feat: add resilient updates and access controls

internal/appupdate/version.go

@@ -0,0 +1,66 @@
+package appupdate
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+
+	"github.com/root-kdw12/hetzner-api-dyndns-records-webinterface/internal/updateprotocol"
+)
+
+type semanticVersion struct {
+	major int
+	minor int
+	patch int
+}
+
+func parseVersion(raw string) (semanticVersion, error) {
+	if !strings.HasPrefix(raw, "v") || strings.ContainsAny(raw, "+-") {
+		return semanticVersion{}, fmt.Errorf("version must use vMAJOR.MINOR.PATCH")
+	}
+	parts := strings.Split(strings.TrimPrefix(raw, "v"), ".")
+	if len(parts) != 3 {
+		return semanticVersion{}, fmt.Errorf("version must use vMAJOR.MINOR.PATCH")
+	}
+	values := make([]int, 3)
+	for index, part := range parts {
+		if part == "" || (len(part) > 1 && part[0] == '0') {
+			return semanticVersion{}, fmt.Errorf("version contains an invalid number")
+		}
+		value, err := strconv.Atoi(part)
+		if err != nil || value < 0 || value > 1_000_000 {
+			return semanticVersion{}, fmt.Errorf("version contains an invalid number")
+		}
+		values[index] = value
+	}
+	return semanticVersion{major: values[0], minor: values[1], patch: values[2]}, nil
+}
+
+func compareVersions(left, right string) (int, error) {
+	a, err := parseVersion(left)
+	if err != nil {
+		return 0, err
+	}
+	b, err := parseVersion(right)
+	if err != nil {
+		return 0, err
+	}
+	av, bv := []int{a.major, a.minor, a.patch}, []int{b.major, b.minor, b.patch}
+	for index := range av {
+		if av[index] < bv[index] {
+			return -1, nil
+		}
+		if av[index] > bv[index] {
+			return 1, nil
+		}
+	}
+	return 0, nil
+}
+
+func validReleaseVersion(version string) bool {
+	if !updateprotocol.ValidVersion(version) {
+		return false
+	}
+	_, err := parseVersion(version)
+	return err == nil
+}