package com.knowledge.base.infrastructure.cache;

import lombok.RequiredArgsConstructor;
import lombok.extern.slf4j.Slf4j;
import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;

import java.util.HashSet;
import java.util.Optional;
import java.util.Set;
import java.util.concurrent.TimeUnit;

/**
 * 使用 Redis 实现的文件缓存服务
 *
 * @author Luke.ye
 * @date 2025/6/7
 */
@Slf4j
@Service
@RequiredArgsConstructor
@ConditionalOnProperty(prefix = "knowledge.base.redis", name = "enable", havingValue = "true", matchIfMissing = true)
public class RedisFileCacheService implements FileCacheService {

    private final StringRedisTemplate redisTemplate;

    private static final String FILE_CACHE_PREFIX = "kb-file";

    private String key(String prefix, String key) {
        return String.format(FILE_CACHE_PREFIX + ":%s:%s", prefix, key);
    }

    @Override
    public Optional<String> getPath(String filename) {
        String value = redisTemplate.opsForValue().get(key("path", filename));
        return Optional.ofNullable(value);
    }

    @Override
    public void cachePath(String filename, String relativePath, long expireMinutes) {
        redisTemplate.opsForValue().set(key("path", filename), relativePath, expireMinutes, TimeUnit.MINUTES);
    }

    @Override
    public void cacheMeta(String filename, String jsonMeta, long expireMinutes) {
        redisTemplate.opsForValue().set(key("meta", filename), jsonMeta, expireMinutes, TimeUnit.MINUTES);
    }

    @Override
    public Optional<String> getMeta(String filename) {
        String value = redisTemplate.opsForValue().get(key("meta", filename));
        return Optional.ofNullable(value);
    }

    @Override
    public Optional<Long> getMTime(String relativePath) {
        String val = redisTemplate.opsForValue().get(key("mtime", relativePath));
        try {
            return val != null ? Optional.of(Long.parseLong(val)) : Optional.empty();
        } catch (NumberFormatException e) {
            log.warn("mtime 解析失败: {}", val, e);
            return Optional.empty();
        }
    }

    @Override
    public void cacheMTime(String relativePath, Long mtime, long expireMinutes) {
        redisTemplate.opsForValue().set(key("mtime", relativePath), String.valueOf(mtime), expireMinutes, TimeUnit.MINUTES);
    }

    @Override
    public void clearPath(String filename) {
        redisTemplate.delete(key("path", filename));
    }

    @Override
    public void clearMTime(String relativePath) {
        redisTemplate.delete(key("mtime", relativePath));
    }

    @Override
    public void clearAll() {
        log.warn("正在清空 Redis 文件缓存，前缀: {}", FILE_CACHE_PREFIX);
        Set<String> keysToDelete = scanKeys(FILE_CACHE_PREFIX + "*");
        if (keysToDelete.isEmpty()) {
            log.info("没有需要清理的文件缓存 Key。");
            return;
        }
        redisTemplate.delete(keysToDelete);
        log.info("已清空 Redis 文件缓存 Key 数量: {}", keysToDelete.size());
    }

    /**
     * 用 scan 命令遍历所有带 prefix 的 key（推荐，不会阻塞大 Redis）
     */
    private Set<String> scanKeys(String pattern) {
        Set<String> keySet = new HashSet<>();
        // 采用 scan，分批遍历，安全高效
        redisTemplate.execute((connection) -> {
            try (var cursor = connection.scan(org.springframework.data.redis.core.ScanOptions.scanOptions()
                    .match(pattern)
                    .count(1000)
                    .build())) {
                cursor.forEachRemaining(item -> keySet.add(new String(item)));
            }
            return null;
        }, false, false);
        return keySet;
    }

}