package main

import (
	"encoding/json"
	"fmt"
	"strings"
)

type routePayload struct {
	Platform string `json:"platform"`
	DeviceID string `json:"device_id"`
}

func extractPlatform(body []byte) (string, error) {
	var msg routePayload
	if err := json.Unmarshal(body, &msg); err != nil {
		return "", fmt.Errorf("invalid JSON: %w", err)
	}

	if msg.Platform != "" {
		return stripVersionSuffix(msg.Platform), nil
	}

	if idx := strings.Index(msg.DeviceID, ":"); idx > 0 {
		return msg.DeviceID[:idx], nil
	}

	return "", fmt.Errorf("missing platform")
}

func stripVersionSuffix(platform string) string {
	if idx := strings.Index(platform, "-v"); idx > 0 {
		return platform[:idx]
	}
	return platform
}