Add flag parsing

flags.go

@@ -0,0 +1,72 @@
+package event
+
+import (
+	"errors"
+	"flag"
+	"fmt"
+	"strconv"
+	"strings"
+)
+
+var (
+	eventTargetURL       *string
+	eventHeaders         *string
+	eventSecondsPerWrite *float64
+	eventRateClasses     *string
+	eventTotalPerSecond  *float64
+
+	ErrInvalidFlags     = errors.New("invalid flags")
+	ErrInvalidHeader    = fmt.Errorf("%w: invalid --event-headers (missing =)", ErrInvalidFlags)
+	ErrInvalidRateClass = fmt.Errorf("%w: invalid --event-rate-classes (missing =)", ErrInvalidFlags)
+)
+
+func RegisterFlags() {
+	eventTargetURL = flag.String("event-target-url", "", "URL to send events to")
+	eventHeaders = flag.String("event-headers", "", "key=value|key=value|... headers to include with events")
+	eventSecondsPerWrite = flag.Float64("event-seconds-per-write", 5.0, "write events to target every N seconds")
+	eventRateClasses = flag.String("event-rate-classes", "", "key=value=rate|key=value=rate|...")
+	eventTotalPerSecond = flag.Float64("event-total-per-second", 0.2, "write on average N total events per second")
+}
+
+func (c *Client) HandleFlags() error {
+	if *eventTargetURL == "" {
+		return nil
+	}
+
+	headers := map[string]string{}
+
+	for _, pair := range strings.Split(*eventHeaders, "|") {
+		parts := strings.SplitN(pair, "=", 2)
+		if len(parts) != 2 {
+			return ErrInvalidHeader
+		}
+
+		headers[parts[0]] = parts[1]
+	}
+
+	target := c.AddTarget(
+		*eventTargetURL,
+		headers,
+		*eventSecondsPerWrite,
+	)
+
+	for _, rc := range strings.Split(*eventRateClasses, "|") {
+		parts := strings.SplitN(rc, "=", 3)
+		if len(parts) != 3 {
+			return ErrInvalidRateClass
+		}
+
+		rate, err := strconv.ParseFloat(parts[3], 64)
+		if err != nil {
+			return fmt.Errorf("%w %w", ErrInvalidRateClass, err)
+		}
+
+		target.AddRateClass(rate, parts[0], parts[1])
+	}
+
+	target.AddRateClass(
+		*eventTotalPerSecond,
+	)
+
+	return nil
+}