multi: Rework client user agent id logic.

internal/semver/semver.go

@@ -0,0 +1,104 @@
+// Copyright (c) 2015-2023 The Decred developers
+// Use of this source code is governed by an ISC
+// license that can be found in the LICENSE file.
+
+// Package semver parses semantic versioning 2.0.0 version strings.
+package semver
+
+import (
+	"fmt"
+	"regexp"
+	"strconv"
+	"strings"
+)
+
+const (
+	// semanticAlphabet defines the allowed characters for the pre-release and
+	// build metadata portions of a semantic version string.
+	semanticAlphabet = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz-."
+)
+
+// semverRE is a regular expression used to parse a semantic version string into
+// its constituent parts.
+var semverRE = regexp.MustCompile(`^(0|[1-9]\d*)\.(0|[1-9]\d*)\.(0|[1-9]\d*)` +
+	`(?:-((?:0|[1-9]\d*|\d*[a-zA-Z-][0-9a-zA-Z-]*)(?:\.(?:0|[1-9]\d*|\d*` +
+	`[a-zA-Z-][0-9a-zA-Z-]*))*))?(?:\+([0-9a-zA-Z-]+(?:\.[0-9a-zA-Z-]+)*))?$`)
+
+// parseUint32 converts the passed string to an unsigned integer or returns an
+// error if it is invalid.
+func parseUint32(s string, fieldName string) (uint32, error) {
+	val, err := strconv.ParseUint(s, 10, 32)
+	if err != nil {
+		return 0, fmt.Errorf("malformed semver %s: %w", fieldName, err)
+	}
+	return uint32(val), err
+}
+
+// checkSemString returns an error if the passed string contains characters that
+// are not in the provided alphabet.
+func checkSemString(s, alphabet, fieldName string) error {
+	for _, r := range s {
+		if !strings.ContainsRune(alphabet, r) {
+			return fmt.Errorf("malformed semver %s: %q invalid", fieldName, r)
+		}
+	}
+	return nil
+}
+
+// ParsedSemVer houses the individual components of a parsed semantic versioning
+// 2.0.0 version string.
+type ParsedSemVer struct {
+	Major         uint32
+	Minor         uint32
+	Patch         uint32
+	PreRelease    string
+	BuildMetadata string
+}
+
+// Parse attempts to parse the various semver components from the provided
+// version string.
+func Parse(s string) (*ParsedSemVer, error) {
+	// Parse the various semver component from the version string via a regular
+	// expression.
+	m := semverRE.FindStringSubmatch(s)
+	if m == nil {
+		err := fmt.Errorf("malformed version string %q: does not conform to "+
+			"semver specification", s)
+		return nil, err
+	}
+
+	major, err := parseUint32(m[1], "major")
+	if err != nil {
+		return nil, err
+	}
+
+	minor, err := parseUint32(m[2], "minor")
+	if err != nil {
+		return nil, err
+	}
+
+	patch, err := parseUint32(m[3], "patch")
+	if err != nil {
+		return nil, err
+	}
+
+	preRel := m[4]
+	err = checkSemString(preRel, semanticAlphabet, "pre-release")
+	if err != nil {
+		return nil, err
+	}
+
+	build := m[5]
+	err = checkSemString(build, semanticAlphabet, "buildmetadata")
+	if err != nil {
+		return nil, err
+	}
+
+	return &ParsedSemVer{
+		Major:         major,
+		Minor:         minor,
+		Patch:         patch,
+		PreRelease:    preRel,
+		BuildMetadata: build,
+	}, nil
+}