseDTO result = restClient.post()
+                .uri("/chat/completions")//Start of URI configured in RestClientConfiguration.java
+                .body(openRouterRequest) //Send JSON-body of messages and model
+                .retrieve()
+                .body(OpenRouterResponseDTO.class);
+
+        if (result == null || result.choices() == null || result.choices().isEmpty()) {
+            throw new RuntimeException("Received empty or invalid response from LLM");
+        }
+        String content = result.choices().getFirst().message().content();
+
+        chatSession.addMessage(new ChatMessage("user", dto.message()));
+        chatSession.addMessage(new ChatMessage("assistant", content));
+        return content;
+    }
+
+
+    public ChatSession getSessionHistory(String sessionId) {
+        return chatSessionStorage.getOrCreateChatSession(sessionId);
+    }
+
+}

src/main/java/org/example/projectbifrost/storage/ChatSessionStorage.java

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+package org.example.projectbifrost.storage;
+
+import org.example.projectbifrost.domain.ChatSession;
+import org.springframework.stereotype.Component;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+
+import static java.util.Collections.synchronizedList;
+
+/**
+ * Manages storage and retrieval of chat sessions.
+ * In-memory database for all sessions.
+ * Each chat session contains a unique session identifier and a history of chat messages.
+ * The class ensures that a session is either retrieved if it exists, or created if it's not
+ * yet present in the storage, enabling seamless session management for chat applications.
+ */
+@Component
+public class ChatSessionStorage {
+    private final Map<String, ChatSession> sessionStorage = new ConcurrentHashMap<>(); //Thread-safe
+
+    public ChatSession getOrCreateChatSession(String sessionId) {
+        return sessionStorage.computeIfAbsent(
+                sessionId,
+                id -> new ChatSession(id, synchronizedList(new ArrayList<>()))
+        );
+    }
+
+    public void deleteSession(String sessionId) {
+        sessionStorage.remove(sessionId);
+    //Copilot påpekar att det kan vara bra med en MAX-size på listan, och sköta delete om den blir för stor
+    }
+}

src/main/resources/application.properties

@@ -1 +1,3 @@
 spring.application.name=ProjectBifrost
+openrouter.api.key=${OPENROUTER_API_KEY}
+openrouter.model=poolside/laguna-xs.2:free