feat: harden growth report orchestration

internal/growthreport/coordinator.go

@@ -42,12 +42,27 @@ func (c *Coordinator) ReserveBudget(ctx context.Context, tokens int64, now time.
 	if c.config.DailyRequests < 1 || c.config.DailyTokens < 1 {
 		return ErrBudgetExhausted
 	}
-	if err := c.increment(ctx, "growth:budget:req:"+tehranDate(now), c.config.DailyRequests, 36*time.Hour, now); err != nil {
+	if c.redis == nil {
 		return ErrBudgetExhausted
 	}
-	if err := c.incrementBy(ctx, "growth:budget:tok:"+tehranDate(now), tokens, c.config.DailyTokens, 36*time.Hour, now); err != nil {
+	if err := c.incrementRedis(ctx, "growth:budget:req:"+tehranDate(now), 1, c.config.DailyRequests, 36*time.Hour); err != nil {
 		return ErrBudgetExhausted
 	}
+	if err := c.incrementRedis(ctx, "growth:budget:tok:"+tehranDate(now), tokens, c.config.DailyTokens, 36*time.Hour); err != nil {
+		return ErrBudgetExhausted
+	}
+	return nil
+}
+
+func (c *Coordinator) incrementRedis(ctx context.Context, key string, amount, limit int64, ttl time.Duration) error {
+	script := redis.NewScript(`local v=redis.call('INCRBY',KEYS[1],ARGV[1]);if v==tonumber(ARGV[1]) then redis.call('PEXPIRE',KEYS[1],ARGV[2]) end;if v>tonumber(ARGV[3]) then return 0 end;return 1`)
+	value, err := script.Run(ctx, c.redis, []string{key}, amount, ttl.Milliseconds(), limit).Int()
+	if err != nil {
+		return err
+	}
+	if value == 0 {
+		return ErrRateLimited
+	}
 	return nil
 }
 func (c *Coordinator) Enter(ctx context.Context) (func(), error) {
@@ -63,6 +78,7 @@ func (c *Coordinator) Publish(ctx context.Context, reportID string) {
 		_ = c.redis.LPush(ctx, "growth:jobs", reportID).Err()
 	}
 }
+
 func (c *Coordinator) increment(ctx context.Context, key string, limit int64, ttl time.Duration, now time.Time) error {
 	return c.incrementBy(ctx, key, 1, limit, ttl, now)
 }