[feat] simple update check

pkg/config/version/checknewer.go

+package version
+
+import (
+	"io/ioutil"
+	"log"
+	"net/http"
+	"os"
+	"runtime"
+	"strings"
+)
+
+const verURI = "https://downloads.leap.se/RiseupVPN/"
+
+// returns true if there's a newer version string published on the server
+// this needs to manually bump latest version for every platform in the
+// downloads server.
+// at the moment, we hardcode RiseupVPN in the path, assuming that all clients
+// stay in sync.
+func CanUpgrade() bool {
+	log.Println("Checking for updates...")
+	uri := verURI
+	switch runtime.GOOS {
+	case "windows":
+		uri += "windows"
+	case "linux":
+		uri += "linux"
+	case "osx":
+		uri += "osx"
+	}
+	uri += "/lastver"
+	resp, err := http.Get(uri)
+	if err != nil {
+		log.Println(err)
+		return false
+	}
+	defer resp.Body.Close()
+	verStr, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		log.Println(err)
+		return false
+	}
+	r := strings.TrimSpace(string(verStr))
+	if strings.Count(r, "\n") > 1 {
+		log.Println("No remote version found at " + uri)
+		return false
+	}
+	canUpgrade := versionOrdinal(r) > versionOrdinal(VERSION)
+	if os.Getenv("DEBUG") == "1" {
+		log.Println(">>> Remote version:  " + r)
+		log.Println(">>> Current version: " + VERSION)
+		if canUpgrade {
+			log.Println("Newer version available")
+		}
+	}
+	return canUpgrade
+}
+
+// https://stackoverflow.com/a/18411978
+func versionOrdinal(version string) string {
+	const maxByte = 1<<8 - 1
+	vo := make([]byte, 0, len(version)+8)
+	j := -1
+	for i := 0; i < len(version); i++ {
+		b := version[i]
+		if '0' > b || b > '9' {
+			vo = append(vo, b)
+			j = -1
+			continue
+		}
+		if j == -1 {
+			vo = append(vo, 0x00)
+			j = len(vo) - 1
+		}
+		if vo[j] == 1 && vo[j+1] == '0' {
+			vo[j+1] = b
+			continue
+		}
+		if vo[j]+1 > maxByte {
+			log.Println("VersionOrdinal: invalid version")
+			return string(vo)
+		}
+		vo = append(vo, b)
+		vo[j]++
+	}
+	return string(vo)
+}

tests/vercheck/.gitignore

+vercheck

tests/vercheck/main.go

+package main
+
+import (
+	"0xacab.org/leap/bitmask-vpn/pkg/config/version"
+	"fmt"
+)
+
+func main() {
+	fmt.Println("Testing version upgrade (checks network)")
+	fmt.Println("-> set DEBUG=1 for details")
+	u := version.CanUpgrade()
+	switch {
+	case u:
+		fmt.Println("can upgrade")
+	case !u:
+		fmt.Println("no new version available")
+	}
+}