feat: add SproutWorkCollect apps

SproutWorkCollect-Backend-Golang/internal/service/ratelimit.go

@@ -0,0 +1,64 @@
+package service
+
+import (
+	"crypto/md5"
+	"fmt"
+	"sync"
+	"time"
+)
+
+// rateLimits defines minimum seconds between the same action by the same user on the same work.
+var rateLimits = map[string]int64{
+	"view":     60,
+	"download": 300,
+	"like":     3600,
+}
+
+// RateLimiter provides per-user, per-action, per-work rate limiting backed by an in-memory store.
+// The store is never persisted; it resets on service restart (same behaviour as the Python version).
+type RateLimiter struct {
+	mu sync.Mutex
+	// fingerprint → actionType → workID → last unix timestamp
+	actions map[string]map[string]map[string]int64
+}
+
+// NewRateLimiter allocates a new empty RateLimiter.
+func NewRateLimiter() *RateLimiter {
+	return &RateLimiter{
+		actions: make(map[string]map[string]map[string]int64),
+	}
+}
+
+// CanPerform returns true and records the timestamp if the rate limit window has elapsed.
+// Returns false if the action is too frequent.
+func (rl *RateLimiter) CanPerform(fingerprint, actionType, workID string) bool {
+	rl.mu.Lock()
+	defer rl.mu.Unlock()
+
+	limit, ok := rateLimits[actionType]
+	if !ok {
+		return true
+	}
+
+	now := time.Now().Unix()
+
+	if rl.actions[fingerprint] == nil {
+		rl.actions[fingerprint] = make(map[string]map[string]int64)
+	}
+	if rl.actions[fingerprint][actionType] == nil {
+		rl.actions[fingerprint][actionType] = make(map[string]int64)
+	}
+
+	last := rl.actions[fingerprint][actionType][workID]
+	if now-last >= limit {
+		rl.actions[fingerprint][actionType][workID] = now
+		return true
+	}
+	return false
+}
+
+// Fingerprint creates an MD5 hex string from IP and User-Agent for rate-limit keying.
+func Fingerprint(ip, userAgent string) string {
+	h := md5.Sum([]byte(ip + ":" + userAgent))
+	return fmt.Sprintf("%x", h)
+}