init

internal/cache/exchange_rate_cache.go

@@ -0,0 +1,192 @@
+package cache
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"strconv"
+	"time"
+
+	"github.com/redis/go-redis/v9"
+
+	"accounting-app/internal/config"
+)
+
+// Redis key constants for exchange rate cache
+const (
+	RatesCacheKey = "exchange_rates:all"
+	RateCacheKey  = "exchange_rates:rate:"
+	SyncStatusKey = "exchange_rates:sync_status"
+)
+
+// SyncStatus represents the synchronization status of exchange rates
+type SyncStatus struct {
+	LastSyncTime   time.Time `json:"last_sync_time"`
+	LastSyncStatus string    `json:"last_sync_status"` // success, failed
+	NextSyncTime   time.Time `json:"next_sync_time"`
+	RatesCount     int       `json:"rates_count"`
+	ErrorMessage   string    `json:"error_message,omitempty"`
+}
+
+// ExchangeRateCache provides Redis caching for exchange rates
+type ExchangeRateCache struct {
+	client     *redis.Client
+	keyPrefix  string
+	expiration time.Duration
+}
+
+// NewExchangeRateCache creates a new ExchangeRateCache instance
+func NewExchangeRateCache(redisClient *RedisClient, cfg *config.Config) *ExchangeRateCache {
+	expiration := cfg.CacheExpiration
+	if expiration == 0 {
+		expiration = 10 * time.Minute // Default to 10 minutes
+	}
+
+	return &ExchangeRateCache{
+		client:     redisClient.Client(),
+		keyPrefix:  "",
+		expiration: expiration,
+	}
+}
+
+// GetAll retrieves all exchange rates from the cache
+// Returns a map of currency code to rate (1 Currency = Rate CNY)
+func (c *ExchangeRateCache) GetAll(ctx context.Context) (map[string]float64, error) {
+	result, err := c.client.HGetAll(ctx, RatesCacheKey).Result()
+	if err != nil {
+		return nil, fmt.Errorf("failed to get all rates from cache: %w", err)
+	}
+
+	if len(result) == 0 {
+		return nil, nil // Cache miss - no data
+	}
+
+	rates := make(map[string]float64, len(result))
+	for currency, rateStr := range result {
+		rate, err := strconv.ParseFloat(rateStr, 64)
+		if err != nil {
+			// Skip invalid rate values
+			continue
+		}
+		rates[currency] = rate
+	}
+
+	return rates, nil
+}
+
+// Get retrieves a single currency's exchange rate from the cache
+// Returns the rate (1 Currency = Rate CNY) or an error if not found
+func (c *ExchangeRateCache) Get(ctx context.Context, currency string) (float64, error) {
+	rateStr, err := c.client.HGet(ctx, RatesCacheKey, currency).Result()
+	if err != nil {
+		if errors.Is(err, redis.Nil) {
+			return 0, fmt.Errorf("rate for currency %s not found in cache", currency)
+		}
+		return 0, fmt.Errorf("failed to get rate for %s from cache: %w", currency, err)
+	}
+
+	rate, err := strconv.ParseFloat(rateStr, 64)
+	if err != nil {
+		return 0, fmt.Errorf("invalid rate value for %s in cache: %w", currency, err)
+	}
+
+	return rate, nil
+}
+
+// SetAll stores all exchange rates in the cache with TTL
+// rates is a map of currency code to rate (1 Currency = Rate CNY)
+func (c *ExchangeRateCache) SetAll(ctx context.Context, rates map[string]float64) error {
+	if len(rates) == 0 {
+		return nil
+	}
+
+	// Convert rates to string map for Redis Hash
+	rateStrings := make(map[string]interface{}, len(rates))
+	for currency, rate := range rates {
+		rateStrings[currency] = strconv.FormatFloat(rate, 'f', 6, 64)
+	}
+
+	// Use pipeline for atomic operation
+	pipe := c.client.Pipeline()
+
+	// Delete existing key to ensure clean state
+	pipe.Del(ctx, RatesCacheKey)
+
+	// Set all rates in hash
+	pipe.HSet(ctx, RatesCacheKey, rateStrings)
+
+	// Set TTL
+	pipe.Expire(ctx, RatesCacheKey, c.expiration)
+
+	_, err := pipe.Exec(ctx)
+	if err != nil {
+		return fmt.Errorf("failed to set rates in cache: %w", err)
+	}
+
+	return nil
+}
+
+// GetSyncStatus retrieves the synchronization status from the cache
+func (c *ExchangeRateCache) GetSyncStatus(ctx context.Context) (*SyncStatus, error) {
+	data, err := c.client.Get(ctx, SyncStatusKey).Bytes()
+	if err != nil {
+		if errors.Is(err, redis.Nil) {
+			return nil, nil // No sync status stored yet
+		}
+		return nil, fmt.Errorf("failed to get sync status from cache: %w", err)
+	}
+
+	var status SyncStatus
+	if err := json.Unmarshal(data, &status); err != nil {
+		return nil, fmt.Errorf("failed to unmarshal sync status: %w", err)
+	}
+
+	return &status, nil
+}
+
+// SetSyncStatus stores the synchronization status in the cache
+func (c *ExchangeRateCache) SetSyncStatus(ctx context.Context, status *SyncStatus) error {
+	if status == nil {
+		return errors.New("sync status cannot be nil")
+	}
+
+	data, err := json.Marshal(status)
+	if err != nil {
+		return fmt.Errorf("failed to marshal sync status: %w", err)
+	}
+
+	// Sync status doesn't expire - it's always relevant
+	err = c.client.Set(ctx, SyncStatusKey, data, 0).Err()
+	if err != nil {
+		return fmt.Errorf("failed to set sync status in cache: %w", err)
+	}
+
+	return nil
+}
+
+// Exists checks if the rates cache exists and is not expired
+func (c *ExchangeRateCache) Exists(ctx context.Context) (bool, error) {
+	exists, err := c.client.Exists(ctx, RatesCacheKey).Result()
+	if err != nil {
+		return false, fmt.Errorf("failed to check cache existence: %w", err)
+	}
+	return exists > 0, nil
+}
+
+// Delete removes all exchange rate data from the cache
+func (c *ExchangeRateCache) Delete(ctx context.Context) error {
+	pipe := c.client.Pipeline()
+	pipe.Del(ctx, RatesCacheKey)
+	pipe.Del(ctx, SyncStatusKey)
+	_, err := pipe.Exec(ctx)
+	if err != nil {
+		return fmt.Errorf("failed to delete cache: %w", err)
+	}
+	return nil
+}
+
+// GetExpiration returns the cache expiration duration
+func (c *ExchangeRateCache) GetExpiration() time.Duration {
+	return c.expiration
+}