Add role ratelimit (#1)

* Add ratelimit configuration.
* Add rate limiting :party:

ratelimit.go

@@ -0,0 +1,84 @@
+package main
+
+import (
+	"os"
+	"time"
+
+	goratecounter "github.com/lukaszraczylo/go-ratecounter"
+)
+
+type RateLimitConfig struct {
+	Req               int    `json:"req"`
+	Interval          string `json:"interval"`
+	RateCounterTicker *goratecounter.RateCounter
+}
+
+var rateLimits map[string]RateLimitConfig
+var ratelimit_intervals = map[string]time.Duration{
+	"milli":  time.Millisecond,
+	"micro":  time.Microsecond,
+	"nano":   time.Nanosecond,
+	"second": time.Second,
+	"minute": time.Minute,
+	"hour":   time.Hour,
+	"day":    time.Hour * 24,
+}
+
+func loadRatelimitConfig() error {
+	paths := [3]string{"/app/ratelimit.json", "./ratelimit.json", "./static/default-ratelimit.json"}
+	for _, path := range paths {
+		file, err := os.Open(path)
+		if err != nil {
+			continue
+		}
+		defer file.Close()
+		decoder := json.NewDecoder(file)
+		config := struct {
+			RateLimit map[string]RateLimitConfig `json:"ratelimit"`
+		}{}
+		err = decoder.Decode(&config)
+		if err != nil {
+			return err
+		}
+
+		for key, value := range config.RateLimit {
+			value.RateCounterTicker = goratecounter.NewRateCounter().WithConfig(goratecounter.RateCounterConfig{
+				Interval: time.Duration(value.Req) * ratelimit_intervals[value.Interval],
+			})
+			cfg.Logger.Debug("Setting ratelimit config for role", map[string]interface{}{"role": key, "interval_provided": value.Interval, "interval_used": ratelimit_intervals[value.Interval], "ratelimit": value.Req})
+			config.RateLimit[key] = value
+		}
+
+		rateLimits = config.RateLimit
+		cfg.Logger.Debug("Rate limit config loaded", map[string]interface{}{"ratelimit": rateLimits})
+		return nil
+	}
+	cfg.Logger.Debug("Rate limit config not found")
+	return os.ErrNotExist
+}
+
+func rateLimitedRequest(userId string, userRole string) (shouldAllow bool) {
+	if rateLimits == nil {
+		cfg.Logger.Debug("Rate limit config not found", map[string]interface{}{"user_role": userRole})
+		return true
+	}
+	// check if userRole is in rateLimits
+	if _, ok := rateLimits[userRole]; !ok {
+		cfg.Logger.Warning("Rate limit role not found", map[string]interface{}{"user_role": userRole})
+		return true
+	}
+
+	if rateLimits[userRole].RateCounterTicker == nil {
+		cfg.Logger.Warning("Rate limit ticker not found", map[string]interface{}{"user_role": userRole})
+		return true
+	}
+
+	rateLimits[userRole].RateCounterTicker.Incr(1)
+	ticker_rate := rateLimits[userRole].RateCounterTicker.GetRate()
+	cfg.Logger.Debug("Rate limit ticker", map[string]interface{}{"user_role": userRole, "user_id": userId, "rate": ticker_rate, "config_rate": rateLimits[userRole].Req, "interval": rateLimits[userRole].Interval, "interval_duration": rateLimits[userRole].Interval})
+	if ticker_rate > float64(rateLimits[userRole].Req) {
+		cfg.Logger.Debug("Rate limit exceeded", map[string]interface{}{"user_role": userRole, "user_id": userId, "rate": ticker_rate, "config_rate": rateLimits[userRole].Req, "interval": rateLimits[userRole].Interval, "interval_duration": rateLimits[userRole].Interval})
+		return false
+	}
+	return true
+}