perf(admin): optimize large-dataset loading for dashboard/users/accounts/ops

backend/internal/handler/admin/snapshot_cache.go

@@ -0,0 +1,95 @@
+package admin
+
+import (
+	"crypto/sha256"
+	"encoding/hex"
+	"encoding/json"
+	"strings"
+	"sync"
+	"time"
+)
+
+type snapshotCacheEntry struct {
+	ETag      string
+	Payload   any
+	ExpiresAt time.Time
+}
+
+type snapshotCache struct {
+	mu    sync.RWMutex
+	ttl   time.Duration
+	items map[string]snapshotCacheEntry
+}
+
+func newSnapshotCache(ttl time.Duration) *snapshotCache {
+	if ttl <= 0 {
+		ttl = 30 * time.Second
+	}
+	return &snapshotCache{
+		ttl:   ttl,
+		items: make(map[string]snapshotCacheEntry),
+	}
+}
+
+func (c *snapshotCache) Get(key string) (snapshotCacheEntry, bool) {
+	if c == nil || key == "" {
+		return snapshotCacheEntry{}, false
+	}
+	now := time.Now()
+
+	c.mu.RLock()
+	entry, ok := c.items[key]
+	c.mu.RUnlock()
+	if !ok {
+		return snapshotCacheEntry{}, false
+	}
+	if now.After(entry.ExpiresAt) {
+		c.mu.Lock()
+		delete(c.items, key)
+		c.mu.Unlock()
+		return snapshotCacheEntry{}, false
+	}
+	return entry, true
+}
+
+func (c *snapshotCache) Set(key string, payload any) snapshotCacheEntry {
+	if c == nil {
+		return snapshotCacheEntry{}
+	}
+	entry := snapshotCacheEntry{
+		ETag:      buildETagFromAny(payload),
+		Payload:   payload,
+		ExpiresAt: time.Now().Add(c.ttl),
+	}
+	if key == "" {
+		return entry
+	}
+	c.mu.Lock()
+	c.items[key] = entry
+	c.mu.Unlock()
+	return entry
+}
+
+func buildETagFromAny(payload any) string {
+	raw, err := json.Marshal(payload)
+	if err != nil {
+		return ""
+	}
+	sum := sha256.Sum256(raw)
+	return "\"" + hex.EncodeToString(sum[:]) + "\""
+}
+
+func parseBoolQueryWithDefault(raw string, def bool) bool {
+	value := strings.TrimSpace(strings.ToLower(raw))
+	if value == "" {
+		return def
+	}
+	switch value {
+	case "1", "true", "yes", "on":
+		return true
+	case "0", "false", "no", "off":
+		return false
+	default:
+		return def
+	}
+}