package database

import (
    "context"
    "crypto/sha256"
    "encoding/json"
    "fmt"
    "time"

    "github.com/redis/go-redis/v9"
)

const (
    BlacklistKeyPrefix = "blacklist:token:"
)

// RedisClient Redis 客户端单例
var RedisClient *redis.Client

// Config Redis 配置
type RedisConfig struct {
    Host     string
    Port     int
    Password string
    DB       int
}

// InitRedis 初始化 Redis 连接
func InitRedis(cfg RedisConfig) error {
    RedisClient = redis.NewClient(&redis.Options{
        Addr:     fmt.Sprintf("%s:%d", cfg.Host, cfg.Port),
        Password: cfg.Password,
        DB:       cfg.DB,
    })

    ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
    defer cancel()

    if err := RedisClient.Ping(ctx).Err(); err != nil {
        return fmt.Errorf("failed to connect to redis: %w", err)
    }

    return nil
}

// CloseRedis 关闭 Redis 连接
func CloseRedis() error {
    if RedisClient != nil {
        return RedisClient.Close()
    }
    return nil
}

// GetRedis 获取 Redis 客户端实例
func GetRedis() *redis.Client {
    return RedisClient
}

// RedisHealthCheck 健康检查
func RedisHealthCheck() error {
    if RedisClient == nil {
        return fmt.Errorf("redis client is not initialized")
    }
    ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
    defer cancel()
    return RedisClient.Ping(ctx).Err()
}

// BlacklistEntry 黑名单条目
type BlacklistEntry struct {
    UserID int64  `json:"user_id"`
    Reason string `json:"reason"`
}

// tokenToHash 将 Token 转换为 SHA256 哈希作为 Key
func tokenToHash(token string) string {
    hash := sha256.Sum256([]byte(token))
    return fmt.Sprintf("%x", hash)
}

// AddToBlacklist 添加 Token 到黑名单
func AddToBlacklist(ctx context.Context, token string, userID int64, banReason string, ttl time.Duration) error {
    if token == "" {
        return fmt.Errorf("token is empty")
    }
    if RedisClient == nil {
        return fmt.Errorf("redis client is not initialized")
    }

    key := BlacklistKeyPrefix + tokenToHash(token)
    entry := BlacklistEntry{UserID: userID, Reason: banReason}
    value, err := json.Marshal(entry)
    if err != nil {
        return fmt.Errorf("failed to marshal blacklist entry: %w", err)
    }

    return RedisClient.Set(ctx, key, value, ttl).Err()
}

// IsBlacklisted 检查 Token 是否在黑名单
func IsBlacklisted(ctx context.Context, token string) (bool, int64, string, error) {
    if token == "" {
        return false, 0, "", nil
    }
    if RedisClient == nil {
        return false, 0, "", fmt.Errorf("redis client is not initialized")
    }

    key := BlacklistKeyPrefix + tokenToHash(token)
    value, err := RedisClient.Get(ctx, key).Result()
    if err == redis.Nil {
        return false, 0, "", nil
    }
    if err != nil {
        return false, 0, "", err
    }

    var entry BlacklistEntry
    if err := json.Unmarshal([]byte(value), &entry); err != nil {
        return false, 0, "", fmt.Errorf("failed to unmarshal blacklist entry: %w", err)
    }

    return true, entry.UserID, entry.Reason, nil
}

// RemoveFromBlacklist 从黑名单移除 Token（用于解封）
func RemoveFromBlacklist(ctx context.Context, token string) error {
    if token == "" {
        return nil
    }
    if RedisClient == nil {
        return fmt.Errorf("redis client is not initialized")
    }

    key := BlacklistKeyPrefix + tokenToHash(token)
    return RedisClient.Del(ctx, key).Err()
}