package store

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"time"

	"github.com/redis/go-redis/v9"
	"github.com/rs/zerolog"

	"base/pkg/metrics"
)

// RedisStore implements Store interface using Redis
type RedisStore[V any] struct {
	client  *redis.Client
	logger  *zerolog.Logger
	metrics *metrics.Metrics
}

// NewRedisStore creates a new Redis store instance
func NewRedisStore[V any](client *redis.Client, logger *zerolog.Logger, metrics *metrics.Metrics) Store[V] {
	return &RedisStore[V]{
		client:  client,
		logger:  logger,
		metrics: metrics,
	}
}

// Get retrieves a value from store by key
func (c *RedisStore[V]) Get(ctx context.Context, key string) (V, bool, error) {
	var zero V

	keyPattern, err := extractKeyPattern(key)
	if err != nil {
		return zero, false, err
	}

	start := time.Now()
	dest, exist, getErr := c.get(ctx, key)
	duration := time.Since(start)

	c.metrics.RecordCacheHit("redis", keyPattern, "get", exist, getErr, duration)
	return dest, exist, err
}

func (c *RedisStore[V]) get(ctx context.Context, key string) (V, bool, error) {
	var zero V

	val, err := c.client.Get(ctx, key).Result()
	if err != nil {
		if errors.Is(err, redis.Nil) {
			return zero, false, nil
		}

		return zero, false, fmt.Errorf("failed to get key %s: %w", key, err)
	}

	newDest := new(V)

	// Try to unmarshal the value
	if err = json.Unmarshal([]byte(val), newDest); err != nil {
		return zero, false, fmt.Errorf("failed to unmarshal cached value for key %s: %w", key, err)
	}

	return *newDest, true, nil
}

// Set stores a value in store with expiration
func (c *RedisStore[V]) Set(ctx context.Context, key string, value V, expiration time.Duration) error {
	return c.set(ctx, key, value, expiration)
}

func (c *RedisStore[V]) set(ctx context.Context, key string, value interface{}, expiration time.Duration) error {
	data, err := marshalValue(key, value)
	if err != nil {
		return err
	}

	err = c.client.Set(ctx, key, data, expiration).Err()

	if err != nil {
		return fmt.Errorf("failed to set key %s: %w", key, err)
	}

	return nil
}

// Delete removes a key from store
func (c *RedisStore[V]) Delete(ctx context.Context, key string) error {
	return c.client.Del(ctx, key).Err()
}

func (c *RedisStore[V]) delete(ctx context.Context, key string) error {
	err := c.client.Del(ctx, key).Err()
	if err != nil {
		return fmt.Errorf("failed to delete key %s: %w", key, err)
	}

	return nil
}

// Exists checks if a key exists in store
func (c *RedisStore[V]) Exists(ctx context.Context, key string) (bool, error) {
	keyPattern, err := extractKeyPattern(key)
	if err != nil {
		return false, err
	}

	start := time.Now()

	exists, err := c.exists(ctx, key)
	duration := time.Since(start)

	c.metrics.RecordCacheHit("redis", keyPattern, "exists", exists, err, duration)

	return exists, err
}

func (c *RedisStore[V]) exists(ctx context.Context, key string) (bool, error) {
	exists, err := c.client.Exists(ctx, key).Result()
	if err != nil {
		return false, fmt.Errorf("failed to check existence of key %s: %w", key, err)
	}

	result := exists > 0
	return result, nil
}

// SetNX sets a value only if the key doesn't exist (atomic operation)
func (c *RedisStore[V]) SetNX(ctx context.Context, key string, value V, expiration time.Duration) (bool, error) {
	keyPattern, err := extractKeyPattern(key)
	if err != nil {
		return false, err
	}

	start := time.Now()

	success, err := c.setNX(ctx, key, value, expiration)
	duration := time.Since(start)

	c.metrics.RecordCacheHit("redis", keyPattern, "setNx", success, err, duration)

	return success, err
}

func (c *RedisStore[V]) setNX(ctx context.Context, key string, value V, expiration time.Duration) (bool, error) {
	var data []byte
	var err error

	// Vry to marshal the value to JSON
	if data, err = json.Marshal(value); err != nil {
		return false, fmt.Errorf("failed to marshal value for key %s: %w", key, err)
	}

	success, err := c.client.SetNX(ctx, key, data, expiration).Result()
	if err != nil {
		return false, fmt.Errorf("failed to set key %s with NX: %w", key, err)
	}

	return success, nil
}

// HMGet retrieves multiple fields from a hash
func (c *RedisStore[V]) HMGet(ctx context.Context, key string, keys ...string) (map[string]V, error) {
	keyPattern, err := extractKeyPattern(key)
	if err != nil {
		return nil, err
	}

	start := time.Now()
	result, getErr := c.hmGet(ctx, key, keys...)
	duration := time.Since(start)

	c.metrics.RecordCacheHit("redis", keyPattern, "hmget", len(result) > 0 && getErr == nil, getErr, duration)
	return result, err
}

func (c *RedisStore[V]) hmGet(ctx context.Context, key string, fields ...string) (map[string]V, error) {
	vals, err := c.client.HMGet(ctx, key, fields...).Result()
	if err != nil {
		return nil, fmt.Errorf("failed to hmget key %s: %w", key, err)
	}

