package db

import (
	"context"
	"log"
	"strings"
	"time"

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

// RedisWrapper wraps go-redis client to implement RedisClient interface.
type RedisWrapper struct {
	client *redis.Client
}

// NewRedisWrapper creates a RedisWrapper from a go-redis client.
func NewRedisWrapper(client *redis.Client) *RedisWrapper {
	return &RedisWrapper{client: client}
}

// InitRedis initializes Redis for presence, rate limiting, and pub/sub (ADR-007).
// Returns nil if Redis is unavailable (non-fatal).
func InitRedis(redisAddress string) *RedisWrapper {
	var options *redis.Options
	var err error

	if strings.Contains(redisAddress, "://") {
		options, err = redis.ParseURL(redisAddress)
		if err != nil {
			log.Printf("Redis configuration warning: %v (rate limiting and presence will be disabled)", err)
			return nil
		}
	} else {
		options = &redis.Options{Addr: redisAddress}
	}

	client := redis.NewClient(options)
	if err := client.Ping(context.Background()).Err(); err != nil {
		log.Printf("Redis connection warning: %v (rate limiting and presence will be disabled)", err)
		client.Close()
		// Start auto-reconnect goroutine
		go redisReconnectLoop(redisAddress, options)
		return nil
	}

	log.Println("Redis connected successfully (presence, rate limiting, pub/sub enabled)")
	return &RedisWrapper{client: client}
}

// redisReconnectLoop attempts to reconnect to Redis with exponential backoff.
func redisReconnectLoop(addr string, baseOptions *redis.Options) {
	backoff := 2 * time.Second
	maxBackoff := 60 * time.Second
	for {
		time.Sleep(backoff)
		testClient := redis.NewClient(baseOptions)
		if err := testClient.Ping(context.Background()).Err(); err != nil {
			log.Printf("Redis reconnect failed: %v (retry in %v)", err, backoff)
			backoff *= 2
			if backoff > maxBackoff {
				backoff = maxBackoff
			}
			testClient.Close()
			continue
		}
		// Reconnected — caller must replace their reference.
		// This is a best-effort background reconnect; the wrapper
		// returned by InitRedis remains nil until a new InitRedis call.
		log.Println("Redis reconnected successfully (background)")
		testClient.Close()
		return
	}
}

// Ping checks Redis connectivity.
func (r *RedisWrapper) Ping(ctx context.Context) error {
	if r == nil || r.client == nil {
		return redis.ErrClosed
	}
	return r.client.Ping(ctx).Err()
}

// Set stores a key with TTL.
func (r *RedisWrapper) Set(ctx context.Context, key string, value interface{}, expiration time.Duration) error {
	return r.client.Set(ctx, key, value, expiration).Err()
}

// Get retrieves a key.
func (r *RedisWrapper) Get(ctx context.Context, key string) (string, error) {
	return r.client.Get(ctx, key).Result()
}

// Del removes keys.
func (r *RedisWrapper) Del(ctx context.Context, keys ...string) error {
	return r.client.Del(ctx, keys...).Err()
}

// Incr increments a key.
func (r *RedisWrapper) Incr(ctx context.Context, key string) (int64, error) {
	return r.client.Incr(ctx, key).Result()
}

// Decr decrements a key.
func (r *RedisWrapper) Decr(ctx context.Context, key string) (int64, error) {
	return r.client.Decr(ctx, key).Result()
}

// Expire sets TTL on a key.
func (r *RedisWrapper) Expire(ctx context.Context, key string, expiration time.Duration) error {
	return r.client.Expire(ctx, key, expiration).Err()
}

// Exists checks if keys exist.
func (r *RedisWrapper) Exists(ctx context.Context, keys ...string) (int64, error) {
	return r.client.Exists(ctx, keys...).Result()
}

// Publish publishes a message to a channel.
func (r *RedisWrapper) Publish(ctx context.Context, channel string, message interface{}) error {
	return r.client.Publish(ctx, channel, message).Err()
}

// PSubscribe subscribes to channels by pattern.
func (r *RedisWrapper) PSubscribe(ctx context.Context, channels ...string) PubSub {
	ps := r.client.PSubscribe(ctx, channels...)
	return &redisPubSubWrapper{ps: ps}
}

// Scan scans keys matching a pattern.
func (r *RedisWrapper) Scan(ctx context.Context, cursor uint64, match string, count int64) ([]string, uint64, error) {
	return r.client.Scan(ctx, cursor, match, count).Result()
}

// Info returns Redis server info.
func (r *RedisWrapper) Info(ctx context.Context, sections ...string) (string, error) {
	return r.client.Info(ctx, sections...).Result()
}

// Close closes the Redis connection.
func (r *RedisWrapper) Close() error {
	if r == nil || r.client == nil {
		return nil
	}
	return r.client.Close()
}

// redisPubSubWrapper wraps go-redis PubSub.
type redisPubSubWrapper struct {
	ps *redis.PubSub
}

func (w *redisPubSubWrapper) ReceiveMessage(ctx context.Context) (*PubSubMessage, error) {
	msg, err := w.ps.ReceiveMessage(ctx)
	if err != nil {
		return nil, err
	}
	return &PubSubMessage{Channel: msg.Channel, Payload: msg.Payload}, nil
}

func (w *redisPubSubWrapper) Close() error {
	return w.ps.Close()
}