// Package cache provides caching for the API Gateway.
package cache

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

	"github.com/redis/go-redis/v9"
	"go.uber.org/zap"
)

// Config for cache manager
type Config struct {
	RedisAddr     string
	RedisPassword string
	RedisDB       int
	DefaultTTL    time.Duration
	MaxEntrySize  int
	KeyPrefix     string
}

// Manager handles caching operations
type Manager struct {
	client *redis.Client
	config Config
	logger *zap.Logger
}

// NewManager creates a cache manager
func NewManager(cfg Config, logger *zap.Logger) (*Manager, error) {
	client := redis.NewClient(&redis.Options{
		Addr:     cfg.RedisAddr,
		Password: cfg.RedisPassword,
		DB:       cfg.RedisDB,
	})

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

	if err := client.Ping(ctx).Err(); err != nil {
		return nil, err
	}

	return &Manager{
		client: client,
		config: cfg,
		logger: logger,
	}, nil
}

// GenerateKey creates cache key from request
func (m *Manager) GenerateKey(parts ...string) string {
	h := sha256.New()
	for _, p := range parts {
		h.Write([]byte(p))
	}
	return m.config.KeyPrefix + hex.EncodeToString(h.Sum(nil))
}

// Get retrieves cached value
func (m *Manager) Get(ctx context.Context, key string) (interface{}, bool) {
	data, err := m.client.Get(ctx, key).Bytes()
	if err != nil {
		return nil, false
	}
	var result interface{}
	if err := json.Unmarshal(data, &result); err != nil {
		return nil, false
	}
	return result, true
}

// Set stores value in cache
func (m *Manager) Set(ctx context.Context, key string, value interface{}, ttl time.Duration) error {
	data, err := json.Marshal(value)
	if err != nil {
		return err
	}
	if len(data) > m.config.MaxEntrySize {
		m.logger.Warn("Cache entry exceeds max size", zap.String("key", key))
		return nil
	}
	if ttl == 0 {
		ttl = m.config.DefaultTTL
	}
	return m.client.Set(ctx, key, data, ttl).Err()
}

// Delete removes value from cache
func (m *Manager) Delete(ctx context.Context, key string) error {
	return m.client.Del(ctx, key).Err()
}

// Close closes Redis connection
func (m *Manager) Close() error {
	return m.client.Close()
}