	result := make(map[string]V, len(fields))
	for i, field := range fields {
		if vals[i] != nil {
			serializedValue, serializeValueErr := serializeValue[V](vals[i])
			if serializeValueErr != nil {
				return nil, serializeValueErr
			}

			result[field] = serializedValue
		}
	}

	return result, nil
}

// HGetAll retrieves multiple fields from a hash
func (c *RedisStore[V]) HGetAll(ctx context.Context, key string) (map[string]V, error) {
	keyPattern, err := extractKeyPattern(key)
	if err != nil {
		return nil, err
	}

	start := time.Now()

	result, getErr := c.hGetAll(ctx, key)
	duration := time.Since(start)

	c.metrics.RecordCacheHit("redis", keyPattern, "hmget", len(result) > 0 && getErr == nil, getErr, duration)
	return result, err
}

func (c *RedisStore[V]) hGetAll(ctx context.Context, key string) (map[string]V, error) {
	vals, err := c.client.HGetAll(ctx, key).Result()
	if err != nil {
		return nil, fmt.Errorf("failed to hmget key %s: %w", key, err)
	}

	result := make(map[string]V)
	for _, field := range vals {
		serializedValue, serializeValueErr := serializeValue[V](field)
		if serializeValueErr != nil {
			return nil, serializeValueErr
		}

		result[field] = serializedValue

	}

	return result, nil
}

// HMSet sets multiple fields in a hash with expiration
func (c *RedisStore[V]) HMSet(ctx context.Context, key string, values map[string]V, expiration time.Duration) error {
	return c.hmSet(ctx, key, values, expiration)
}

func (c *RedisStore[V]) hmSet(ctx context.Context, key string, values map[string]V, expiration time.Duration) error {
	if len(values) == 0 {
		return nil
	}

	// Convert values to string format for Redis hash
	hashValues := make(map[string]interface{}, len(values))
	for field, value := range values {
		serializedValue, err := json.Marshal(value)
		if err != nil {
			return err
		}
		hashValues[field] = serializedValue
	}

	// Set hash fields
	err := c.client.HMSet(ctx, key, hashValues).Err()
	if err != nil {
		return fmt.Errorf("failed to hmset key %s: %w", key, err)
	}

	// Set expiration if specified
	if expiration > 0 {
		err = c.client.Expire(ctx, key, expiration).Err()
		if err != nil {
			return fmt.Errorf("failed to set expiration for key %s: %w", key, err)
		}
	}

	return nil
}

// SetMultiple stores multiple key-value pairs with expiration
func (c *RedisStore[V]) SetMultiple(ctx context.Context, items map[string]V, expiration time.Duration) error {
	if len(items) == 0 {
		return nil
	}

	return c.setMultiple(ctx, items, expiration)
}

func (c *RedisStore[V]) setMultiple(ctx context.Context, items map[string]V, expiration time.Duration) error {
	pipe := c.client.Pipeline()

	for key, value := range items {
		data, err := marshalValue(key, value)
		if err != nil {
			return err
		}

		pipe.Set(ctx, key, data, expiration)
	}

	_, err := pipe.Exec(ctx)
	if err != nil {
		return fmt.Errorf("failed to set multiple keys: %w", err)
	}

	return nil
}

func marshalValue(key string, value interface{}) ([]byte, error) {
	data, err := json.Marshal(value)
	if err != nil {
		if str, ok := value.(string); ok {
			return []byte(str), nil
		}

		return nil, fmt.Errorf("failed to marshal value for key %s: %w", key, err)
	}

	return data, nil
}

// DeleteMultiple removes multiple keys from store
func (c *RedisStore[V]) DeleteMultiple(ctx context.Context, keys ...string) error {
	if len(keys) == 0 {
		return nil
	}

	return c.deleteMultiple(ctx, keys...)
}

func (c *RedisStore[V]) deleteMultiple(ctx context.Context, keys ...string) error {
	if len(keys) == 0 {
		return nil
	}

	err := c.client.Del(ctx, keys...).Err()
	if err != nil {
		return fmt.Errorf("failed to delete multiple keys: %w", err)
	}

	return nil
}

// DeletePattern removes all keys matching the pattern from store
func (c *RedisStore[V]) DeletePattern(ctx context.Context, pattern string) error {
	return c.deletePattern(ctx, pattern)
}

func (c *RedisStore[V]) deletePattern(ctx context.Context, pattern string) error {
	var cursor uint64

	for {
		var keys []string
		var err error

		// Use SCAN to find keys matching the pattern (non-blocking)
		keys, cursor, err = c.client.Scan(ctx, cursor, pattern, 100).Result()
		if err != nil {
			return fmt.Errorf("failed to scan keys with pattern %s: %w", pattern, err)
		}

		// Delete found keys
		if len(keys) > 0 {
			err = c.client.Del(ctx, keys...).Err()
			if err != nil {
				return fmt.Errorf("failed to delete keys matching pattern %s: %w", pattern, err)
			}
		}

		// If cursor is 0, we've scanned all keys
		if cursor == 0 {
			break
		}
	}

	return nil
}