package com.xly.config;

import dev.langchain4j.data.message.ChatMessage;
import dev.langchain4j.data.message.ChatMessageDeserializer;
import dev.langchain4j.data.message.ChatMessageSerializer;
import dev.langchain4j.store.memory.chat.ChatMemoryStore;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import java.time.Duration;
import java.util.ArrayList;
import java.util.List;

/**
 * Redis 持久化的 ChatMemoryStore —— 会话记忆按 conversationId 存到 Redis，重启/换实例不丢，
 * 也让「重登录后接回上一次会话」成立（会话状态按稳定身份+conversationId 存，而非按 token）。
 *
 * <p>键：{@code chat:mem:{conversationId}}；值：LangChain4j 序列化后的消息 JSON。30 天 TTL。
 */
@Component
public class RedisChatMemoryStore implements ChatMemoryStore {

    private static final String PREFIX = "chat:mem:";
    private static final Duration TTL = Duration.ofDays(30);

    private final StringRedisTemplate redis;

    public RedisChatMemoryStore(StringRedisTemplate redis) {
        this.redis = redis;
    }

    @Override
    public List<ChatMessage> getMessages(Object memoryId) {
        String json = redis.opsForValue().get(PREFIX + memoryId);
        if (json == null || json.isBlank()) {
            return new ArrayList<>();
        }
        return ChatMessageDeserializer.messagesFromJson(json);
    }

    @Override
    public void updateMessages(Object memoryId, List<ChatMessage> messages) {
        redis.opsForValue().set(PREFIX + memoryId, ChatMessageSerializer.messagesToJson(messages), TTL);
    }

    @Override
    public void deleteMessages(Object memoryId) {
        redis.delete(PREFIX + memoryId);
    }
}